Testing the $ϕ$-nuclear potential in pion-induced $ϕ$ meson production on nuclei near threshold

Abstract

The near-threshold pion-induced $ϕ$ production off nuclei has been studied in the kinematical conditions of the HADES experiment using a collision model based on the nuclear spectral function. Starting from the elementary reaction ${π^-}p \to ϕn$, absolute differential and integral cross sections for the production of $ϕ$ mesons off a light carbon and a heavy tungsten target have been calculated and compared to the recently reported experimental cross sections. The absolute cross section values are shown to be sensitive to the effective nuclear scalar $ϕ$ and neutron potentials while the transparency ratio is governed by the $ϕN$ absorption cross section. The experimental data are found to be consistent with an attractive $ϕ$-nucleus potential of $\approx$ -(50--100) MeV at normal nuclear matter density $ρ_0$ and an effective $ϕN$ absorption cross section of $\approx$ 12--25 mb. The extracted $ϕ$-nucleus potential is deeper than previous theoretical and experimental findings as well as those obtained in the present work within the ($tρ$) approximation with accounting for Pauli correlations from the spin-averaged $ϕ$-$p$ scattering length reported in a recent ALICE experiment.