Gamma-radiation of excited nuclear discrete levels in peripheral heavy ion collisions

We study a new process of peripheral heavy ion collisions in which a nucleus is
excited to the discrete state and then emits gamma-rays. Large nuclear Lorentz
factor allows to observe the high energy photons. On one hand it gives a
significant background of gamma-rays in the nuclear fragmentation region and
on the other hand it can be used for the nuclear beam intensity monitoring by
TOTEM CMS. We show that a two step process, in which at first the electron
positron pair is produced by virtual photons of nucleus and then the electron
(positron) excites the nucleus has large cross-section about 5 barn. The
energy and angular distributions of the secondary photons emitted by nucleus in
such process is calculated. The secondary photons have the energies up to 26
GeV and fly to the angles of a few hundred mikroradians along the beam
direction for Ca-Ca collisions at LHC energies.

Document number: 2001-1/641

Authors: V.L.Korotkikh, K.A.Chikin