Abstract
The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D^{0} mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of sqrt[s_{NN}]=86.6 and 110.4GeV, respectively. The J/ψ and D^{0} production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σ_{J/ψ}=652±33(stat)±42(syst) nb/nucleon and σ_{D^{0}}=80.8±2.4(stat)±6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.
Highlights
The argon with nucleon-nucleon center-of-mass energies of J=ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ=ψ 1⁄4 652 Æ 33ðstatÞ Æ 42ðsystÞ nb=nucleon and σD0 1⁄4 80.8 Æ 2.4ðstatÞ Æ 6.3ðsystÞ μb=nucleon, where the first uncertainty is statistical and the second is systematic
In the high-density and high-temperature regime of quantum chromodynamics (QCD), the production of heavy quarks in nucleus-nucleus interactions is well suited to study the transition between ordinary hadronic matter and the hot and dense quark-gluon plasma (QGP)
Heavy quarks are produced only in the early stages of the interaction, because their masses are significantly higher than the QGP critical temperature, Tc ∼ 156 MeV [1]
Summary
The mass distributions obtained after all selection criteria are applied to the entire pHe data set, with the fit functions superimposed. The systematic uncertainty related to the determination of the signal yields includes the contribution from b-hadron decays and the mass fit. The systematic uncertainty related to the mass fit is evaluated using alternative models for signal and background shapes that reproduce the mass shapes well Another source of uncertainty is associated with the accuracy of the simulation used to compute the acceptances and efficiencies. This systematic uncertainty includes the statistical uncertainty due to the finite size of the simulation sample and the differences in the distributions of the transverse momentum and rapidity between data and simulation. The cccross section shows a small tension with respect to theoretical calculations as already observed at 200 GeV, while the J=ψ cross-section measurement is in
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