Speaker
Description
All information about the initial state of partons in a nucleon/nucleus before a hard scattering takes place is encoded in universal, non-perturbative functions collectively known as “parton distribution functions” (PDFs). Depending on the physical processes and kinematic region studied, different PDFs can be extracted, e.g., unpolarised/polarised PDFs, generalised PDFs, etc. In the perturbative approach, their determination is based on global fits to available data, measured in appropriate processes. The most widely studied and best known PDFs are those of a free proton in the collinear regime, and the cleanest experiment for their extraction is the Deep Inelastic Scattering (DIS) of lepton and proton. When the proton is replaced by a nucleus, the observed cross-sections differ non trivially; under the assumption that the perturbative framework is applicable, the nuclear forces holding together the nucleus seem to affect the distribution of momentum of the partons inside each bound nucleon. Therefore, a set of medium-modified or nuclear PDFs (nPDFs) are required to describe processes involving nuclei. Unlike the free proton PDF case for which DIS data from the HERA collider are available, in the nuclear case only fixed target experiments have been conducted to date. These have a limited kinematic coverage and as a consequence the nPDFs are far less constrained than those in free protons. This picture will changed drastically with the EIC, that will measure DIS off a variety of nuclei in collider mode, putting for the first time proton and nuclear experiments at the same level. In this talk I will discuss the possibilities of improving nPDFs at the EIC using DIS and other observables.
