Measurement of the fragmentation fraction ratio f_s/f_dand its dependence on B meson kinematics

The relative production rate of B⁰ _sand B⁰mesons is determined with the hadronic decays B⁰ _s→ D⁻ _sπ⁺and B⁰→ D⁻K⁺. The measurement uses data corresponding to 1.0 fb⁻¹of pp collisions at a centre-of-mass energy of √s = 7TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, f_s/f_d, is measured to be 0.238 ± 0.004 ± 0.015 ± 0.021, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain f_s/f_d= 0.256 ±0.020. The dependence of f_s/f_don the transverse momentum and pseudorapidity of the B meson is determined using the decays B⁰ _s→ D⁻ _sπ⁺and B⁰→ D⁻π⁺. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays B⁰→ D⁻K⁺and B⁰→ D⁻π⁺is measured to be 0.0822 ± 0.0011 (stat) ± 0.0025 (syst).