Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System

TL;DR

This paper reports an improved measurement of the CP violation parameter sin2phi_1 in the neutral B meson system, using a large data sample from the Belle detector, providing more precise insights into CP violation in the Standard Model.

Contribution

The study presents a more precise measurement of sin2phi_1 using an extensive dataset and improved analysis techniques, enhancing the understanding of CP violation in B mesons.

Findings

Measured sin2phi_1 = 0.719 +/- 0.074(stat) +/- 0.035(syst)

Achieved improved statistical and systematic precision over previous measurements

Supports the Standard Model prediction of CP violation in B mesons.

Abstract

We present an improved measurement of the standard model CP violation parameter sin2phi_1 (also known as sin2beta) based on a sample of 85 times 10^6 B Bbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed in a J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K^{*0}, or J/psi K_L CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time interval between the two B meson decay points, we obtain sin2phi_1 = 0.719 +/- 0.074(stat) +/- 0.035(syst).