Pionic Hydrogencollaboration © 2007
Webmaster: D.Gotta
Design: M.Nekipelov
In order to improve the quality of the energy calibration the copper fluorescence X-rays were replaced by choosing a muonic-atom transition as energy standard. The mass of the muon is known by two orders of magnitude better than the one of the pion. As the pionic nitrogen and muonic oxygen (5-4) transition have almost the same energy, a simultanuous measurement of both transitions became feasible when using an nitrogen/oxygen gas mixture. With this method, an improvement in the accuracy is achieved by a factor of about 3 compared to the copper calibration. Measurement of the charged pion mass using X-ray spectroscopy of exotic atoms Phys. Lett. B 759 (2016) 583
Crystal spectrometers in Johann set-up require for ultimate energy determination a calibration line with a Bragg angle as close as possible to the line under study. The detector described was set up for the simultanuous measurement of such line pairs in measurements determining the charged pion mass and the pion-nucleon scattering lengths from pionic hydrogen. A large area CCD X-ray detector for exotic atom spectroscopy Nucl. Instrum. Meth. A 484 (2002) 419
Exotic-atom X-rays emitted from atoms originating from molecular targets exhibit a significant Doppler broadening. The broadening is especially pronounced for diatomic systems like nitrogen and oxygen, which play a key role in the ultimate precision determination of the pion mass. The Doppler broasdening has been quantified from a direct measurement comparing pionic neon with pionic nitrogen and muonic oxygen. First direct observation of Coulomb explosion during the formation of exotic atoms Phys. Rev. Lett. 84 (2000) 4573
The precise determination of the mass of the negatively charged pion from exotic-atom X-ray spectroscopy relies on the knowledge on the remaining electrons at the instant of X-ray emission. Such an uncertainty can be avoided by using dilute gases of low Z elements as targets where during the atomic de-exciatation cascade the pion is able to eject all electrons. Due to the short cascade time refilling from atomic colllisons is strongly suppressed. The measurement of pionic nitrogen resolves the ambiguity from a measurement of pionic magnesium using a solid state target, which stems from the unknown status of the electronic K shell. The energy calibration is performed by means of copper Kα fluorescence X-rays the natural line width of which limits the accuracy to about 4ppm for the pion mass. A new determination of the mass of the charged pion Phys. Lett. B 416 (1998) 50