Quark distributions in nuclei and deep inelastic scattering of charged leptons

Abstract

Deep inelastic scattering experiments with charged leptons have shown that the quark and gluon distributions in nuclei are different from those in free nucleons. The global features of the observed effect can be described by many ‘simple’ models but obviously more experimental information is needed to decide definitely which explanation is correct. As a first step a measurement of the A dependence has already been performed at low Q2 in a SLAC experiment {66}. This has taken data with several targets ranging from deuterium and helium to gold. Preliminary results indicate a mild increase of the effect at high x with A up to the highest mass numbers, final results are expected shortly. A low angle experiment will be performed this autumn by the EMC to study for several nuclei the region at low x and low Q2 where shadowing and nuclear effects seem to counteract each other. Measurements on several targets at higher Q2 will be done by the two muon experiments EMC and BCDMS at CERN and data from different targets are also being compared by several neutrino experiments {67}. The EMC has already performed some studies of hadronic final states from nuclear targets and intends to continue this investigations with an upgraded apparatus. This group also tries to get out more information on the gluon distribution in different nuclei by comparing J/~ events from hydrogen, deuterium and iron.