Amplitude analysis and branching fraction measurement of Bs->J/\psi K+K-

TL;DR

This paper presents an amplitude analysis of the Bs->J/psi K+K- decay, identifying resonant structures, measuring the branching fraction, and determining properties of intermediate states using LHCb data.

Contribution

It introduces a modified Dalitz plot analysis for this decay mode, revealing detailed resonance contributions and precise measurements of branching fractions and resonance parameters.

Findings

Resonant structures include (1020), f0(980), f'2(1525)

Measured branching fraction: (7.70 1.0) 7 10^{-4}

Mass and width of f'2(1525) are 1522.2 MeV and 84 MeV

Abstract

An amplitude analysis of the final state structure in the Bs->J/\psi K+K- decay mode is performed using 1.0/fb of data collected by the LHCb experiment in 7 TeV center-of-mass energy pp 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 non-resonant S-wave contribution. The largest resonant component is the \phi(1020), accompanied by f0(980), f'2(1525), and four additional resonances. The overall branching fraction is measured to be B(Bs->J/\psi K+K-)=(7.70 +/-0.08 +/- 0.39 +/- 0.60)x 10^(-4), where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of Bs 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.