Precision Measurement of the (3p - 1s) XRay Transition in Muonic Hydrogen 1, 2

The (3p - 1s) Xray transition to the muonic hydrogen ground state was measured with a high� resolution crystal spectrometer. 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 hyper� fine splitting can be reported. The measurement supplements studies on line broadening effects induced by Coulomb deexcitation hindering the direct extraction of the pionnucleon scattering lengths from pionic hydrogen and deuterium Xray lines.