A study of B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- decays: measurement of the ratio of branching fractions and search for direct CP-violating charge asymmetries

TL;DR

This study measures the ratio of branching fractions and searches for direct CP violation in B+/- decays to J/psi pi+/- and J/psi K+/- using data from the BABAR detector, finding no significant asymmetries.

Contribution

First measurement of the branching fraction ratio and CP asymmetries in B+/- --> J/psi pi+/- and J/psi K+/- decays with a large data set.

Findings

Branching fraction ratio BF(B+/- --> J/psi pi+/-)/BF(B+/- --> J/psi K+/-) = 3.91%

CP asymmetries A_pi and A_K are consistent with zero

Observed 51+/-10 signal events for B+/- --> J/psi pi+/- decays

Abstract

We have studied the B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- decays using a 20.7 fb-1 data set collected with the BABAR detector. We observe a signal of 51+/-10 B^+/- --> J/psi pi^+/- events and determine the ratio BF(B^+/- --> J/psi pi^+/-)/BF(B^+/- --> J/psi K^+/-) to be [3.91 +/- 0.78 (stat.) +/- 0.19 (syst.)]%. The CP-violating charge asymmetries for the B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- decays are determined to be A_pi = 0.01 +/- 0.22 (stat.) +/- 0.01 (syst.) and A_K = 0.003 +/- 0.030 (stat.) +/- 0.004 (syst.).