Contributor info: Prof. Detlev Gotta

D. Gotta, L. M. Simons

SciPost Phys. Proc. 5, 014 (2021) · published 6 September 2021 | Toggle abstract · pdf

The measurement of strong-interaction shift and broadening in pionic hydrogen and deuterium yields pion-nucleon scattering lengths as well as the threshold pion-production strength on isoscalar NN pairs. Results from recent high-resolution experiments at PSI using crystal spectrometers allow important comparisons with the outcome of the modern low-energy description of QCD within the framework of effective field theories.

D. Gotta, L. M. Simons

SciPost Phys. Proc. 5, 013 (2021) · published 6 September 2021 | Toggle abstract · pdf

The cyclotron trap was developed at SIN/PSI to increase the stopping density of nega- tively charged particle beams for the formation of exotic atoms in low pressure gases. A weak focusing magnetic field, produced by superconducting solenoids, is used. Particles are injected radially through the fringe field to a moderator, which decelerates them into orbits bound by the field. Further deceleration by moderators and/or low-pressure gases leads the particles to the center of the device, where they can be stopped or eventually extracted. Experiments became feasible with this technique, such as those dealing with pionic hydrogen/deuteriumat SIN/PSI.Muonic hydrogen laser experiments also became possible with the extraction of muons from the cyclotron trap. The formation of antipro- tonic hydrogen in low pressure targets led to successful experiments at LEAR/CERN.

M. Daum, D. Gotta

SciPost Phys. Proc. 5, 010 (2021) · published 6 September 2021 | Toggle abstract · pdf

The most precise values of the mass of the negatively charged pion have been determined from several measurements of X-ray wavelengths for transitions in pionic atoms at PSI. The Particle Data Group gives the average $m_{\pi^-}= (139.570 61 \pm 0.000 24) MeV/c^2$.