Zakopane 2026 Conference on Nuclear Physics

Several experiments aiming at studying the low energy parts of the Electric Dipole response (the so called Pygmy Dipole Resonance, PDR) in nuclei were carried out during the years and are presently being made. Use of different probes and techniques was made and nuclei in different mass regions were investigated.
The interest in the PDR states is related to their astrophysical implications in the nucleosynthesis and also because the underlying structure of the PDR is under active debate and scrutiny. The PDR’s isospin splitting was revealed in complementary experiments with isoscalar and isovector probes exciting states in several nuclei, suggesting that the PDR splits into a lower-energy isoscalar surface mode and a higher-energy component with an isovector admixture from IVGDR. Some possible evidence for the electric pygmy quadrupole states was also found.
More recent directions concern the search of E1 decay from states with angular momentum higher than zero and experiments detecting gamma-rays from fission products.
A difficul task is to identify pygmy states in nuclei at finite temperature and for this purpose dedicated experimental efforts are being made. Indeed, this signal is of great interest because the nucleosynthesis in the stellar environment involves nuclei which are not necessarely in the ground states.
To underline the importance of the PDR investigations selected results, open problems and future plans will be presented and discussed. Special emphasis is given to the plans with the PARIS detector arrays.

I will present selected results on nuclear giant and pygmy resonances at zero and finite temperatures based on the recent advancements of the nuclear many-body theory [1-6]. The theory will be compactly introduced in a model-independent quantum field theory framework using only the bare fermionic interaction as an input, enabling controllable approximations. A special focus will be placed on the emergent scale of the quasiparticle-vibration coupling (qPVC), with the order parameter associated with the qPVC vertex, and an efficient treatment of the nuclear many-body problem organized around the qPVC hierarchy [1-3].

Self-consistent solutions of the relativistic Bethe-Salpeter-Dyson equation for the nuclear response function will be presented and discussed. Low-multipole neutral and charge-exchange resonances in calcium, nickel, and tin mass regions will be analyzed in the context of the role of high-complexity configurations in reproducing spectral data [2,3,7]. Finite-temperature theory and implementations for astrophysically relevant low-energy dipole strength, beta decay rates, and electron capture rates will be overviewed in light of the temperature dependence of the nuclear spectral properties [4,5]. Recent developments in computing transitions between nuclear excited states, providing a microscopic alternative to statistical descriptions, will be presented as a promising new avenue for supporting both experimental programs and stellar modeling [8].

References
[1] E. Litvinova and Y. Zhang, Microscopic response theory for strongly-coupled superfluid fermionic systems, Phys. Rev. C 106, 064316 (2022).
[2] E. Litvinova, On the dynamical kernels of fermionic equations of motion in strongly-correlated media, Eur. Phys. J. A59, 291 (2023).
[3] J. Novak, M. Q. Hlatshwayo, and E. Litvinova, Response of strongly coupled fermions on classical and quantum computers, arXiv:240502255.
[4] E. Litvinova and H. Wibowo, Finite-temperature relativistic nuclear field theory: an application to the dipole response, Phys. Rev. Lett. 121, 082501 (2018).
[5] E. Litvinova, C. Robin, and H. Wibowo, Temperature dependence of nuclear spin-isospin response and beta decay in hot astrophysical environments, Phys. Lett. B800, 135134 (2020).
[6] S. Bhattacharjee and E. Litvinova, Response of superfluid fermions at finite temperature, arXiv:2412.20751, Phys. Rev. C (2026).
[7] M. Markova, P. von Neumann-Cosel, and E. Litvinova, Systematics of the low-energy electric dipole strength in the Sn isotopic chain, Phys. Lett. B860, 139216 (2025).
[8] R. Li, E. Litvinova, M. Harakeh et al., First evidence for the J>1 components of the pygmy dipole resonance in neutron-rich nuclei, arXiv:2510.27125.

Finite-temperature effects play a crucial role in shaping exotic nuclear excitations. Thermal unblocking and the weakening of pairing correlations can significantly modify excitation modes of different multipolarities, leading to the emergence of strength that is suppressed at zero temperature. A microscopic description of these effects is therefore important for nuclear structure studies and for astrophysical applications involving hot, neutron-rich systems [1–3].

In this talk, I present a unified study of nuclear excitations at finite temperature based on the finite-temperature relativistic quasiparticle random-phase approximation within the covariant energy density functional framework. I first examine how temperature affects electric and magnetic excitation modes, with emphasis on the role of pairing reduction and thermally unblocked configurations. I then discuss the temperature evolution of the pygmy dipole resonance and the emergence of thermally induced low-energy dipole strength in neutron-rich nuclei [4]. Finally, I address the consequences for electromagnetic γ-ray strength functions, highlighting the redistribution and enhancement of low-energy E1 and M1 strength relevant for hot stellar environments [5].

References
[1] E. Yüksel, G. Colò, E. Khan, Y. F. Niu, and K. Bozkurt, “Multipole excitations in hot nuclei within the finite temperature quasiparticle random phase approximation framework,” Phys. Rev. C 96, 024303 (2017).
[2] E. Yüksel, G. Colò, E. Khan, and Y. F. Niu, “Nuclear excitations within microscopic EDF approaches: Pairing and temperature effects on the dipole response,” Eur. Phys. J. A 55, 230 (2019).
[3] A. Kaur, E. Yüksel, and N. Paar, “Finite-temperature effects in magnetic dipole transitions,” Phys. Rev. C 109, 024305 (2024).
[4] A. Kaur, E. Yüksel, and N. Paar, “Hot pygmy dipole strength in nickel isotopes,” Phys. Rev. C 112, L051304 (2025).
[5] A. Kaur, E. Yüksel, and N. Paar, “Electric and magnetic γ-ray strength functions at finite temperature,” Phys. Rev. C 112, 014307 (2025).

N.S. Martorana$^{1}$, C. Cardella$^{1}$, E.G. Lanza$^{1}$, L. Acosta$^{2}$, M.V. Andrés$^{3}$, F. Camera$^{4,5}$, A. Castoldi$^{5,6}$, E. De Filippo$^{1}$, E. Geraci$^{1,7,8}$, A. Giaz$^{5}$, B. Gnoffo$^{1,7}$, C. Guazzoni$^{5,6}$, C. Maiolino$^{9}$, E.V. Pagano$^{9}$, L. Pellegri$^{10,11}$, S. Pirrone$^{1}$, G. Politi$^{1,7}$, F. Risitano$^{1,8,12}$, F. Rizzo$^{7,8,9}$, P. Russotto$^{9}$, M. Trimarchi$^{1,12}$, G. Verde$^{1}$, O. Wieland$^{5}$, C. Zagami$^{8,9}$
and the NUSDAF collaboration

1 INFN-Sezione di Catania, Catania, Italy
2 Instituto de Estructura de la Materia, CSIC, Spain
3 Departamento de FAMN, Facultad de Física, Sevilla, Spain
4 Università degli studi di Milano, Milano, Italy
5 INFN Sezione di Milano, Milano, Italy
6 DEIB Politecnico di Milano, Milano, Italy
7 Università degli Studi di Catania, Catania, Italy
8 CSFNSM, Catania, Italy
9 INFN-LNS, Catania, Italy
10 School of Physics, University of the Witwatersrand, South Africa
11 iThemba Laboratory for Accelerator Based Sciences, South Africa
12 Dipartimento MIFT, Università di Messina, Messina, Italy

The Pygmy Dipole Resonance (PDR) is a low-lying electric dipole (E1) excitation observed in neutron-rich nuclei, located around the nucleon binding energy. It is macroscopically interpreted as an oscillation of the neutron skin against the nuclear core, although its precise nature, whether collective or arising from a series of no-coherent single-particle excitations, remains an open question. A notable feature of the PDR is its isospin mixing, which allows it to be excited by both isoscalar and isovector probes [1–3]. Experimental studies have shown that the PDR can indeed be populated with both types of probes. In stable nuclei, a splitting is observed in the excitation region below the neutron separation threshold: in the low-lying region the dipole states are excited by both isoscalar and isovector probes, while in the higher-lying one only the excitation by the isovector probes is present [1–3]. This phenomenon, referred to as isospin splitting, appears to be absent in unstable nuclei, where the PDR has been measured above the neutron separation threshold [4–5]. The investigation of the PDR is of great interest not only for nuclear structure studies, but also for constraining the neutron-skin thickness, probing the symmetry energy term of EoS, and improving models of astrophysical processes such as r-process nucleosynthesis [1]. A deeper understanding of the PDR requires systematic investigations with both isoscalar and isovector probes over a wide range of nuclear isotopes and both below and above the neutron emission threshold. In this contribution, an overview of recent results on PDR studies in unstable nuclei is presented, together with future perspectives aimed at improving our understanding of this mode through the use of radioactive ion beams. In particular, future experimental campaigns at FRIB, proposed within the NUSDAF initiative, will be discussed, focusing on advanced studies of the PDR along the Ni isotopic chain through the investigation of both γ and neutron decay channels. First theoretical calculations for Ni isotopes, as well as simulation studies on the feasibility of detecting both neutron and γ decay channels, will also be presented. In addition, benefiting from the high quality and intensity of radioactive beams at FRIB, the program plans to use some existing equipment. Possible perspectives that may be offered by doing experiments at FRIB with more efficient high energy gamma detectors (such as PARIS, among others) will also be discussed.

[1] A. Bracco et al., Progr. in Particle and Nuclear Physics 106, 360-433 (2019) and references therein
[2] D. Savran et al., Progr. In Particle and Nuclear Physics 70, 210-245 (2013) and references therein
[3] E.G. Lanza et al., Progr. in Part. and Nucl. Phys.,129, 104006, (2023) and references therein
[4] O. Wieland et al., Phys. Rev. Lett. 102, 092502 (2009)
[5] N.S. Martorana et al. In: Physics Letters B 782, 112 116 (2018)

Extreme shape coexistence, of which shape isomers observed in actinide nuclei at spin zero are peculiar examples, is also at the origin of the phenomenon of superdeformation in rapidly rotating nuclei. Nevertheless, the studies of superdeformation have developed virtually in a completely independent manner from other shape-coexistence investigations, mainly because they were carried out almost always in the high-spin regime, while the others were related to low-spin phenomena [1,2].
In this talk, we will focus on Ni isotopes, where example of shape-isomer-like 0+ excitations have been found in 66Ni and 64Ni [3,4], and we will discuss new results on 62Ni, in which superdeformed rotational bands at high spin, decaying out at around spin 8, are known [5]. Following a neutron capture experiment with the FIPPS spectrometer at ILL, ten 0+ excited states below 6.5 MeV have been observed in 62Ni, with a fragmented gamma decay, in close agreement with predictions from state-of-the-art Monte Carlo Shell Model calculations. This allowed to identify, among them, the band-head of the superdeformed rotational band at high spins, which turns out to be fragmented over highly deformed and triaxial 0+ configurations.
The work allows to make a connection between shape coexistence at spin 0 and superdeformation at high spins, and to trace, microscopically, the origin of the fragmented decay pattern of the superdeformed band [6].

[1] S. Leoni, B. Fornal, A. Bracco, Y. Tsunoda, T. Otsuka, Prog. Part. Nuc. Phys. 139 (2024) 104119.
[2] S. Leoni, B. Fornal, N. Marginean, and J. N. Wilson, Eur. Phys. J. Spec. Top. 233 (2024) 1061.
[3] S. Leoni, et al., Phys. Rev. Lett. 118 (2017) 162502.
[4] N. Marginean, et al., Phys. Rev. Lett. 125 (2020) 102502.
[5] M. Albers et al., Phys. Rev. C 94 (2016) 034301.
[6] C. Costache, et al., in preparation.

