Prompt D-0, D+, and D*(+) production in Pb-Pb collisions at root S-NN=5.02 TeV

The production of prompt D-0, D+, and D*(+) mesons was measured at midrapidity (vertical bar y vertical bar < 0.5) in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair root S-NN = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decay channels and their production yields were measured in central (0-10%) and semicentral (30-50%) collisions. The measurement was performed up to a transverse momentum (p(T)) of 36 or 50 GeV/c depending on the D meson species and the centrality interval. For the first time in Pb-Pb collisions at the LHC, the yield of D-0 mesons was measured down to p(T) = 0, which allowed a model-independent determination of the p(T)-integrated yield per unit of rapidity (dN/dy). A maximum suppression by a factor 5 and 2.5 was observed with the nuclear modification factor (R-AA) of prompt D mesons at p(T) = 6-8 GeV/c for the 0-10% and 30-50% centrality classes, respectively. The D-meson R-AA is compared with that of charged pions, charged hadrons, and J/psi mesons as well as with theoretical predictions. The analysis of the agreement between the measured R-AA, elliptic (v(2)) and triangular (v(3)) flow, and the model predictions allowed us to constrain the charm spatial diffusion coefficient D-s. Furthermore the comparison of R-AA and v(2) with different implementations of the same models provides an important insight into the role of radiative energy loss as well as charm quark recombination in the hadronisation mechanisms.Peer reviewe

Forward rapidity J/psi production as a function of charged-particle multiplicity in pp collisions at root s=5.02 and 13 TeV

The production of J/psi is measured as a function of charged-particle multiplicity at forward rapidity in proton-proton (pp) collisions at center-of-mass energies root s = 5.02 and 13 TeV. The J/psi mesons are reconstructed via their decay into dimuons in the rapidity interval (2.5 ), at both the colliding energies. Measurements are compared with available ALICE results at midrapidity and theoretical model calculations. First measurement of the mean transverse momentum () of J/psi in pp collisions exhibits an increasing trend as a function of dN(ch)/d eta/ showing a saturation towards high charged-particle multiplicities.Peer reviewe

Investigating charm production and fragmentation via azimuthal correlations of prompt D mesons with charged particles in pp collisions at root s=13 TeV

Angular correlations of heavy-flavour and charged particles in high-energy proton-proton collisions are sensitive to the production mechanisms of heavy quarks and to their fragmentation as well as hadronisation processes. The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in proton-proton collisions at a centre-of-mass energy of root s = 13 TeV with the ALICE detector is reported, considering D-0, D+, and D*(+) mesons in the transverse-momentum interval 3 0.3 GeV/c and pseudorapidity vertical bar eta vertical bar < 0.8. This measurement has an improved precision and provides an extended transverse-momentum coverage compared to previous ALICE measurements at lower energies. The study is also performed as a function of the charged-particle multiplicity, showing no modifications of the correlation function with multiplicity within uncertainties. The properties and the transverse-momentum evolution of the near- and awayside correlation peaks are studied and compared with predictions from various Monte Carlo event generators. Among those considered, PYTHIA8 and POWHEG+PYTHIA8 provide the best description of the measured observables. The obtained results can provide guidance on tuning the generators.Peer reviewe

Measurement of inclusive charged-particle b-jet production in pp and p-Pb collisions at root S-NN =5.02 TeV

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Measurement of prompt D-s(+)-meson production and azimuthal anisotropy in Pb-Pb collisions at root s(NN)=5.02 TeV

The production yield and angular anisotropy of prompt D-s(+) mesons were measured as a function of transverse momentum (p(T)) in Pb-Pb collisions at a centre-of-mass energy per nucleon pair root s(NN) = 5.02 TeV collected with the ALICE detector at the LHC. D-s(+) mesons and their charge conjugates were reconstructed at midrapidity (vertical bar y vertical bar phi pi(+), with phi -> K-K+, in the p(T) intervals 2 10 GeV/c, the measured D-s(+)-meson nuclear modification factor R-AA is consistent with the one of non-strange D mesons within uncertainties, while at lower p(T) a hint for a D-s(+)-meson R-AA larger than that of non-strange D mesons is seen. The enhanced production of D-s(+) relative to non-strange D mesons is also studied by comparing the p(T)-dependent D-s(+)/D-0 production yield ratios in Pb-Pb and in pp collisions. The ratio measured in Pb-Pb collisions is found to be on average higher than that in pp collisions in the interval 2 < p(T) < 8 GeV/c with a significance of 2.3 sigma and 2.4 sigma for the 0-10% and 30-50% centrality intervals. The azimuthal anisotropy coefficient v(2) of prompt D-s(+) mesons was measured in Pb-Pb collisions in the 30-50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured R-AA, D-s(+)/D-0 ratio, and v(2) as a function of p(T) are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark-gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The p(T)-integrated production yield of D-s(+) mesons is compatible with the prediction of the statistical hadronisation model. (c) 2022 European Organization for Nuclear Research, ALICE. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).Peer reviewe

Production of light (anti)nuclei in pp collisions at root s=13 TeV

Understanding the production mechanism of light (anti)nuclei is one of the key challenges of nuclear physics and has important consequences for astrophysics, since it provides an input for indirect dark-matter searches in space. In this paper, the latest results about the production of light (anti)nuclei in pp collisions at root s = 13TeV are presented, focusing on the comparison with the predictions of coalescence and thermal models. For the first time, the coalescence parameters B-2 for deuterons and B-3 for helions are compared with parameter-free theoretical predictions that are directly constrained by the femtoscopic measurement of the source radius in the same event class. A fair description of the data with a Gaussian wave function is observed for both deuteron and helion, supporting the coalescence mechanism for the production of light (anti)nuclei in pp collisions. This method paves the way for future investigations of the internal structure of more complex nuclear clusters, including the hypertriton.Peer reviewe

First study of the two-body scattering involving charm hadrons

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Production of light (anti)nuclei in pp collisions at √s=5.02 TeV

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Observation of a multiplicity dependence in the p(T)-differential charm baryon-to-meson ratios in proton-proton collisions at root s=13 TeV

The production of prompt D-0, D-s(+) and Lambda(+)(c) hadrons, and their ratios, D-s(+)/D-0 and Lambda(+)(c)/D-0, are measured in proton-proton collisions at root s = 13 TeV at midrapidity (vertical bar y vertical bar < 0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (p(T)) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange D-s(+)/D-0 ratio indicates no significant multiplicity dependence, the baryon-to-meson P-T-differential Lambda(+)(c)/D-0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3 sigma for 1 < p(T) < 12 GeV/c, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The Lambda(+)(c)/D-0 ratios as a function of p(T) present a similar shape and magnitude as the Lambda/K-s(0) ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charmhadron formation, with analogous multiplicity dependence. The p(T)-integrated ratios, extrapolated down to p(T) = 0, do not show a significant dependence on multiplicity within the uncertainties. (C) 2022 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe

Measurement of beauty production via non-prompt D-0 mesons in Pb-Pb collisions at root s(NN)=5.02 TeV

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