Speaker
Dr
Viktor Begun
(UJK)
Description
Statistical models of hadron production have become one of the cornerstones of our understanding of ultra-relativistic heavy-ion collisions [1]. However, the measured proton abundances in Pb+Pb collisions at sqrt(sNN) = 2.76 TeV at LHC do not agree with the most common versions of the thermal models. Besides the proton anomaly, the same LHC data exhibits the low-transverse-momentum enhancement of pion spectra by about 25-50% with respect to the predictions of various thermal and hydrodynamic models [2].
In the recent work [3] we connect the proton anomaly with the pion enhancement effect and show that the two problems may be solved naturally within the statistical model which assumes chemical non-equilibrium at the freeze-out and a special combination of freeze-out geometry and flow - the Krakow single-freeze-out model in the Monte-Carlo version implemented in THERMINATOR [4].
We find a remarkable agreement between our model and the measured transverse-momentum spectra of pions and kaons. Although the protons are not included in the fit, our model explains well their spectrum, in addition to their yield. We also find a satisfactory description of hyperons with the same parameters.
Correct description of the low-transverse-momentum enhancement of pions within our model suggests that it may be interpreted as a signature of the onset of pion condensation in ultra-relativistic heavy-ion collisions at the LHC energies. This is so, since the freeze-out conditions in the model are very close to the pion condensation point.
[1] P. Braun-Munzinger, D. Magestro, K. Redlich, J. Stachel, Phys. Lett. B 518, 41 (2001).
[2] B. Abelev et al. [ALICE Collaboration], Phys. Rev. Lett. 109, 252301 (2012); Phys. Rev. C 88, 044910 (2013).
[3] V. Begun, W. Florkowski, M. Rybczynski, arXiv:1312.1487 [nucl-th].
[4] M. Chojnacki, A. Kisiel, W. Florkowski and W. Broniowski, Comput. Phys. Commun. 183, 746 (2012).
Primary author
Dr
Viktor Begun
(UJK)
Co-authors
Maciej Rybczynski
(Jan Kochanowski University (PL))
Wojciech Florkowski
(Institute of nuclear Physics, Krakow)
