Branching Fractions and CP Asymmetries in B0 -> pi0pi0, B+ -> pi+pi0 and B+ -> K+pi0 Decays and Isospin Analysis of the B -> pipi System

TL;DR

This paper reports measurements of branching fractions and CP asymmetries in B meson decays to pi pi and K pi final states, using data from the BaBar experiment, and performs an isospin analysis to constrain the CKM angle alpha.

Contribution

First precise measurements of B0 -> pi0pi0 branching fraction and asymmetry, and an isospin analysis constraining the CKM angle alpha.

Findings

B(B0 -> pi0pi0) = (1.17 +- 0.32 +- 0.10) x 10^-6

Upper bound on |alpha - alpha_eff| of 35 degrees at 90% C.L.

Significance of B0 -> pi0pi0 signal is 5.0 sigma.

Abstract

Based on a sample of 227 million BBbar pairs collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the branching fraction B(B0 -> pi0pi0) = (1.17 +- 0.32 +- 0.10) x 1e-6, and the asymmetry C(pi0pi0) = -0.12 +- 0.56 +- 0.06. The B0 -> pi0pi0 signal has a significance of 5.0 sigma. We also measure B(B+ -> pi+pi0) = (5.8 +- 0.6 +- 0.4) x 1e-6, B(B+ -> K+pi0) = (12.0 +- 0.7 +- 0.6) x 1e-6, and the charge asymmetries A(pi+pi0) = -0.01 +- 0.10 +- 0.02 and A(K+pi0) = 0.06 +- 0.06 +- 0.01. Using isospin relations we find an upper bound on the angle difference |alpha - alpha(eff)| of 35 degrees at the 90% C.L.