Improved Measurement of CP-Violation Parameters sin(2phi1) and |lambda|, B Meson Lifetimes, and B0-B0bar Mixing Parameter Delta m_d

TL;DR

This paper reports precise measurements of CP-violation parameters, B meson lifetimes, and mixing parameters using a large data sample, confirming standard model predictions and providing the most accurate values to date.

Contribution

It provides the most precise measurements of sin(2phi1), |lambda|, B meson lifetimes, and Delta m_d, improving the accuracy of key parameters in B physics.

Findings

sin(2phi1) = 0.728 +/- 0.056 (stat) +/- 0.023 (syst)

B meson lifetime ratio exceeds five standard deviations from unity

Results are consistent with standard model expectations

Abstract

We present a precise measurement of the standard model CP-violation parameter sin(2phi1), the direct CP violation parameter |lambda|, the lifetimes of charged and neutral B mesons and their ratio, and the B0-B0bar mixing parameter Delta m_d based on a sample of 152 x 10^6 BB-bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One of two B mesons is fully reconstructed in a CP-eigenstate or a flavor-eigenstate decay channel. 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 sin(2phi1) = 0.728 +/- 0.056(stat) +/- 0.023(syst), |lambda| = 1.007 +/- 0.041(stat) +/- 0.033(syst), tau_B0 = 1.534 +/- 0.008(stat) +/- 0.010(syst) ps, tau_B+ = 1.635 +/- 0.011(stat) +/- 0.011(syst) ps, tau_B+/tau_B0 = 1.066 +/- 0.008(stat) +/- 0.008(syst) and Delta m_d = 0.511 +/- 0.005(stat) +/- 0.006(syst) ps-1. The results for sin(2phi1) and |lambda| are the most precise measurements performed so far, and are consistent with the standard model expectations. The significance of the observed deviation from unity in the lifetime ratio exceeds five standard deviations.