Speaker
Description
Up to $6^{th}$ order cumulants of fluctuations of net baryon-number,
net electric charge and net strangeness as well as correlations among
these conserved charge fluctuations are now being calculated in lattice
QCD. These cumulants provide a wealth of information on the properties
of strong-interaction matter in the transition region from the low
temperature hadronic phase to the quark-gluon plasma phase.
We use results from our $6^{th}$ order Taylor expansion of the QCD equation
of state to construct expansions for second and fourth order cumulants
of conserved charges and their correlations, e.g. the second order cumulants
can be calculated up to ${\cal O} (\mu_B^4)$ in the baryon chemical
potential. We show that these low order cumulants strongly constrain the
applicability range of hadron resonance gas model calculations. We point
out that the latter is inappropriate to describe equilibrium properties
of cumulants at finite $\mu_B$ already at $T\sim 155$ MeV.
For vanishingly small baryon chemical potential, we show that fourth
order cumulant ratios calculated in QCD start to deviate from hadron
resonance gas model calculations already at about 155 MeV, and
the sixth order cumulants differ from HRG model calculations even earlier.
Even some second order cumulants like the correlations between net-baryon
number and net strangeness or net electric charge differ significantly at
temperatures above 155 MeV in QCD and HRG model calculations. Since these
cumulants are calculated at vanishing chemical potential they can be compared
to measurements at the LHC.
| Preferred Track | Correlations and Fluctuations |
|---|---|
| Collaboration | Other |
