Marco Monteno

Heavy flavors in AA collisions: production, transport and final spectra

A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (AA) collisions—addressing within a comprehensive framework the initial

Heavy-flavour production in high-energy d-Au and p-Pb collisions

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Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC

production, the propagation in the hot medium until decoupling and the final hadronization and decays—is presented. The initial hard production of

Development of heavy-flavour flow-harmonics in high-energy nuclear collisions

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LANGEVIN DYNAMICS OF HEAVY FLAVORS IN RELATIVISTIC HEAVY-ION COLLISIONS

pairs is simulated using the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. Outcomes of the calculations are compared to experimental data in pp collisions and are used as a validated benchmark for the study of medium effects. In the AA case, the propagation of the heavy quarks in the medium is described in a framework provided by the relativistic Langevin equation. For the latter, different choices of transport coefficients are explored (either provided by a perturbative calculation or extracted from lattice-QCD simulations) and the corresponding numerical results are compared to experimental data from RHIC and the LHC. In particular, outcomes for the nuclear modification factor RAA and for the elliptic flow v2 of D/B mesons, heavy-flavor electrons and non-prompt J/ψ’s are displayed.

Heavy-flavour dynamics in proton-proton and nucleus-nucleus collisions at LHC

A bstractSoft-hadron measurements in high-energy collisions of small systems like p-Pb and d-Au show peculiar qualitative features (long-range rapidity correlations, flattening of the pT -spectra with increasing hadron mass and centrality, non-vanishing Fourier harmonics in the azimuthal particle distributions) suggestive of the formation of a strongly-interacting medium displaying a collective behaviour, with a hydrodynamic flow as a response to the pressure gradients in the initial conditions. Hard observables (high-pT jet and hadron spectra) on the other hand, within the current large systematic uncertainties, appear only midly modified with the respect to the benchmark case of minimum-bias p-p collisions. What should one expect for heavy-flavour particles, initially produced in hard processes but tending, in the nucleus-nucleus case, to approach kinetic equilibrium with the rest of the medium? This is the issue we address in the present study, showing how the current experimental findings are compatible with a picture in which the formation of a hot medium even in proton-nucleus collisions modifies the propagation and hadronization of heavy-flavour particles.

Heavy-flavour transport: from large to small systems

The stochastic dynamics of c and b quarks in the fireball created in nucleus-nucleus collisions at RHIC and LHC is studied employing a relativistic Langevin equation, based on a picture of multiple uncorrelated random collisions with the medium. Heavy-quark transport coefficients are evaluated within a pQCD approach, with a proper HTL resummation of medium effects for soft scatterings. The Langevin equation is embedded in a multi-step setup developed to study heavy-flavor observables in pp and AA collisions, starting from a NLO pQCD calculation of initial heavy-quark yields, complemented in the nuclear case by shadowing corrections, k_T-broadening and nuclear geometry effects. Then, only for AA collisions, the Langevin equation is solved numerically in a background medium described by relativistic hydrodynamics. Finally, the propagated heavy quarks are made hadronize and decay into electrons. Results for the nuclear modification factor R_AA of heavy-flavor hadrons and electrons from their semi-leptonic decays are provided, both for RHIC and LHC beam energies.

Heavy flavours in high-energy nuclear collisions: quenching, flow and correlations

A bstractWe employ the POWLANG transport setup, developed over the last few years, to provide new predictions for several heavy-flavour observables in relativistic heavy-ion collisions from RHIC to LHC center-of-mass energies. In particular, we focus on the development of the flow-harmonics v2 and v3 arising from the initial geometric asymmetry in the initial conditions and its associated event-by-event fluctuations. Within the same transport framework, for the sake of consistency, we also compare the nuclear modification factor of the pT spectra of charm and beauty quarks, heavy hadrons and their decay electrons. We compare our findings to the most recent data from the experimental collaborations. We also study in detail the contribution to the flow harmonics from the quarks decoupling from the fireball during the various stages of its evolution: although not directly accessible to the experiments, this information can shed light on the major sources of the final measured effect.

Heavy flavor in nucleus-nucleus and proton-nucleus: quenching, flow and correlations

We study the stochastic dynamics of c and b quarks, produced in hard initial processes, in the hot medium created after the collision of two relativistic heavy ions. This is done through the numerical solution of the relativistic Langevin equation. The latter requires the knowledge of the friction and diffusion coefficients, whose microscopic evaluation is performed treating separately the contribution of soft and hard collisions. The evolution of the background medium is described by ideal/viscous hydrodynamics. Below the critical temperature the heavy quarks are converted into hadrons, whose semileptonic decays provide single-electron spectra to be compared with the current experimental data measured at RHIC. We focus on the nuclear modification factor RAA and on the elliptic-flow coefficient v2, getting, for sufficiently large pT, a reasonable agreement.

Heavy-flavor flow-harmonics in high-energy nuclear collisions: time-development and eccentricity fluctuations

We present recent results for heavy-quark observables in nucleus-nucleus collisions at LHC energies, obtained by the POWLANG transport setup. The initial creation of cc¯ and bb¯ pairs is simulated with a perturbative QCD approach (POWHEG+PYTHIA) and validated through comparison to experimental data of proton-proton collisions. In the nucleus-nucleus case, the propagation of the heavy quarks in the plasma is studied with the relativistic Langevin equation, here solved using weak-coupling transport-coefficients. Successively, the heavy quarks hadronize in the medium. We compute the nuclear modification factor RAA and the elliptic flow v2 of the final D mesons, as well as D – h correlations, and compare our results to experimental data from the ALICE and CMS Collaborations.