Analysis of the resonant components in Bs->J/\psi\pi+\pi-

TL;DR

This paper analyzes the resonant components of the decay Bs->J/psi pi+ pi- using LHCb data, revealing a dominant S-wave pi+ pi- system and a high CP-odd fraction, which aids CP violation studies.

Contribution

It provides the first detailed analysis of the decay structure and CP content of Bs->J/psi pi+ pi- using a modified Dalitz plot approach with LHCb data.

Findings

Pi+ pi- system is predominantly S-wave.

CP-odd fraction exceeds 97.7% at 95% CL.

First measurement of branching fraction ratio to J/psi phi.

Abstract

The decay Bs->J/\psi\pi+\pi- can be exploited to study CP violation. A detailed understanding of its structure is imperative in order to optimize its usefulness. An analysis of this three-body final state is performed using a 1.0/fb sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. The \pi+\pi- system is shown to be dominantly in an S-wave state, and the CP-odd fraction in this Bs decay is shown to be greater than 0.977 at 95% confidence level. In addition, we report the first measurement of the J/\psi\pi+\pi- branching fraction relative to J/\psi\phi\ of (19.79 +/- 0.47 +/- 0.52)%.