Evidence for the B0->rho0rho0 Decay and Implications for the CKM Angle alpha

TL;DR

This paper reports evidence for the B0->rho0rho0 decay, measures its branching fraction and polarization, and discusses implications for the CKM angle alpha, based on data from the BABAR experiment.

Contribution

First evidence for B0->rho0rho0 decay with measured branching fraction and polarization, impacting the understanding of CKM angle alpha.

Findings

Evidence for B0->rho0rho0 with 3.0 sigma significance

Measured branching fraction B = (1.16 +0.37-0.36 +-0.27) x 10^{-6}

Longitudinal polarization fraction f_L = 0.86 +0.11-0.13 +-0.05

Abstract

We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 348 million Upsilon(4S)->BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find evidence for B0->rho0rho0 with 3.0 sigma significance and measure the branching fraction B = (1.16 +0.37-0.36 +-0.27) 10^{-6} and longitudinal polarization fraction f_L = 0.86 +0.11-0.13 +-0.05. As a consequence, the uncertainty on the CKM unitarity angle alpha due to penguin contributions in B->rhorho decays is estimated to be 18 degrees at 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates. All results are preliminary.