Spectroscopy as a test of Coulomb's law - A probe of the hidden sector

TL;DR

High precision atomic spectroscopy can test Coulomb's law and constrain new particles like hidden photons, with future experiments on muonic atoms offering potential to discover physics beyond the standard model.

Contribution

The paper extends Coulomb's law tests to larger mass ranges using atomic and exotic atom spectroscopy, and evaluates hidden photon explanations for muonic hydrogen discrepancies.

Findings

Spectroscopy constrains hidden photons and minicharged particles.

Future muonic atom experiments could explore new physics parameter space.

Hidden photon explanation for muonic hydrogen discrepancy is ruled out by Lamb shift measurements.

Abstract

High precision spectroscopy can provide a sensitive tool to test Coulomb's law on atomic length scales. This can then be used to constrain particles such as extra "hidden" photons or minicharged particles that are predicted in many extensions of the standard model, and which cause small deviations from Coulomb's law. In this paper we use a variety of transitions in atomic hydrogen, hydrogenic ions, and exotic atoms to probe Coulomb's law. This extends the region of pure Coulomb's law tests to larger masses. For hidden photons and minicharged particles this region is already tested by other astrophysical and laboratory probes. However, future tests of true muonium and muonic atoms are likely to probe new parameter space and therefore have good discovery potential for new physics. Finally, we investigate whether the discrepancy between the theoretical calculation of the 2s_{1/2}^{F=1} - 2p_{3/2}^{F=2} transition in muonic hydrogen and its recent experimental measurement at PSI can be explained by the existence of a hidden photon. This explanation is ruled out by measurements of the Lamb shift in ordinary hydrogen.