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

TL;DR

This paper reports updated measurements of CP-violating asymmetries in B0 to pi+pi- decays using a large data sample from the BaBar experiment, providing more precise values of the parameters S_pi_pi and C_pi_pi.

Contribution

It presents the first updated measurements of CP-violating parameters in B0 to pi+pi- decays with improved statistical precision using BaBar data.

Findings

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

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

Analyzed 227 million B meson decays

Abstract

We present preliminary updated measurements of the CP-violating parameters $S_{\pi\pi}$ and $C_{\pi\pi}$ in $B^0\to\pi^+\pi^-$ decays. Using a sample of 227 million $\Upsilon(4S)\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ collider at SLAC, we observe $467\pm 33$ signal decays and measure $S_{\pi\pi}$ and $C_{\pi\pi} = -0.30\pm 0.17 ({\rm stat})\pm 0.03 ({\rm syst})$, and $C_{\pi\pi} = -0.09\pm 0.15 ({\rm stat})\pm 0.04 ({\rm syst})$.