The Effects Of Different Z(3) Symmetry Breaking Patterns On Quark Deconfinement Transition

The study of deconfinement transition is a frontier and hot topic in particle and nuclear physics.For SU(3)pure gauge theory,the deconfinement transition at high temperature corresponds to the spontaneous Z(3)symmetry breaking.Nevertheless,the Z(3)symmetry is broken explicitly by the dynamical quarks in QCD.At present,the relationship between Z(3)symmetry breaking and QCD deconfinement transition is still unclear.For the three degenerate flavors,there is a Z(3)symmetric QCD-like theory if the flavor-dependent imaginary chemical potentials form a arithmetic sequence with a special common difference i2?T/3,which is the so-called Z(3)-QCD.In this paper,we investigate the relationship between Z(3)symmetry breaking and QCD deconfinement transition by employing a Z(3)-QCD effective model i.e.,Polyakov-loop extended NJL(PNJL)model.The Z(3)symmetry of Z(3)-QCD can be broken in two patterns:(1)Modifying the common difference of the chemical potential sequence;(2)Breaking the mass degeneracy.This may lead to the Roberge-Weiss(RW)transitions:the Z(3)-QCD effective potentials corresponding to the three Z(3)sectors will be separated each other at high temperature.It is important to investigate the nature of RW transitions,since they can affect the deconfmement transition.We study the RW transitions by introducing the imaginary chemical potentials(?u,?d,?s)/iT=(?-2C?/3,?,?+2C?/3),(C?[0,1]).For the first symmetry breaking pattern,the RW transitions appear at ?=(2k-1)?/3,(k?Z),which is same to the traditional one.When C decreases from one to zero,the RW transition becomes stronger and thus has a greater impact on the deconfinement transition.Meanwhile,the deconfinement transition gradually degenerates from the first-order order to crossover.For the second symmetry breaking pattern,the RW transitions appear at ?=2k?/3.The deconfinement transition always keeps the first-order when the mass difference between the strange and light quarks increases.This indicates the Z(3)symmetry breaking caused by the mass difference is quite weaker and the crossover deconfinement transition does not happen.When two kinds of symmetry breaking patterns coexist,the location of RW transition have a shift with the C changing from one to zero,which will lead to the shift of deconfinement transition line in the phase diagram.