Deep Inelastic Scattering of Polarized Electrons off Polarized He: Nuclear Effects and the Neutron Spin Structure Functions

Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He are analyzed in terms of a spin dependent spectral function taking into account S′ and D waves in 3He, as well as Fermi motion and binding effects. A simple and reliable equation relating the neutron and 3He spin structure functions is proposed. The spin structure functions (SSF) of the nucleon g 1 and g N 2 provide information on the spin distribution among the nucleon partons and can allow important tests of various models of hadron’s structure [1]. The proton SSF g 1 has been measured in [2]; the first data on the neutron SSF were recently obtained by the E142 and SMC collaborations [3, 4]; future experiments [5] will improve the knowledge on g 1 and g n 1 and will provide first measurements of g 2 and g n 2 . The neutron SSF are obtained from the spin asymmetry measured in Deep Inelastic Scattering (DIS) of longitudinally polarized electrons off polarized nuclear targets, viz. ~ 2H and ~ 3He. As is well known, the use of ~ 3He targets, which will be considered in this talk, is motivated by the observation that, in the simplest picture of He (all nucleons in S wave), protons have opposite spins, so 1 Invited talk at VI Workshop on “Perspectives in Nuclear Physics at Intermediate Energies”, ICTP, Trieste, May 3-7, 1993 (World Scientific, Singapore).