Measurements of Branching Fractions and CP-Violating Asymmetries in B0 --> pi+pi-, K+pi-, K+K- Decays

TL;DR

This paper reports updated measurements of branching fractions and CP asymmetries in B0 decays to pion and kaon pairs, based on data from the BABAR detector, providing insights into CP violation in the B meson system.

Contribution

It provides the first comprehensive update on branching fractions and CP asymmetries for B0 decays to pi+pi-, K+pi-, and K+K- using a large data sample from BABAR.

Findings

Measured BF(B0 --> pi+pi-) = (5.4+/-0.7+/-0.4) x 10^{-6}

Measured BF(B0 --> K+pi-) = (17.8+/-1.1+/-0.8) x 10^{-6}

Set an upper limit BF(B0 --> K+K-) < 1.1 x 10^{-6} at 90% C.L.

Abstract

We present updated measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons. The results are obtained from a data sample of about 60 million Y(4S) --> B-anti-B decays collected between 1999 and 2001 by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The sample contains 124^{+16}_{-15} pi-pi, 403+/-24 K-pi, and 0.6^{+8.0}_{-7.4} K-K candidates, from which we measure the following quantities: BF(B0 --> pi+pi-) = (5.4+/-0.7+/-0.4) x 10^{-6}, BF(B0 --> K+pi-) = (17.8+/-1.1+/-0.8) x 10^{-6}, BF(B0 --> K+K-) < 1.1 x 10^{-6} (90% C.L.} A_Kpi = -0.05+/-0.06+/-0.01 [-0.14,+0.05], S_pipi = -0.01+/-0.37+/-0.07 [-0.66,+0.62], C_pipi = -0.02+/-0.29+/-0.07 [-0.54,+0.48], where the errors are statistical and systematic, respectively, and the asymmetry limits correspond to the 90% confidence level. These results are preliminary.