Measurement of the $b$-quark production cross-section in 7 and 13 TeV $pp$ collisions

Abstract

Measurements of the cross section for producing b quarks in the reaction $pp \to b\overline{b}X$ are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity $\eta$ in the range $2 < \eta < 5$ 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 $\eta$ range are $72.0 \pm 0.3 \pm 6.8$ and $154.3 \pm 1.5 \pm 14.3 \mu b$ for 7 and 13 TeV. The ratio is $2.14 \pm 0.02 \pm 0.13$, 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 $\eta$ than the model prediction.