Short-Range Correlation Studies on $^{12}C$ with 6-9~GeV/c Proton Beams

Reactions at beam momenta and momentum transfers of several GeV/c can probe nuclei on a size scale where nucleon-nucleon short-range correlations (SRCs) are expected to be dominant. We will report on measurements of the $^{12}C(p,2p+n)$ reaction at Brookhaven National Laboratory at beam momenta of 6 to 9~GeV/c. For that experiment, the primary reaction was quasi-elastic knockout of a proton from $^{12}C$, followed by emission of a coincident neutron. For neutron momenta $\ge k_F$~(220 MeV/c), the reconstructed momentum of the knocked-out proton, and the measured momentum of the detected coincident neutron are nearly back-to-back in the laboratory frame of reference, which is a strong kinematic signature of SRCs~[1]. After correction for neutron-detection efficiency, solid angle coverage, and absorption of the incoming and outgoing nucleons, we find that $92\pm 18$\% of nuclear protons with momenta $\ge 275$~MeV/c have correlated neutron partners~[2]. \medskip \medskip \noindent [1] A. Tang et al., Phys. Rev. Lett. 90 042301 (2003). \noindent [2] E. Piasetzky et al., Phys. Rev. Lett. 97 162504 (2006).