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Accueil > Recherche > (GRIFON) GRoupe Interactions FOndamentales et nature du Neutrino

ProRad (english)



ProRad : Measurement of the proton charge radius by electron scattering
The proton puzzle originates from the significant difference between the proton charge radius R measured in atomic physics and that measured in subatomic physics. Despite a large number of possible explanations ranging from experimental questions to physics beyond the Standard Model, existing data do not allow to reach a consensus. In this context, the ProRad project (Proton Radius) aims to study this problem by measuring the electron elastic scattering off proton at small angle and with incident electrons energy in the 30 to 70 MeV domain.
The high-performance electron beam of the Research and Applications Platform with Electrons (PRAE) will provide very accurate measurements of the proton electric form factor at very low energy transfer, thereby helping to understand the differences between the results from atomic and subatomic physics. This objective requires the development of complex technologies, in particular a beam energy compression system, a high precision spectrometer for the beam energy measurement and a jet of liquid hydrogen serving as a pure target. Any deviation from 1 (the electric charge of the proton) of the electric form factor would indicate the existence of unexpected or genuine physical effects and/or possible effects of physics beyond the Standard Model. Accurate experimental data in this unexplored energy range will allow a more precise determination of the proton charge radius, to finally confirm or solve the problem.