In this invited contribution, I will present recent results from $(d,p)$ experiments performed with the Super-Enge Split-Pole Spectrograph at the John D. Fox Accelerator Laboratory of Florida State University [1] to study single-particle strengths in $fp$-shell nuclei [2-4]. After briefly highlighting the capabilities of the experimental setup [1,5], I will focus on three specific examples. First, I will provide a brief overview on our results obtained for the neutron-adding strengths in the $N=29$ isotone $^{53}$Cr [3], comparing to strengths measured earlier for $^{55}$Fe [6]. Then, I will pivot and focus on the rich dataset which we obtained for $^{50}$Ti. I will briefly point out similarities and differences between the fragmentation of neutron-adding strengths for excited states of even-$A$ $^{50}$Ti and odd-$A$ $^{51}$Ti, before I discuss $1^+$ and $1^-$ states of $^{50}$Ti populated in the $(d,p)$ reaction. By comparing to observables obtained from complementary experiments, I will make a case for how $(d,p)$ can be used to study the microscopic origin of the spin-flip $M1$ resonance [4] and of the low-energy $E1$ strength, often referred to as pygmy dipole resonance (PDR) [2,7].

The experimental program at the FSU John D. Fox Laboratory is supported by the U.S. National Science Foundation (PHY-2412808 and PHY-2405485) and by the U.S. National Nuclear Security Administration (DE-NA0004150) as part of CENTAUR. Support from Florida State University is gratefully acknowledged.

References:

1. M. Spieker and S. Almaraz-Calderon, Frontiers in Physics 12, 1511394 (2024).
2. M. Spieker, L. T. Baby, A. L. Conley, B. Kelly, M. Müscher, R. Renom, T. Schüttler, and A. Zilges, Phys. Rev. C
   108, 014311 (2023).
3. M. Spieker, L. A. Riley, M. Heinze, A. L. Conley, B. Kelly, P. D. Cottle, R. Aggarwal, S. Ajayi, L. T. Baby, S. Baker,
   I. Conroy, I. B. D’Amato, J. Esparza, S. Genty, I. Hay, K. W. Kemper, M. I. Khawaja, P. S. Kielb, A. N. Kuchera,
   E. Lopez-Saavedra, A. B. Morelock, J. Piekarewicz, A. Sandrik, V. Sitaraman, E. Temanson, C. Wibisono, and
   I. Wiedenhoever, Phys. Rev. C 112, 064331 (2025).
4. B. Kelly, M. Spieker, U. Friman-Gayer, L. T. Baby, T. Beck, A. L. Conley, S. W. Finch, J. Isaak, Krishichayan,
   E. Litvinova, H. Pai, N. Pietralla, D. Savran, W. Tornow, N. Tsoneva, A. Volya, and V. Werner, Phys. Rev. Lett.
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Collective dynamics in atomic nuclei emerge from the coherent motion of many nucleons and provide important insight into how nuclei respond to external perturbations. Resonant photon scattering, or nuclear resonance fluorescence, provides a clean and selective experimental probe of this response. Since real photons couple directly to nuclear charge and current distributions, they can excite and resolve electric and magnetic dipole modes with minimal distortion from the interaction mechanism. This talk will present recent resonant photon-scattering studies performed with quasi-monochromatic, highly polarized photon beams at the High Intensity Gamma-ray Source (HIγS) at the Triangle Universities Nuclear Laboratory. Emphasis will be placed on the use of high-resolution photon scattering to map dipole-strength distributions, identify fine structure and multipole character through polarization asymmetries and angular distributions, and extract reduced transition probabilities as well as photon-strength functions. These observables provide sensitive tests of the microscopic structure of dipole excitations, including strength fragmentation and the emergence of low-energy collectivity. The results will be confronted with state-of-the-art theoretical calculations and compared with complementary data from hadron-induced reactions. These comparisons highlight the distinct selectivity of photon beams and contribute to the interpretation of collective modes relevant to nuclear structure, reaction theory, and astrophysical applications.

Study of photo-nuclear reactions is crucial for understanding nuclear structure and astrophysical processes. The PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project [1] aims to systematically investigate these reactions in stable nuclei with mass numbers below 60, both experimentally and theoretically. We use virtual photon exchange through proton scattering and high-intensity real-photon beams from laser Compton scattering to excite target nuclei. The subsequent decay particles and gamma-rays are detected to measure the photo-absorption cross-section and the decay branching ratio for each decay channel, covering the giant dipole resonance.
Several nuclear models, including anti-symmetrized molecular dynamics, mean-field type models, large-scale shell model, and ab initio models, will be employed to predict the systematic behavior of photo-nuclear reactions. It is also challenging to describe theoretically the decay process of GDR, a well-ordered collective motion, through direct, pre-equilibrium, and the thermal equilibrium compound nuclei.The primary objective of the PANDORA project is to elucidate the energy loss mechanisms of ultra-high-energy cosmic ray (UHECR) nuclei during intergalactic propagation.
UHECRs, observed on Earth up to energies above 10^20 eV by large cosmic-ray air-shower observatories such as Pierre Auger and Telescope Array, remain a mystery in terms of origin, acceleration mechanisms, and composition. Recent analyses suggest a heavier mass composition for UHECRs at the highest energies. UHECR nuclei are predicted to lose energy primarily by emitting particles following photo-nuclear excitation by cosmic microwave background photons. Thus, understanding photonuclear reaction cross-sections and decay branching ratios is essential for interpreting the energy and mass evolution of UHECRs.
I will introduce the experimental method [2] for studying the electric dipole excitation of nuclei and photo-nuclear reactions by proton scattering at the Research Center for Nuclear Physics, Osaka University, and report on the experiments conducted in 2023 and 2025.

References
[1] A. Tamii et al., PANDORA White Paper, Euro. Phys. J. A. 59, 208 (2024).
[2] P. von Neumann-Cosel and A. Tamii, Euro. Phys. J. A 55, 110, (2019)

The discovery of β-delayed neutron emission followed closely that of nuclear fission[1], and the phenomenon was quickly incorporated, into the Bohr-Wheeler compound-nucleus picture[2]. Since that era, β-delayed particle emission has been discussed largely within a two-step statistical framework (the Pandemonium theory [3]).

Over the past decade, several observations have placed this view under severe strain. Among them, unexpectedly strong γ/neutron competition above the neutron separation energy has been reported [4] [5]. An even more striking case is the β decay of the neutron-rich nucleus 83Ga, where high-energy γ emission (up to∼5–8 MeV) competes with neutron emission from states located well above threshold [6]. This extraordinary, totally unexpected behaviour was questioned , calling for a dedicated re-measurement of the high-energy part of the spectrum.

We therefore performed a dedicated experiment at the ALTO facility using the PARIS γ-ray spectrometer coupled to the BEDO decay station. The improved efficiency at high energy and the enhanced segmentation enable a more reliable characterization of the high-energy γ spectra and a more robust extraction of γ-ray intensities. Beyond the 83Ga case, we also carried out a systematic study across the N=50 region (including the β decays of 80Ga and 82Ga) in order to identify structural conditions under which dynamics beyond the purely statistical compound-nucleus description may emerge. The results will be presented and discussed in connection with a microscopic (though phenomenological) structure-driven interpretation that includes the doorway-state concept in its original sense, as introduced by Feshbach and collaborators.

[1] R. B. Roberts, L. R. Hafstad, R. C. Meyer, and P. Wang, The Delayed Neutron Emission which Accompanies Fission of Uranium and Thorium, Phys. Rev. 55, 664, April 1939.
[2] N. Bohr and J. A. Wheeler , The Mechanism of Nuclear Fission, Phys. Rev., 56:426–450, September 1939.
[3] J. C. Hardy et al., The essential decay of pandemonium, Phys. Lett. B, 71(2):307–310, November 1977.
[4] J. L. Tain et al., Enhanced γ-Ray Emission from Neutron Unbound States Populated in β Decay. Phys. Rev. Lett., 115(6), August 2015.
[5] A. Spyrou et al., Strong Neutron-γ Competition above the Neutron Threshold in the Decay of 70Co, Phys. Rev. Lett. 117, 142701, September, 2016
[6] A. Gottardo et al. , Unexpected high-energy γ emission from decaying exotic nuclei, Phys. Lett. B, 772:359–362 (2017)

Near-threshold narrow resonances in light nuclei are crucial for nuclear structure studies: they are expected to provide information on the onset of clusterization phenomena, and they also play a key role in nucleosynthesis reactions in stars. A famous example is the Hoyle state in $^{12}$C. In this context, the $\gamma$ decay from near-threshold states, with branches of the order of $10^{-3}$–$10^{-6}$ with respect to particle emission, is one of the most powerful probes of their wave function.

In this contribution we will investigate, at first, the possible existence of a narrow resonance in $^{11}$B, lying just above the proton-decay threshold, which was originally suggested to explain the observation of an unexpectedly large proton emission after the $\beta^-$ decay of $^{11}$Be [1]. An explorative experiment performed in 2021 with GALILEO+TRACE at Laboratori Nazionali di Legnaro reported an upper limit of $1.12\cdot10^{-3}$ for the $\gamma$-ray branch from this possible resonance (with limited statistical confidence) [2], slightly above theoretical predictions from the Shell Model Embedded in the Continuum (SMEC) [3,4]. More recently, in October 2025, the same $^6\text{Li}(^6\text{Li},\text{p}\gamma)$ fusion-evaporation reaction was performed using a significantly improved setup consisting in the AGATA spectrometer coupled to the upgraded highly-segmented silicon charged-particle detector TRACE [5] and the silicon CD detector SAURON. Owing to the high statistics collected, a sensitivity of $\leq10^{-4}$ on the $\gamma$-decay branching ratio is expected. The data analysis is currently ongoing, and preliminary results will be presented.

As a second case, we will briefly discuss a similar investigation carried out for $^{14}$C, which was populated through the $^9\text{Be}(^6\text{Li},\text{p}\gamma)$ fusion-evaporation reaction at Argonne National Laboratory with the GRETINA+ORRUBA setup [6]. One of the aims of the experiment was the estimate of the $\gamma$-decay branch from the $2_2^+$ state located just above the neutron separation energy. An upper limit of $4.0 \cdot 10^{-5}$ was obtained for this branch, providing an additional constraint to the theoretical interpretation of its decay properties.

[1] Y. Ayyad, B. Olaizola, W. Mittig et al., Phys. Rev. Lett. 123, 082501 (2019).
[2] S. Bottoni, G. Corbari, S. Leoni et al., Phys. Lett. B 855, 138851 (2024).
[3] J. Okołowicz, M. Płoszajczak and W. Nazarewicz, Phys. Rev. Lett. 124, 042502 (2020).
[4] J. Okołowicz, M. Płoszajczak and W. Nazarewicz, J. Phys. G.: Nucl. Part. Phys. 49, 10LT01 (2022).
[5] S. Capra, D. Mengoni, J.A. Dueñas et al., Nucl. Instr. Meth. A 935, 178-184 (2019).
[6] G. Corbari, M. Ciemała, S. Bottoni et al., submitted to Phys. Lett. B.

