Inclusive b-hadron production cross section with muons in pp collisions at sqrt(s) = 7 TeV

TL;DR

CMS measures inclusive b-hadron production in pp collisions at sqrt(s)=7 TeV using muons with pT>6 GeV and |η|<2.1, tagging b-jets via track-jets and the pT_rel observable. A binned likelihood fit to the $p_T^{rel}$ distributions separates signal from udsg and charm backgrounds. The result is $\sigma = 1.32 \pm 0.01$ (stat) $\pm 0.30$ (syst) $\pm 0.15$ (lumi) μb in the visible region, with differential cross sections consistent in shape with PYTHIA and MC@NLO predictions (data lying between the two). This study provides a QCD test of heavy-flavor production at LHC energies and complements CMS results from fully reconstructed B mesons.

Abstract

A measurement of the b-hadron production cross section in proton-proton collisions at sqrt(s)=7 TeV is presented. The dataset, corresponding to 85 inverse nanobarns, was recorded with the CMS experiment at the LHC using a low-threshold single-muon trigger. Events are selected by the presence of a muon with transverse momentum greater than 6 GeV with respect to the beam direction and pseudorapidity less than 2.1. The transverse momentum of the muon with respect to the closest jet discriminates events containing b hadrons from background. The inclusive b-hadron production cross section is presented as a function of muon transverse momentum and pseudorapidity. The measured total cross section in the kinematic acceptance is sigma(pp to b+X to mu + X') =1.32 +/- 0.01 (stat) +/- 0.30 (syst) +/- 0.15 (lumi) microbarns.

Figures (2)

• Figure 1: Distribution of muon transverse momentum $p_\perp^{\mathrm{rel}}$ with respect to the closest track-jet in data and results of the maximum likelihood fit. The black full circles correspond to the data distribution, while the black line is the result of the fitting procedure. The red dashed and the blue dotted line are the simulated b and cudsg distributions, respectively.
• Figure 2: Differential cross section (left) $\frac{d\sigma}{d{p^\mu_\mathrm{T}}}(\text{pp}\rightarrow\xspace \text{b}+X\rightarrow\xspace \mu +X', |{\eta^\mu}|<2.1)$, and (right) $\frac{d\sigma}{d{\eta^\mu}}(\text{pp}\rightarrow\xspace \text{b}+X\rightarrow\xspace \mu +X', {p^\mu_\mathrm{T}}> 6 \hbox{,Ge V}\xspace)$. The two possible muon charges are not distinguished and the process $\text{pp}\rightarrow\xspace \bar{\text{b}}+X\rightarrow\xspace \mu +X'$ is included. The black points are the CMS measurements. Vertical error bars showing the statistical error are smaller than the point size in most bins, the horizontal bars indicate the bin width. The yellow band shows the quadratic sum of statistical and systematic uncertainties. The systematic uncertainty (11%) of the luminosity measurement is not included. The solid blue line shows the mc@nlo result and the dashed blue lines illustrate the theoretical uncertainty as described in the text. The solid red line with dots shows the pythia result.