sin2phi1 with 45 Million BBbar Pairs at Belle

TL;DR

This paper reports an improved measurement of the CP violation parameter sin2phi1 using 45 million BBbar pairs at Belle, confirming the Standard Model prediction with high statistical significance.

Contribution

It provides a more precise measurement of sin2phi1 using a large data sample and multiple decay channels at the Belle experiment.

Findings

Measured sin2phi1 = 0.82 +/- 0.12(stat) +/- 0.05(syst)

Enhanced precision over previous measurements

Supports the Standard Model CP violation framework

Abstract

We present an improved measurement of the standard model CP violation parameter sin2phi1 (also known as sin2beta) based on a sample of 45 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEK asymmetric-energy e^+e^- collider. One neutral B meson is reconstructed in a J/psi Ks, psi(2s) Ks, chi_c1 Ks, eta_c Ks, J/psi K*, or J/psi KL CP-eigenstate decay channel and the flavor of accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain sin2phi1 = 0.82 +/- 0.12(stat) +/- 0.05(syst).