Search for the decay D[superscript 0] → π[superscript +]π[superscript -]μ[superscript +]μ[superscript -]

Abstract

A search for the D[superscript 0]→π[superscript +]π[superscript −]μ[superscript +]μ[superscript −] 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[superscript −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[superscript 0]→π[superscript +]π[superscript −]ϕ(→μ[superscript +]μ[superscript −]), under the assumption of a phase-space model, is found to be B(D[superscript 0]→π[superscript +]π[superscript −]μ[superscript +]μ[superscript −])/B(D[superscript 0]→π[superscript +]π[superscript −]ϕ(→μ[superscript +]μ[superscript −]))<0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D[superscript 0]→π[superscript +]π[superscript −]μ[superscript +]μ[superscript −])<5.5 × 10[superscript −7] at 90% confidence level. This is the most stringent to date.