Interpreting the electron EDM constraint

Abstract

The ACME collaboration has recently announced a new constraint on the electron EDM, |d e |< 1.1×10 −29 e cm, from measurements of the ThO molecule. This is a powerful constraint on CP-violating new physics: even new physics generating the EDM at two loops is constrained at the multi-TeV scale. We interpret the bound in the context of different scenarios for new physics: a general order-of-magnitude analysis for both the electron EDM and the CP-odd electronnucleon coupling; 1-loop SUSY, probing sleptons above 10 TeV; 2-loop SUSY, probing multi-TeV charginos or stops; and finally, new physics that generates the EDM via the charm quark or top quark Yukawa couplings. In the last scenario, new physics generates a "QULE operator" (q f σ µνū f ) · ( σ µνē ), which in turn generates the EDM through RG evolution. If the QULE operator is generated at tree level, this corresponds to a previously studied leptoquark model. For the first time, we also classify scenarios in which the QULE operator is generated at one loop through a box diagram, which include SUSY and leptoquark models. The electron EDM bound is the leading constraint on a wide variety of theories of CP-violating new physics interacting with the Higgs boson or the top quark. We argue that any future nonzero measurement of an electron EDM will provide a strong motivation for constructing new colliders at the highest feasible energies. arXiv:1810.07736v1 [hep-ph] 17 Oct 2018 there are many motivations for searching for physics beyond the Standard Model, three of the most important are the matter-antimatter asymmetry of our universe, the existence of dark matter, and the fine-tuning puzzle of the Higgs boson mass. The matter-antimatter asymmetry clearly indicates a need for new CP-violating physics, which could first be detected through its indirect effect on the electron EDM. As we will discuss below, EDMs also have interesting connections with WIMP dark matter (in specific models) and with the fine-tuning problem.The possibility of testing heavy new physics through electric dipole moment measurements has been studied extensively; reviews include [11][12][13][14]. Here we attempt to briefly summarize some of the important history of the topic, with apologies for inevitable omissions. Some early theoretical studies of lepton EDMs appeared already in the 1970s [15,16]. Many of the early studies of CP violation in supersymmetric theories focused on the neutron EDM [17][18][19], but studies of the electron EDM in supersymmetry commenced [20] shortly after a suggestion of Gavela and Georgi that lepton EDMs could be effective probes of new physics [21]. Subsequently, a variety of additional sources of EDMs were studied, such as 3-gluon operators [22] or two-loop diagrams mediated by electroweak bosons [23,24]. A variety of new physics scenarios have been shown to predict interesting EDMs, including: stops in SUSY [25]; electroweakinos in SUSY [26] and specifically split SUSY [27,28]; two Higgs doublet models [24,[29][30][31]; SUSY beyond the MSSM [32,33]; and fermionic...

The metastable Q 3Δ2 state of ThO: a new resource for the ACME electron EDM search

“…This represents an order of magnitude improvement compared to the previous best results [2][3][4]. The ACME limit on d e significantly constrains the parameter space for potential new time-reversal symmetry (T) violating interactions mediated by particles in the mass range of 3-30 TeV [5]. Improved measurements will probe even higher energy scales.…”

Laser-cooled polyatomic molecules for improved electron electric dipole moment searches

“…Experimental probes of the electric dipole moment of the electron (eEDM) provide strong constraints on theories of particle physics beyond the Standard Model (BSM) [1][2][3][4][5][6]. The most stringent limit on an eEDM has been realized in experiments using a diatomic molecule, ThO, in a 3 Δ 1 state, limiting the eEDM to < 1.1×10 −29 e cm [7,8].…”

P , T -Violating and Magnetic Hyperfine Interactions in Atomic Thallium

“…Electric dipole moments (EDM) of elementary particles, atoms and molecules give rise to spatial parity (P) and time-reversal (T ) violating interactions [1] and are a powerful probe for physics beyond the standard model (BSM) [2]. Current single-source limits [3][4][5] on the electron EDM, for instance, can probe New Physics (NP) up to an energy scale of 1000 TeV [6] (radiative stability approach) or even greater [7], surpassing the current sensitivity of the Large Hadron Collider for corresponding sources of NP.…”