Comparing proton momentum distributions in A = 2 and 3 nuclei via 2H 3H and 3He (e,e′p) measurements

Abstract We report the first measurement of the ( e , e ′ p ) reaction cross-section ratios for Helium-3 ( He 3 ), Tritium ( H 3 ), and Deuterium (d). The measurement covered a missing momentum range of 40 ≤ p m i s s ≤ 550 MeV / c , at large momentum transfer ( 〈 Q 2 〉 ≈ 1.9 (GeV/c)2) and x B > 1 , which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with plane-wave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for He 3 /d and H 3 /d extend to just above the typical nucleon Fermi-momentum ( k F ≈ 250 MeV/c) and differ from each other by ∼ 20 % , while for He 3 / H 3 they agree within the measurement accuracy of about 3%. At momenta above k F , the measured He 3 / H 3 ratios differ from the calculation by 20 % − 50 % . Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the He 3 / H 3 cross-section ratio for this measurement by less than 5%. If these calculations are correct, then the differences at large missing momenta between the He 3 / H 3 experimental and calculated ratios could be due to the underlying NN interaction, and thus could provide new constraints on the previously loosely-constrained short-distance parts of the NN interaction.