Direct Observation of Proton-Neutron Short-Range Correlation Dominance in Heavy Nuclei

Area of Science:

• Nuclear Physics
• Quantum Chromodynamics

Background:

• Short-range correlated (SRC) nucleon pairs are crucial for understanding nuclear structure.
• Heavy asymmetric nuclei provide a unique environment to study SRC pair dynamics.

Purpose of the Study:

• To directly measure proton-proton (pp) and neutron-proton (np) pair knockout from various heavy nuclei.
• To compare experimental results with theoretical models, specifically the generalized contact formalism (GCF).

Main Methods:

• Measured triple coincidence A(e,e^{'}np) and A(e,e^{'}pp) reactions.
• Utilized carbon, aluminum, iron, and lead targets.
• Operated at high momentum transfer (Q^{2}>1.5 ext{ (GeV/c)}^{2}) and Bjorken scaling (x_{B}>1.1).

Main Results:

• The measured pp to np reduced cross-section ratio was approximately 6% for all nuclei.
• After correcting for single-charge exchange, the ratio decreased to ~3%.
• GCF calculations showed good agreement with experimental data using both phenomenological and chiral nucleon-nucleon potentials.

Conclusions:

• The findings support a lower pp to np SRC pair ratio in heavy nuclei.
• The generalized contact formalism effectively describes the experimental data, suggesting reduced scale and scheme dependence.
• High-momentum nuclear states are predominantly influenced by nucleons within SRC pairs.