Influence of anisotropic $\mathrm{\Lambda }\mathrm{/}\mathrm{\Sigma }$ creation on the ${\mathrm{\Xi }}^{-}$ mutiplicity in subthreshold proton-nucleus collisions

We present an analysis of ${\mathrm{\Xi }}^{-}$ baryon production in subthreshold proton–nucleus ($p+A$) collisions in the framework of a BUU type transport model. We propose a new mechanism for $\mathrm{\Xi }$ production in the collision of a secondary $\mathrm{\Lambda }$ or $\mathrm{\Sigma }$ hyperon and a nucleon from the target nucleus. We find that the ${\mathrm{\Xi }}^{-}$ multiplicity in $p+A$ collisions is sensitive to the angular distribution of hyperon production in the primary $N+N$ collision. Using reasonable assumptions on the unknown elementary cross sections we are able to reproduce the ${\mathrm{\Xi }}^{-}$ multiplicity and the ${\mathrm{\Xi }}^{-}\mathrm{/}(\mathrm{\Lambda }+{\mathrm{\Sigma }}^0)$ ratio obtained in the HADES experiment in $p$+Nb collisions at $\sqrt{s_{NN}}=$ 3.2 GeV energy.