n-p Short-Range Correlations from (p,2p + n) Measurements

We studied the \(^{12}\)C(p,2p+n) reaction at beam momenta of 5.9, 8.0 and 9.0 GeV/c. For quasielastic (p,2p) events we reconstructed {\bf p_f} the momentum of the knocked-out proton before the reaction; {\bf p_f} was then compared (event-by-event) with {\bf p_n}, the measured, coincident neutron momentum. For \(|p_n|\) > k\(_F\) = 0.220 GeV/c (the Fermi momentum) a strong back-to-back directional correlation between {\bf p_f} and {\bf p_n} was observed, indicative of short-range n-p correlations. From {\bf p_n} and {\bf p_f} we constructed the distributions of c.m. and relative motion in the longitudinal direction for correlated pairs. After correcting for detection efficiency, flux attenuation and solid angle, we determined that 49 \(\pm\) 13 % of events with \(|p_f|\) > k_F had directionally correlated neutrons with \(|p_n|\) > k\(_F\). Thus short-range 2N correlations are a major source of high-momentum nucleons in nuclei.