Speaker
Description
At finite baryon density, the nature of the QCD crossover and the possible existence of a critical endpoint (CEP) depend on which universality class governs the transition. In the analytic description of QCD thermodynamics in the complex $\mu_B$ plane in terms of Lee--Yang zeros, the crossover transition on the real $\mu_B$ axis is controlled by the Lee--Yang edge singularity closest to that axis. At low temperature and high density, the key question is whether this nearest singularity is associated with the chiral critical line or with a $Z(2)$ line emerging from a putative CEP.
We investigate this question using $(2+1)$-flavor lattice QCD simulations at $T!\simeq!108$~MeV, a temperature where several lattice and functional approaches place or bracket the CEP. From baryon-number fluctuations computed at imaginary baryon chemical potential, we extract the position of the Lee--Yang edge and map it to the real $(T,\mu_B)$ plane using scaling relations from the \emph{chiral} universality class. This yields a first-principles determination of the crossover line down to $T!\approx!108$~MeV without any input on the small-$\mu_B$ curvature. The resulting crossover band is consistent with existing lattice results at low $\mu_B$ and with phenomenological freeze-out curves from heavy-ion collisions.
The absence of a critical singularity on the real $\mu_B$ axis at $T!\simeq!108$~MeV, together with the success of the chiral mapping, indicates that the crossover boundary in this region is governed by chiral criticality, suggesting that any QCD critical endpoint, if it exists, should be located at temperatures below 108 MeV [1].
[1] D. A. Clarke, H.-T. Ding, J.-B. Gu, S.-T. Li, S. Mukherjee, P. Petreczky, C. Schmidt, H.-T. Shu, and K.-F. Ye, work in progress
| Is the talk given on behalf of the Collaboration? | no |
|---|---|
| Topic area | Critical Point |