Improved Measurements of CP-Violating Asymmetry Amplitudes in B0 -> pi+pi- Decays

TL;DR

This paper reports updated measurements of CP-violating parameters in B0 -> pi+pi- decays, using a large data sample from the BaBar detector, providing more precise values for S_pipi and C_pipi.

Contribution

The study provides the most recent and precise measurements of CP asymmetry parameters in B0 decays, improving upon previous results with a larger data set and refined analysis techniques.

Findings

Measured S_pipi = -0.30 ± 0.17 (stat) ± 0.03 (syst)

Measured C_pipi = -0.09 ± 0.15 (stat) ± 0.04 (syst)

Observed 467 ± 33 signal decays

Abstract

We present updated measurements of the CP-violating parameters S_pipi and C_pipi in B0 -> pi+pi- decays. Using a sample of 227 million Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we observe 467 +- 33 signal decays and measure S_pipi = -0.30 +- 0.17 (stat) +- 0.03 (syst), and C_pipi = -0.09 +- 0.15 (stat) +- 0.04 (syst).