Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton

• Published in: arXiv.org 2015-05
• Main Authors: Doria, L, Janssens, P, Achenbach, P, C Ayerbe Gayoso, Baumann, D, Bensafa, I, Benali, M, Beričič, J, Bernauer, J C, Böhm, R, Bosnar, D, Correa, L, D'Hose, N, Defaÿ, X, Ding, M, Distler, M O, Fonvieille, H, Friedrich, J, Friedrich, J M, Laveissière, G, Makek, M, Marroncle, J, Merkel, H, Mihovilovič, M, Müller, U, Nungesser, L, Pasquini, B, Pochodzalla, J, Postavaru, O, Potokar, M, Ryckbosch, D, S Sánchez Majos, Schlimme, B S, Seimetz, M, Širca, S, Tamas, G, Van de Vyver, R, L Van Hoorebeke, A Van Overloop, Walcher, Th, Weinriefer, M
• Format: Article
• Language: English
• Subjects: Elastic scattering; Electron beams; Polarimeters; Polarization; Recoil protons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1505.06106

Double-polarization observables in the reaction \(\vec{e}p \rightarrow e'\vec{p'}\gamma{}\) have been measured at \(Q^2=0.33 (GeV/c)^2\). The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil proton polarimeter. From the double-polarization observables the structure function \(P_{LT}^\perp\) is extracted for the first time, with the value \((-15.4 \pm 3.3 (stat.)^{+1.5}_{-2.4} (syst.)) GeV^{-2}\), using the low-energy theorem for Virtual Compton Sattering. This structure function provides a hitherto unmeasured linear combination of the generalized polarizabilities of the proton.