First observation of B 0 s →J/ψf 0 (980) decays

Abstract

Using data collected with the LHCb detector in proton-proton collisions at a centreof-mass energy of 7 TeV, the hadronic decay B0 s → J/ψf0(980) is observed. This CP eigenstate mode could be used to measure mixing-induced CP violation in the B0 s system. Using a fit to the π +π − mass spectrum with interfering resonances gives Rf0/φ ≡ Γ(B0 s→J/ψf0, f0→π+π−) Γ(B0 s→J/ψφ, φ→K+K−) = 0.252+0.046+0.027 −0.032−0.033. In the interval ±90 MeV around 980 MeV, corresponding to approximately two full f0 widths we also find R′ ≡ Γ(B0 s→J/ψπ+π−, |m(π+π−)−980 MeV|<90 MeV) Γ(B0 s→J/ψφ, φ→K+K−) = 0.162 ± 0.022 ± 0.016, where in both cases the uncertainties are statistical and systematic, respectively. Keywords: LHC, Hadronic B decays, B0 s meson PACS: 14.40.Nd, 13.25.Hw, 14.40.Be