The identification of vibrational dynamics in the low-lying excitation spectra of deformed nuclei continues to be an open challenge in nuclear structure physics. In algebraic, phenomenological, or geometric models, the lowest vibrational shape affecting oscillations that can be built on a deformed ground state include the quadrupole ($\lambda = 2$) and the octupole ($\lambda = 3$) modes. Quadrupole oscillations are typically described in terms of $\beta$ and $\gamma$ one-phonon vibrational modes (lowest lying K$^{\pi}=0^+$ and K$^{\pi}=2^+$ bands), and excited bands (K$^{\pi}=0^+,2^+,4^+$ bands) as $\beta\beta$, $\beta\gamma$, and $\gamma\gamma$ two-phonon excitations, that is (2$^+ \otimes 2^+$) quadrupole phonons. The quadrupole mode of oscillations along the symmetry axis result in $\beta$ vibrations with K$^{\pi}=0^+$ and those breaking axial symmetry, result in $\gamma$ vibrations with a projection of K$^{\pi}=2^+$ on the symmetry axis. The discussions on the nature of numerous low-lying bands observed in the spectra of deformed nuclei continue. Are they indeed vibrations built on the ground state? Or are they coexisting minima of other shapes? The discussions have led to a reexamination of the nature of vibrational excitations. Vibrational excitations built on the ground state of a deformed nucleus are expected to show the same degree of deformation, the same dynamic and kinetic moments of inertia with some dispersion, and where there is enough information the same intrinsic quadrupole moment for transitions from the same band connecting to the ground state band.

There are a number of two-phonon vibrational excitations identified in deformed nuclei, two-phonon $\beta\beta$ vibrational type in $^{178}$Hf, and a potential $\beta\gamma$ type in $^{162}$Dy, and several cases of potential $\gamma\gamma$, K$^{\pi}=4^+$ bands in the rare-earth region of well-deformed nuclei. The ratios of the two-phonon to one phonon vibrational excitations energies are theoretically expected to be at twice the single phonon values. The B(E2) ratios of the two-phonon $\gamma\gamma$ to single-phonon to ground state values are expected to be 2.78 for K$^{\pi}=4^+$ and 5.0 for K$^{\pi}=0^+$. Results from current measurements and interpretations will be presented and discussed.

Isospin symmetry arises from the charge independence of nucleon–nucleon interactions, but it is broken by the Coulomb interaction. Although a small effect, its precise determination is essential for understanding isobaric analogue states and their role in β decay.
In self-conjugate N = Z nuclei, electromagnetic selection rules forbid electric dipole (E1) γ decay. Therefore, the observation of E1 strength provides a sensitive probe of isospin mixing. The giant dipole resonance (GDR), an E1 mode, is widely used to quantify this effect [1-3].
Following early measurements in $^{28}$Si and $^{32}$S [4-6], which indicated an increase of isospin mixing with mass number A, our Milano group carried out a systematic study in N = Z nuclei in the range A = 60–80 [1-3]. In particular, $^{80}$Zr and $^{60}$Zn were investigated at LNL-INFN using GARFIELD, AGATA and GALILEO arrays coupled to BaF$_2$ or LaBr$_3$:Ce detectors, allowing the extraction of isospin mixing and its temperature dependence.
As the most recent case within this program, we studied $^{72}$Kr at a nuclear temperature of ~1.3 MeV via GDR γ decay. Measurements were performed at the Bucharest Tandem Laboratory using the ELIGANT array [7] for the reactions $^{32}$S + $^{40}$Ca (I = 0) and $^{31}$P + $^{40}$Ca (reference, I ≠ 0).
Statistical-model analysis yields an isospin mixing parameter of (3.5 ± 0.8)%, confirming the predicted temperature dependence. By combining all results, we present a systematic study of isospin mixing as a function of mass and temperature. Finally, the extracted isospin-symmetry-breaking correction δ$_C$, relevant for superallowed Fermi β transitions, is consistent with β-decay data, theoretical predictions, and previous measurements [8].

References
[1] A. Corsi et al., “Measurement of isospin mixing at a finite temperature in $^{80}$Zr via giant dipole resonance decay,” Physical Rewiev C, vol. 84, p. 041304(R), 2011
[2] S. Ceruti et al., “Isospin mixing in $^{80}$Zr: From finite to zero temperature,” Physical Rewiev Letters, vol. 115, p. 222502, 2015.
[3] G. Gosta et al., “Probing isospin mixing with the giant dipole resonance in the $^{60}$Zn compound nucleus,” Physical Rewiev C, vol. 103, p. L041302, 2021.
[4] M. Harakeh, et al., “Role of isospin in the statistical decay of the giant dipole resonance built on excited states” Phys. Lett. B 176 (1986) 297
[5] J. Behr, et al., “Restoration of isospin symmetry in highly excited compound nuclei” Phys. Rev. Lett. 70 (1993) 3201.
[6] M. Kicińska-Habior, et al., “Giant dipole radiation and isospin purity in highly excited $^{32}$S nuclei”, Nucl. Phys. A 731 (2004) 138.
[7] P.-A. Söderström et al., “Eligant-Gn-ELI gamma above neutron threshold: The gamma-neutron setup,” Nuclear Inst. and Methods in Physics Research, A, vol. 1027, p. 16617, 2022.
[8] A. Giaz et al., “Probing the Isospin Mixing in the $^{72}$Kr Compound Nucleus via GDR γ Decay” Physics Letters B, 868 (2025) 139653.

The commissioning of a proton cyclotron for hadron therapy at the Cyclotron Centre Bronowice (CCB) of the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow has enabled the use of proton beams for nuclear physics experiments. Among others, an experimental campaign was carried out aiming at study the γ decay from excited atomic states, such as giant and pygmy resonances.
The employed experimental method was based on coincidence measurement of scattered protons registered by the KRATTA [1] array and gamma rays emitted from the decay of excited nuclei measured using LaBr$_3$ detectors together with PARIS [3] phoswiches.

One of the main goals of the experiments was to study a very rare phenomenon – the decay of GQR (giant quadrupole resonance) via γ-ray emission to the ground state. Previously such phenomenon was observed only once, in 1980s [3]. In recent experiment we have confirmed the existence of the GQR gamma-decay and measured the branching ratio between GQR gamma decay to ground state and neutron emission for $^{208}$Pb [4]. Similar measurements were also performed for $^{120}$Sn.

During the talk the experimental method, the used equipment as well as the obtained results will be presented. In addition, the outlook for the continuation of such studies will be discussed.

References
[1] J. Łukasik et al., Nucl. Instrum. Methods Phys. Res., Sect. A709, 120 (2013);
[2] A. Maj et al., Acta Phys. Pol. B 40, 565 (2009);
[3] J.R. Beene, et al., Phys. Rev. C 39, 1307 (1989);
[4] B. Wasilewska et al., Phys. Rev. C 105, 014310 (2022).

The 4n system 8He, comprising several features of a 2n and 4n sub-system is interesting by its internal correlations leading to the possibility to study several aspects of clustering in light nuclei. 8He, in particular it’s coulomb breakup, studied in a recent experiment, will be presented and discussed. The relation to previously obtained information will be drawn and future prospects arising at the FAIR facility will be presented.

We study the coupling between nuclear shape and rotation in even-even nuclei using a microscopic five-dimensional collective Hamiltonian based on relativistic density functional theory.

First, we identify wobbling motion—a precession of the total angular momentum about the medium axis—in triaxial nuclei such as ruthenium, palladium, and osmium. Using spin coherent state maps, we show that wobbling can also appear in γ-soft xenon isotopes, dynamically induced by the largest moment of inertia despite the absence of rigid triaxiality.

Second, we quantify shape-rotation entanglement via the von Neumann entropy. By comparing six representative nuclei, we reveal distinct entropy behaviors linked to triaxiality, γ-softness, and γ-rigidity. Along the hafnium isotopic chain, the entropy follows a three-stage evolution: it drops when prolate deformation stabilizes, stays flat under axial symmetry, and rises again when γ-softness and shape coexistence reappear. This entropy trend is linked to an experimentally measurable B(E2) ratio, making entanglement entropy a novel signature of nuclear shape evolution.

Overall, our work connects a specific collective wobbling mode to a general measure of quantum entanglement, offering new insights into shape-rotation coupling across the nuclear chart.

Many-body Green's function theory stands out among microscopic theories for its capability to encapsulate infromation on ground state properties, response and single particle spectroscopy within the same framework. Different aspects of the many-body correlations and dynamics of a given nucleus can then be investigated simultaneously with the same microscopic approach.

The first part of the talk will focus on ongoing work to extend self-consistent Green's function (SCGF) theory to describe pairing effects in the presence of collective excitations--the so called Gorkov-ADC(3) framework [1]--with recent applications to nuclear matter [2]. I will then cover exploitation of diagrammatic Monte Carlo methods [3] for devising first principle optical potentials [4].

The second part of the talk will cover recent results regarding the structure near the Ar and Ca isotopic chains. In particlar, I will further discuss the analysis of a recent GANIL experiment that provided evidence for a charge bubble in 46Ar and linked this to an atypical shell closure at Z=18 and N=28 [5].

[1] C. Barbieri, T. Duguet and V. Somà, Phys. rev. C 105, 044330 (2022).
[2] F. Marino, C. Barbieri, and G. Colò, arXiv:2601.03763 and Phys. Rev. C (2026) in print.
[3] S. Brolli, C. Barbieri and E. Vigezzi, Phys. Rev. Lett. 134, 182502 (2025).
[4] S. Brolli and C. Barbieri, arXiv:2605.30527 (2026).
[5] A. Idini, C. Barbieri and P. Navrátil, Phys. Rev. Lett. 123, 092501 (2019).
[6] D. Brugnara et al., arXiv:2506.23228.

A major goal of nuclear theory is to explain the structure and properties of atomic nuclei in an ab initio approach starting from nuclear forces fixed in free-space scattering. Apart from the two nucleon forces, the three-body forces are also important in describing systems from light nuclei to nuclear matter. However, an accurate and simultaneous ab initio prediction for both light nuclei and nuclear matter has been a long- standing challenge in nuclear physics, due to the significant uncertainties associated with the three-nucleon forces.

In a series of recent works, we have developed a deep-learning-based ab initio framework, FeynmanNet, which achieves high variational accuracy with polynomial scaling in the nucleon number. In particular, it demonstrates that both light nuclei and nuclear matter can be well described simultaneously in the relativistic ab initio calculations, even in the absence of three-nucleon forces, and a correlation between the properties of light nuclei and the nuclear saturation is revealed.

References:
[1] Y. L. Yang and P. W. Zhao, Phys. Lett. B 835, 137587 (2022).
[2] Y. L. Yang and P. W. Zhao, Phys. Rev. C 107, 034320 (2023).
[3] Y. L. Yang and P. W. Zhao, Phys. Rev. Lett. 134, 242502 (2025).
[4] Y. L. Yang and P. W. Zhao, Chin. Phys. Lett. 42, 051201 (2025).
[5] Y. L. Yang, E. Epelbaum, J. Meng, L. Meng, and P. W. Zhao, Phys. Rev. Lett. 135, 172502 (2025)

The optical potential is a well-established and widely used tool to describe nucleon-nucleus scattering processes. Within this approach, it is possible to compute the scattering observables for elastic processes across a wide region of the nuclear landscape and extend its usage to inelastic scattering and other types of reactions.

Since phenomenological approaches lack predictive power, we strongly believe that a microscopic approach will be the preferred tool to make reliable predictions, in particular for upcoming experiments concerning exotic nuclei.

The Watson multiple scattering theory provides a successful framework to derive such an optical potential for intermediate energies.
In its simplest formulation, derived at the first order, the optical potential is obtained as the folding integral of the nucleon-nucleon scattering matrix and the target density, representing the two fundamental ingredients of the model. After many years of advances in theoretical nuclear physics, it is now possible to calculate these two quantities using the same nucleon-nucleon interaction that is the
only input of our calculations.
Results obtained within this framework will be presented for light- and medium-mass nuclei, adopting different ab initio approaches to calculate the densities, such as the No-Core Shell Model and Self-Consistent Green’s Function [1-7]. Novel extensions of the model, such as the calculation of nucleus-nucleus collisions [8] or inelastic transitions [9] will also be presented.

