# The 2009 Europhysics Conference on High Energy Physics

Jul 16 – 22, 2009
Kraków, Poland
Europe/Warsaw timezone

## Exclusive leptonic and radiative B meson decays at Belle

Jul 17, 2009, 9:15 AM
15m
Large (Kraków, Poland)

### Large

#### Kraków, Poland

The Auditorium Maximum of the Jagiellonian University 33 Krupnicza Street 31-123 Kraków
Flavour Physics

### Speaker

Shohei Nishida (KEK)

### Description

Measurement of the Differential Branching Fraction and Forward-Backward Asymmetry for $B \to K^{(*)} \ell^+ \ell^-$ We study $B \to K^{(*)} \ell^+ \ell^-$ decays based on a data sample of 657 million $B\bar{B}$ pairs collected with the Belle detector at the KEKB $e^+ e^-$ collider. We report the differential branching fraction, isospin asymmetry, $K^{*}$ polarization, and the forward-backward asymmetry ($A_{FB}$) as functions of $q^2=M_{\ell\ell}^{2} c^2$. The fitted $A_{FB}$ spectrum tends to be higher than the Standard Model expectation in all $q^2$ bins. The measured branching fractions are $\mathcal{B}$($B \to K^* \ell^+ \ell^-$) = $(10.7^{+1.1}_{-1.0}\pm0.9) \times 10^{-7}$ and $\mathcal{B}$($B \to K \ell^+ \ell^-$) = $(4.8^{+0.5}_{-0.4}\pm0.3) \times 10^{-7}$, with the muon to electron ratios $R_{K^*}$ = 0.83 $\pm 0.17 \pm 0.05$ and $R_{K}$ = 1.03 $\pm 0.19 \pm 0.06$, respectively. Search for purely leptonic decays $B^+ \to l^+ \nu$ The purely leptonic decay $B^+ \to l^+ \nu$ ($l = e, \mu$) is highly suppressed in the Standard Model due to lepton helicity mismatch but can be strongly enhanced in New Physics scenarios. We present a search for the decays $B^+ \to e^+ \nu$ and $B^+ \to \mu^+ \nu$ using a large data sample recorded by the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. Evidence for $B \to K \eta' \gamma$ We report the results of a search for the radiative decay $B \to K \eta' \gamma$and find evidence for $B^+ \to K^+ \eta' \gamma$. The results are obtained from a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. Measurements of time-dependent $CP$ violation and branching fractions in radiative $B \to \phi K \gamma$ and $B \to \omega K \gamma$ decays We report measurements of time-dependent $CP$-violation parameters in radiative $B^0 \to \phi K_S^0 \gamma$ and $B^0 \to \omega K_S^0 \gamma$ decays using a large data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^+e^-$ collider. These measurements are sensitive to right-handed currents from new physics. We also report updated measurements of branching fractions in $B \to \phi K^{+}(K_S^0) \gamma$ decays and new measurements of $B \to \omega K^{+}(K_S^0) \gamma$ decays.

 Slides