Eventi INFN Sezione di Bari

Both in the primordial Universe and in heavy-ion collisions for a very short time interval the produced matter is so hot to be a soup of elementary particles.
This also holds for the microscopic QCD degrees of freedom –quarks, antiquarks and gluons — no longer (not yet) confined into color-neutral structures, but free to carry and exchange color over distances larger than the typical hadronic size.
Later on, both in the early Universe and in heavy-ion experiments, the temperature drops until the hot QCD matter undergoes a smooth transition to a color-confined phase and the system becomes a fluid of ordinary hadrons. Hence, how to infer the existence of the above deconfined phase experienced by the system if in heavy-ion experiments the only strongly-interacting particles reaching the detectors are hadrons? The situation looks even worse in cosmology, where the first experimental signals refer to 380.000 years after this QCD transition. As already done at the beginning of the XX century in discovering the granular structure of matter, the application of transport theory to describe the random motion of Brownian particles allows one to get rich information also on what cannot be directly seen.

More than 100 years after the works of Einstein and Perrin, the Brownian particles to which we are interested are no longer small grains of resin, but charm and beauty quarks, whose propagation in the deconfined fireball produced in nuclear collisions is described by a relativistic generalization of the Langevin equation.

In my seminar I will discuss which information on the properties of the hot QCD matter can be extracted from a theory-to-data comparison, stressing the systematic uncertainties intrinsic to the calculations or arising from hadronization, whose occurence in the presence of a reservoir of nearby color charges I will also try to model.

Speaker: Andrea Beraudo (INFN Torino)
4 Giugno 2025 ore 15:15 Aula A (Dipartimento di Fisica)

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