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FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

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Chiral hadronic model including resonances<br />

Collaborators: Philip Rau 1,2 , Jan Steinheimer 1 , Stefan Schramm 1 , Horst Stöcker 1,3<br />

1 <strong>FIAS</strong>, 2 Institut für Theoretische Physik, Goethe Universität <strong>Frankfurt</strong>, 3 GSI - Helmholtzzentrum für Schwerionen-<br />

<strong>for</strong>schung, Darmstadt.<br />

We extended the existing effective chiral flavour SU(3) model <strong>for</strong> the QCD equation of state which was developed<br />

in <strong>Frankfurt</strong> over the last years to include all hadronic resonances up to masses of m ≤ 2.6 GeV. All<br />

particles are coupled to the scalar σ-field and the vector ω-field. We introduce a parameter rv controlling the<br />

coupling strength to the repulsive vector fields and thus primarily affecting the particles’ abundancies. There<strong>for</strong>e,<br />

by varying rv we are able to study the impact of heavier resonances on the phase diagram of strongly<br />

interacting matter with particular interest on the chiral phase transition.<br />

By studying the thermodynamic properties of our model we observe a good agreement to latest continuum<br />

extrapolated lattice data if we chose a physically reasonable vector coupling close to one. This finding is<br />

supported by our results <strong>for</strong> the susceptibilities of conserved charges on the phase transition which are again<br />

comparable to lattice QCD <strong>for</strong> rv ∼ 1. However, in this case our model rules out a first order phase transition in<br />

favour of a smooth cross over transition not only at vanishing baryochemical potentials µB = 0 but in the whole<br />

µB-regime ruling out the postulated existence of a critical end point.<br />

T [MeV]<br />

200<br />

180<br />

160<br />

140<br />

120<br />

100<br />

isentropes, r v =0.9<br />

5A GeV<br />

10A GeV<br />

20A GeV<br />

30A GeV<br />

40A GeV<br />

80<br />

60<br />

40<br />

20<br />

0<br />

0<br />

isentropes <strong>for</strong><br />

EoS with rv =0.9<br />

200 400 600<br />

PT line<br />

<strong>for</strong> rv =0.4<br />

PT at T=0 <strong>for</strong><br />

rv =0.8 rv =1.0<br />

800 1000 1200 1400 1600 1800<br />

µ B [MeV]<br />

χ s /T 2<br />

0.8<br />

0.7<br />

0.6<br />

0.5<br />

0.4<br />

0.3<br />

0.2<br />

0.1<br />

0<br />

r s = 0.97, µ B = 0<br />

int. HRG<br />

HRG<br />

p4, N τ = 8<br />

asqtad, N τ =12<br />

hisq, N τ =8<br />

stout, cont.<br />

130 140 150 160 170 180 190 200 210 220<br />

T [MeV]<br />

a): QCD phase diagram from our model with isentropes <strong>for</strong> various beam energies <strong>for</strong> a vector coupling rv ∼ 1<br />

where there is only a broad crossover phase transition. The shown phase transition line depicts the situation <strong>for</strong><br />

the lowest reasonable coupling strength rv = 0.4. b): Strange quark susceptibility from our model at µB = 0<br />

(blue dashed line) compared to lattice QCD results from various lattice actions. Good agreement is obtained<br />

with latest continuum extrapolated data up to the critical temperature Tc.<br />

Related publications in <strong>2011</strong>:<br />

1) P. Rau, J. Steinheimer, S. Schramm and H. Stöcker, Baryon resonances in a chiral hadronic model <strong>for</strong> the<br />

qcd equation of state, arXiv:1109.3621 [hep-ph], accepted by Phys. Rev. C.<br />

2) P. Rau, J. Steinheimer, S. Schramm and H. Stöcker, Resonance states in an effective chiral hadronic model,<br />

arXiv:1201.3834 [hep-ph].<br />

43

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