Rau, P.

Schramm, S.

Steinheimer, J.

Stöcker, H.

GSI Repository

QCD phase structure and conserved charge fluctuations in a chiral effectivemodel∗P. Rau1, J. Steinheimer1, S. Schramm1, and H. Sto¨cker22GSI, Darmstadt, Germany; 1FIAS, Goethe University, FrankfurtUsing the well-established chiral effective model forQCD matter, which includes all known hadrons up tom = 2.6 GeV and quarks, this study examines the phasestructure of QCD matter and fluctuations of conservedcharges focussing on the chiral and deconfinement phasetransition. At small baryochemical potentials the effectivemodel shows a smooth cross over in both order parametersand, at larger potentials, does not give indications for theexistence of a first order phase transition and a critical endpoint. Compared to lattice QCD and thermal model fits ofexperimental data the chiral transition from the effectivemodel is in line with recent data (Fig. 1).At the phase transition conserved charges show largefluctuations which can be measured by susceptibilitycoefficients χ. Baryon number fluctuations are largelysuppressed by the finite volume of hadrons and thesuppressive particle interactions with vector fields (Fig. 2).It shows that in the hadronic phase below Tc couplingstrengths are of the order of the nucleon couplings.However, in the quark sector above Tc, large fluctuationsfound in lattice QCD restrain quark vector couplings closeto zero and particles at T > Tc are almost acting like anideal gas. With this model a realistic equation of statehas been compiled which can be used for studying heavyion collisions in dynamic models as well as neutron starproperties.lattice Tc(μB): PRD83, 014504 (2011)Cleymans: PRC73, 034905 (2006)Andronic: PLB673, 142 (2009)chiral model: PRC85, 025204 (2012)ALICE: NPA904, 535c (2013)STAR: PRC79, 034909 (2009)NA49: PRC85, 044921 (2012) 100 110 120 130 140 150 160 170 0  50  100  150  200  250  30020013062.417.32760μB [MeV]T [MeV]Figure 1: Chiral transition at small μB from lattice QCD(gray band) and from the chiral model (black line) con-trasted to freeze-out curves from statistical and thermalmodel fits for SPS to LHC energies (√sNN in GeV).∗Work supported by HIC4FAIR 0 0.1 0.2 0.3 50  100  150  200  250  300  350χ2B/T2T [MeV]SB limitHRGint. HRG+q, gqv=0int. HRG+q, gqv=4HISQ, cont.stout, cont.μB = 0Figure 2: Second-order baryon number susceptibility of thehadron resonance gas (black line) and of the full modelincluding hadrons and quarks (blue lines). Strong vectorcouplings suppress fluctuations and the Stefan-Boltzmannlimit at high T may only be reached for vanishing quarkvector couplings gqv (dashed blue line).Related publications in 2013:1. P. Rau, J. Steinheimer, S. Schramm and H. Sto¨cker,Chiral Hadronic Mean Field Model including QuarkDegrees of Freedom, J. Phys. G 40, 085001 (2013).2. P. Rau, J. Steinheimer, S. Schramm and H. Sto¨cker,Conserved Charge Fluctuations in a Chiral HadronicModel including Hadrons and Quarks, arXiv:1308.4319[hep-ph] (to be published in PLB).THEORY-10 GSI SCIENTIFIC REPORT 2013262 doi:10.15120/GR-2014-1-THEORY-10

QCD phase structure and conserved charge fluctuations in a chiral effective model

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QCD phase structure and conserved charge fluctuations in a chiral effective model

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