---
author:
- |
    V.A. Baskov, A.V. Koltsov, A.I. L’vov, A.I. Lebedev, L.N. Pavlyuchenko, , E.V. Rzhanov, S.S. Sidorin, G.A. Sokol\
    P.N. Lebedev Physical Institute, Leninsky prospect 53, Moscow 119991, Russia\
    Email:
- |
    S.V. Afanasiev, A.I. Malakhov\
    Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980, Moscow region, Russia
- |
    A.S. Ignatov, V.G. Nedorezov\
    Institute for Nuclear Research, 60-letiya Oktyabrya prospekt 7a, Moscow 117312, Russia
title: 'Studies of eta-mesic nuclei at the LPI electron synchrotron'
---

Introduction: $\eta$-mesic nuclei {#introduction-eta-mesic-nuclei .unnumbered}
=================================

$\eta$-mesic nuclei, i.e. nuclear systems $_\eta A$ having the $\eta$-meson bound in a nuclear orbit by strong interaction with $A$ nucleons, have been predicted long ago [@haider86; @liu86] — soon after recognizing the attractive character of the $\eta N$ interaction at low energies [@bhalerao85]. Observations and investigations of these exotic systems would be very valuable for understanding meson-baryon interactions in free space and in nuclei and for studies of properties of hadrons in the dense nuclear matter.

[r]{}[0.5]{} ![image](fig-eta-cs.eps){width="40.00000%"}

The $\eta$-meson, together with pions and kaons, belongs to the SU(3) octet of pseudoscalar mesons and has, therefore, a similar $q\bar q$ space structure. In contrast to the pion, however, the pseudoscalar coupling of $\eta$ to the 