Status of the MUSE experiment
The 5.6q difference in proton radii measured with мp atoms and with ep atoms and scattering remains an unexplained puzzle. MUSE will measure the мp and ep elastic scatterings in the same experiment at the same time. The experiment determines cross-sections, two-photon effects, form-factors, and radii and allows мp and ep to be compared with reduced systematic uncertainties. These data should provide the best test of the lepton universality in a scattering experiment to date, about an order of magnitude improvement over previous tests, a 7q radius determination, and improved two-photon measurements.
R. Pohl, A. Antognini, F. Nez, F.D. Amaro, F. Biraben, et al. The size of the proton. Nature 466, 213 (2010). https://doi.org/10.1038/nature09250
A. Antognini et al. Proton structure from the measurement of 2S-2P transition frequencies of muonic hydrogen. Science 339, 417 (2013).
J. Bernauer et al. (A1 Collaboration). High-precision determination of the electric and magnetic form factors of the proton. Phys. Rev. Lett. 105, 242001 (2010). https://doi.org/10.1063/1.3647361
X. Zhan, K. Allada, D. Armstrong, J. Arrington, W. Bertozzi et al. High-precision measurement of the proton elastic form factor ratio мpGE/GM at low Q2. Phys. Lett. B 705, 59 (2011). https://doi.org/10.2172/978833
R. Pohl, R. Gilman, G. Miller, K. Pachucki. Muonic hydrogen and the proton radius puzzle. Annu. Rev. Nucl. Part. Sci. 63, 175 (2013). https://doi.org/10.1146/annurev-nucl-102212-170627
R. Pohl, G.A. Miller, R. Gilman et al. Workshop on the proton radius puzzle at the Trento European Center for Theory in Nuclear Physics and Related Areas (2012) https://ectstar.fbk.eu/node/49.
C. Carlson, R. Hill, S. Karshenboim, M. Vanderhaeghen et al. Workshop on the proton radius puzzle at the Mainz Institute for Theoretical Physics (2014).
R. Pohl, G. A. Miller, R. Gilman et al. Workshop on the proton radius puzzle at the Trento European Center for Theory in Nuclear Physics and Related Areas (2016) https://ectstar.fbk.eu/node/1659.
S. Agostinelli et al. GEANT4: A Simulation toolkit. Nucl. Instrum. Meth. A 506, 250 (2003).
R. Milner et al. The OLYMPUS experiment. Nuclear Inst. and Methods in Physics Research A 741, 1 (2014).
W. Erni et al. Technical design report for the P ANDA (AntiProton Annihilations at Darmstadt) straw tube tracker. Europ. Phys. J. A 49, 1 (2013).