Accessing the gluonic structure of light nuclei at a future electron-ion collider
Heikki Mäntysaari, Björn Schenke
Abstract
We show how exclusive vector meson production off light ions can be used to probe the spatial distribution of small-$x$ gluons in the deuteron and $^{3}\mathrm{He}$ wave functions. In particular, we demonstrate how short-range repulsive nucleon-nucleon interactions affect the predicted coherent $J/\mathrm{\ensuremath{\Psi}}$ production spectra. Fluctuations of the nucleon substructure are shown to have a significant effect on the incoherent cross section above $|t|\ensuremath{\gtrsim}0.2\phantom{\rule{4pt}{0ex}}{\mathrm{GeV}}^{2}$. By explicitly performing the Jalilian-Marian--Iancu--McLerran--Weigert--Leonidov--Kovner (JIMWLK) evolution, we predict the $x$ dependence of coherent and incoherent cross sections in the electron-ion collider energy range. In addition to the increase of the average size of the nucleus with decreasing $x$, both the growth of the nucleons and subnucleonic hot spots are visible in the cross sections. The decreasing length scale of color charge fluctuations with decreasing $x$ is also present, but may not be observable for $|t|<1\phantom{\rule{4pt}{0ex}}{\mathrm{GeV}}^{2}$, if subnucleonic spatial fluctuations are present.