References

[1] M. Vorabbi, P. Finelli, C. Giusti, Phys. Rev. C93, 034619 (2016)
[2] M. Vorabbi, P. Finelli, C. Giusti, Phys. Rev. C96, 044001 (2017)
[3] M. Vorabbi, P. Finelli, C. Giusti, Phys. Rev. C98, 064602 (2018)
[4] M. Vorabbi, M. Gennari, P. Finelli, C. Giusti, P. Navratil, Phys. Rev. Lett. 124, 162501 (2020)
[5] M. Vorabbi, M. Gennari, P. Finelli, C. Giusti, P. Navratil, Phys. Rev. C103 024604 (2021)
[6] M. Vorabbi, M. Gennari, P. Finelli, C. Giusti, P. Navratil, Phys. Rev. C105 014621 (2022)
[7] M. Vorabbi ,C. Barbieri ,V. Somà ,P. Finelli , and C. Giusti, Phys.Rev. C109 (2024) 3, 034613
[8] M. Vorabbi, M. Gennari, P. Finelli, C. Giusti, P. Navratil, Phys. Rev. Lett. 135,172501 (2025)
[9] M. Vorabbi, M. Gennari, P. Finelli, C. Giusti, P. Navratil, submitted to Phys.Rev. C (2026)

Atomic nuclei are ideal probes to test fundamental symmetries. For instance, nuclei are used as targets to detect dark matter particles, and electric dipole moments of nuclei can help to unveil why there is more matter than antimatter in the universe.

Nuclear $\beta\beta$ decays also play a paramount role. If no neutrinos happen to be emitted in the decay, this would immediately imply that the neutrino and the antineutrino are the same particle, as proposed by Ettore Majorana in the early days of quantum field theory. Nonetheless, the rate of the Majorana $\beta\beta$ decays depend on nuclear matrix elements that need to be predicted by nuclear theory, as these decays have not been observed yet experimentally.

In this talk, I will present recent advancements on the calculation of the rates of Majorana $\beta\beta$ decays, with emphasis on the impact of the nuclear structure of the initial and final states of the transition. To conclude, I will also propose how nuclear structure experiments can help to constrain the values of the Majorana $\beta\beta$ decay rates.

The nuclear shell structure serves as the backbone for exploring the complex nuclear structure that emerges from nucleon-nucleon interactions. In recent years, it has become the forefront for both experimental and theoretical research in nuclear physics. Recent studies indicate that the shell structure is altered by the extreme proton-to-neutron number ratio in neutron-rich exotic nuclei, a phenomenon known as {\it shell evolution}. Shell evolution plays a vital role in understanding nuclear shell structures across the nuclear chart. In this context, we have investigated the shell structures using the state-of-the-art ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) approach. Over the past two decades, chiral effective field theory has become a powerful framework for deriving nuclear forces from first principles. We employ modern two- and three-nucleon interactions derived from chiral effective field theory, using spin-tensor decomposition to examine the impact of individual interaction components. I will discuss the development of shell structures by analyzing the roles of two-nucleon (2N) and three-nucleon (3N) tensor forces.

Recent experiments have shown that fission fragments carry intrinsic angular momentum with essentially no correlation between fragments, motivating new theoretical studies. Different microscopic models will be discussed to understand the generation of fragment spin in fission. These approaches, based on time-dependent density functional theory and a time-dependent collective Hamiltonian, investigate the origin of angular momentum during and after scission. By comparing projection techniques with simple estimates from the uncertainty principle, fragment spin is shown to emerge from the quantum uncertainty between orientation angle and angular momentum, together with the effects of fragment deformation.

Nuclear energy density functional (EDF) theory provides a unified framework for describing both static and dynamical properties of nuclei and extended nuclear matter. In particular, its time-dependent extension enables microscopic studies of non-equilibrium phenomena in strongly paired systems, such as those expected in the inner crust of neutron stars, where nuclei coexist with a superfluid neutron background. In this talk, I will present recent developments in time-dependent EDF approaches for nuclear superfluids, with emphasis on large-scale simulations of real-time dynamics [1]. I will discuss the motion of a quantized vortex interacting with a nuclear impurity embedded in superfluid neutron matter, highlighting the microscopic origin of vortex–nucleus forces. I will also introduce a dynamical scheme for extracting effective mass parameters of neutron-rich nuclei immersed in a superfluid medium, providing insight into collective inertial properties beyond static approaches [2]. These results establish a consistent microscopic picture of dynamical processes in neutron star crusts and provide new insights into the rotational dynamics of neutron stars, including mechanisms relevant to pulsar glitches.

[1] D. Pȩcak, A. Zdanowicz, N. Chamel, P. Magierski, G. Wlazłowski, Time-dependent nuclear energy-density functional theory toolkit for neutron star crust: Dynamics of a nucleus in a neutron superfluid, Phys. Rev. X 14, 041054 (2024)
[2] A. Zdanowicz, D. Pęcak, P. Magierski, G. Wlazłowski, Dynamical scheme for computing the mass parameter of a system in a medium, Phys. Rev. C 112, 045804 (2025)

The synthesis of superheavy elements is a major foundational scientific problem of joint interest to both the fields of physics and chemistry. Experimentally, fusion-evaporation reactions are commonly employed for the synthesis of superheavy nuclei, but thus far have only resulted in neutron-deficient superheavy nuclei.
The pursuit of the "island of stability" for superheavy nuclei thus requires novel reaction mechanisms. Multinucleon transfer (MNT) reactions provide a promising pathway for synthesizing neutron-rich heavy and superheavy nuclei, and have attracted extensive attention both experimentally and theoretically, becoming a major topic in nuclear physics. However, due to the complex mass and angle distributions of MNT reaction products, significant challenges exist in their collection and separation [1]. Therefore, the investigation of MNT reactions requires a close integration of experiment and theory.

Covariant density functional theory (CDFT), based on effective field theory and density functional concepts, has achieved great success in the microscopic, self-consistent, and unified description of nuclear structure properties. Its time-dependent extension, known as time-dependent covariant density functional theory (TD-CDFT), is a powerful microscopic tool for the study of nuclear reactions and decays, and has been successfully applied to fusion, fission, and quasifission phenomena. For the study of MNT reactions, since the product wave functions are not eigenstates of the particle number or angular momentum operators, the application of TD-CDFT to MNT requires the combination of particle number projection and angular momentum projection techniques.

In this work, the TD-CDFT approach incorporating particle number and angular momentum projection has been developed to investigate the mass and spin distributions of products in MNT reactions. By calculating the cross-sections for several reaction systems and comparing the results with experimental data, the reliability of the theoretical model in reproducing experimental observations is verified [2]. Furthermore, ternary quasifission in actinide collisions is explored, predicting a possible pathway for the synthesis of neutron-rich heavy nuclei [3]. Finally, the spin distribution and its correlations among the reaction products are analyzed, revealing that, as nucleon transfer increases, the spins of the products become larger and the distributions broader. This effect arises from the conversion of orbital angular momentum into intrinsic spin due to friction between the projectile and target nuclei. Entanglement Shanon entropy analysis of the product spins indicates weak correlations among fragments [4].

[1] Xiaohong Zhou, Zhiyuan Zhang, Zaiguo Gan, et al., Research program of superheavy elements and nuclides based on HIAF (in Chinese). Sci Sin-Phys Mech Astron 50, 112002 (2020).
[2] Dan Dan Zhang, Dario Vretenar, Tamara Nik\v si\' c, Peng Wei Zhao, and Jie Meng, Multinucleon transfer with time-dependent covariant density functional theory, Phys. Rev. C 109, 024614 (2024).
[3] Dan Dan Zhang, Bo Li, Dario Vretenar, Tamara Nik\v si\' c, Zheng Xue Ren, Peng Wei Zhao, and Jie Meng, Ternary quasifission in collisions of actinide nuclei, Phys. Rev. C 109, 024316 (2024).
[4] Dan Dan Zhang, Dario Vretenar, Tamara Nik\v si\' c, Peng Wei Zhao, and Jie Meng, Intrinsic spin distributions in multinucleon transfer reactions, Phys. Lett. B 869, 139828 (2025).

Most current neutron star EoS inferences are intentionally agnostic: they reconstruct the cold beta-equilibrated pressure-density relation without committing to a microscopic composition. This is appropriate for masses, radii, and tidal deformabilities. Still, it leaves out quantities that depend on the off-equilibrium energy functional, such as composition, frozen sound speeds, direct-Urca thresholds, buoyancy, and transport inputs. Therefore, we developed a framework that, under the nucleonic hypothesis, remains agnostic about the effective microphysics by using a flexible metamodel for the energy density as a function of density and asymmetry: The aim is not to replace fully agnostic inference, but to provide a composition-aware null model that can be validated against alternative parametrisations in the same way as barotropic frameworks are compared today. This new framework may be useful both for Bayesian inference of composition-sensitive observables and as a compact alternative to tabulated EoSs in simulations, with finite-temperature extensions under development.
Based on: "An Asymptotically Causal Metamodel for Neutron Star Equations of State", Montefusco et al. (2026), https://arxiv.org/abs/2604.00196

Time-dependent density functional theory (TDDFT) provides a fundamental framework for describing nuclear collective time-dependent processes, ranging from small-amplitude collective oscillations to large-amplitude phenomena such as fission and heavy-ion reactions. However, due to its mean-field nature, TDDFT accounts only for one-body dissipation effects and fails to describe the spreading widths of one-body observables.

To address this limitation, we develop the configuration-interaction time-dependent density functional theory (CI-TDDFT). This method expands the nuclear wave function in terms of a set of correlated time-dependent Slater determinants and rigorously follows the Dirac–Frenkel time-dependent variational principle. As a first application, we present an illustrative study of the excitation energies and widths of giant monopole resonances in 58Ni and 60Ni. Compared to TDDFT, CI-TDDFT provides a more accurate description of the widths of giant monopole resonances.

Atomic nuclei are complex many-body systems with a number of constituents ranging from very few to several hundred [1-2]. Among the difficult aspects, nuclei are self-bound systems that require treating a continuum of wave functions in Hilbert space. The nuclear strong interaction is poorly understood and highly non-perturbative, with the onset of multi-body interactions beyond the usual two-body interactions. Nuclear physics also faces the exponential growth of the Hilbert space as the number of constituents increases. For these reasons, the exact treatment of these systems on classical computers, starting from the interaction, is still restricted to a few percent of the nuclear chart.
Quantum technologies and associated quantum algorithms appear in this context as disruptive technologies that might surpass the current limitations in the coming years [3]. We have initiated a long-term project to explore the use of quantum computers in nuclear physics and related many-body problems. Inspired by strategies used in classical computing, several novel approaches have been proposed to obtain the ground or low-lying states in many-body systems. A significant effort has been made to use the symmetry-breaking/symmetry-restoration method [2,4,5]. Based on the use of projectors through phase estimation, quantum oracles, or classical shadow, the Quantum Variation After Variation was formulated. Several methods were proposed to access excited states, including the Quantum Krylov, Quantum equation of motion, or Quantum Generator Coordinate Method [6,7,8]. These methods will be highlighted, along with their applications to the nuclear physics many-body problem. Recent results on methods to describe ground and excited states for the proton-neutron pairing will be discussed [9,10], and Green’s function will be presented [11].

