Measurement of the fragmentation fraction ratio f(s)/f(d) and its dependence on B meson kinematics

The relative production rate of B-s(0) and B-0 mesons is determined with the hadronic decays B-s(0) -> D-s(-)pi(+) and B-0 -> D- K+. The measurement uses data corresponding to 1.0 fb(-1) of pp collisions at a centre-of-mass energy of root s = 7 TeV 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(d) on the transverse momentum and pseudorapidity of the B meson is determined using the decays B-s(0) -> D-s(-)pi(+) and B-0 -> D-pi(+). 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 B-0 -> D-K+ and B-0 -> D-pi(+) is measured to be 0.0822 +/- 0.0011 (stat) +/- 0.0025 (syst).