Search for B0 -> rho0rho0 and Non-Resonant B0 -> 4pi Decays

TL;DR

This paper reports a search for specific B0 meson decay modes involving rho0 and f0(980) resonances, setting upper limits on their branching fractions based on data from the Belle detector, with some evidence for B0 -> rho0rho0.

Contribution

First measurement and upper limits for B0 decays to rho0rho0 and related charmless four-pion final states using Belle data.

Findings

Measured B(B0 -> rho0rho0) < 1.6 x 10^{-6} at 90% CL

Non-resonant B0 -> 4pi decay branching fraction < 17.3 x 10^{-6} at 90% CL

No significant signals for other decay modes

Abstract

We search for the decay B0 -> rho0rho0 and other possible charmless modes with a pi+pi-pi+pi- final state, including B0 -> rho0f0(980), B0 -> f0(980)f0(980), B0 -> f0(980)pipi, B0 -> rho0pipi and non-resonant B0 -> 4pi. These results are obtained from a data sample containing 520 x 10^6 BBar pairs collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. We measure a branching fraction of (0.9 +/- 0.4^{+0.3}_{-0.4}) x 10^{-6}, or B(B0 -> rho0rho0) < 1.6 x 10^{-6} at the 90% confidence level. The significance including systematic uncertainties is 1.8\sigma. These values correspond to the final state being longitudinally polarized. We also measure the branching fraction of non-resonant B0 -> 4pi decay to be (10.2 +/- 4.7^{+2.3}_{-1.5}) x 10^{-6} with 2.1\sigma significance, and set the 90% confidence level upper limit B(B0 -> 4pi) < 17.3 x 10^{-6}. For the other related decays, B0 -> rho0f0(980), B0 -> f0(980)f0(980), B0 -> f0(980)pipi and B0 -> rho0pipi, no significant signals are observed and upper limits on the branching fractions are set.