Speaker
Min-Zu Wang
(NTU)
Description
Study of $B^+ \to p \bar{\Lambda} \pi^+ \pi^-$ at Belle
We study charmless $B^+$ decays to $p \bar{\Lambda} \pi^+ \pi^-$ final state using a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. There are significant signals found with $p \bar{\Lambda}$ mass peaking near threshold. The branching fraction as well as the differential branching fraction as a function of the mass of the $p \bar{\Lambda}$ system are presented. We also search for intermediate three-body decays using the same final state particles. Observation or evidence of possible intermediate three-body decays are reported.
Observation of $B^0 \to \Lambda\bar{\Lambda}K^0$ and $B^0 \to \Lambda\bar{\Lambda}K^{*0}$ at Belle
We study the charmless decays $B \to \Lambda\bar{\Lambda} h$, where $h$ stands for $\pi^+$, $K^+$, $K^0$, $K^{*+}$, or $K^{*0}$, using a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. We observe $B^0 \to \Lambda\bar{\Lambda}K^0$ and $B^0 \to \Lambda\bar{\Lambda}K^{*0}$ with branching fractions of $(4.76^{+0.84}_{-0.68} (stat.) \pm 0.61 (syst.)) \times 10^{-6}$ and $(2.46^{+0.87}_{-0.72} \pm 0.34) \times 10^{-6}$, respectively. The significances of these signals in the threshold-mass enhanced mass region, $M_{\Lambda\bar{\Lambda}} < $ 2.85 GeV/$c^2$, are $12.4\sigma$ and $9.3\sigma$, respectively. We also update the branching fraction $\mathcal{B} (B^+ \to \Lambda\bar{\Lambda}K^+) = (3.38^{+0.41}_{-0.36}\pm 0.41 )\times 10^{-6}$ with better accuracy, and report the following measurement or 90\% confidence level upper limit in the threshold-mass-enhanced region: $\mathcal{B} (B^+ \to \Lambda\bar{\Lambda}K^{* +}) = (2.19^{+1.13}_{-0.88} \pm 0.33) \times 10^{-6}$ with 3.7$\sigma$ significance; $\mathcal{B} (B^+ \to \Lambda\bar{\Lambda}\pi^+) < 0.94 \times 10^{-6}$. A related search for $B^0 \to \Lambda\bar{\Lambda}\bar{D}^0$ yields a branching fraction $\mathcal{B} (B^0 \to \Lambda\bar{\Lambda}\bar{D}^0 ) = (1.05_{-0.44}^{+0.57} \pm 0.14)\times 10^{-5}$. This may be compared with the large, $\sim 10^{-4}$, branching fraction observed for $B^0 \to p\bar{p}\bar{D^0}$. The $M_{\Lambda\bar{\Lambda}}$ enhancements near threshold and related angular distributions for the observed modes are also reported.
Primary author
Min-Zu Wang
(NTU)
