Details

Autor(en) / Beteiligte

• Adikaram, D
• Rimal, D
• Bennett, R P
• Arrington, J
• Adhikari, K P
• Amaryan, M J
• Anderson, M D
• Avakian, H
• Ball, J
• Battaglieri, M
• Bedlinskiy, I
• Biselli, A S
• Boiarinov, S
• Celentano, A
• Colaneri, L
• Contalbrigo, M
• Crede, V
• Dashyan, N
• De Sanctis, E
• Dodge, G E
• Dupre, R
• Elouadrhiri, L
• Fradi, A
• Garillon, B
• Gilfoyle, G P
• Giovanetti, K L
• Girod, F X
• Gohn, W
• Gothe, R W
• Griffioen, K A
• Guidal, M
• Guo, L
• Hafidi, K
• Hanretty, C
• Hattawy, M
• Hicks, K
• Holtrop, M
• Hughes, S M
• Hyde, C E
• Ilieva, Y
• Ishkhanov, B S
• Jenkins, D
• Jiang, H
• Jo, H S
• Joo, K
• Joosten, S
• Kalantarians, N
• Keller, D
• Khandaker, M
• Kim, A
• Kim, W
• Klein, A
• Koirala, S
• Kubarovsky, V
• Kuhn, S E
• Livingston, K
• Lu, H Y
• MacGregor, I J D
• Markov, N
• Mattione, P
• Mayer, M
• Mestayer, M D
• Meyer, C A
• Mirazita, M
• Mokeev, V
• Moody, C I
• Moutarde, H
• Camacho, C Munoz
• Niccolai, S
• Niculescu, G
• Osipenko, M
• Park, K
• Pasyuk, E
• Peña, C
• Pisano, S
• Pogorelko, O
• Price, J W
• Procureur, S
• Puckett, A J R
• Rizzo, A
• Rossi, P
• Sabatié, F
• Salgado, C
• Schumacher, R A
• Simonyan, A
• Skorodumina, I
• Smith, E S
• Smith, G D
• Sober, D I
• Stepanyan, S
• Stoler, P
• Taiuti, M
• Voutier, E
• Walford, N K
• Wei, X
• Wood, M H
• Zachariou, N
• Zana, L
• Zhao, Z W
• Zonta, I

Titel

Towards a resolution of the proton form factor problem: new electron and positron scattering data

Ist Teil von

• Physical review letters, 2015-02, Vol.114 (6), p.062003-062003, Article 062003

Ort / Verlag

United States: American Physical Society

Erscheinungsjahr

2015

Link zum Volltext

Quelle

PROLA - Physical Review Online Archive

Beschreibungen/Notizen

• There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45  GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75  GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3  GeV(2).