Measurements of prompt charm production cross-sections in pp collisions at s = 5 $$ \sqrt{s}=5 $$ TeV

Abstract

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5 TeV. The data sample corresponds to an integrated luminosity of 8.60 ± 0.33 pb −1 collected by the LHCb experiment.The production cross-sections of D 0 , D + , D + s , and D * + mesons are measured in bins of charm meson transverse momentum, p T , and rapidity, y. They cover the rapidity range 2.0 < y < 4.5 and transverse momentum ranges 0 < p T < 10 GeV/c for D 0 and D + and 1 < p T < 10 GeV/c for D + s and D * + mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < p T < 8 GeV/c are determined to be σ(pp → D 0 X) = 1004 ± 3 ± 54 µb, σ(pp → D + X) = 402 ± 2 ± 30 µb, σ(pp → D + s X) = 170 ± 4 ± 16 µb, σ(pp → D * + X) = 421 ± 5 ± 36 µb, where the uncertainties are statistical and systematic, respectively. The LHCb collaboration 36 IntroductionMeasurements of charm production cross-sections in proton-proton collisions are important tests of perturbative quantum chromodynamics [1][2][3][4]. Predictions of charm meson cross-sections have been made at next-to-leading order using the generalised mass variable flavour number scheme (GMVFNS) [3,[5][6][7][8][9] and at fixed order with next-to-leading-log resummation (FONLL) [1,2,[10][11][12][13]. These are based on a factorisation approach, where the cross-sections are calculated as a convolution of three terms: the parton distribution functions of the incoming protons; the partonic hard scattering rate, estimated as a perturbative series in the coupling constant of the strong interaction; and a fragmentation function that parametrises the hadronisation of the charm quark into a given type of charm hadron. Predictions are also obtained from Monte Carlo programs implementing NLO perturbative QCD, where the partonic final state is matched to parton shower simulations [1]. The range -1 - JHEP06(2017)147of rapidity, y, and of the momentum component transverse to the beam axis, p T , accessible to the LHCb experiment enables quantum chromodynamics calculations to be tested in a region where the momentum fraction, x, of the initial state partons can reach values below 10 −4 . In this region the uncertainties on the gluon density function are large, exceeding 30% [1,14], and LHCb measurements can be used to constrain it. This paper presents measurements of charm hadron production cross-sections at a proton-proton centre-of-mass energy of √ s = 5 TeV. Ratios of cross-sections at different √ s benefit from cancellations in experimental uncertainties on the measured cross-sections as well as theoretical uncertainties on the predictions [2], allowing for precise comparisons. Measurements of charm production cross-sections in pp collisions at √ s = 5 TeV also define the reference for the determination of nuclear modification factors in heavy ion collisions at that nucleon-nucleon centre-of-mass energy, recorded in 2015 at the Large Hadron Collider (LHC).Measurements of charm pro...

Study of prompt D 0 meson production in pPb collisions at s N N = 5 $$ \sqrt{s_{\mathrm{N}\;\mathrm{N}}}=5 $$ TeV

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