Speaker
Christian Schmidt
(University of Bielefeld)
Description
We analyze cumulant ratios of net-baryon number fluctuations
calculated in (2+1)-flavor QCD in next-to-leading order (NLO) Taylor
expansions in terms of temperature and the conserved charge chemical
potentials for baryon number, strangeness and electric charge. We
approximate the conditions met in heavy ion collision by enforcing
strangeness neutrality and a constant baryon number to electric charge
ratio. We show that fourth-order results are sufficient to model dense
matter created in heavy ion collisions with center-of-mass energies
down to $s^{1/2}_{NN} \sim 20 GeV$ and use Sixth-order results to
estimate truncation errors. We discuss to what extent the pattern seen
in the RHIC beam energy scan of up to 4th order cumulants of electric
charge and proton (baryon) number fluctuations can be understood in
terms of QCD equilibrium thermodynamics.
The results are based on lattice calculations performed with the
Highly Improved Staggered Quark action (HISQ) in the temperature range
140 MeV < T < 330 MeV, with lattice sizes 24^3 \times 6, 32^3
\times 8 and 48^3 \times 12. The strange quark mass is tuned to its
physical value and we use a strange to light quark mass ratio m_s/m_l
= 20, which in the continuum limit corresponds to a pion mass of
about 160 MeV.
Author
Christian Schmidt
(University of Bielefeld)
