Large Long-Distance Contributions to the Electric Dipole Moments of Charged Leptons in the Standard Model.

Yasuhiro Yamaguchi,Nodoka Yamanaka

doi:10.1103/physrevlett.125.241802

Abstract

We reevaluate the electric dipole moment (EDM) of charged leptons in the standard model using hadron effective models. We find unexpectedly large EDM generated by the hadron level long-distance effect, d_{e}=5.8×10^{-40}, d_{μ}=1.4×10^{-38}, and d_{τ}=-7.3×10^{-38} e cm, with an error bar of 70%, exceeding the conventionally known four-loop level elementary contribution by several orders of magnitude.

Highlights

Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai 319-1195, Japan and RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198, Japan
We find unexpectedly large electric dipole moment (EDM) generated by the hadron level long-distance effect, de 1⁄4 5.8 × 10−40, dμ 1⁄4 1.4 × 10−38, and dτ 1⁄4 −7.3 × 10−38 e cm, with an error bar of 70%, exceeding the conventionally known four-loop level elementary contribution by several orders of magnitude
The experimental upper limit of the electron EDM was successively updated since the 1960s [6,10,12,14,19,20,21,22,23,24,25] and currently shows a record of jdej < 1.1 × 10−29 e cm [14]

Summary

Yasuhiro Yamaguchi*

Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai 319-1195, Japan and RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198, Japan. We reevaluate the electric dipole moment (EDM) of charged leptons in the standard model using hadron effective models. The measurements of the electron EDM using paramagnetic systems are especially attracting attention thanks to their relativistic enhancement by the strong internal electric field [17], extensively calculated in theoretical works [18]. The Weinberg operator (chromo-EDM of gluons) is very small, yielding an EDM to the neutron of Oð10−40Þ e cm [43] This extreme suppression is due to the antisymmetry of the Jarlskog invariant [44] in the exchange of flavor, which is an important consequence of the Glashow-Iliopoulos-Maiani (GIM) mechanism [42,45,46], leading to the cancellation of almost equal terms and bringing additional factors of quark masses.

Published by the American Physical Society

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