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A: Fachverband Atomphysik

A 13: Highly Charged Ions and their Applications II

A 13.3: Talk

Tuesday, March 3, 2026, 11:45–12:00, N 25

Stringent Constraints on New Pseudoscalar & Vector Bosons from Precision Hyperfine Splitting Measurements — •Cedric Quint¹, Fabian Heiße¹, Joerg Jaeckel², Lutz Leimenstoll², Christoph H. Keitel¹, and Zoltán Harman¹ — ¹Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg — ²Insitute for Theoretical Physics, Philosophenweg 16, 69120 Heidelberg

Axion-like particles and similar new pseudoscalar as well as vector bosons coupled to nucleons and electrons are predicted to lead to spin-dependent forces in atoms and ions. We argue that hyperfine structure measurements in hydrogen- and lithium-like charge states are a sensitive probe to this effect. Employing specific differences of these splittings reduces uncertainties due to nuclear effects in hyperfine structure calculations and measurements. Using this, we show that existing measurements on Be provide competitive limits in the region m_φ 100 keV, improving upon existing constraints by up to a factor of 2 for pseudoscalar couplings. We also find that future measurements on Cs have a further factor of 2 − 2.5 improved discovery potential for pseudoscalars and an order of magnitude for new vector bosons when compared with the corresponding current constraints.
Reference: 2506.03274

Keywords: New Physics; Hyperfine Structure; Specific Difference