The Proton Structure in and out of Muonic Hydrogen

Laser spectroscopy of muonic atoms has been recently used to probe properties of light nuclei with unprecedented precision. We introduce nuclear effects in hydrogen-like atoms, nucleon structure quantities (form factors, structure functions, polarizabilities), and their effects in the Lamb shift and hyperfine splitting (HFS) of muonic hydrogen (mu H). Updated theory predictions for the Lamb shift and HFS in mu H are presented. We review the challenges of the ongoing effort to measure the ground-state HFS in mu H and its impact on our understanding of the nucleon spin structure. To narrow down this search, we present a novel theory prediction obtained by scaling the measured HFS in hydrogen while leveraging radiative corrections. We also summarize recent developments in the spectroscopy of simple atomic and molecular systems and emphasize how they allow for precise determinations of fundamental constants, bound-state QED tests, and New Physics searches.

Automated summary

This article introduces the application of laser spectroscopy in studying light nuclei properties, with a focus on the nuclear effects and nucleon structure quantities in the Lamb shift and hyperfine splitting of muonic hydrogen. It presents new theoretical predictions and discusses challenges in measurements, as well as recent developments in spectroscopy of simple atomic and molecular systems.