Probing new hadronic forces with heavy exotic atoms

Abstract

We explore the potential of precision spectroscopy of heavy exotic atoms where electrons are substituted by negative hadrons to detect new force carriers with hadronic couplings. The selected transitions are unaffected by nuclear contact terms, thus enabling highly accurate calculations using bound-state QED, provided that the nuclear polarization is under control. Alternatively, we demonstrate that the dipole polarizability, a fundamental property of nuclei, can be extracted from the spectroscopy of exotic atoms in a novel way by combining two transitions while maintaining high sensitivity to new physics. Based on existing data, we extracted world-leading bounds on mediator masses ranging from $0.1\,$MeV to $10\,$MeV for two benchmark models and show that forthcoming experiments could enhance the sensitivity to new physics by two orders of magnitude.

Figures (3)

• Figure 1: $\bar{p}^{132}\rm{Xe}$ projections with $R_\sigma=10^{-6}$. The projected bound in dotted (dot-dashed) blue is for the $\left(10,9\right)\rightarrow\left(9,8\right)$ transition with (without) 50% polarizability error that constitutes a 10 ppm uncertainty to the NPol contribution. In dashed light blue we show the bound for combining two transitions: $\left(11,10\right)\rightarrow\left(10,9\right)$ and $\left(10,9\right)\rightarrow\left(9,8\right)$ to reduce the sensitivity to NPol.
• Figure 2: New bounds (shaded solid) and projections (dashed) from this work compared to existing bounds from $\bar{p}\,^4$He and HD$^{+}$ (shaded gray area).
• Figure 3: Same as Fig. \ref{['fig:new gHgN bound']} with Left: the $uds$-scalar model. Right: the $B$-boson model with additional bounds from NA64, CODATA, and new anomaly-canceling fermions (see main text for details).