Observation of Large Missing-Momentum (e, E'p) Cross-Section Scaling and the Onset of Correlated-Pair Dominance in Nuclei

We report the measurement of x(B) scaling in (e, e'p) cross-section ratios off nuclei relative to deuterium at large missing momentum of 350 <= p(miss) <= 600 MeV/c. The observed scaling extends over a kinematic range of 0.7 <= x(B) <= 1.8, which is significantly wider than 1.4 <= x(B) <= 1.8 previously observed for inclusive (e, e') cross-section ratios. The x(B)-integrated cross-section ratios become constant (i.e., scale) beginning at p(miss) approximate to k(F), the nuclear Fermi momentum. Comparing with theoretical calculations we find good agreement with generalized contact formalism calculations for high missing momentum (>375 MeV/c), suggesting the observed scaling results from interacting with nucleons in short-range correlated (SRC) pairs. For low missing momenta, mean-field calculations show good agreement with the data for p(miss) < k(F), and suggest a potential non-negligible contribution to the measured cross-section ratios from scattering off single, uncorrelated, nucleons up to p(miss) approximate to 350 MeV/c. Therefore, SRCs become dominant in nuclei at p(miss) approximate to 350 MeV/c, well above the nuclear Fermi Surface of k(F) approximate to 250 MeV/c.