Searches for electric dipole moments of elementary particles with radioactive molecules

Prof. Robert Berger (Philipps-Universitaet Marburg, Germany)

The current standard model of particle physics accommodates violations of combined parity (P) and charge reversal (C) symmetry, one of the ingredients considered fundamentally necessary to yield an imbalance in the abundance of matter compared to antimatter. According to common belief, however, CP-violating effects within the standard model remain yet too small to account for the apparent predominance of matter over antimatter in our universe, which triggered the search for other sources of CP-violation beyond the standard model. One appealing route, complementary to collider experiments, is to attempt to detect sizeable electric dipole moments (EDMs) of elementary particles. Those moments require forces being odd with respect to both time-reversal (T) and parity (P) symmetry and are linked via that CPT-theorem indirectly to CP-violation.

Heavy-elemental radioactive molecules [1-6] have emerged in recent years as an intriguing platform to search for EDMs both in the leptonic and the hadronic sector, because well-chosen molecular systems allow to strongly enhance CP-violating effects caused by different sources [7]. In this talk, I will discuss theoretical aspects, progress, opportunities and challenges in the search for EDMs of elementary particles by spectroscopy of small radioactive molecules and plan to indicate also briefly additional molecular routes to detect new physics [8].

[1] Isaev, Hoekstra, Berger, Phys. Rev. A, 82 (2010) 052521.
[2] Gaul, Marquardt, Isaev, Berger, Phys. Rev. A 99 (2019) 032509.
[3] Garcia Ruiz et al., Nature, 581 (2020) 396;
Udrescu et al., Phys. Rev. Lett. 127 (2021) 03301;
Udrescu et al., Nat. Phys. 20 (2024) 202;
Wilkins et al, Science 390 (2025) 386.
[4] Arrowsmith-Kron et al., Rep. Prog. Phys 87 (2024) 084301.
[5] Athanasakis-Kaklamanakis et al., 648 (2025) 562.
[6] Zuelch, Gaul, Giesen, Garcia Ruiz, Berger, arXiv:2203.10333.
[7] Gaul, Berger, J. High Energ. Phys. 2024 (2024) 100.
[8] Zuelch, Gaul, Berger, arXiv:2511.10791.