Probing the Deuteron at Very Large Internal Momenta

Area of Science:

• Nuclear Physics
• Electromagnetic Interactions
• Deuteron Structure

Background:

• Understanding the deuteron's internal structure is crucial for nuclear physics.
• Previous measurements of ^{2}H(e,e^{'}p)n cross sections provided limited data at higher neutron recoil momenta.
• The plane wave impulse approximation (PWIA) is a theoretical framework used to describe electron scattering from nuclei.

Purpose of the Study:

• To measure ^{2}H(e,e^{'}p)n cross sections at high 4-momentum transfer (Q^{2}=4.5±0.5 (GeV/c)^{2}).
• To extend measurements to higher neutron recoil momenta (p_{r} up to ∼1.0 GeV/c) and specific angles (θ_{nq}=35°, 45°, and 75°).
• To compare experimental data with theoretical calculations, including PWIA, final state interactions, meson exchange currents, and isobar currents.

Main Methods:

• Experimental measurement of electron-deuteron scattering cross sections using a high-momentum transfer.
• Data acquisition at fixed neutron recoil angles relative to the momentum transfer.
• Comparison of experimental results with theoretical models.

Main Results:

• New cross section data were obtained for neutron recoil momenta up to ∼1.0 GeV/c, consistent with previous measurements up to ∼500 MeV/c.
• At θ_{nq}=35° and 45°, PWIA was found to be the dominant contribution to the cross section due to suppressed final state interactions and other effects.
• A significant discrepancy was observed between the new data and recent theoretical calculations for neutron recoil momenta exceeding 700 MeV/c.

Conclusions:

• The study provides valuable experimental data for ^{2}H(e,e^{'}p)n cross sections at high momentum transfer and recoil momenta.
• The results highlight limitations of current theoretical models in describing deuteron structure at high momentum transfers.
• Further theoretical developments are needed to reconcile the observed discrepancies, particularly concerning contributions beyond the PWIA.