Photoproduction of top in peripheral heavy ion collisions

Abstract

In relativistic heavy ion collisions, top quarks can be produced by photon-gluon fusion when a photon from the Weizs\"acker-Williams virtual photon field of one nucleus interacts with a gluon in the other nucleus. Photoproduction with heavy ions at the Large Hadron Collider (LHC) will be the first accessible non-hadronic top production channel. We calculate the $t \bar t$ photoproduction cross sections, pair mass and top quark rapidity distributions in peripheral heavy ion collisions. The cross sections are sensitive to the top quark charge and the large-$Q^2$ gluon distribution in the nucleus. We find a cross section of 94 pb in calcium-calcium collisions, leading to 190 pairs in a one month ($10^6$ sec) LHC run. We also find $p$Pb and $p$Ca cross sections of 5.8 and 3.4 pb respectively, resulting in 6 and 34 $t\bar t$ pairs per month.