Abstract
We present results for fluctuations of the baryon number for QCD at nonzero temperature and chemical potential. These are extracted from solutions to a coupled set of truncated Dyson-Schwinger equations for the quark and gluon propagators of Landau-gauge QCD with $N_f = 2 + 1$ quark flavors, that has been studied previously. We discuss the changes of fluctuations and ratios thereof up to fourth order for several temperatures and baryon chemical potential up to and beyond the critical endpoint. In the context of preliminary STAR data for the skewness and kurtosis ratios, the results are compatible with the scenario of a critical endpoint at large chemical potential and slightly offset from the freeze-out line. We also discuss the caveats involved in this comparison.
Highlights
Extracting the location of a putative critical endpoint (CEP) of QCD from heavy-ion collisions is one of the major goals of the Beam Energy Scan (BES) program [1,2] at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and the future Compressed Baryonic Matter (CBM) experiment [3] at the Facility for Antiproton and Ion Research (FAIR).Theoretically it is by no means clear that such a critical endpoint exists
Model calculations suggest that the continuous crossover becomes steeper with increasing chemical potential and merges into a second-order CEP followed by a region of a first-order phase transition at
We present our updated result for the QCD phase diagram with Nf 1⁄4 2 þ 1 quark flavors, which closely resembles the one already published in Refs. [26,29]
Summary
Extracting the location of a putative critical endpoint (CEP) of QCD from heavy-ion collisions is one of the major goals of the Beam Energy Scan (BES) program [1,2] at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and the future Compressed Baryonic Matter (CBM) experiment [3] at the Facility for Antiproton and Ion Research (FAIR). [22,23] for review articles This notion is supported by results from Dyson-Schwinger equations [24,25,26,27,28], see Ref. Various ratios of cumulants of these conserved quantities can be extracted from experiment in event-by-event analyses and compared to corresponding ratios of fluctuations that can be determined in theoretical calculations, see, e.g., Refs. Results for QCD with heavy quarks and at physical quark masses (Nf 1⁄4 2 þ 1 and Nf 1⁄4 2 þ 1 þ 1) but zero chemical potential agree with corresponding lattice results, see Ref. This work is organized as follows: In Sec. II we detail our method to extract fluctuations from the quark propagator and derivatives thereof.
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