Search for the decay modes D0 -> e+e-, D0 -> mu+mu-, and D0 -> e mu

TL;DR

This paper searches for rare D0 meson decay modes into electron, muon pairs, and mixed e mu states, setting upper limits on their branching fractions using data from the BABAR detector, with no significant signals observed.

Contribution

First search for D0 decays into e+e-, mu+mu-, and e mu modes with new upper limits on their branching fractions.

Findings

No significant excess observed in e+e- and e mu channels.

An excess in mu+mu- channel is consistent with background fluctuation.

Upper limits on branching fractions are set at 90% confidence level.

Abstract

We present searches for the rare decay modes D0 to e+e-, D0 to mu+mu- and D0 to e mu in continuum e+e- to cbar c events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468 f^-1. These decays are highly GIM suppressed but may be enhanced in several extensions of the Standard Model. Our observed event yields are consistent with the expected backgrounds. An excess is seen in the D0 to mu+mu- channel, although the observed yield is consistent with an upward background fluctuation at the 5% level. Using the Feldman-Cousins method, we set the following 90% confidence level intervals on the branching fractions: B(D0 to e+e-)<1.7 x 10^-7, B(D0 to mu+mu-) within [0.6, 8.1] x 10^-7, and B(D0 to e mu)<3.3 x 10^-7.