Strange Hadron Production in Au + Au Collisions at $$\sqrt {{{s}_{{NN}}}} = 3{-} 27$$ GeV with UrQMD

We study model dependence of strange hadron spectra ( $$K_{S}^{0}$$ , $$\\Lambda $$ , $$\\Xi $$ , $$\\Omega $$ ) on transverse momentum, rapidity, and collision centrality in Au + Au collisions in the range of energies $$\\sqrt {{{s}_{{NN}}}} = 3{-} 27$$ GeV using the UrQMD model. The results are compared with the data from RHIC Beam Energy Scan (BES) program. While the model shows reasonable agreement for $$K_{S}^{0}$$ spectra, it systematically underestimates the yields of strange and multi-strange hadrons over the entire energy range, with the discrepancy increasing with the strangeness content. The antibaryon-to-baryon and hadron-to-pion ratios are qualitatively reproduced, but significant quantitative deviations persist. These results demonstrate that, in its present form, the UrQMD model does not provide a satisfactory description of strange hadron observables at $$\\sqrt {{{s}_{{NN}}}} = 3{-} 27$$ GeV, indicating the need for additional physical mechanisms beyond hadronic rescattering to account for strangeness production in high-density nuclear matter.