Observation of deconfinement in a cold dense quark medium

Abstract

In this paper we study the confinement/deconfinement transition in lattice SU(2) QCD at finite quark density and zero temperature. The simulations are performed on an 324 lattice with rooted staggered fermions at a lattice spacing a = 0.044 fm. This small lattice spacing allowed us to reach very large baryon density (up to quark chemical potential μq > 2000 MeV) avoiding strong lattice artifacts. In the region μq ∼ 1000 MeV we observe for the first time the confinement/deconfinement transition which manifests itself in rising of the Polyakov loop and vanishing of the string tension σ. After the deconfinement is achieved at μq > 1000 MeV, we observe a monotonous decrease of the spatial string tension σs which ends up with σs vanishing at μq > 2000 MeV. From this observation we draw the conclusion that the confinement/deconfinement transition at finite density and zero temperature is quite different from that at finite temperature and zero density. Our results indicate that in very dense matter the quark-gluon plasma is in essence a weakly interacting gas of quarks and gluons without a magnetic screening mass in the system, sharply different from a quark-gluon plasma at large temperature.