Measurement of the b-Quark Production Cross Section in 7 and 13 TeV pp Collisions

Measurements of the cross section for producing b quarks in the reaction p p → b anti-b X are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2 < η < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered η range are 72.0 ± 0.3 ± 6.8 and 154.3 ± 1.5 ± 14.3 μb for 7 and 13 TeV. The ratio is 2.14 ± 0.02 ± 0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower η than the model prediction.