Electroproduction of charmonia off nuclei

Abstract

In a recent publication we calculated elastic charmonium production in $\mathrm{ep}$ collisions, employing realistic charmonia wave functions and dipole cross sections, and found good agreement with the data in a wide range of s and ${Q}^{2}$. Using the ingredients from those calculations we calculate exclusive electroproduction of charmonia off nuclei. Here new effects become important, (i) color filtering of the $c\overline{c}$ pair on its trajectory through nuclear matter, (ii) dependence on the finite lifetime of the $c\overline{c}$ fluctuation (coherence length), and (iii) gluon shadowing in a nucleus compared to the one in a nucleon. Total coherent and incoherent cross sections for C, Cu, and Pb as functions of s and ${Q}^{2}$ are presented together with some differential cross sections. The results can be tested with future electron-nucleus colliders or in peripheral collisions of ultrarelativistic heavy ions.