Search for the decay modes D0 → e+e−, D0 → μ+μ−, and D0 → e±μ∓

Abstract

We present searches for the rare decay modes D 0 → e + e − , D 0 → μ + μ − , and D 0 → e ± μ ∓ in continuum e + e − → c ¯ c events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468 fb − 1 . These decays are highly Glashow-Iliopoulos-Maiani 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 D 0 → μ + μ − 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 ( D 0 → e + e − ) < 1.7 × 10 − 7 , B ( D 0 → μ + μ − ) within [ 0.6 , 8.1 ] × 10 − 7 , and B ( D 0 → e ± μ ∓ ) < 3.3 × 10 − 7 .