The Electric Dipole Form Factor of the Nucleon in Chiral Perturbation Theory to Sub-leading Order

Understand

The electric dipole form factor (EDFF) of the nucleon stemming from the QCD theta term and from the quark color-electric dipole moments is calculated in chiral perturbation theory to sub-leading order.

• This is the lowest order in which the isoscalar EDFF receives a calculable, non-analytic contribution from the pion cloud.
• In the case of the theta term, the expected lower bound on the deuteron electric dipole moment is |d_d| > 1.4 10^(-4) \theta e fm.
• The momentum dependence of the isovector EDFF is proportional to a non-derivative time-reversal-violating pion-nucleon coupling, and the scale for momentum variation ---appearing, in particular, in the radius of the form factor--- is the pion mass.