Measurement of the ratio B(B_s^0 → J/ψf_0(980))/B(B_s^0 → J/ψϕ(1020)) in pp collisions at √s = 7 TeV

A measurement of the ratio of the branching fractions of the B_s^0 meson to J/ψf_0(980) and to J/ψϕ(1020) is presented. The J/ψ, f_0(980), and ϕ(1020) are observed through their decays to μ^+μ^−, π^+π^−, and K^+K^−, respectively. The f_0 and the ϕ are identified by requiring |Mπ^+π^− − 974 MeV|<50 MeV| and |MK^+K^− − 1020 MeV|<10 MeV. The analysis is based on a data sample of pp collisions at a centre-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5.3 fb^(−1). The measured ratio is B(B_s^0→J/ψf_0)B(f_0→π^+π^−)/B(B_s^0→Jψϕ)B(ϕ→K^+K^−)=0.140±0.008(stat)±0.023(syst), where the first uncertainty is statistical and the second is systematic.