Curvature of the chiral pseudocritical line in QCD

Abstract

We determine the curvature of the pseudocritical line of strong interactions by means of numerical simulations at imaginary chemical potentials. We consider Nf=2+1 stout improved staggered fermions with physical quark masses and the tree level Symanzik gauge action, and explore two different sets of lattice spacings, corresponding to temporal extensions Nt=6 and Nt=8. Both the renormalized chiral condensate and the renormalized chiral susceptibility are used to locate the transition. The determinations obtained from the two quantities are in good agreement, a preliminary continuum extrapolation yields κ=0.013(2)(1). We also investigate the impact of a nonzero strange quark chemical potential and compare our results to previous determinations in the literature, discussing the possible sources of systematic errors affecting the various procedures

Curvature of the QCD chiral pseudocritical line from analytic continuation

“…In the spirit of analytic continuation, this information could give hints for or against a critical point for real chemical potential. While our data don't show any influence of a possible endpoint nearby, it must be said that the Roberge-Weiss endpoint (which, in the setup with µ s = 0, lies at µ l,I /(πT ) ∼ 0.45 [7]) seems not to have any influence on these quantities either.…”

“…For finite size effects, we refer to the analysis already done in a previous study [7]. In that work, using data coming from N t = 6 lattices, we have shown that finite size effects are negligible on lattices having aspect ratio ≥ 4.…”

“…For small values of µ B it has also been possible to study T c (µ B ) at the physical point with two main methods to circumvent the sign problem, namely the Taylor expansion approach [1,2,3] and analytic continuation from an imaginary chemical potential [4], which was recently employed in [5,6] and in the work presented here [7]. Given the invariance of QCD under charge conjugation and expecting analyticity in µ B , the behaviour of T c with µ B should be of the form 1) where, in the last part of the equation, the imaginary baryon chemical potential µ B,I = −iµ B has been introduced.…”

“…In order to do this, we tuned the quark masses as a function of β following the line of constant physics obtained in [11] (see [7] for details).…”

Influence of magnetic fields on the color screening masses

“…[7][8][9]. In recent lattice studies [10,11] it has been shown that the potential gets modified and relevant consequences may arise at the level of heavy meson production and spectrum (see [12,13] and the references herein). In particular, at zero temperature the interaction becomes anisotropic due to the string tension σ which decreases in the direction parallel to the external field B, while it grows on the orthogonal plane; at larger T , in the confined regime below the pseudo-critical temperature T c , the external field is responsible of a precocious loss of the deconfining properties, in agreement with the picture of a decreasing T c due to the field itself.…”