Investigation of Proton-Proton Short-Range Correlations via theC12(e,e′pp)Reaction

Abstract

We investigated simultaneously the 12C(e,e'p) and 12C(e,e'pp) reactions at Q2=2 (GeV/c)2, xB=1.2, and in an (e, e'p) missing-momentum range from 300 to 600 MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5+/-2)% of the 12C(e,e'p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e'p) missing-momentum vector, an experimental signature of correlations.

Hard photo-disintegration of proton pairs in ³He nuclei

“…If one adopts the view that large momentum transfer reactions select initial states in which all the quarks and nucleons are close together, it is much more likely that there is a short-range, and thus high-momentum, pn pair than pp pair. This is what has been found in recent studies for nucleons above the Fermi surface that have momenta of several hundred MeV/c [78,79].…”

“…These nucleon-nucleon correlations cause the ratio of pp to np pairs to be ∼5% in the relative momentum range of 300-600 MeV/c for both high-energy electron and proton scattering [77][78][79]. Starting with such a pair and final state re-scattering might lead to the observed relative transverse momentum and would explain the relatively small cross sections.…”

Final-state interactions in two-nucleon knockout reactions

“…[18], denoted KinA. It corresponds with a very selective phase space whereby the scattered electron and leading proton are detected with two high resolution spectrometers at the fixed central angles 19.…”

“…First, the kinematics of the A(e, e pp) crosssection measurements with the CEBAF Large Acceptance Spectrometer (CLAS) [21] covering a very large phase space. Second, the kinematics of an experimental setup with a very restricted phase-space coverage [18]. We extract the nuclear transparencies for two-nucleon knockout and compare them to single-particle knockout transparencies extracted from A(e, e p) measurements.…”

Hard QCD Processes in the Nuclear Medium

“…[26][27][28]). In these experiments, the probe and a removed proton are detected and their momenta measured, allowing the missing momentum to be calculated.…”