References:

[1] Quantum computing with and for many-body physics, Ayral, P. Besserve,
D. Lacroix and E. A. Ruiz Guzman, Eur. J. Phys. A. 59, 227 (2023), arXiv:2303.04850 [Review]

[2] Symmetry breaking/symmetry preserving circuits and symmetry restoration on quantum computers: A quantum many-body perspective, D. lacroix, E. A. Ruiz Guzman and P. Siwach, Eur. Phys. J. A 59, 3 (2023). arXiv:2208.11567 [Review]

[3] Quantum Computing for High-Energy Physics: State of the Art and Challenges. Summary of the QC4HEP Working Group, A. Di Meglio et al, PRX Quantum 5, 037001 (2024) , arxiv:2307.03236. [White paper]

[4] Restoring symmetries in quantum computing using Classical Shadows, Edgar Andres Ruiz Guzman, Denis Lacroix, Eur. J. Phys. A 60, 112 (2024). arXiv:2311.04571

[5] Restoring broken symmetries using quantum search oracles, E. A. Ruiz Guzman and D. Lacroix, Phys. Rev. C 107, 034310 (2023), arXiv:2210.11181

[6] Entanglement in selected Binary Tree States: Dicke/Total spin states, particle number projected BCS states, D. Lacroix, Phys. Rev. C 110, 034310 (2024), arxiv:2405.04665

[7] Neutron-proton pairing correlations described on quantum computers, Jing Zhang, Denis Lacroix and Yann Beaujeault-Taudière, submitted to Phys. Rev. C, arXiv:2408.17294

[8] Solving the Lipkin model using quantum computers with two qubits only with a hybrid quantum-classical technique based on the Generator Coordinate Method, Yann Beaujeault-Taudière and Denis Lacroix, Phys. Rev. C 109, 024327 (2024), arXiv:2312.04703

[9] Neutron-proton pairing correlations described on quantum computers, Jing Zhang, Denis Lacroix and Yann Beaujeault-Taudière, submitted to Phys. Rev. C, arXiv:2408.17294

[10] Excited states from ADAPT-VQE convergence path in many-body broblems: application to nuclear pairing problem and H_4 molecule dissociation, Jing Zhang, and Denis Lacroix, Phys. Lett. B869, 139841 (2025), arXiv:2506.22275

[11] Quantum simulations of Green's functions for small superfluid systems, Samuel Aychet-Claisse, Denis Lacroix, Vittorio Somà, Jing Zhang, Phys. Rev. C 113, 044324 (2026), arXiv:2509.02272

Quantum computing offers a fundamentally new paradigm for simulating the real-time dynamics of quantum many-body systems, overcoming the exponential scaling limitations of classical approaches. By encoding quantum states directly into qubits and leveraging entanglement as a computational resource, quantum algorithms can efficiently capture the complex correlations that govern nuclear reactions. This capability opens the door to accurate, first-principles simulations of reaction mechanisms, including strongly interacting and highly non-equilibrium regimes that remain intractable today. As quantum hardware and algorithms mature, they have the potential to transform our understanding of nuclear dynamics, enabling predictive modeling with unprecedented fidelity.
Realizing this potential requires a sequence of algorithmic components, including efficient preparation of the initial nuclear wavefunction [1,2], controlled time evolution under the relevant Hamiltonian, and the extraction of physical observables through carefully designed measurement protocols. Each of these stages presents distinct challenges, from encoding correlated initial states to mitigating errors during long-time evolution and reconstructing scattering information from quantum measurements. To accurately describe continuum dynamics and reaction products, it is advantageous to employ first-quantized representations, which scale favorably with system size and provide a natural framework for asymptotic state represenation, while requiring explicit enforcement of fermionic antisymmetry [3,4].
In this talk, I present a unified framework for quantum simulation of nuclear reactions, spanning both state preparation and observable extraction. I discuss projection-based techniques for preparing nuclear states with well-defined quantum numbers and correlations, viewing state preparation itself as a form of time evolution [1,2]. Building on these methods, I introduce an approach in which scattering clusters are initialized as wave packets and evolved to asymptotic separation within a finite computational volume [5]. By computing appropriate overlap functions, scattering matrix elements at fixed energy can be obtained via Fourier transform. This strategy requires only unitary time evolution beyond state preparation, making it well suited for implementation on quantum hardware.
I will show how this framework enables the ab initio calculation of differential and total cross sections for two-cluster reactions, including inelastic processes where clusters transition between internal eigenstates [5]. Numerical examples illustrating these capabilities will be presented.
Acknowledgment: LA-UR-26-22966. This work was carried out under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. 89233218CNA000001.

References:
[1] I. Stetcu, A. Baroni, and J. Carlson, Phys. Rev. C 105 (2022) 064308
[2] E. Rule, I. Stetcu, and J. Carlson, Phys. Rev. C 110 (2024) 064003
[3] E. Rule et al., Quantum 10 (2026) 2056
[4] I. Stetcu, arXiv:2512.16138
[5] E. Rule and I. Stetcu, arXiv:2603.26881

An accurate description of many-body dynamics in nuclear physics is a major challenge for classical simulation techniques. Hamiltonian simulation on digital quantum computers offer the possibility of reducing the computational cost when tackling these problems. In this talk, I will discuss recent advances in the simulation of both nuclear and neutrino systems using quantum computers and show some results obtained with current generation devices.

Nuclear many-body calculations on classical computers typically involve Monte Carlo simulations. These suffer from the fermionic sign problem where the signal-to-noise ratio diminishes as the system size grows. Moreover, these simulations are performed in Euclidean which complicates calculations of real-time dynamics from such simulations. Quantum computation avoids these issues by unitary evolution in real-time. In this talk, I present several algorithms to calculate elastic and inelastic reaction matrix elements on quantum computers. Results for two-particle phase shifts, E1 transition matrix elements and mass gap calculations are presented.

Quantum computers have the potential to efficiently tackle problems that grow exponentially in complexity on classical computers. In the context of simulating physical systems, they may help reduce the problems related to the rapid expansion of Hilbert space with increasing particle number and handle highly entangled states more effectively.

In this contribution, we explore prospects for using quantum computers for nuclear structure problems. We present some applications of a low-depth variational quantum algorithm [1] to solve problems in nuclear structure, including the preparation of ground and excited states within the nuclear shell model approach. Here, we implement a new qubit-mapping strategy for the Variational Quantum Eigensolver (VQE) in nuclear shell-model calculations, in which each Slater determinant (SD) is encoded into a single qubit state, rather than mapping qubits to individual single-particle states.

References:
[1] C. Sarma, and P. D. Stevenson, Discov. Quantum Sci. 2, 6 (2026).

At the VITO beamline at ISOLDE, we use optical pumping to polarise nuclear spins of beams of different short-lived nuclei [1]. We then use the resulting anisotropic emission of beta radiation in a variety of fields, from nuclear structure, via material science, all the way to biology.
Recently, we have used $^{47,49,51}$K for a proof-of-principle experiment in decay spectroscopy of spin-polarized beams, in which we studied angular correlations between asymmetrically emitted beta particles and gamma-radiation or neutrons [2]. The aim is to use the measured beta-decay asymmetry factors to determine spins and parities of excited states in neutron-rich nuclei, especially beta-delayed neutron emitters relevant for the r process nucleosynthesis.
Furthermore, we use the spin-polarised beams for ultra-sensitive nuclear magnetic resonance detected via beta-decay asymmetry ($\beta$-NMR). By using liquid samples we have narrowed the linewidth of $\beta$-NMR resonances by two orders of magnitude, allowing to achieve ppm levels in the accuracy of magnetic moments of short-lived isotopes [3]. We have now combined this approach with nuclear DFT and atomic calculations to determine the so-called hyperfine anomaly in $^{47}$K [4], paving the way for studies of the composition and distribution of nuclear magnetisation in different short-lived nuclei [5].
This contribution will present the VITO experimental setups, followed by the results of the above-mentioned proof-of-principle studies, concluding with a layout of an rf-laser spectroscopy end station for precise hyperfine-anomaly studies.

1. M. Kowalska et al., J. Phys. G: Nucl. Part. Phys. 44 (2021) 084005
2. M. Piersa-Silkowska et al., CERN-INTC-2023-026/ INTC-P-662 (2023), and https://ep-news.web.cern.ch/content/isoldes-new-beta-decay-station-unlocks-advanced-decay-spectroscopy-experiments-laser (2025)
3. R. Harding et al., Phys. Rev. X 10 (2020) 041061, J. Croese et al, NIMB 1020 (2021), 165862, M. Jankowski et al JINST 21 (2026) P01003
4. M.L. Bissell et al, submitted, https://arxiv.org/abs/2603.20090
5. M.L. Bissell et al, CERN-INTC-2023-014 / INTC-P-655 (2023)

Charge-changing reactions (CCRs) at intermediate energies are an experimentally simple yet valuable tool for exploring the complex reaction mechanisms and exotic structures of rare isotopes.
Based on years of experimental studies at RIBLL2/HIRFL and FRS/GSI, our collaboration has investigated CCRs of more than 60 p-sd shell nuclei on various targets at approximately 300 and 900 MeV/nucleon.
Benefiting from this extensive and systematic dataset, we have demonstrated the indispensable role of charge-particle evaporation after neutron removals in CCR. We found an empirical yet robust method to infer the charge radii of isotopes of p-shell nuclei and suggest a heavy isotope target as the optimal choice. I will present some selected new results from our CCR studies and the perspective on using the Heavy-ion Accelerator Facility (HIAF).

Refs:
[1] J.C. Zhang et al., Physical Review X 15(2025)031004
[2] X.D. Xu et al., Science Bulletin 70(2025)1026.
[3] J. W. Zhao et al., Physics Letters B 858 (2024) 139082.
[4] J.C. Zhang et al., Science Bulletin 69 (2024) 1647.
[5] G.S. Li et al., Physics Letters B 859 (2024) 139143
[6] J.W. Zhao et al., Physics Letters B 847 (2023) 138269.
[7] C.J. Wang et al., Chinese Physics C 47 (2023) 084001.

The Gamma-Ray Energy Tracking Array (GRETA) is 4pi detector designed to study a broad science program in nuclear structure over a wide range of beam energies and velocities from Coulomb barrier to 100’s MeV/A. It combines highly segmented HPGe crystals with advanced digital electronics and signal processing to identify individual gamma-ray interaction points within the crystals to simultaneously achieve high energy resolution, high efficiency, and good background rejection (peak-to-total).

The GRETA Project started in 2017, following nearly a decade of successful science with the predecessor GRETINA array and completed construction and initial commissioning of all technical systems (mechanical, electronics and computing) with a subset of Quad Detector modules at LBNL in the summer of 2025. It is currently being installed at the Facility for Rare Isotope Beams (FRIB), with first science measurements expected early 2027. I will review the GRETA project, both science and technical as well performance, and the progression toward anticipated first science at FRIB.

The AGATA γ-ray tracking array represents the state of the art in in-beam gamma-ray spectroscopy, exploiting the high segmentation of High Purity Germanium detectors to achieve position sensitivity and gamma-ray tracking via pulse-shape analysis [1,2]. Installed in April 2022 at the Tandem–ALPI–PIAVE accelerator complex of INFN Laboratori Nazionali di Legnaro, AGATA has operated with beam energies spanning 7–8 MeV/u for the heaviest ions up to 20–25 MeV/u for the lightest.
Routinely coupled to the PRISMA heavy-ion magnetic spectrometer, and complemented by silicon detector arrays for light charged particles, AGATA has addressed a broad physics programme: shell evolution, quadrupole and octupole collectivity, astrophysically motivated measurements, and systematic Coulomb-excitation studies.
This presentation will provide an overview of the performance of AGATA and show selected recent achievements such as the double double octupole phonon in 96Zr and lifetime measurements in the heavy Os-Pt region near N=126.

References
[1] A. Akkoyun et al., Nucl. Instrum. Methods A 668, 26 (2012).
[2] J. J. Valiente-Dobón et al., Nucl. Instrum. Methods A 1049, 168040 (2023).

