The ever-changing proton radius
Dr. Miha Mihovilovic (Kernphysik Mainz)

The discrepancy between the proton charge radius determined by Lamb shift measurements in muonic hydrogen and the radius obtained from elastic scat-tering submits all existing data to scrutiny and questions our understanding of QED. To provide new insight into the problem, several new experiments are underway. They are complemented by extensive theoretical efforts fo-cused on processes influencing the Lamb shift extractions as well as ways to interpret the form-factor measurements. Features and challenges of these new experiments will be discussed, together with the results of the most recent measurements and prospects for future studies.