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, using data from the BaBar experiment, providing insights into CP violation in the B meson system.

Contribution

The study provides the first measurements of these decay modes and CP asymmetries with a large data sample, improving precision over previous results.

Findings

Measured B(B0 -> pi+pi-) = (5.4 +- 0.7 +- 0.4) x 10^-6

Measured B(B0 -> K+pi-) = (17.8 +- 1.1 +- 0.8) x 10^-6

Set an upper limit on B(B0 -> K+K-) < 1.1 x 10^-6 (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) to BB 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 pipi, 403+-24 Kpi, and 1+8-7 KK candidates, from which we measure the following quantities: B(B0 -> pi+pi-) = (5.4 +- 0.7 +- 0.4) x 10^(-6) B(B0 -> K+pi-) = (17.8 +- 1.1 +- 0.8) x 10^(-6) B(B0 -> K+K-) < 1.1 x 10^-6 (90% C.L.) Kpi asymmetry = -0.05 +- 0.06 +- 0.01, 90% C.L. [-0.14, +0.05] Spipi = -0.01 +- 0.37 +- 0.07, 90% C.L. [-0.66, +0.62] Cpipi = -0.02 +- 0.29 +- 0.07, 90% C.L. [-0.54, +0.48] where the errors are statistical and systematic, respectively. These results are preliminary.