Among challenging problems in physics is the understanding of emergent collective excitation modes in interacting quantum many-body systems in terms of the microscopic degrees of freedom. The study of evolution of properties of nuclei, as function of excitation energy, angular momentum and isospin, open avenues to search for simple patterns to identify and better understand hidden aspects of the nucleus.

Among various phenomenon, nuclei can also vibrate in surprisingly ordered ways. Vibrations that have played a central role in revealing nature’s fundamental laws, can be explored starting from things as simple as a pendulum to more complex gravitational waves. In nuclei phonons represent quantized collective excitations. Multiphoton states occur when two or more phonon are excited. The study of multi-phonon excitations opens a window into the collective dynamics of many-body systems, whether they be atoms in a solid or nucleons in a nucleus. The investigations and the evolution of the structure moving away from stability and the study of difficult to study odd-odd nuclei, where orderly collective motion is usually hidden by chaotic individual particle behaviour, could help to better understand the driving force of valence neutrons and protons and the dynamical behaviour of surface vibrations.

In this talk will discuss the structural evolution of the neutron-rich Nb isotopes as a function of spin and isospin. The neutron-rich Nb isotopes studied here were produced as fission fragments in reactions with a $^{238}$U beam at 6.2 MeV/u on a $^{9}$Be target at GANIL. The spectrometer (VAMOS++) coupled to a γ-ray tracking array AGATA along with the EXOGAM array, were used to identify the excited states of the fission fragments. These measurements were combined with independently obtained high-fold γ-ray coincidence measurements employing a $^{252}$Cf source at Gammasphere array (when at LBL, USA). These powerful complementary techniques allowed the characterization of the Nb isotopic chain all the way till $^{109}$Nb. The present measurements allowed to investigate the evolution of these isotopes very far from the valley of stability and demonstrate the first evidence illustrating the robustness of vibration excitations in the presence of an odd valence proton and neutron including possible coexisting shapes beyond the N=60 transitional region.

Gamma-ray spectroscopy is a powerful tool to measure electromagnetic observables offering a glimpse into the structure of neutron-rich nuclei. The advent of $\gamma$-ray tracking arrays like AGATA has indeed opened new possibilities in this field, in particular when AGATA is coupled to setups providing a high sensitivity for weak reaction channel selection.
Since 2022, the second AGATA physics campaign at LNL is ongoing. The study of neutron-rich nuclei with fusion-fission and multi-nucleon transfer reactions has been one of the main subjects tackled. The AGATA-PRISMA setup measured $\gamma$ rays emitted by the reaction products identified in mass and atomic number in PRISMA on an event-by-event basis.
In the talk, we will present results from several experiments already performed, exploiting fusion-fission reactions with a $^{208}$Pb beam and multi-nucleon transfer reactions with a variety of beams. Neutron-rich nuclei were explored around the N=20-28, N=40, N=50 and N=126 (sub)shell closures, measuring both level energies and lifetimes, helping to understand shell structure evolution in these key regions of the Segrè chart.

The region around the doubly magic nucleus 100Sn provides a unique testing ground for nuclear structure models at the proton drip line and near the (N=Z) line. Recent experiments performed at the Radioactive Isotope Beam Factory (RIBF), Japan, using the DALI2+ gamma-ray spectrometer have enabled new spectroscopic studies in this key region.

In this contribution, I will report on the first in-beam gamma-ray spectroscopy of 100Sn. Excited states were populated via proton-induced neutron-knockout reactions from neutron-deficient 101,102Sn isotopes, providing the first direct information on the excitation spectrum of this doubly magic nucleus. The results offer new insights into the robustness of the (Z=N=50) shell closures and the nature of proton and neutron excitations across the shell gaps.

In addition, recent Coulomb-excitation measurements of 98Pd, 100Cd, and 102Sn along N=52 will be presented. The extracted transition strengths, together with large-scale shell-model calculations, provide stringent constraints on the effective proton and neutron charges in the vicinity of 100Sn. The results indicate enhanced neutron polarization effects and contribute to a consistent description of quadrupole collectivity in this region.

The experimental findings will be discussed in the broader context of shell evolution, effective charges, and the doubly magic character of 100Sn.

Coulomb excitation of the even–even isotopes $^{130}$Sn and $^{134}$Sn was performed at the HIE-ISOLDE facility using post-accelerated radioactive ion beams at 4.4 MeV/u impinging on various targets. De-exciting γ rays were detected with the high-efficiency Miniball spectrometer in coincidence with scattered particles. The extracted B(E2) transition strengths resolve the long-standing discrepancy between experimental and theoretical estimates of quadrupole collectivity in $^{130}$Sn and $^{134}$Sn. The newly determined spectroscopic quadrupole moments are consistent with zero, emphasizing the near-spherical character of nuclei surrounding the $^{132}$Sn core. These findings establish stringent benchmarks for large-scale shell-model calculations employing realistic interactions and elucidate the evolution of quadrupole collectivity in the neutron-rich Z=50 region. The results confirm an enhanced B(E2) strength in $^{132}$Sn relative to its neighboring isotopes, providing firm experimental evidence for a local maximum of collectivity at the doubly magic nucleus.

Supported by the German BMBF 05P21PKFN9 and 05P21RDCI2 and European Union’s Horizon Europe Framework research and innovation programme under grant agreement no. 101057511

Recent experimental innovations have driven major progress in nuclear fission research, a phenomenon fundamentally governed by the interplay of collective dynamics and quantum mechanical effects. Breakthroughs in inverse kinematics experiments alongside the development of complete detection setups now enable event-by-event reconstruction of the fission process with unprecedented precision. These advances provided access to new observables, including complete isotopic fission fragments distributions as a function of excitation energy, fission probabilities and manifold correlations between the properties of fission fragments and the neutrons and $\gamma$-rays they emit. Moreover, these techniques enable the study of unstable or short-lived fissioning systems, significantly expanding the range of nuclei which can be probed, and offering a path toward a comprehensive, potentially universal, description of the fission process across the nuclear chart. At the same time, recent results obtained with conventional approaches based on direct kinematics are providing increasingly accurate complementary information. Intense effort is invested to take advantage of the new findings for better constraining the theories which are being developed in parallel.

This presentation will review the main experimental advances achieved in recent years, including state of the art detection systems and modern analysis techniques. A selection of results that have reshaped our understanding of nuclear fission, or that continue to challenge long standing knowledge, will be presented. Current challenges and future opportunities for the field will also be discussed.

Nuclear fission remains one of the most complex scientific problems of our times. Complete information on fission products and the related fission spectrum plays a key role in applied nuclear technology and in basic science. Yet, accurate and precise measurements are often very complex and expensive, technically difficult to perform, or even impossible if the target nuclei are too short-lived, making accurate fission modeling especially important. Since the beginning of nuclear science, physics models of fission have been heavily data-driven in order to provide enough flexibility to match experimental measurements. At the same time, fundamental fission theory based on a fully quantum-mechanical description of the fission process has made spectacular progress in the past decade. Some of the knowledge gained is beginning to be translated into concrete guidelines or inputs for evaluations. In this presentation, I will discuss the state of the art of fundamental fission theory by reviewing the main accomplishments of the past decade and discussing some of the open questions in the field.

Nuclear fission is a complex quantum many-body process governed by the interplay between macroscopic liquid-drop properties and microscopic shell effects, which together determine the final fragment configuration. While early macroscopic approaches predicted predominantly symmetric mass splits for many systems, it is now well established that the quantum shell structure of the nascent fragments plays a decisive role in shaping the fission outcome. In particular, deformed shell gaps can favor asymmetric mass divisions, giving rise to the characteristic heavy-light fragment pattern observed across a broad range of fissioning nuclei. Recent high-precision measurements have identified a new region of asymmetric fission driven by shell effects in the light fragments, demonstrating that fragment-structure effects remain dominant even in previously unexplored areas of the nuclear chart.

To investigate this newly identified island of asymmetric fission, a dedicated experiment was performed at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany, employing inverse kinematics at relativistic energies with the state-of-the-art R$^3$B/SOFIA setup. We report measurements of fission-fragment charge distributions for 100 exotic fissioning systems, establishing a direct link between the neutron-deficient sub-lead region and the well-known actinide region. These data provide a comprehensive mapping of the asymmetric-fission island and deliver clear experimental evidence for the decisive role of the deformed proton shell at $Z=36$ in sub-lead fission.

In addition, we systematically investigated global odd-even staggering in the fission-fragment charge distributions as a function of the fissioning system. Our analysis demonstrates that shell structure in the fissioning nucleus itself contributes significantly to the observed staggering.

The interplay between macroscopic liquid-drop properties and microscopic effects represents a fundamental challenge in nuclear fission [1]. This competition can be probed through excitation-energy distributions, as experimental evidence shows a systematic attenuation of structure-dependent effects, thereby progressively revealing the underlying macroscopic component of the potential-energy surface. In this context, fission-fragment isotopic yields provide a sensitive observable for quantifying this evolution [2,3]. In the actinide region, fission at low energy is characteristically dominated by asymmetric mass splits driven by shell effects; however, increasing excitation energy reduces these structure-induced asymmetries and enhances the relative contribution of symmetric fission modes [4].

This specific approach is part of a systematic research campaign at GANIL designed to exploit transfer- and fusion-induced fission reactions in inverse kinematics [5-7]. A $^{238}$U beam at 5.88 AMeV impinged on four different targets ($^{27}$Al, $^{24}$Mg, $^{nat}$B and $^{9}$Be), populating a variety of actinides at low-to-moderate excitation energies. The use of inverse kinematics allows for the full isotopic identification (A, Z) and kinematic reconstruction of one of the fission fragments using the VAMOS++ spectrometer [8] in combination with the AGATA gamma-ray array [9]. Additionally, the use of SPIDER silicon telescope to detect the target-like recoil produced in the transfer reaction, enables an event-by-event characterisation of the fissioning system [6].

In this framework, the present study focuses on the evolution of fission-fragment isotopic yield distributions for selected actinides as a function of excitation energy. Furthermore, the impact of the incoming channel in the fission dynamics is investigated by comparing the fission-fragment production from different reactions leading to the same fissioning system.

References

[1] V. Strutinsky, Nuclear Physics A 95, 420–442 (1967).
[2] K.-H. Schmidt et al., Reports on Progress in Physics 81, 106301 (2018).
[3] A. N. Andreyev et al., Reports on Progress in Physics 81, 016301 (2017).
[4] K. Nishio et al., Phys. Rev. C 111, 044609 (2025).
[5] M. Caamaño et al., Phys. Rev. C 88, 024605 (2013).
[6] C. Rodríguez-Tajes et al., Phys. Rev. C 89, 024614 (2014).
[7] D. Ramos et al., Phys. Rev. C 97, 054612 (2018).
[8] M. Rejmund et al., Nuclear Instruments and Methods in Physics Research Section A 646, 184–191 (2011).
[9] E. Clément et al., Nuclear Instruments and Methods in Physics Research Section A 855, 1–12 (2017).

This study [1] explores the role of nucleon exchange for the generation of the fission fragment angular momenta. For a number of typical fission cases, samples of 10,000 shape evolutions are generated by Langevin simulation [2] and, subsequently, for each such evolution, the nucleon exchange transport theory previously developed for damped nuclear reactions [3] is used to obtain the development of the fragment spin-spin distribution within the Fokker-Planck transport framework. The characteristic evolution of both parallel and perpendicular spin components is discussed. A common feature is that the rotational modes fall out of equilibrium before scission when the temperature rises rapidly while the concurrent shrinking of the neck suppresses further exchange. A number of fission observables are extracted from the event ensembles: the distribution of the magnitude of the fragment spin and its orientation relative to the fission axis, as well as the correlation between the two spins and the distribution of their opening angle. The dependence of these observables on the mass asymmetry is also examined.

