Abstract
We report the direct observation of the excited L=1 state B_(s2)(*) in fully reconstructed decays to B+K-. The mass of the B_(s2)(*) meson is measured to be 5839.6+/-1.1(stat)+/-0.7(syst) MeV/c(2), and its production rate relative to the B+ meson is measured to be [1.15+/-0.23(stat)+/-0.13(syst)]%.
Highlights
Background parameterizationBin widths/positionsValue of PDG mass uncertainties Momentum scaleResolution uncertainty TotalTheoretical models predict that the Bs2 meson, excluding phase-space factors, should decay with equal branching ratios into B K and B K
We report the direct observation of the excited L 1 state Bs2 in fully reconstructed decays to B K
Since the mass difference in the decay Bs2 ! B K is very small, the rate should be strongly suppressed by a factor proportional to P =P5, where P (P) is the momentum in the center-of-mass frame of the kaon in the decay Bs2 ! B K (B K) [5]
Summary
45:78 0:35 MeV [1] These photons are not reconstructed in this analysis, so that for such events the invariant mass of the reconstructed decay products is shifted down by E. The broad resonances decay via S-wave processes and are expected to have widths of a few hundred MeV=c2. Such states are difficult to distinguish, in effective mass spectra, from the combinatorial background. The narrow resonances decay via D-wave processes (L 2) and should have widths of approximately 1 MeV=c2 [5], which are strongly dependent on their masses. The CDF collaboration has reported the observation of two narrow resonances consistent with the Bs1 and Bs2 states [6]
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