Speaker
Zaida Conesa del Valle
(IPN Orsay (CNRS/IN2P3 - Université Paris-Sud))
Description
The experimental laboratory to create and study strongly interacting matter under extreme conditions of temperature and energy density are ultra-relativistic heavy-ion collisions. A transition of hadronic matter to a Quark Gluon Plasma (QGP) phase is predicted by lattice Quantum ChromoDynamics for high enough temperatures. Heavy quarks (charm and beauty) and quarkonia are produced in the early stages of the interaction and probe the entire medium evolution. Their production has been measured in heavy-ion collisions at the LHC with the ALICE detector.
Open heavy-flavour production is affected by heavy-quark in-medium energy loss. Heavy-flavour hadron spectra are modified in the most central Pb--Pb collisions at a centre-of-mass energy $\sqrt{s_{NN}}=2.76$ TeV per nucleon--nucleon pair, with respect to those of pp collisions at the same energy. The second harmonic of the azimuthal distribution Fourier decomposition, $v_2$, of heavy-flavour hadrons is positive for non-central collisions at intermediate transverse momentum, suggesting that heavy quarks take part in the system collective motion.
A small fraction of heavy quarks ends up forming quarkonia ($J/\psi$, $\psi^{\prime}$, $\Upsilon$). The inclusive $p_{\rm T}$-integrated $\Jpsi$ yield is suppressed in the most central Pb--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV, with respect to that of pp collisions at the same energy. The comparison of these results with the measurements performed at RHIC energies, suggests that mechanisms for both breaking-up or recombining the heavy-quark bound states are at play at the LHC. The measurements of heavy-flavour hadrons in p--Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV demonstrate that the medium modifications observed in Pb-Pb collisions are not dominated by effects due to the presence of cold nuclear matter but have to be attributed to genuine effects due to the formation of a hot and dense QGP phase.
Heavy-flavour hadron measurements with the ALICE detector will be presented. The results in Pb--Pb and p--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV and 5.02 TeV, respectively, will be discussed.
Primary author
Zaida Conesa del Valle
(IPN Orsay (CNRS/IN2P3 - Université Paris-Sud))