[1] J. Randrup, P. Nadtochy, C. Schmitt, K. Mazurek, Correlated fission fragment spin dynamics, Phys. Rev. C, 113 (2026) 044605
[2] G.D. Adeev, A.V. Karpov, P.N. Nadtochii, and D.V.Vanin, Multidimensional Stochastic Approach to the Fission Dynamics of Excited Nuclei, Phys. Part. Nucl. 36, 378 (2005)
[3] J. Randrup, Theory of transfer-induced transport in nuclear collisions, Nucl. Phys. A 327, 490 (1979).

Nuclear fission has shaped both our understanding of the atomic nucleus and many of the technologies that define the modern world. Nearly ninety years after its discovery, it continues to challenge fundamental theory while underpinning applications from national security and nonproliferation to energy production to astrophysics and nuclear medicine.

In this talk, I will focus on research areas where basic science questions and application-driven needs genuinely intersect. I will use concrete examples—fission cross sections, fragment angular distributions, fission product yields, prompt and beta-delayed emissions—to show how microscopic physics propagates through the nuclear data pipeline into the evaluated libraries used by most technologies. Along the way, I will “open the hood” on how these evaluations are produced and maintained in practice.

Finally, in an era of AI-driven workflows and large-scale optimization, I will revisit what we really mean by uncertainties and information content in both fundamental and applied fission research. Whether you are after sharper arguments for your favorite fission project, deeper insight into how the data behind your engineering tools are built, or new ways your measurements and calculations can have an impact, this presentation aims to give you something you can carry back into your work.

Despite the notorious advances in different theoretical models [1] and the development of new experimental setups that increase the access to the fission observables [2], there are still several phenomena in the fission process that are not reproduced with enough accuracy and whose origin is unclear. One of these occurrences is the so-called "Thorium Anomaly", which refers to the observed fission probabilities [3] and fission yields [4] around Thorium, that deviate from the behaviour of heavier actinides [5]. The scarce dataset and limited number of observables prevent so far to fully comprehend this sudden variation. The correlation between several parameters would allow to shed light on the current understanding.

Following the advantages of inverse-kinematics, a new experiment was conducted with the newly accelerated 232Th beam at Coulomb energies. Fusion, inelastic scattering and transfer reactions produced with a 12C target permitted to populate fissioning systems such as 232Th, 233Pa or 234U. The utilized experimental setup consisted on the VAMOS++ spectrometer [6], which was in charge of obtaining the isotopic identification of complete fission fragment distributions and their velocity vector. Moreover, the magnetic spectrometer was combined with a highly stripped silicon detector (PISTA), that allows the event-by-event identification of the fissioning system and the reconstruction of its excitation energy with high resolution [7] by measuring the target-like partner. The combination of both devices permits to systematically study the correlation between the fission observables for several nuclei, within the same configuration.

In this work, the elemental and isotopic fission fragment yields of 232Th will be presented. Having a simultaneous measurement of these yields with the excitation energy of the corresponding fissioning system, the evolution of these observables can also be investigated. The comparison between Thorium yields and heavier actinides gives more experimental insight into the understanding of the "Thorium anomaly".

References
[1] Schunck, N and Robledo, LM , Reports on Progress in Physics 79 (2016) 116301.
[2] Schmidt, K. H., Benlliure, J., & Junghans, A. R. (2001). Fission of nuclei far from stability. Nuclear Physics A, 693(1-2), 169-189.
[3] Back, B. B., Britt, H. C., Garrett, J. D., & Hansen, O. (1972). Subbarrier fission resonances in Th isotopes. Physical Review Letters, 28(26), 1707
[4] Berriman, A. C., Hinde, D. J., Jeung, D. Y., Dasgupta, M., Haba, H., Tanaka, T., ... & Williams, E. (2022). Energy dependence of p+ Th 232 fission mass distributions: Mass-asymmetric standard I and standard II modes, and multichance fission. Physical Review C, 105(6), 064614
[5] Schmidt, K. H., et al. (2024). Identifying and overcoming deficiencies of nuclear data on the fission of light actinides by use of the GEF code. Annals of Nuclear Energy, 208, 110784.
[6] M.Rejmund et al., Nuclear Instruments and Methods in Physics Research A 646 (2011) 184-191.
[7] Bégué - Guillou, L., Lemasson, A., Morfouace, P., Ramos, D., Taieb, J., Frankland, J. D., ... & Tonchev, A. P. (2026). Performance of the Particle-Identification Silicon-Telescope Array coupled with the VAMOS++ magnetic spectrometer. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1090, 171671.

As demonstrated by the extensive experimental and theoretical work conducted over the past decades, nuclear fission is a highly complex process. This complexity arises primarily from the interplay of diverse aspects of both reaction dynamics and nuclear structure, which together determine the observables measurable in the laboratory. Recent studies have shown that coincidences among multiple observables are crucial to unravel the intricacies of fission and ensure an unambiguous interpretation of the data. In this context, an innovative experimental setup was developed at GANIL, coupling for the first time the VAMOS++ heavy-ion spectrometer with the new-generation PARIS scintillator array. While VAMOS++ accurately identifies the mass and charge of the fission fragments, PARIS detects with unprecedented quality the coincident gamma rays over their full dynamical range, alongside information on coincident neutrons. This contribution presents the first experiment using PARIS@VAMOS, dedicated to fission induced by fusion and nucleon transfer in 238U + 9Be collisions around the barrier. A selection of results illustrates the performance of the setup in terms of efficiency, resolution, and sensitivity, highlighting the variety of topics that can be addressed. In particular, the so-called fission gamma bump and its highly probable connection to the Pygmy Dipole Resonance are demonstrated through calculations employing microscopic nuclear level densities and gamma strength functions [1]. This connection has a dual impact: it establishes the gamma bump as a relevant signature of post-scission dynamics, and it proposes fission as a new probe of soft dipole modes, complementary to conventional approaches.

References

[1] N. Kumar, Ch. Schmitt, M. Ciemała, et al., "First experimental isotopic mapping of the fission “γ-bump” and its connection to the Pygmy dipole resonance", Phys. Lett. B 878 (2026) 140506

Among the various processes of cosmic nucleosynthesis, the rapid neutron-capture process (r-process) plays a decisive role in the production of elements heavier than iron. A characteristic feature of the r-process abundance distribution is the so-called “rare-earth peak” around mass number A~160. The origin of this peak has been theoretically attributed to possible changes in nuclear shell structure and the presence of deformed shell gaps near N~100 [1-4]. Furthermore, while β-delayed neutron emission in the neutron-rich rare earth region is thought to play a key role in the formation of the A≈160 peak, experimental data in this mass region are scarce, and the detailed nature of the shell structure remains unclear.
We therefore have systematically investigated decay modes and structures in the neutron-rich rare-earth region using β-γ and isomer spectroscopy of A=150~160 Nd, Ce, Ba nuclei. The experiment was performed using RIBF facility in RIKEN Nishina Center. These neutron-rich nuclei were produced using in-flight fission of a 345 MeV/u $^{238}$U beam. Fission fragments were separated and transported by the BigRIPS and ZeroDegree spectrometer. Nuclei of interest were identified by measuring the time-of-flight and magnetic rigidity in the second stage of BigRIPS and by measuring the energy loss using the ion chamber at the final focal plane, F11. The secondary beam was implanted into an active stopper, WAS3Abi to perform β-γ spectroscopy using EURICA Ge cluster detector array. We obtained the results indicating β-delayed neutron emission in $^{158}$Nd for the first time.
In the presentation, the latest result of beta-gamma spectroscopy of $^{157,158}$Nd will be reported and its relevance to the rare-earth peak will be discussed.
This work is partially supported by JSPS KAKENHI Grant Number 26H01418.
[1] M.R. Mumpower, G.C. McLaughlin, R. Surman: Phys. Rev. C85, L021303 (2012).
[2] R. Surman, J. Engel, J. Bennett, and B. Meyer: Phys. Rev. Lett. 79, 1809 (1997).
[3] S. Shibagaki, T. Kajino, G. J. Mathews, S. Chiba, S. Nishimura, and G. Lorusso: Astrophys. J. 816, 1 (2015).
[4] S. Goriely, et al.: Phys. Rev. Lett. 111, 242502 (2013).

In the process of $\beta$-delayed fission ($\beta$DF), an excited state populated in the daughter nucleus after $\beta$ decay undergoes fission. The achievable excitation energy is limited by $Q_\beta$ value, which is typically $\lesssim$ 10 MeV. Therefore, $\beta$DF allows us to access so called low-energy fission, which is sensitive to nuclear structure, and to study its properties, such as fission fragment mass distributions, fission barriers, etc. [1,2]. Moreover, $\beta$DF plays an important role in the nucleosynthesis as it contributes to the termination and fission recycling in the $r$ process [3].

More than a decade ago, our collaboration started a unique experimental campaign dedicated to $\beta$DF studies at ISOLDE (CERN), in which several isotopes in the neutron-deficient lead region were measured [1,4-6]. In this contribution, our follow-up $\beta$DF experiments, which aimed at extending the studies to $^{178}$Au and to neutron-rich isotopes $^{230,232,234}$Ac, will be reported.

Isotope $^{178}$Au has two $\beta$-decaying states, which we studied individually by employing selective power of RILIS to obtain isomerically pure beams. Such measurement gives an additional possibility to explore spin dependence of fission, because of the strong spin selectivity of $\beta$ decay. No $\beta$DF events were observed for isotopes of interest despite collection of high statistics. Therefore, upper limits of $\beta$DF probabilities were determined. The limit for $^{230}$Ac was almost two orders of magnitude lower than the literature value [7], thus, questioning the observation of $\beta$DF for this isotope. The results will be discussed in the context of experimental systematics of $\beta$DF probabilities and partial half-lives.

[1] A. N. Andreyev, M. Huyse and P. Van Duppen, Rev. Mod. Phys. 85, 1541 (2013).
[2] A. N. Andreyev, K. Nishio, and K.-H. Schmidt, Rep. Prog. Phys. 81, 016301 (2018).
[3] S. Goriely et al., Phys. Rev. Lett. 111, 242502 (2013).
[4] L. Ghys et al., Phys. Rev. C 90, 041301(R) (2014).
[5] V. L. Truesdale et al., Phys. Rev. C 94, 034308 (2016).
[6] B. Andel et al., Phys. Rev. C 102, 014319 (2020).
[7] Y. Shuanggui et al., Eur. Phys. J A 10, 1 (2001).

One of the most important fission quantities is the fission barrier as it defines the fission cross sections. The most direct (and often the only) way to obtain fission barriers is to measure the fission probability as a function of the excitation energy of nuclei formed by transfer and inelastic scattering reactions. The measurement of the fission probability together with the probabilities for the de-excitation channels that compete with fission (e.g. gamma or multiple neutron emission) sets strong constraints on the description of the de-excitation process and can lead to a significant reduction of the uncertainty of the fission barrier parameters. However, the measurement of gamma or neutron-emission probabilities in standard experiments is very difficult due to the very low detection efficiencies for gamma rays and low-energy neutrons, and the intense background of gamma rays and neutrons emitted by the fission fragments. Moreover, so far, the decay probabilities have only been measured for nuclei close to the valley of stability due to the difficulty to produce and handle radioactive targets.
We are developing a project that studies for the first time fission in inverse kinematics at a heavy-ion storage ring. This allows one to measure with unrivalled precision the fission probability and the probabilities for all the de-excitation modes competing with fission of nuclei located far from stability.
In this talk, I will present our new methodology and the results of the first two experiments that we have successfully performed at the ESR storage ring of the GSI/FAIR facility in Darmstadt, Germany. In these experiments, we have achieved a significant breakthrough by measuring for the first time the fission, gamma-ray, neutron and even two- and three-neutron emission probabilities simultaneously. The measurement of all these probabilities enables the precise determination of fission barriers and other fundamental quantities, including particle transmission coefficients, gamma-ray strength functions, and nuclear level densities. All these quantities will be employed to infer (n,f), (n,gamma), (n,n'), (n,2n), and (n,3n) cross sections.

