Neutron electric dipole moment from QCD sum rules.

摘要

The electric dipole moments of nucleons (NEDM, {dollar}dsb{lcub}N{rcub}{dollar}) are calculated using the method of QCD sum rules. Our calculations are based on the parity ({dollar}/!!!P{dollar}) and time reversal ({dollar}/!!!T{dollar}) violating parameter {dollar}barTheta{dollar} in QCD and establish a functional dependence of the NEDM on {dollar}barTheta{dollar}, without assuming a perturbative expansion of this symmetry breaking parameter. The results obtained from the QCD sum rules approach are shown to be consistent with the general symmetry constraints on {dollar}/!!!P{dollar} and {dollar}/!!!T{dollar} in QCD; including the necessity of quark masses, spontaneous chiral symmetry breaking, and the {dollar}Usb{lcub}A{rcub}{dollar}(1) anomaly. Given the current experimental upper bound on the neutron electric dipole moment (nEDM), {dollar}dsb{lcub}n{rcub}le 10sp{lcub}-26{rcub}ecdot cm{dollar}, we find {dollar}barThetale 10sp{lcub}-10{rcub}{dollar}. This is compatible with previous calculations of nEDM using different techniques.