The proton structure in and out of muonic hydrogen

TL;DR

This paper discusses how muonic hydrogen spectroscopy reveals nuclear and nucleon structure effects on atomic energy levels, providing updated theoretical predictions and exploring implications for fundamental physics and nucleon spin understanding.

Contribution

It introduces nuclear effects and nucleon structure contributions to muonic hydrogen energy levels, offering new theoretical predictions and analysis methods.

Findings

Updated Lamb shift and HFS predictions for muonic hydrogen.

A novel scaling method for hyperfine splitting measurements.

Insights into nucleon spin structure from spectroscopy data.

Abstract

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 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.