Comparing Proton Momentum Distributions in A = 2 and 3 Nuclei Via \u3csup\u3e2\u3c/sup\u3eH \u3csup\u3e3\u3c/sup\u3eH and \u3csup\u3e3\u3c/sup\u3eHe (e,e′p) Measurements

We report the first measurement of the (e, e\u27 p) reaction cross-section ratios for Helium-3 (3He), Tritium (3H), and Deuterium (d). The measurement covered a missing momentum range of 40 ≤ pmiss ≤ 550 MeV/c, at large momentum transfer ({Q2} ≈ 1.9 (GeV/c)2) and xB \u3e 1, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with planewave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for 3He/d and 3H/d extend to just above the typical nucleon Fermi-momentum (kF ≈ 250 MeV/c) and differ from each other by ∼ 20%, while for 3He/3H they agree within the measurement accuracy of about 3%. At momenta above kF , the measured 3He/3H ratios differ from the calculation by 20% −50%. Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the 3He/3H cross-section ratio for this measurement by less than 5%. If these calculations are correct, then the differences at large missing momenta between the 3He/3H 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

Probing Few-Body Nuclear Dynamics via ³H and ³He (e e\u27p) pn Cross-Section Measurements

We report the first measurement of the (e, e\u27p) three-body breakup reaction cross sections in helium-3 (3He) and tritium (3H) at large momentum transfer [\u3c Q2\u3e ≈ 1.9 (GeV/c)2] and xB\u3e 1 kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta 40 ≤ pmiss ≤ 500 MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross sections are compared with state-of-the-art ab initio calculations. Overall good agreement, within ± 20%, is observed between data and calculations for the full pmiss range for 3H and for 100 ≤ pmiss ≤ 350 MeV/c for 3He. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at pmiss \u3e 250 MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of 3He plus 3H, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire pmiss range. This validates current models of the ground state of the three-nucleon system up to very high initial nucleon momenta of 500 MeV/c

Probing Few-Body Nuclear Dynamics via H 3 and He 3 ( e , e ′ p ) pn Cross-Section Measurements

© 2020 American Physical Society. We report the first measurement of the (e,e′p) three-body breakup reaction cross sections in helium-3 (He3) and tritium (H3) at large momentum transfer [⟨Q2 ≈1.9 (GeV/c)2] and xB>1 kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta 40≤pmiss≤500 MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross sections are compared with state-of-the-art ab initio calculations. Overall good agreement, within ±20%, is observed between data and calculations for the full pmiss range for H3 and for 100≤pmiss≤350 MeV/c for He3. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at pmiss>250 MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of He3 plus H3, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire pmiss range. This validates current models of the ground state of the three-nucleon system up to very high initial nucleon momenta of 500 MeV/c