Abstract:
In nucleus–nucleus collisions at ultra-relativistic energies, a new kind of matter is created: the Quark–Gluon Plasma. Peter Braun-Munzinger, Anar Rustamov, and Johanna Stachel report on the phase diagram of hadronic matter at high temperature and low net baryon density. A connection is made between the experimentally determined chemical freeze-out points and the pseudo-critical temperature for the chiral crossover transition computed in lattice QCD. The role of fluctuations giving experimental access to the nature of the chiral phase transition will be summarized. Azimuthal anisotropies of hadron distributions show that the Quark–Gluon Plasma formed in high-energy collisions is strongly coupled, allowing us to deduce bulk and shear viscosities. In the hot and dense plasma, partons lose a large fraction of their energy, and this observation leads to the determination of another medium parameter: a jet transport coefficient. Quarkonia and their role as a probe of deconfinement form the final topic of their contribution.
The phase structure of strongly interacting matter at low temperature and high density is discussed by Kenji Fukushima. In this region of the phase diagram that is probed, for example, in neutron stars, different phases and phase transitions are expected on theoretical grounds. Astrophysical observations and the observation of gravitational waves lead to important constraints for calculations modeling the transitions into a quarkyonic regime, into quark matter, or color-superconducting states. The theoretical challenges to locate a conjectured critical end point in the QCD phase diagram are discussed.
P. Braun-Munzinger, A. Rustamov, J. Stachel, „QCD under extreme conditions“, Eur.Phys.J.C
83, 1125 (2023).
https://link.springer.com/article/10.1140/epjc/s10052-023-11949-2
Related to Project A01, A02, C05, C06