Study of CP-violating asymmetries in B^0 --> pi^+pi^-, K^+pi^- decays

TL;DR

This paper reports measurements of CP-violating asymmetries in B meson decays to pi+pi- and K+pi-, providing insights into matter-antimatter asymmetry with data from the BABAR detector.

Contribution

It presents the first measurements of time-dependent CP asymmetries in B0 to pi+pi- decays and updates charge asymmetry in B0 to K+pi- decays using a large dataset.

Findings

Measured CP asymmetry parameters S_pi pi and C_pi pi with large uncertainties.

Updated charge asymmetry A_K pi consistent with zero.

Collected 33 million B meson decays at the BABAR detector.

Abstract

We present a measurement of the time-dependent CP-violating asymmetries in neutral B decays to the $\pi^+\pi^-$ CP eigenstate, and an updated measurement of the charge asymmetry in $B^0\to K^+\pi^-$ decays. In a sample of 33 million $\Upsilon(4S)\to B\bar B$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric $B$ Factory, we find $65^{+12}_{-11}$ $\pi^+\pi^-$ and $217\pm 18$ $K^+\pi^-$ candidates and measure the asymmetry parameters $S_{\pi\pi} = 0.03^{+0.53}_{-0.56}\pm 0.11$, $C_{\pi\pi} = -0.25^{+0.45}_{-0.47}\pm 0.14$, and ${\cal A}_{K\pi} = -0.07 \pm 0.08 \pm 0.02$, where the first error is statistical and the second is systematic.