sin2phi_2(alpha)) from Belle

TL;DR

This paper reports a measurement of CP-violating asymmetries in B0 -> pi+pi- decays using data from the Belle detector, providing key parameters that test the Standard Model's description of CP violation.

Contribution

First measurement of CP-violating parameters in B0 -> pi+pi- decays at Belle with detailed asymmetry analysis.

Findings

CP asymmetry parameters S_pipi and A_pipi measured

Results are consistent with Standard Model predictions

Provides constraints on the CKM angle alpha

Abstract

We present a measurement of CP-violating asymmetries in B0 -> pi+pi- decays based on 41.8 fb-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain the CP-violating asymmetry parameters S_pipi = -1.21 + 0.38 - 0.27 (stat) + 0.16 - 0.13 (syst) and A_pipi = +0.94 + 0.25 - 0.31 (stat) +- 0.09 (syst).