Improved Measurement of the Partial-Rate CP Asymmetry in B+ -> K0pi+ and B- -> K0bar pi- Decays

TL;DR

This paper presents an improved measurement of CP asymmetry in B meson decays to K0 pi, using a large data sample from the Belle detector, providing more precise constraints on CP violation.

Contribution

The study offers a more precise measurement of partial-rate CP asymmetry in B+ and B- decays, improving upon previous results with a larger data set and refined analysis techniques.

Findings

Measured Acp(K0pi+-) = 0.07 with uncertainties

90% CL interval for Acp(K0pi+-) is -0.10 to 0.22

Results are consistent with Standard Model predictions

Abstract

We report an improved measurement of the partial-rate CP asymmetry in B+ => K0pi+ and B- => K0bar pi- decays. The analysis is based on a data sample of 85 million BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB e+ e- storage ring. We measure Acp(K0pi+-) = 0.07^{+0.09 +0.01}_{-0.08 -0.03}, where the first and second errors are statistical and systematic, respectively; the corresponding 90% confidence-level interval is -0.10 < Acp(K0pi+-) < 0.22 .