Search for the lepton-flavour violating decay D0→e±μ∓

Abstract A search for the lepton-flavour violating decay D 0 → e ± μ ∓ is made with a dataset corresponding to an integrated luminosity of 3.0 fb − 1 of proton–proton collisions at centre-of-mass energies of 7 TeV and 8 TeV , collected by the LHCb experiment. Candidate D 0 mesons are selected using the decay D ⁎ + → D 0 π + and the D 0 → e ± μ ∓ branching fraction is measured using the decay mode D 0 → K − π + as a normalization channel. No significant excess of D 0 → e ± μ ∓ candidates over the expected background is seen, and a limit is set on the branching fraction, B ( D 0 → e ± μ ∓ ) 1.3 × 10 − 8 , at 90% confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.