Measurements of time-dependent CP violation in B^0 -> psi(2S) K_S decays

TL;DR

This paper presents precise measurements of time-dependent CP violation parameters in B^0 decays to psi(2S) K_S, confirming consistency with previous results and enhancing understanding of CP violation in the B meson system.

Contribution

The study provides improved measurements of CP violation parameters in B^0 -> psi(2S) K_S decays using a large data sample, with results aligning with prior findings.

Findings

Measured S parameter: +0.72 +/- 0.09(stat) +/- 0.03(syst)

Measured A parameter: +0.04 +/- 0.07(stat) +/- 0.05(syst)

Results agree with previous B^0 -> J/psi K^0 measurements

Abstract

We report improved measurements of time-dependent CP violation parameters for B^0(\bar{B}^0) -> psi(2S) K_S. This analysis is based on a data sample of 657x10^6 BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. We fully reconstruct one neutral B meson in the psi(2S) K_S CP-eigenstate decay channel, and the flavor of the accompanying B meson is identified to be either B^0 or \bar{B}^0 from its decay products. CP violation parameters are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays: S (psi(2S) K_S) = +0.72 +/- 0.09(stat) +/- 0.03(syst), A (psi(2S) K_S) = +0.04 +/- 0.07(stat) +/- 0.05(syst). These results are in agreement with results from measurements of B^0 -> J/psi K^0.