Amplitude analysis and branching fraction measurement of B¯s0→J/ψK+K-

Abstract

An amplitude analysis of the final state structure in the ¯¯¯ B 0 s → J / ψ K + K − decay mode is performed using 1.0 fb − 1 of data collected by the LHCb experiment in 7 TeV center-of-mass energy p p collisions produced by the LHC. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. Resonant structures are observed in the K + K − mass spectrum as well as a significant nonresonant S -wave contribution over the entire K + K − mass range. The largest resonant component is the ϕ ( 1020 ) , accompanied by f 0 ( 980 ) , f ′ 2 ( 1525 ) , and four additional resonances. The overall branching fraction is measured to be B ( ¯¯¯ B 0 s → J / ψ K + K − ) = ( 7.70 ± 0.08 ± 0.39 ± 0.60 ) × 10 − 4 , where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of ¯¯¯ B 0 s to B − mesons produced. The mass and width of the f ′ 2 ( 1525 ) are measured to be 1522.2 ± 2.8 + 5.3 − 2.0 MeV and 84 ± 6 + 10 − 5 MeV , respectively. The final state fractions of the other resonant states are also reported.