Direct versus resolved photons in DPS in photoproduction on proton and nuclei

Abstract

We study the process of double parton scattering (DPS) associated with the photoproduction at a future Electron-Ion collider (EIC) and HERA. We show that in the case of the resolved photon the 1 to 2 processes lead, even at small transverse momenta of the hard processes , to the increase of the DPS by a factor of order 1.6 in the significant part of the phase space, relative to the predictions of the mean field based models . Moreover we study the kinematic region where direct photon contribution is dominant and show it s boundaries for charm and light quark jets. For charmed jets we see that the relevant region is $x_{\gamma }\ge 0.2-0.4$. This region is even enhanced if we consider the photoproduction on the nuclei.

Comments: 21 pages,16 figures