We report the first observation of the radiative hyperonic B decay B+→pΛ̄γ, using a 140fb-1 data sample recorded on the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. The measured branching fraction is B(B+→pΛ̄γ)= (2.16-0.53+0.58±0.20)×10-6. We examine its MpΛ̄ distribution and observe a peak near threshold. This feature is expected by the short-distance b→sγ transition. A search for B+→pΣ̄ 0γ yields no significant signal, and we set a 90% confidence-level upper limit on the branching fraction of B(B+→pΣ̄0γ)<4. 6×10-6.
Bibliographical noteFunding Information:
We thank the staffs at Fermilab and collaborating institutions, and acknowledge support from the DOE and NSF (USA); CEA and CNRS/IN2P3 (France); FASI, Rosatom and RFBR (Russia); CAPES, CNPq, FAPERJ, FAPESP and FUNDUNESP (Brazil); DAE and DST (India); Colciencias (Colombia); CONACyT (Mexico); KRF and KOSEF (South Korea); CONICET and UBACyT (Argentina); FOM (The Netherlands); PPARC (United Kingdom); MSMT (Czech Republic); CRC Program, CFI, NSERC and WestGrid Project (Canada); BMBF and DFG (Germany); SFI (Ireland); The Swedish Research Council (Sweden); Research Corporation; Alexander von Humboldt Foundation; and the Marie Curie Program.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)