The J/ψ mesons are reconstructed in the e+e- decay channel and the measurements are performed at midrapidity. The pT-differential inclusive J/ψ production cross sections are measured in the pT range 0 < pT < 40 GeV/c. The high momentum reach was achieved thanks to the ALICE electromagnetic calorimeter trigger, which allows the measurement of electrons at high pT. Several calculations within the NRQCD framework and the ICEM approach are compared with the measurement, providing a reasonable description of the measurements within the theoretical uncertainties over the entire pT range.
The ALICE detector is capable of separating at midrapidity prompt and non-prompt J/ψ mesons, the latter originating from the decays of beauty hadrons, down to very low transverse momentum. Starting from non-prompt J/ψ cross section measurements, the beauty quark production cross sections at midrapidity can be extrapolated down to pT = 0. The ALICE results are found to be consistent with similar measurements from lower energy experiments. Both FONLL and NNLO calculations are in agreement with the data, considering the uncertainties. The NNLO calculations are slightly higher than FONLL and have lower uncertainties, resulting in a general better description of the experimental data points.
Figure on the left shows Inclusive J/ψ production cross section compared with the corresponding calculations obtained as the sum of the prompt J/ψ component (obtained using ICEM, NLO NRQCD or LO NRQCD+CGC) and the non-prompt contribution from FONLL. The bottom panel shows the ratios between the model calculations and a fit to the data points.
Figure on the right shows the dσbb/dy at midrapidity as a function of the centre-of-mass energy. The ALICE measurement at √s = 5.02 TeV corresponds to the weighted average of non-prompt D mesons and non-prompt J/ψ. Results from dielectron measurements from the ALICE collaboration, obtained using either PYTHIA or POWHEG simulations, are also shown. FONLL and NNLO calculations in the rapidity range |y|< 0.9, with the corresponding uncertainty bands, are superimposed.
Further reading:
ALICE Collaboration, arXiv:2108.01906
ALICE Collaboration, arXiv:2108.02523