Abstract Spectroscopy of muonic atoms provides a powerful probe for new short-range interactions predicted by theories beyond the Standard Model (SM). In this work, we derive new constraints on both spin-independent and spin-dependent non-Newtonian gravity by leveraging the outstanding sensitivity of these systems. For spin-independent Yukawa-type forces, we analyze two complementary approaches: the 2S-2P 2 S - 2 P Lamb shift in the muonic helium-4 ion and the deuteron–proton squared charge radii difference obtained from the muonic hydrogen–deuterium isotope shift. The found constraints have reached a competitive level at sub-picometer scales, with the isotope shift method yielding the most stringent bounds for the entire sub-nanometer range and significantly surpassing limits derived exclusively from electronic atom spectroscopy for 10^-12 m λ ≲ 10 - 12 m. For spin-dependent effects, we analyze the influence of the gravitational spin–orbit coupling on the 2P₃/₂-2P₁/₂ 2 P 3 / 2 - 2 P 1 / 2 fine-structure splitting in muonic helium, establishing new limits on post-Newtonian parameters. These bounds are shown to be more restrictive than those from other leading experimental techniques for ranges 10^-11 m λ ≲ 10 - 11 m. Our findings highlight the widespread usefulness of muonic atoms in exploring new fundamental physics at short-distance scales.
Matias et al. (Tue,) studied this question.