  The beam energy dependence of net baryon number susceptibilities is studied
in the framework of the hadron resonance gas model with the attractive and
repulsive van der Waals interactions between baryons. The collision energy
dependences for the skewness $S\sigma$ and kurtosis $\kappa\sigma^2$ deviate
significantly from the Poisson baseline and demonstrate the existence of rich
structures at moderate collision energies. This behavior may result from the
critical end point of the nuclear liquid-gas first order phase transition. In
particular, $\kappa\sigma^2$ shows a non-monotonic energy dependence, and, in
contrast to the standard scenario for the QCD critical point, it does not
decrease at low collision energies. It is also found that the measurable net
proton fluctuations differ significantly from the net baryon fluctuations when
interactions between baryons cannot be neglected. The results are compared with
the experimental net proton number fluctuations measured by the STAR
collaboration.
