Nucleon electric dipole moments and the isovector parity-and time-reversal-odd pion–nucleon coupling
The isovector time-reversal- and parity-violating pion–nucleon coupling g_π^(1) is uniquely sensitive to dimension-six interactions between right-handed light quarks and the Standard Model Higgs doublet that naturally arises in left-right symmetric models. Recent work has used the g_π^(1)-induced one-loop contribution to the neutron electric dipole moment d_n, together with the present experimental d_n bound, to constrain the CP-violating parameters of the left-right symmetric model. We show that this and related analyses are based on an earlier meson theory d_n computation that is not consistent with the power-counting appropriate for an effective field theory. We repeat the one-loop calculation using heavy baryon chiral perturbation theory and find that the resulting d_n sensitivity to g_π^(1) is suppressed, implying more relaxed constraints on the parameter space of the left-right symmetric model. Assuming no cancellations between this loop contribution and other contributions, such as the leading order EDM low-energy constant, the present limit on d_n implies |g_π^(1)|≲1.1×10^(−10).
Additional Information© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). Funded by SCOAP3. Received 14 February 2014. Received in revised form 11 June 2014. Accepted 8 July 2014. Available online 14 July 2014. Editor: W. Haxton. We thank Ulf Meißner for helpful comments on the manuscript. This work is supported in part by the DFG and the NSFC through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD" (JdV), and by the US Department of Energy under contracts DE-AC02-05CH11231 (EM), DE-FG02-08ER41531 (C-YS, HP and MJRM), and DE-SC0011095 (C-YS and MJRM).
Published - 1-s2.0-S0370269314005000-main.pdf
Submitted - 1401.5366v2.pdf