Measurement of the ratio $B(B^0_s \to J/\psi f_0(980))$ / $B(B^0_s \to J/\psi \phi(1020))$ in pp collisions at $\sqrt s$ = 7 TeV

A measurement of the ratio of the branching fractions of the B[0,s] meson to J/psi f0(980) and to J/psi phi(1020) is presented. The J/psi, f0(980), and phi(1020) are observed through their decays to mu+ mu-, pi+ pi-, and K+ K-, respectively. The f0 is identified by requiring abs( M[pi+,pi-] - 974 MeV ) < 50 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, corresponding to an integrated luminosity of 5.3 inverse femtobarns. The measured ratio is B(B[0,s] to J/psi f0(980)) B(f0 to pi+ pi-) / B(B[0,s] to J/psi phi(1020)) B(phi(1020) to K+ K-) = 0.140 +/- 0.008 +/- 0.023, where the first uncertainty is statistical and the second is systematic.