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

Abstract

The near-threshold pion-induced $\phi$ 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 ${\pi^-}p \to {\phi}n$, absolute differential and integral cross sections for the production of $\phi$ 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 $\phi$ and neutron potentials while the transparency ratio is governed by the ${\phi}N$ absorption cross section. The experimental data are found to be consistent with an attractive ${\phi}$-nucleus potential of $\approx$ -(50--100) MeV at normal nuclear matter density $\rho_0$ and an effective ${\phi}N$ absorption cross section of $\approx$ 12--25 mb. The extracted $\phi$-nucleus potential is deeper than previous theoretical and experimental findings as well as those obtained in the present work within the ($t{\rho}$) approximation with accounting for Pauli correlations from the spin-averaged $\phi$-$p$ scattering length reported in a recent ALICE experiment.