Speaker
Maciej Rybczynski
(Jan Kochanowski University (PL))
Description
The exploration of the QCD phase diagram particularly the search for a phase transition from hadronic to partonic degrees of freedom and possibly a critical endpoint, is one of the most challenging tasks in present heavy-ion physics. As observed by the NA49 experiment, several hadronic observables in central Pb+Pb collisions at the CERN SPS show qualitative changes in their energy dependence. These features are not observed in elementary interactions and indicate the onset of a phase transition in the SPS energy range [1,2].
The existence of a critical point is expected to result in the increase of event-by-event fluctuations of various hadronic observables [3,4] provided that the freeze-out of the measured hadrons occurs close to its location in the phase diagram and the evolution of the final hadron phase does not erase the fluctuations
signals. A selection of NA49 results on particle multiplicity, transverse momentum, azimuthal angle fluctuations and the proton intermittency from the scan of the phase diagram will be presented and discussed [5,6].
A new technique to study fluctuations of the chemical composition of the hadronic system produced in nuclear collisions, the identity method, will be introduced and its properties will be discussed. Preliminary results from Pb+Pb collisions registered by the NA49 experiment at the CERN SPS will be shown.
References:
[1] C. Alt et al., Phys. Rev. C 77 (2008) 024903
[2] M. Gazdzicki et al., J. Phys. G 30 (2004) S701
[3] M.A.Stephanov,K.Rajagopal,E.V.Shuryak, Phys.Rev. D 60, 114028 (1999).
[4] B.Berdnikov,K.Rajagopal, Phys. Rev. D 61, 105017 (2000).
[5] T.Anticic et al., Phys. Rev. C 79, 044904 (2009).
[6] C.Alt et al., Phys. Rev. C 78, 034914 (2008).
Author
Maciej Rybczynski
(Jan Kochanowski University (PL))
