Bounds on fifth forces at the sub-Angstrom length scale

TL;DR

This paper establishes new experimental limits on hypothetical fifth-force interactions at sub-Angstrom scales by analyzing precision spectroscopic data of exotic atomic systems, constraining potential new physics beyond the Standard Model.

Contribution

It provides the first constraints on fifth-force interactions at sub-Angstrom distances using laser spectroscopy and muon-catalyzed fusion data, within a quantum electrodynamical framework.

Findings

Laser spectroscopic data constrain fifth-force strength to less than 10^{-8} of electromagnetic at <1 Å.

Muon-catalyzed fusion experiments limit fifth-force strength to about 10^{-5} of electromagnetic at <0.05 Å.

Results set new bounds on hypothetical particles mediating short-range forces.

Abstract

Constraints on a possible fifth-force interaction between hadrons are derived based on an analysis of results from laser precision frequency measurements of antiprotonic helium atoms, both $\bar{p}\,^{4}$He$^{+}$ and $\bar{p}\,^{3}$He$^{+}$ species, and from experiments on resonant formation rates of $dd\mu^{+}$-ions in muon-catalyzed fusion processes. A comparison is made between accurate experimental data and first-principles theoretical descriptions of the exotic systems within a quantum electrodynamical framework. The agreement between theory and experiment sets limits on a possible additional hadron-hadron interaction written in the form of a Yukawa potential $V_5(r)=\alpha_5 \exp(-r/\lambda)/r$, with $\lambda$ representing the characteristic length scale associated with the mass of a hypothetical force-carrying particle via $\lambda=\hbar/(m_5c)$. The laser spectroscopic data of antiprotonic helium set a constraint of $\alpha_5/\alpha_{EM} < 10^{-8}$ for $\lambda < 1$ \AA, while the binding energy of the muonic molecular deuterium ion delivers a constraint of $\alpha_5/\alpha_{EM} \sim 10^{-5}$ for $\lambda < 0.05$ \AA, where $\alpha_{EM}$ represents the strength of the electromagnetic interaction or the fine structure constant.