Eta meson rescattering effects in the p + 6Li --> eta + 7Be reaction near threshold

TL;DR

This paper models eta meson rescattering effects in the p + 6Li --> eta + 7Be reaction near threshold, revealing a double hump structure in the cross section due to final state interactions.

Contribution

It introduces a cluster-based reaction model and few-body calculations to analyze eta-7Be interactions, highlighting the role of rescattering effects.

Findings

Double hump structure in total cross section due to eta rescattering.

Rescattering effects involve multiple scatterings on 3He and alpha clusters.

Angular momentum states L=1 and L=3 contribute to the structure.

Abstract

The p + 6Li --> eta + 7Be reaction has been investigated with an emphasis on the eta meson and 7Be interaction in the final state. Considering the 6Li and 7Be nuclei to be alpha-d and alpha-3He clusters respectively, the reaction is modelled to proceed via the p + d [alpha] --> 3He [\alpha] + eta reaction with the alpha remaining a spectator. The eta meson interacts with 7Be via multiple scatterings on the 3He and alpha clusters inside 7Be. The individual eta-3He and eta-alpha scatterings are evaluated using few body equations for the eta-3N and eta-4N systems with a coupled channel eta-N interaction as an input. Calculations including four low-lying states of 7Be lead to a double hump structure in the total cross section corresponding to the $L = 1 (J = (1/2)^-, (3/2)^-)$ and $L = 3 (J = (5/2)^-, (7/2)^-)$ angular momentum states. The humps arise due to the off-shell rescattering of the eta meson on the 7Be nucleus in the final state.