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

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(miss) <= 550 MeV/c, at large momentum transfer (< Q(2)> approximate to 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) approximate to 250 MeV/c) and differ from each other by similar to 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. (C) 2019 The Author(s). Published by Elsevier B.V.