Measurement of B meson production cross-sections in proton-proton collisions at $ \sqrt{s}=7 $ TeV

Abstract

The production cross-sections of B mesons are measured in pp collisions at a centre-of-mass energy of 7 TeV, using data collected with the LHCb detector corresponding to a integrated luminosity of 0.36 fb −1 . The B + , B 0 and B 0 s mesons are reconstructed in the exclusive decays B + → J/ψ K + , B 0 → J/ψ K * 0 and B 0 s → J/ψ φ, with J/ψ → µ + µ − , K * 0 → K + π − and φ → K + K − . The differential cross-sections are measured as functions of B meson transverse momentum p T and rapidity y, in the range 0 < p T < 40 GeV/c and 2.0 < y < 4.5. The integrated cross-sections in the same p T and y ranges, including charge-conjugate states, are measured to be σ(pp → B + + X) = 38.9 ± 0.3 (stat.) ± 2.5 (syst.) ± 1.3 (norm.) µb, σ(pp → B 0 + X) = 38.1 ± 0.6 (stat.) ± 3.7 (syst.) ± 4.7 (norm.) µb, σ(pp → B 0 s + X) = 10.5 ± 0.2 (stat.) ± 0.8 (syst.) ± 1.0 (norm.) µb,where the third uncertainty arises from the pre-existing branching fraction measurements.Keywords: Hadron-Hadron Scattering, Heavy quark production 5 Results and conclusion 6The LHCb collaboration 13 IntroductionMeasurements of beauty production in multi-TeV proton-proton (pp) collisions at the LHC provide important tests of quantum chromodynamics. State of the art theoretical predictions are given by the fixed-order plus next-to-leading logarithm (FONLL) approach [1][2][3]. In these calculations, the dominant uncertainties arise from the choice of the renormalisation and factorisation scales, and the assumed b-quark mass [4]. The primary products of bb hadronisation are B + , B 0 , B 0 s and their charge-conjugate states (throughout the paper referred to as B mesons) formed by oneb quark bound to one of the three light quarks (u, d and s). Accurate measurements of the cross-sections probe the validity of the production models. At the LHC, bb production has been studied in inclusive b → J/ψ X decays [5, 6] and semileptonic [7,8] decays. Other measurements, using fully reconstructed B mesons, have also been performed by the LHCb and CMS collaborations [9][10][11][12].In this paper, a measurement of the production cross-sections of B mesons (including their charge-conjugate states) is presented. This study is performed in the transverse momentum range 0 < p T < 40 GeV/c and rapidity range 2.0 < y < 4.5 using data, corresponding to a integrated luminosity of 0.36 fb −1 , collected in pp collisions at centreof-mass energy of 7 TeV by the LHCb experiment. The B mesons are reconstructed in the exclusive decays B + → J/ψ K + , B 0 → J/ψ K * 0 and B 0 s → J/ψ φ, with J/ψ → µ + µ − , K * 0 → K + π − and φ → K + K − .The LHCb detector [13] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The detector includes a high-precision tracking system consisting of a silicon-strip vertex detector surrounding the pp interaction region, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power of about 4 Tm, and three stations of silicon-st...

Charm production and QCD analysis at HERA and LHC

“…Their values are consistent with the recent determination from ee, ep and pp data [266]. The fragmentation fractions for beauty hadrons are taken from [247].…”

“…LHCb measured B + , B 0 and B 0 s production using data corresponding to an integrated luminosity of 0.36 fb −1 in the region of rapidity 2.0 < y < 4.5 and transverse momentum 0 < p T < 40 GeV in pp collisions at a centre-of-mass energy of 7 TeV [247]. The analysis was based on fully reconstructed decays of beauty hadrons in the following decay modes:…”

“…-the combined HERA-I inclusive ep NC and CC DIS cross sections [2] (datasets 1-4) serve to constrain the core of the PDFs; the analysis is restricted to the inclusive data with virtuality Q 2 > Q 2 min = 3.5 GeV 2 to ensure the applicability of pQCD; -the combined HERA charm data [60] and ZEUS beauty [30] data (datasets 5-6) were used to constrain the gluon PDF and the charm and beauty masses; -the LHCb charm [177] and beauty [247] data (datasets 7-14) -the new ingredients of the study -serve to constrain the gluon PDF at low x.…”

“…58 Note that in this and the next sections Q 2 denotes the PDF factorisation scale and not the virtuality of ep scattering, x denotes the longitudinal fraction of the proton momentum and not the Bjorken variable, y denotes rapidity and not inelasticity, unless otherwise stated explicitly. 59 The region x 10 −4 will be referred to as low x. Such data exist from the LHCb Collaboration, which has measured charm and beauty production in the forwardrapidity region 2.0 < y < 4.5 at the centre-of-mass energy √ s = 7 TeV [177,247]. 60 The measured quantities are one-particle inclusive charm-and beauty-hadron production cross sections in the p T ranges 0 < p T < 8 GeV and 0 < p T < 40 GeV for the charm and beauty measurements, respectively.…”

Measurement of D-meson production at mid-rapidity in pp collisions at $${\sqrt{s}=7}$$ s = 7 TeV

“…In previous analyses, an alternative method based on the ratio of the FONLL cross sections for feed-down and prompt D mesons was also used in the estimation of the systematic uncertainties. In this analysis it was no longer used, on the basis of the observation that FONLL calculations at LHC energies provide a good description of the production cross sections of B 0 , B + and B 0 s mesons at both central and forward rapidity, while it underestimates prompt charm production [43][44][45][46][47][48]. Hence, the uncertainty due to the B feed-down correction is significantly reduced and more symmetric as compared to our previous publications.…”