Studies of eta-mesic nuclei at the LPI electron synchrotron

TL;DR

This paper reviews eta-mesic nuclei searches and reports new experimental results from the LPI electron synchrotron, showing evidence of eta absorption in nuclei through correlated particle pairs and estimating the photoproduction cross section.

Contribution

It presents new experimental data on eta-mesic nuclei formation and decay, highlighting the observation of two-nucleon absorption processes and estimating the photoproduction cross section.

Findings

Detection of correlated (pi+ n) and (p n) pairs from eta absorption.

Evidence of two-nucleon absorption of eta in carbon nuclei.

Estimated photoproduction cross section less than 10 microbarn.

Abstract

A brief review of searches for eta-mesic nuclei is presented with emphasis on photoreactions and results of a new experiment done at the LPI electron synchrotron are reported. Decay products of eta-mesic nuclei presumably formed by photons in a carbon target, namely correlated back-to-back (pi+ n) and (p n) pairs, have been studied with a two-arm time-of-flight setup. The obtained data show that apart from previously observed (pi+ n) pairs from one-nucleon annihilation of stopped etas (via eta N --> pi N) correlated (p n) pairs from two-nucleon absorption of eta in the nucleus (via eta NN --> NN) are also ejected with a comparable rate. The cross section of eta-mesic nuclei photoproduction off carbon was estimated from the obtained data to be less than 10 microbarn.