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

Abstract

The near-threshold pion-induced $\varphi$ 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 ${\pi }^{-}p\to \varphi n$, absolute differential and integral cross sections for the production of $\varphi$ 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 $\varphi$ and neutron potentials while the transparency ratio is governed by the $\varphi N$ absorption cross section. The experimental data are found to be consistent with an attractive $\varphi$-nucleus potential of $\approx$ -(50--100) MeV at normal nuclear matter density ${\rho }_0$ and an effective $\varphi N$ absorption cross section of $\approx$ 12--25 mb. The extracted $\varphi$-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 $\varphi$-$p$ scattering length reported in a recent ALICE experiment.

Comments: 19 pages, 6 figures, references and some additional comments are added