First observation of B0s → J/ψ f0(980) decays

Abstract

Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the hadronic decayB0s→J/ψf0(980) is observed. ThisCP eigenstate mode could be used to measure mixing-induced CP violation in theB0ssystem. Using a fit to theπ+π−mass spectrum with interfering resonances givesRf0/φ≡Γ(B0s→J/ψf0, f0→π+π−)Γ(B0s→J/ψφ, φ→K+K−)= 0.252+0.046+0.027−0.032−0.033. In the interval±90 MeV around980 MeV, corresponding to approximately two fullf0widths we also findR′≡Γ(B0s→J/ψπ+π−,|m(π+π−)−980 MeV|<90 MeV)Γ(B0s→J/ψφ, φ→K+K−)= 0.162±0.022±0.016, where in both casesthe uncertainties are statistical and systematic, respectively