Probing few-body nuclear dynamics via 3H and 3He (e,e'p)pn cross-section measurements

Abstract

We report the first measurement of the \eep three-body breakup reaction cross sections in helium-3 (${}^3$He) and tritium (${}^3$H) at large momentum transfer ($⟨Q^2⟩\approx 1.9$ (GeV/c)${}^2$) and $x_B>1$ kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta $40\le p_{miss}\le 500$ 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 $\pm 20\%$, is observed between data and calculations for the full $p_{miss}$ range for ${}^3$H and for $100\le p_{miss}\le 350$ MeV/c for ${}^3$He. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at $p_{miss}>250$ MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of ${}^3$He plus ${}^3$H, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire $p_{miss}$ 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.

Comments: Accepted for publication in PRL. 8 pages, 3 figures, and online supplementary materials