Hadron Medium Modifications

Proton recoil polarization in quasielastic electron scattering is a powerful tool to study properties of nucleons bound in the nuclear medium. The most precise results have been obtained at Jefferson Lab in the 4He(e, e′ p)3 H reaction at four momentum transfers of Q2 = 0.8 (GeV/c)2 and at 1.3 (GeV/c)2. The ratio of polarization-transfer components, P′x/P′z, is significantly reduced compared to the ratio obtained in elastic 1H(e, e′ p) scattering. This depletion is well described with models which include in-medium modifications of the proton form factor or, alternatively, by strong charge-exchange final-state interactions. A future experiment will measure the dependence of this effect on the momentum of the struck nucleon in both, the 4He(e, e′ p)3H and 2H(e, e′ p)n reactions.