The subtraction function contribution to the two-photon exchange

• Vladyslava Sharkovska (PSI - Paul Scherrer Institut)

Room: WBGB/021 The two-photon exchange (TPE) contribution to lepton-proton scattering and atomic transitions plays a particularly important role, as it brings about the main relative theoretical uncertainty. I will explain how the so-called 'subtraction function' enters the data-driven evaluation of the TPE as its model-dependent bit, and talk about the ways to address this model-dependence.

HyperMu: Measuring the Ground State HFS in Muonic Hydrogen

• Siddharth Rajamohanan (Jgu mainz)

Room: WBGB/021 Precision measurements on atoms and ions are a powerful tool for testing bound-state QED theory and the Standard Model. Experiments done in the last decade by the CREMA collaboration on muonic Hydrogen and Helium have given a more accurate understanding of the lightest nuclei charge radius. Our present experiment aims at a measurement of ground state Hyperfine Splitting in muonic hydrogen up to a relative accuracy of 1 ppm using pulsed laser spectroscopy. This allows us to determine the Zemach radius, which encodes the magnetic properties of the proton. A brief report on the unique laser system, multi-pass cavity, and scintillation detection system of the experiment is presented.