LHCb

Abstract:

Decays of Ξb− and Ωb− baryons to Λc+h−h′− final states, with h−h′− being π−π−, K−π− and K−K− meson pairs, are searched for using data collected with the LHCb detector. The data sample studied corresponds to an integrated luminosity of 8.7 fb−1 of pp collisions collected at centre-of-mass energies s = 7, 8 and 13 TeV. The products of the relative branching fractions and fragmentation fractions for each signal mode, relative to the B−→Λc+p¯π− mode, are measured, with Ξb−→Λc+K−π−, Ξb−→Λc+K−K− and Ωb−→Λc+K−K− decays being observed at over 5 σ significance. The Ξb−→Λc+K−π− mode is also used to measure the Ξb− production asymmetry, which is found to be consistent with zero. In addition, the B−→Λc+p¯K− decay is observed for the first time, and its branching fraction is measured relative to that of the B−→Λc+p¯π− mode.

Abstract:

A search for radiative decay of Bs0 mesons to orbitally excited K+K− states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The dikaon spectrum in the mass range mKK < 2400 MeV/c2 is dominated by the ϕ(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f2(1270), f2′(1525) and f2(2010) meson states, the overall tensor contribution to the amplitude is measured to beFf2=16.8±0.5stat.±0.7syst.%, mostly dominated by the f2′(1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the fit fractions along with constructive interference leads to the relative branching ratio measurementBBs0→f2′γBBs0→ϕγ=19.4−0.8+0.9stat.−0.5+1.4syst.±0.5B%, where the last uncertainty is due to the ratio of measured branching fractions to the K+K− final state. This result represents the first observation of the radiative Bs0→f2′1525γ decay, which is the second radiative transition observed in the Bs0 sector.

Abstract:

Using annihilation data corresponding to an integrated luminosity of 2.93 taken at the center-of-mass energy GeV with the BESIII detector, a joint amplitude analysis is performed on the decays and (non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays , , , and are observed in both channels. With the obtained amplitude model, the -even fractions of and (non-η) are determined to be % and %, respectively. The branching fractions of and (non-η) are measured to be % and %, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of when used to determine the CKM angle via the decay.