# $\phi$ meson mass and decay width in nuclear matter and nuclei

## TL;DR

This paper investigates how the mass and decay width of the $4e1$ meson change in nuclear matter using an effective Lagrangian approach, revealing a small mass decrease and significant width broadening, with implications for $4e1$-nucleus interactions.

## Contribution

It provides a detailed calculation of $4e1$ meson properties in nuclear matter considering medium-modified kaon masses and explores $4e1$-nucleus bound states, incorporating form factor sensitivity analysis.

## Key findings

- $4e1$ mass decreases by a few percent at normal nuclear density.
- Decay width of $4e1$ increases by an order of magnitude.
- Results are stable against variations in the cutoff parameter.

## Abstract

The mass and decay width of the $\phi$ meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $\phi$ self-energy, employing the medium-modified kaon masses, calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. At normal nuclear matter density we find a downward shift of the $\phi$ mass by a few percent, while the decay width is enhanced by an order of magnitude. For a large variation of the cutoff mass parameter, the results for the $\phi$ mass and the decay width turn out to vary very little. Our results support results in the literature which suggest that one should observe a small downward mass shift and a large broadening of the decay width. In order to explore the possibility of studying the binding and absorption of $\phi$ mesons in nuclei, we also present the single-particle binding energies and half-widths of $\phi$-nucleus bound states for some selected nuclei.