Possibility to study eta-mesic nuclei and photoproduction of slow eta-mesons at the GRAAL facility

TL;DR

This paper proposes an experiment at the GRAAL facility to study eta-mesic nuclei and eta-nucleus interactions through decay modes observed with a photon beam, supported by simulations and yield estimates.

Contribution

It introduces a new experimental approach to investigate eta-mesic nuclei and eta-nucleus interactions using the GRAAL detector and photon beam, including simulation results.

Findings

Simulation results support feasibility of the experiment

Estimated yields indicate measurable signals

Potential to observe eta decay modes inside nuclei

Abstract

A new experiment is proposed with the aim to study eta-mesic nuclei and low-energy interactions of eta with nuclei. Two decay modes of eta produced by a photon beam inside a nucleus will be observed, namely a collisional decay \eta N \to \pi N inside the nucleus and the radiative decay \eta \to \gamma \gamma outside. In addition, a collisional decay of stopped S_{11}(1535) resonance inside the nucleus, S_{11}(1535) N \to N N, will be studied. The experiment can be performed using the tagged photon beam at ESRF with the end-point energy 1000 MeV and the GRAAL detector which includes a high-resolution BGO calorimeter and a large acceptance lead-scintillator time-of-flight wall. Some results of simulation and estimates of yields are given.