Line shape of the muH(3p - 1s) hyperfine transitions

TL;DR

This paper reports high-resolution measurements of muonic hydrogen hyperfine transitions, confirming hyperfine level populations and Doppler broadening effects, which enable testing cascade models and extracting strong-interaction parameters.

Contribution

It provides the first direct experimental confirmation of hyperfine level populations and Doppler broadening in muonic hydrogen transitions, aiding fundamental physics tests.

Findings

Confirmation of statistical hyperfine level populations

Observation of Doppler broadening due to Coulomb de-excitation

Measurement of hyperfine splitting values

Abstract

The (3p - 1s) X-ray transition to the muonic hydrogen ground state was measured with a high resolution crystal spectrometer. A Doppler effect broadening of the X-ray line was established which could be attributed to different Coulomb de-excitation steps preceding the measured transition. The assumption of a statistical population of the hyperfine levels of the muonic hydrogen ground state was directly confirmed by the experiment and measured values for the hyperfine splitting can be reported. The results allow a decisive test of advanced cascade model calculations and establish a method to extract fundamental strong-interaction parameters from pionic hydrogen experiments.