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

TL;DR

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

Contribution

First evidence for B0->rho0rho0 decay with precise measurements, impacting the understanding of CKM angle alpha and penguin contributions in B decays.

Findings

Evidence for B0->rho0rho0 with 3.5 sigma significance

Measured branching fraction BR = (1.07+-0.33+-0.19)10^-6

Longitudinal polarization fraction f_L = 0.87+-0.13+-0.04

Abstract

We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 384 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 3.5 sigma significance and measure the branching fraction BR = (1.07+-0.33+-0.19)10^-6 and longitudinal polarization fraction f_L = 0.87+-0.13+-0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the CKM unitarity angle alpha due to penguin contributions in B-> rho rho decays is 18 degrees at the 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates.