https://doi.org/10.1140/epja/s10050-021-00508-6
Regular Article - Experimental Physics
Elastic positron–proton scattering at low Q
1
North Carolina A&T State University, 27411, Greensboro, NC, USA
2
Jefferson Lab, 23601, Newport News, VA, USA
3
Department of Physics and Astronomy, Mississippi State University, 39762, Starkville, MS, USA
4
Department of Physics, Duke University, 27708, Durham, NC, USA
5
Triangle Universities Nuclear Laboratory, 27708, Durham, NC, USA
6
Department of Physics, University of Virginia, 22904, Charlottesville, VA, USA
7
Energy Systems, 95616, Davis, CA, USA
8
Physics Division, Argonne National Laboratory, 60439, Lemont, IL, USA
9
Department of Physics, Syracuse University, 13244, Syracuse, NY, USA
Received:
25
February
2021
Accepted:
30
May
2021
Published online:
19
June
2021
Systematic differences in the the proton’s charge radius, as determined by ordinary atoms and muonic atoms, have caused a resurgence of interest in elastic lepton scattering measurements. The proton’s charge radius, defined as the slope of the charge form factor at Q = 0, does not depend on the probe. Any difference in the apparent size of the proton, when determined from ordinary versus muonic hydrogen, could point to new physics or need for the higher order corrections. While recent measurements seem to now be in agreement, there is to date no high precision elastic scattering data with both electrons and positrons. A high precision proton radius measurement could be performed in Hall B at Jefferson Lab with a positron beam and the calorimeter based setup of the PRad experiment. This measurement could also be extended to deuterons where a similar discrepancy has been observed between the muonic and electronic determination of deuteron charge radius. A new, high precision measurement with positrons, when viewed alongside electron scattering measurements and the forthcoming MUSE muon scattering measurement, could help provide new insights into the origins of the proton radius puzzle, and also provide new experimental constraints on radiative correction calculations.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021
