Neutron Electric Dipole Moment from Gauge-String Duality.

Area of Science:

• Nuclear Physics
• Quantum Chromodynamics (QCD)

Background:

• The electric dipole moment (EDM) of nucleons is a crucial observable in probing new physics beyond the Standard Model.
• Understanding nucleon EDMs requires sophisticated theoretical models that capture the complexities of Quantum Chromodynamics (QCD).

Purpose of the Study:

• To compute the electric dipole moment of nucleons within the Witten-Sakai-Sugimoto large N_{c} QCD model.
• To investigate the role of vector meson dominance and topological theta angle in nucleon EDMs.

Main Methods:

• Utilizing the Witten-Sakai-Sugimoto model, which describes baryons as instantonic solitons in a five-dimensional effective action.
• Analyzing the dipole electromagnetic form factor of nucleons induced by a finite topological theta angle.
• Evaluating the contribution of individual vector meson modes.

Main Results:

• The dipole electromagnetic form factor exhibits complete vector meson dominance.
• A small number of vector meson modes are sufficient for accurate estimation.
• The neutron electric dipole moment is calculated as d_{n}=1.8×10^{-16}θ e cm.
• The proton electric dipole moment is found to be the negative of the neutron's.

Conclusions:

• The large N_{c} QCD model provides a framework for calculating nucleon EDMs.
• Vector meson dominance plays a significant role in the nucleon EDM calculation.
• The model predicts a specific value for the neutron EDM, offering a testable prediction.