Measurement of sin2beta with Hadronic and Previously Unused Muonic J/psi Decays

TL;DR

This paper measures the CP-violation parameter sin2beta using B0 decays to J/psi and K0_S, including previously unused muonic and hadronic J/psi decay modes, with results consistent with the Standard Model.

Contribution

It introduces a novel measurement of sin2beta utilizing hadronic and unconventional muonic J/psi decay channels, expanding the analysis methods in CP violation studies.

Findings

Measured sin2beta = 1.56 +/- 0.42 (stat.) +/- 0.21 (syst.)

Reconstructed 100 +/- 17 events with non-standard J/psi decays

Demonstrated feasibility of using hadronic and unconventional muonic J/psi decays for CP violation measurements

Abstract

We report a measurement of the CP-violation parameter sin2beta with B^0 -> J/psi K^0_S decays in which the J/psi decays to hadrons or to muons that do not satisfy our standard identification criteria. With a sample of 88 million BBbar events collected by the BaBar detector at the PEP-II asymmetric-energy $B$ factory at SLAC, we reconstruct 100 +/- 17 such events, with J/psi -> pi^+ pi^- pi^0 being the most prevalent, and measure sin2beta = 1.56 +/- 0.42 (stat.) +/- 0.21 (syst.).