Net baryon number probability distribution near the chiral phase transition

We discuss the properties of the net baryon number probability distribution near the chiral phase transition to explore the effect of critical fluctuations. Our studies are performed within Landau theory, where the coefficients of the polynomial potential are parametrized, so as to reproduce the mean-field (MF), the Z(2), and the O(4) scaling behaviors of the cumulants of the net baryon number. We show that in the critical region the structure of the probability distribution changes, depending on the values of the critical exponents. In the MF approach, as well as in the Z(2) universality class, the contribution of the singular part of the thermodynamic potential tends to broaden the distribution. By contrast, in the model with O(4) scaling, the contribution of the singular part results in a narrower net baryon number probability distribution with a wide tail. (orig.)