Search for the decay D0→π+π−μ+μ−

Abstract A search for the D 0 → π + π − μ + μ − decay, where the muon pair does not originate from a resonance, is performed using proton–proton collision data corresponding to an integrated luminosity of 1.0 fb − 1 recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D 0 → π + π − ϕ ( → μ + μ − ) , under the assumption of a phase-space model, is found to be B ( D 0 → π + π − μ + μ − ) / B ( D 0 → π + π − ϕ ( → μ + μ − ) ) 0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B ( D 0 → π + π − μ + μ − ) 5.5 × 10 − 7 at 90% confidence level. This is the most stringent to date.