Momentum dependence of near-threshold photoproduction of ${\Xi }^{-}$ hyperons off nuclei and their properties in the nuclear medium

Abstract

We study the near-threshold inclusive photoproduction of ${\Xi }^{-}$ hyperons off ${}^{12}$C and ${}^{184}$W target nuclei within a first-collision model relying on the nuclear spectral function and including incoherent ${\Xi }^{-}$ production in direct elementary $\gamma p\to K^{+}{K}^{+}{\Xi }^{-}$ and $\gamma n\to K^{+}{K}^0{\Xi }^{-}$ processes. The model takes into account the impact of the nuclear effective scalar $K^{+}$, $K^0$, ${\Xi }^{-}$ and their Coulomb potentials on these processes as well as the absorption of final ${\Xi }^{-}$ hyperons in nuclear matter, the binding of intranuclear nucleons and their Fermi motion. We calculate the absolute differential cross sections and their ratios for the production of ${\Xi }^{-}$ hyperons off these nuclei at laboratory polar angles $\le$ 45${}^{\circ }$ by photons with energies of 2.5 and 3.0 GeV, with and without imposing the phase space constraints on the ${\Xi }^{-}$ emission angle in the respective $\gamma p$ center-of-mass system. We also calculate the momentum dependence of the transparency ratio for ${\Xi }^{-}$ hyperons for the ${}^{184}$W/${}^{12}$C combination at these photon energies. We show that the ${\Xi }^{-}$ momentum distributions (absolute and relative) at the adopted initial photon energies possess, contrary to the transparency ratio for ${\Xi }^{-}$ hyperons, a definite sensitivity to the considered changes in the scalar ${\Xi }^{-}$ nuclear mean-field potential at saturation density ${\rho }_0$ in the low-momentum range of 0.1--0.8 GeV/c. Therefore, the precise measurements of these distributions in a dedicated experiment at the CEBAF facility will provide valuable information on the ${\Xi }^{-}$ in-medium properties, which will be supplementary to that inferred from studying of the ($K^{-}$,$K^{+}$) reactions at initial momenta of 1.6--1.8 GeV/c.

Comments: 25 pages, 14 figures