# Review of experimental and theoretical status of the proton radius puzzle

## TL;DR

This paper reviews the current experimental and theoretical understanding of the proton radius puzzle, highlighting discrepancies in measurements and recent developments impacting fundamental physics.

## Contribution

It provides a comprehensive overview of the status of measurements, theories, and implications related to the proton radius puzzle, emphasizing recent progress and unresolved issues.

## Key findings

- Discrepancy between muonic hydrogen and electron-based measurements
- Recent theoretical models attempt to explain the puzzle
- Implications for fundamental constants and physics theories

## Abstract

The discrepancy between the measured Lamb shift in muonic hydrogen and expectations from electron-proton scattering and regular hydrogen spectroscopy has become known as the proton radius puzzle, whose most "mundane" resolution requires a $> 5 \sigma$ shift in the value of the fundamental Rydberg constant. I briefly review the status of spectroscopic and scattering measurements, recent theoretical developments, and implications for fundamental physics.