Search for the decay D0 → γγ and measurement of the branching fraction for D0 → π0π0

Abstract

We search for the rare decay of the D 0 meson to two photons, D 0 → γ γ , and present a measurement of the branching fraction for a D 0 meson decaying to two neutral pions, B ( D 0 → π 0 π 0 ) . The data sample analyzed corresponds to an integrated luminosity of 470.5 fb − 1 collected by the BABAR detector at the PEP-II asymmetric-energy e + e − collider at SLAC. We place an upper limit on the branching fraction, B ( D 0 → γ γ ) < 2.2 × 10 − 6 , at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B ( D 0 → π 0 π 0 ) = ( 8.4 ± 0.1 ± 0.4 ± 0.3 ) × 10 − 4 .