First measurement of proton's charge form factor at very low $Q^2$ with initial state radiation

M. Mihovilovič , A.B. Weber , P. Achenbach , T. Beranek , J. Beričič , J.C. Bernauer , R. Böhm , D. Bosnar , M. Cardinali , L. Correa (1) , L. Debenjak , A. Denig , M.O. Distler , A. Esser , M.I. Ferretti Bondy , H. Fonvieille (1) , J.M. Friedrich , I. Friščić , K. Griffioen , M. Hoek , S. Kegel , Y. Kohl , H. Merkel , D.G. Middleton , U. Müller , L. Nungesser , J. Pochodzalla , M. Rohrbeck , S. Sánchez Majos , B.S. Schlimme , M. Schoth , F. Schulz , C. Sfienti , S. Širca , S. Štajner , M. Thiel , A. Tyukin , M. Vanderhaeghen , M. Weinriefer

1 LPC - Laboratoire de Physique de Clermont

We report on a new experimental method based on initial-state radiation (ISR) in e – p scattering, which exploits the radiative tail of the elastic peak to study the properties of electromagnetic processes and to extract the proton charge form factor ( GEp ) at extremely small Q2 . The ISR technique was implemented in an experiment at the three-spectrometer facility of the Mainz Microtron (MAMI). This led to a precise validation of radiative corrections far away from elastic line and provided first measurements of GEp for 0.001≤Q2≤0.004(GeV/c)2 .

Mots clés: 12.20.-m; 25.30.Bf; 41.60.-m; Initial state radiation; Proton; Form factor; Radiative corrections; form factor: charge; p: charge; radiation: initial-state interaction; electron p: scattering; Lamb shift; Bethe-Heitler; elastic scattering; beam: current; spectrometer; microtron; Mainz Linac; experimental methods; numerical calculations; experimental results

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des Hautes Energies - Expérience [hep-ex]

M. Mihovilovič, A.B. Weber, P. Achenbach, T. Beranek, J. Beričič, et al.. First measurement of proton's charge form factor at very low $Q^2$ with initial state radiation. Phys.Lett.B, 2017, 771, pp.194-198. ⟨10.1016/j.physletb.2017.05.031⟩. ⟨hal-01554811⟩