  We study the QCD phase diagram on the plane of temperature T and quark
chemical potential mu, modelling the strong interactions with the linear sigma
model coupled to quarks. The phase transition line is found from the effective
potential at finite T and mu taking into accounts the plasma screening effects.
We find the location of the critical end point (CEP) to be
(mu^CEP/T_c,T^CEP/T_c) sim (1.2,0.8), where T_c is the (pseudo)critical
temperature for the crossover phase transition at vanishing mu. This location
lies within the region found by lattice inspired calculations. The results show
that in the linear sigma model, the CEP's location in the phase diagram is
expectedly determined solely through chiral symmetry breaking. The same is
likely to be true for all other models which do not exhibit confinement,
provided the proper treatment of the plasma infrared properties for the
description of chiral symmetry restoration is implemented. Similarly, we also
expect these corrections to be substantially relevant in the QCD phase diagram.
