  Within a Bayesian statistical framework using a Gaussian Process emulator for
an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model
simulator of heavy-ion reactions at intermediate energies, we infer from the
HADES proton flow data the posterior probability distribution functions of
in-medium baryon-baryon scattering cross section modification factor X with
respect to free-space and the corresponding incompressibility K of nuclear
matter as well as their correlation function. The mean value of X is found to
be $X=1.32^{+0.28}_{-0.40}$ at 68\% confidence level assuming the nuclear
incompressibility K will not exceed 400 MeV, providing circumstantial evidence
for enhanced baryon-baryon scattering cross sections in hot and dense nuclear
matter.
