  Experimental results of the transverse momentum distributions of phi mesons
and $\Omega$ hyperons produced in gold-gold (Au-Au) collisions with different
centrality intervals, measured by the STAR Collaboration at different energies
(7.7, 11.5, 19.6, 27, and 39 GeV) in the beam energy scan (BES) program at the
relativistic heavy ion collider (RHIC), are approximately described by the
single Erlang distribution and the two-component Schwinger mechanism.
Meanwhile, the STAR experimental transverse momentum distributions of
negatively charged particles, produced in Au-Au collisions at RHIC BES
energies, are approximately described by the two-component Erlang distribution
and the single Tsallis statistics. The excitation functions of free parameters
are obtained from the fit to the experimental data. A weak softest point in the
string tension in $\Omega$ hyperon spectra is observed at 7.7 GeV.
