E007 $d_{Ra}, d_{Xe}$
Radium-225 and xenon-129 electric dipole moments Status REVIEWED VERIFIED High Code: NO Priority Low
PDG / equivalent values
| Observable | Value | Year | Experiment / source | Provenance |
|---|---|---|---|---|
| Radium-225 atomic electric dipole moment | 1.4e-23 e cm | 2016 | Bishof et al., Phys. Rev. C 94, 025501 (2016); arXiv:1606.04931 | source ↑ |
| First Radium-225 atomic electric dipole moment measurement | 5e-22 e cm | 2015 | Parker et al., Phys. Rev. Lett. 114, 233002 (2015); arXiv:1504.07477 | source ↑ |
| Xenon-129 atomic electric dipole moment | ? e cm | 2019 | Sachdeva et al., Phys. Rev. Lett. 123, 143003 (2019); arXiv:1909.12800 | source ↑ |
| Independent Xenon-129 atomic electric dipole moment measurement | ? e cm | 2019 | Allmendinger et al., Phys. Rev. A 100, 022505 (2019); arXiv:1904.12295 | source ↑ |
Why this constrains the RS scan
Warped anarchic flavor models generically contain new CP phases. Loop
matching can generate quark EDMs, chromo-EDMs, the Weinberg three-gluon
operator, and semileptonic CP-odd operators. Diamagnetic atoms do not map
directly onto one elementary dipole; their dominant hadronic response is
usually expressed through nuclear Schiff moments and CP-odd hadronic
interactions. \(^{225}\mathrm{Ra}\) is especially useful because octupole
deformation enhances Schiff-moment sensitivity, while \(^{129}\mathrm{Xe}\)
offers a mature noble-gas co-magnetometer platform with different nuclear and
atomic systematics.
What's changed since the original paper
Relative to the 2008 warped-flavor baseline of
CsakiFalkowskiWeiler:RSFlavor2008, Ra and Xe EDMs moved from mostly
future context into direct experimental inputs. Argonne reported the first
\(^{225}\mathrm{Ra}\) EDM measurement in 2015
parker2015\_arxiv1504\_07477.txt and improved it in 2016 by a
factor of \(36\) bishof2016\_arxiv1606\_04931.txt. The 2016 Ra
paper also records planned upgrades aimed at substantially better statistical
reach with controlled systematics bishof2016\_arxiv1606\_04931.txt.
The deposited Argonne program page Argonne:Ra225EDMPage states the
physical motivation: \(^{225}\mathrm{Ra}\) has experimentally useful nuclear
properties and enhanced sensitivity to T-odd, P-odd effects relative to
\(^{199}\mathrm{Hg}\).
For Xe, the 2019 comagnetometer measurements
sachdeva2019\_arxiv1909\_12800.txt and
allmendinger2019\_arxiv1904\_12295.txt established
\(10^{-27}\ e\,\mathrm{cm}\)-level direct limits. The DFG
Heidelberg upgrade proposal DFG:Xe129Upgrade2026 aims to improve
the \(^{129}\mathrm{Xe}\) EDM reach. KU Leuven's RaF/AcF
molecular project KULeuven:RaFMoleculeProject2023 is not a direct
Ra-atom limit, but it is relevant future context because embedding
octupole-enhanced Ra or Ac nuclei in dipolar molecules can enhance
Schiff-moment sensitivity.Validity and model dependence
The direct atom-EDM limits are robust null searches for P- and T-violating
energy shifts. Their interpretation in an RS pipeline is highly
model-dependent: one must choose a CP-odd low-energy operator basis, run and
match through QCD thresholds, and adopt hadronic, nuclear, and atomic
coefficients. These entries should therefore be treated as EDM-adjacent
loop/nuclear-translation probes, not as direct \(\Delta F=2\) quark-scan
constraints.
Code coverage in this repo
NO. The sidecar
code\_coverage block records the required
greps over quarkConstraints/, qcd/,
flavorConstraints/, neutrinos/, yukawa/,
warpConfig/, solvers/, scanParams/, and
tests/ found no Ra, Xe, Schiff-moment, diamagnetic-atom, chromo-EDM,
or Weinberg-operator implementation. The only nearby dipole code is the
off-diagonal \(\mu\to e\gamma\) helper at
flavorConstraints/muToEGamma.py:3,
flavorConstraints/muToEGamma.py:21, and
flavorConstraints/muToEGamma.py:81; that code is not an atomic or
hadronic EDM calculation.Implementation difficulty
HIGH. A live E007 constraint needs new CP-odd quark/gluon and
semileptonic matching, RG evolution to hadronic scales, and separate
nuclear/atomic response layers for Ra and Xe. The existing
SLL/SLR/VLL/VRR/LR \(\Delta F=2\) basis and the \(\mu\to e\gamma\) dipole
helper do not cover this observable.
Reason: Requires new CP-odd quark/gluon and semileptonic operator matching, RG evolution through QCD thresholds, and separate nuclear/atomic response models for Ra and Xe Schiff-moment dominated observables. Existing $\Delta F = 2$ and $\mu \to e \gamma$ code paths do not provide this observable.
Key references
Process-local source keys before bibliography consolidation:
Bishof:Ra225EDM2016, Parker:Ra225EDM2015,
Sachdeva:Xe129EDM2019, Allmendinger:Xe129EDM2019,
Argonne:Ra225EDMPage, DFG:Xe129Upgrade2026,
KULeuven:RaFMoleculeProject2023, and
CsakiFalkowskiWeiler:RSFlavor2008.