  Higher-order cumulants of the net-baryon multiplicity distributions are
predicted to be sensitive to the properties of the nuclear matter created in
high-energy nuclear collisions. In this talk, we present the collision
centrality and acceptance (rapidity and transverse momentum) dependence of the
ratio of the 6$^{{\rm th}}$- to the 2$^{\rm nd}$-order cumulant ratio
($C_{6}/C_{2}$) of net-proton in Au+Au collisions at $\sqrt{s_{\rm NN}}=54.4$
and 200 GeV measured by the STAR detector at RHIC. The new results are compared
to hadron transport model and lattice QCD calculations.
