Study of CP-Violating Asymmetries in B0 -> pi+pi- Decays

TL;DR

This paper reports a measurement of CP-violating asymmetries in B0 -> pi+pi- decays using data from the Belle detector, providing insights into matter-antimatter asymmetry in the universe.

Contribution

It presents the first measurement of CP asymmetries in B0 -> pi+pi- decays with detailed statistical and systematic analysis.

Findings

Measured CP asymmetry parameters: Spipi = -1.21 +0.38/-0.27, Apipi = +0.94 +0.25/-0.31.

Results suggest significant CP violation in B0 -> pi+pi- decays.

Data supports the presence of CP-violating effects consistent with the Standard Model.

Abstract

We present a measurement of CP-violating asymmetries in B0 -> pi+pi- decays based on a 41.8 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We fully reconstruct one neutral B meson as a B0 -> pi+pi- CP eigenstate and identify the flavor of the accompanying B meson from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain the CP-violating asymmetry parameters Spipi = -1.21 +0.38/-0.27(stat) +0.16/-0.13(syst) and Apipi = +0.94 +0.25/-0.31(stat) +/- 0.09(syst).