We determine the (pseudo)critical lines of QCD with two degenerate staggered fermions at nonzero temperature and quark or isospin density, in the region of imaginary chemical potentials; analytic continuation is then used to prolongate to the region of real chemical potentials. We obtain an accurate determination of the curvatures at zero chemical potential, quantifying the deviation between the case of finite quark and of finite isospin chemical potential. Deviations from a quadratic dependence of the pseudocritical lines on the chemical potential are clearly seen in both cases: we try different extrapolations and, for the case of nonzero isospin chemical potential, confront them with the results of direct Monte~Carlo simulations. Finally we find that, as for the finite quark density case, an imaginary isospin chemical potential can strengthen the transition until turning it into strong first order.

The production of forward jets separated by a large rapidity gap at LHC, the so-called Mueller–Navelet jets, is a fundamental testfield for perturbative QCD in the high-energy limit. Several analyses...

We determine the continuum limit of the curvature of the pseudocritical line of QCD with $n_f=2+1$ staggered fermions at nonzero temperature and quark density. We perform Monte Carlo simulations at imaginary baryon chemical potentials with Highly Improved Staggered Quarks (HISQ), adopting the HISQ/tree action discretization as implemented in the code by the MILC Collaboration. Couplings are adjusted so as to move on a line of constant physics, as determined in Ref. [1], with the strange quark mass $m_s$ fixed at its physical value and a light-to-strange mass ratio $m_l/m_s=1/20$. The chemical potential is set at the same value for the three quark species, ${\mu }_l={\mu }_s\equiv \mu$. We attempt an extrapolation to the continuum using the results on lattices with temporal size up to $L_t=12$. Our estimate for the continuum value of the curvature $\kappa$ at zero baryon density, $\kappa =0.020(4)$, is compared with recent lattice results and with experimental determinations of the freeze-out curve.

We study the production of Mueller–Navelet jets at 13 TeV LHC, within collinear factorization and including the BFKL resummation of energy l