Dr Patrik Adlarson (Johannes Gutenberg Universität-Mainz)Dr Vahe Sokhoyan (Johannes Gutenberg Universität-Mainz)
One of today’s most pressing question in nuclear physics is the understanding of the so-called "proton radius puzzle". The puzzle originates from a striking discrepancy between the electric charge radius of the proton, extracted from the muonic hydrogen Lamb shift, compared to measurements based on electron-proton scattering experiments and atomic transition measurements in electronic hydrogen. Solving this problem requires experiments approaching the problem in new ways. To address this puzzle, we will perform a high- precision measurement of the differential ep-scattering cross section in the region of low momentum transfer at the Mainz Microtron (MAMI). To perform this experiment, a new-generation detector, consisting of a Hydrogen Time Projection Chamber (TPC) and Forward Tracking System will be constructed, and a new electron beam line at MAMI will be built. The experimental setup will allow us to measure the energy and angle of the recoil proton with unprecedented accuracy as well as the angle of the forward scattered electron. This is a completely new approach compared to other experiments, which mainly focus on the electron angle. A test measurement with a TPC prototype will be conducted at MAMI in August 2017, which will serve as basis for the main experiment.