Study of B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- Decays: Measurement of the Ratio of Branching Fractions and Search for Direct CP Violation

TL;DR

This paper 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, providing insights into CP violation and decay dynamics.

Contribution

First measurement of the ratio of branching fractions and charge asymmetries for B+/- --> J/psi pi+/- and J/psi K+/- decays with a large data sample from BABAR.

Findings

Ratio BF(B+/- --> J/psi pi+/-)/BF(B+/- --> J/psi K+/-) = 5.37%

Charge asymmetry A_pi = 0.123, consistent with no direct CP violation

Charge asymmetry A_K = 0.030, consistent with no direct CP violation

Abstract

We study B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- decays in a sample of about 89 million BB~ pairs collected with the BABAR detector at the PEP-II asymmetric B-factory at SLAC. We observe a signal of 244 +/- 20 B^+/- --> J/psi pi^+/- events and determine the ratio BF(B^+/- --> J/psi pi^+/-)/BF(B^+/- --> J/psi K^+/-) to be [5.37 +/- 0.45 (stat.) +/- 0.11 (syst)]%. The charge asymmetries for the B^+/- --> J/psi pi^+/- and B^+/- --> J/psi K^+/- decays are determined to be A_pi = 0.123 +/- 0.085 (stat.) +/- 0.004 (syst.) and A_K = 0.030 +/- 0.015 (stat.) +/- 0.006 (syst.), respectively.