Séminaire spécialisé

jeudi 15 mai 2014 à 16:00

Amphi G. Besse

Quarkonia suppression in a quark gluon plasma produced in high energies heavy ion collisions

Roland Katz

Subatech (groupe Théorie)

The six quarks and antiquarks are the fundamental bricks of matter that build up composite particles called hadrons. The most famous and stable of which are the protons and neutrons, the components of atomic nuclei. More unstable hadrons like the
quarkonia (bound states of heavy quark/antiquark pairs) can also be produced in high energy particle colliders (e.g. LHC). Via the exchange of gluons, the strong interaction confines the quarks and antiquarks within the hadron and makes them impossible to be
observed independently. The theory of elementary particles (Standard Model) predicts the existence of a new state of matter where the quarks and gluons are deconfined: the Quark-Gluon Plasma (QGP). The latter may have existed at the first moments of the
Universe after the Big Bang and can, in theory, be re-produced in heavy ion collisions at high energy colliders. As the QGP life-time (~10-21 s) and size (~ 10-15 m) are really small in these experiments, proving its existence and describing its properties are quite a
challenge. One of the QGP possible indirect observables is the suppression of the quarkonia, i.e. a characteristic decrease of the detected amount of quarkonia in comparison to proton-proton collisions, in which no QGP production is possible. This suppression has indeed been observed experimentally, but is still poorly understood. Treating the heavy quark/antiquark pair as an open quantum system, we study its fate inside an hydrodynamic QGP, by considering its binding potential and some thermalisation processes via Langevin stochastic forces.