Angular momentum generation in nuclear fission remains one of the most intriguing and least understood aspects of the fission process. Although fission has been studied for more than eight decades, major questions persist regarding how angular momentum is generated at scission, how it is shared between the fragments and the orbital angular momentum, and how it correlates with excitation energy, deformation, and neutron emission. These questions are of central importance for our fundamental understanding of collective motion in nuclei and nuclear de-excitation processes.
In this talk, old and recent experimental and theoretical developments in the study of fission fragment angular momentum will be reviewed. Particular emphasis will be placed on modern approaches for extracting angular momentum from experimental observables. Special focus will be given to isomeric yield ratio measurements performed at the IGISOL facility using Penning trap techniques. Furthermore, theoretical descriptions of angular momentum generation and evolution in fission models such as GEF and FREYA will be discussed. Results obtained with different analysis frameworks, including the Manchester Spin Method and the TALYS-based Uppsala Spin Method, will also be presented and compared.
The talk will further address current challenges, including the role of fragment deformation and moments of inertia, the treatment of spin cut-off parameters, excitation energy sharing at scission, and the correlation between excitation energy and angular momentum. Finally, perspectives for future progress will be outlined, including the need for new high-precision measurements, improved theoretical descriptions of scission dynamics, and better constraints on angular momentum generation mechanisms in the different types of particle-induced fission.

Studies in heavy-ion induced fusion-fission process has established itself as one of the major branches of low and medium energy nuclear structure and reaction physics. A plethora of dynamical processes manifest through the fusion-fission of two atomic nuclei over a wide range of projectile energy. The process of fission followed by fusion of two heavy nuclei or survival of the Compound Nucleus (CN) against fission and formation of Evaporation Residues (ER) are deeply connected with various factors like, nuclear shell structure, target-projectile mass asymmetry, projectile energy, angular momentum distribution in the CN etc. Other than studying the dynamical effect associated with fusion and subsequent fission (or survival against fission) of heavy CN, there is also the long-standing desire to understand formation of very heavy or Super Heavy Elements (SHE). In this talk we plan to review the present status of heavy-ion induced fusion-fission processes at energies above the Coulomb Barrier. We would like to touch upon aspects of fission followed by complete and incomplete fusion and processes like fast and quasi-fission. We will be primarily drawing from our measurements carried out at Inter University Accelerator Centre, New Delhi using the Hybrid Recoil mass Analyser (HYRA) coupled with the TIFR 4π Sum-Spin spectrometer. We will summarise what we have learnt so far and what are the unresolved problems. Detailed analyses using both Statistical and Dynamical Model formalisms will be presented. We will also discuss the very important role of dissipative mechanism or nuclear viscosity in the survival of the CN against fission.
It is worth noting that the Giant Dipole Resonance (GDR) is another fascinating mode of nuclear collective motion. In this talk, we will make an effort to discuss the underlying fundamental aspects of correlated nuclear motion at finite temperature and angular momentum through two different but most prominent collective motions, fission and GDR. We will address the common link of viscosity and how far the collectivity exists, an evergreen question in GDR, but can also be invoked in fission physics.

As a source of neutrons within the nuclear chain reaction, prompt fission neutrons are of decisive importance for nuclear physics applications. Their average neutron multiplicity impacts the amount of neutrons available for further fissions, while their energy distribution impacts the probability for neutrons to escape the core of a nuclear reactor and do structural damages to the vessel. New high precision measurements of prompt fission neutron spectra (PFNS) and average prompt neutron multiplicity have been done at the WNR facility of the Los Alamos Neutron Science Center. The PFNS of the major actinides $^{239}$Pu, $^{235}$U and $^{238}$U were measured as a function of the incoming neutron energy by double time of flight for incoming neutron energies above 1 MeV with two different methods. While results of two methods will be shown, we will detail one type of measurement, performed with respect to the well known PFNS and average neutron multiplicity of $^{252}$Cf spontaneous fission.
The setup consisted of a high efficiency and fast-timing fission chamber coupled to the liquid scintillators array Chi-Nu or VENDETA (VErsatile Neutron DETector Array). Prompt fission neutron energies between 150 keV and 12 MeV can be measured, for incident neutron energies from 0.7 to 800 MeV. Average neutron multiplicities and mean neutron energies were extracted from the PFNS measurement as a function of the incoming neutron energy. Up to 25 MeV of incoming neutron energies, relative uncertainties are below 0.5% on the average neutron multiplicity and below 0.8% on the mean energy. The energy range measured and the level of precision achieved allow us to observe the opening of alternative fission channels, such as second chance fission. Beyond the need for evaluated nuclear data libraries and nuclear applications, this level of precision also provide constrains on fission models such as GEF and CGMF, and on partial fission cross sections. The experimental method will be detailed and the results will be compared to existing data, evaluations and fission models for discussion.

Nuclear fission results in two excited fragments which de-excite very quickly via the emission of prompt neutrons and gamma rays. These emissions can be detected and contain a wealth of information about the fission process itself, especially from the correlations between the emitted particles. The particular difficulty in studying fission is that this emission occurs from two moving sources at almost the same point in space and at the same time. There are many experimental approaches available to help understand the fission process [1][2][3], and of particular relevance is the role of angular momentum. In this presentation the focus will be on the technique of high-resolution gamma ray coincidence spectroscopy both within a particular fragment and between fragment partners. The information that can be extracted will be reviewed, along with the limitations of the approach, and future promising avenues of research will be outlined.

[1] S. Cannarozzo, et al., Phys. Rev. C 111, L031601 (2025)
[2] M. Travar et al. Phys. Lett. B 817 136293 (2021)
[3] J.N. Wilson et al., Nature 590 566 (2021)

Multi-humped fission barriers, as they occur in the actinide region, give rise to fission isomerism. Such barrier shapes can be described within various theoretical models. Experimentally measured observables of nuclear fission isomers—such as the half-life, excitation energy of the fission isomer, kinetic energy of the fission fragments, and the isomer-to-ground-state population ratio—allow for testing theoretical predictions and verifying the role of shell effects in nuclear structure.
Studies of the fission isomer properties of 240,242Am were performed at the IGISOL facility at the JYFL Accelerator Laboratory, University of Jyväskylä, Finland. Fission isomeric states were populated via deuteron-induced fusion–evaporation reactions on a

242

Pu target. The decays of the fission isomers were detected using silicon detectors calibrated with a 252Cf fission source.
The measurements provided detailed information on kinetic energy spectra, total kinetic energies, and mass distributions for 240,242Am. A new method was proposed to derive post-neutron-emission mass distributions, as well as proton- and neutron-number multiplicity distributions of the fission fragments, from their kinetic energy distributions. In addition, the emission probabilities of prompt neutrons in the fission process were extracted. Using data for the 252Cf fission isomer as a reference, the validity of the method was verified.

The obtained results for 240,242Am and 252Cf are consistent with GEF model predictions and previous measurements. These findings contribute to a better understanding of shell effects and fission barrier structures in the actinide region.

For six decades, Jerzy Dudek has made seminal contributions to the study of the rich variety of shapes and symmetries in atomic nuclei at the extremes of angular momentum, excitation energy, deformation, isospin and mass. Throughout this incredibly exciting period, the interplay between experiment and theory has been an exhilarating demonstration of the power of the scientific method, with fascinating, and often unexpected, aspects of atomic nuclei being revealed by increasingly sensitive detector systems, coupled with bold predictions from new highly sophisticated theoretical calculations. Jerzy, and his collaborators, have been deeply involved, and usually at the vanguard, at every twist and turn on this long and winding road. This presentation will reflect on a selection of these topics and his significant contributions, along with a brief glimpse towards some of the extraordinary physics opportunities of the future.

At high temperatures, quantum shell effects in atomic nuclei diminish. Nuclear stability is then described by classical surface tension and Coulomb repulsion. As angular momentum increases, Coriolis and centrifugal forces drive shape transitions. Historically, similar phenomena were predicted for rotating stellar objects. These include the Jacobi instability (oblate to triaxial ellipsoid transition) and the Poincare instability (triaxial to pear-shape transition). Liquid drop models predict these transitions in hot, rotating nuclei. Specifically, the Lublin-Strasbourg Drop (LSD) model facilitated the experimental discovery of the Jacobi transition and the prediction of the Poincare transition.
This talk presents key highlights of the collaboration between Jerzy Dudek and experimental groups on these nuclear shape transitions.

Atomic nuclei are strongly-interacting quantum many-body systems and are characterized by a set of good quantum numbers such as angular momentum and parity. Such quantum numbers imply that the nuclear Hamiltonian conserves fundamental symmetries such as invariance by rotation, translation, reflection, etc. Yet, many of the regular patterns observed in the excitation spectrum of nuclei are most conveniently explained if one assumes that nuclei are deformed and do not obey these fundamental symmetries. This spontaneous symmetry breaking is a cornerstone of nuclear theory. While the axial quadrupole shape is the form of nuclear deformation that explains most of the experimental data, higher-order symmetries of the nuclear shape cannot be dismissed. In this talk, I will review why exotic tetrahedral and octahedral shapes could occur in nuclei and what the experimental fingerprints of these modes could be.

The research project presented in this contribution combines the well established achievements elaborated already during the preceding century and the more recent ones mainly related to the exotic nuclear shape symmetries. It focuses on the realistic applications of the phenomenological nuclear mean field theory in low energy nuclear structure phenomena. This involved in particular the physics of nuclear shapes, including shape evolution and competition, symmetries and spontaneous symmetry breaking, nuclear rotation including high spin physics as well as rotational band properties involving band crossings, back-bending, angular momentum alignment, staggering phenomena including exotic identical band manifestations as one of the powerful structure identification tools. The term universal refers to the fact that Hamiltonian in question operates with 8 parameters optimized for all nuclei of the Nuclear Mass Table and employed without modifications.

Nuclear super-deformation at high spins played a distinct role in the discussed research. Prediction of the whole super-deformed island in Rare Earth nuclei preceded by one year its first experimental identification in $^{152}$Dy by Twin and collaborators. From perspective, combining theory and experimental efforts allowed discovering powerful symmetries known today as pseudo-spin and pseudo-SU(3) symmetries. The latter contributed to prediction of even stronger deformation effects: nuclear hyper-deformation.

The mentioned theory efforts were regularly transmitted to the US community thanks to regular Gordon (GRS) conference invitations, cf., in 1987, 1991, 1993, followed in the years 2000. As one of the consequences, the discussed theory impact was brought into one of the most important experimental nuclear physics projects of those times: multi-detector system GAMMASPHERE. Already at the proposal writing level the search of super-, and hyper-deformations was strongly emphasized$^1$.

Another branch of investments profiting from advances in the nuclear mean-field was focused on the very special molecular symmetries in nuclei, tetrahedral and octahedral ones -- also referred to as high-rank symmetries. In terms of the mean-field physics both of these symmetries manifest 4-dimensional irreducible representations; as a consequence certain nucleon levels are 4-fold degenerate (in contrast to 2-fold Kramers degeneracy).

Numerous encouraging consequences of these symmetries as well as the world first identifications will be presented as the second part.

$^1)$ The AI reports dated 2026 -- about the vivid discussions of those times and reactions from the GRS community -- mention explicitly terms such as Dudek plots and `famous Dudek'ism about tetrahedral nuclei'. With permission of organizers this AI words will be explained in September...