Observation of large missing-momentum ( e , e ′ p ) cross-section scaling and the onset of correlated-pair dominance in nuclei

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We report the measurement of ${x}_{B}$ scaling in $(e,{e}^{\ensuremath{'}}p)$ cross-section ratios off nuclei relative to deuterium at large missing momentum of $350\ensuremath{\le}{p}_{\mathrm{miss}}\ensuremath{\le}600 \mathrm{MeV}/c$. The observed scaling extends over a kinematic range of $0.7\ensuremath{\le}{x}_{B}\ensuremath{\le}1.8$, which is significantly wider than $1.4\ensuremath{\le}{x}_{B}\ensuremath{\le}1.8$ previously observed for inclusive $(e,{e}^{\ensuremath{'}})$ cross-section ratios. The ${x}_{B}$-integrated cross-section ratios become constant (i.e., scale) beginning at ${p}_{\mathrm{miss}}\ensuremath{\approx}{k}_{F}$, the nuclear Fermi momentum. Comparing with theoretical calculations we find good agreement with generalized contact formalism calculations for high missing momentum ($>375 \mathrm{MeV}/c$), 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 ${p}_{\mathrm{miss}}<{k}_{F}$, and suggest a potential non-negligible contribution to the measured cross-section ratios from scattering off single, uncorrelated, nucleons up to ${p}_{\mathrm{miss}}\ensuremath{\approx}350 \mathrm{MeV}/c$. Therefore, SRCs become dominant in nuclei at ${p}_{\mathrm{miss}}\ensuremath{\approx}350 \mathrm{MeV}/c$, well above the nuclear Fermi Surface of ${k}_{F}\ensuremath{\approx}250 \mathrm{MeV}/c$.

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