Towards a resolution of the proton form factor problem: new electron and positron scattering data - IN2P3 - Institut national de physique nucléaire et de physique des particules
Journal Articles Physical Review Letters Year : 2015

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

D. Adikaram , D. Rimal , L. B. Weinstein , B. Raue , P. Khetarpal , R. P. Bennett , J. Arrington , W. K. Brooks , K. P. Adhikari , A. V. Afanasev , M. J. Amaryan , M. D. Anderson , J. Ball (1) , M. Battaglieri , I. Bedlinskiy , A. S. Biselli , J. Bono , S. Boiarinov , W. J. Briscoe , V. D. Burkert , D. S. Carman , A. Celentano , S. Chandavar , G. Charles (1) , L. Colaneri , P. L. Cole , M. Contalbrigo , A. d'Angelo , N. Dashyan , R. de Vita , E. de Sanctis , A. Deur , C. Djalali , G. E. Dodge , R. Dupre (2) , H. Egiyan , A. El Alaoui , L. El Fassi , P. Eugenio , G. Fedotov , S. Fegan , A. Filippi , J. A. Fleming , A. Fradi , G. P. Gilfoyle , K. L. Giovanetti , F. X. Girod , J. T. Goetz , W. Gohn , E. Golovatch , R. W. Gothe , K. A. Griffioen , M. Guidal (2) , L. Guo , K. Hafidi , H. Hakobyan , N. Harrison , M. Hattawy (2) , K. Hicks , M. Holtrop , S. M. Hughes , C. E. Hyde , Y. Ilieva , D. G. Ireland , B. S. Ishkhanov , D. Jenkins , H. Jiang , K. Joo , S. Joosten , M. Khandaker , W. Kim , A. Klein , F. J. Klein , S. Koirala , V. Kubarovsky , S. E. Kuhn , H. Y. Lu , I . J . D. Macgregor , N. Markov , M. Mayer , B. Mckinnon , M. D. Mestayer , C. A. Meyer , M. Mirazita , V. Mokeev , R. A. Montgomery , C. I. Moody , H. Moutarde , A Movsisyan , C. Muñoz Camacho (2) , P. Nadel-Turonski , S. Niccolai (2) , G. Niculescu , M. Osipenko , A. I. Ostrovidov , K. Park , E. Pasyuk , S. Pisano (2) , O. Pogorelko , S. Procureur (1) , Y. Prok , D. Protopopescu , A. J. R. Puckett , M. Ripani , A. Rizzo , G. Rosner , P. Rossi , F. Sabatié (1) , D. Schott , R. A. Schumacher , Y. G. Sharabian , A. Simonyan , I. Skorodumina , E. S. Smith , G. D. Smith , D. I. Sober , N. Sparveris , S. Stepanyan , S. Strauch , V. Sytnik , M. Taiuti , Ye Tian , A. Trivedi , M. Ungaro , H. Voskanyan , E. Voutier (3) , N. K. Walford , D. P. Watts , X. Wei , M. H. Wood , N. Zachariou , L. Zana , J. Zhang , Z. W. Zhao , I. Zonta
D. Adikaram
  • Function : Author
D. Rimal
  • Function : Author
L. B. Weinstein
  • Function : Author
B. Raue
  • Function : Author
P. Khetarpal
  • Function : Author
R. P. Bennett
  • Function : Author
J. Arrington
  • Function : Author
W. K. Brooks
  • Function : Author
K. P. Adhikari
  • Function : Author
A. V. Afanasev
  • Function : Author
M. J. Amaryan
  • Function : Author
M. D. Anderson
  • Function : Author
M. Battaglieri
  • Function : Author
I. Bedlinskiy
A. S. Biselli
  • Function : Author
J. Bono
  • Function : Author
S. Boiarinov
  • Function : Author
W. J. Briscoe
  • Function : Author
V. D. Burkert
  • Function : Author
D. S. Carman
  • Function : Author
A. Celentano
S. Chandavar
  • Function : Author
L. Colaneri
  • Function : Author
P. L. Cole
  • Function : Author
M. Contalbrigo
  • Function : Author
A. d'Angelo
N. Dashyan
  • Function : Author
R. de Vita
  • Function : Author
E. de Sanctis
  • Function : Author
A. Deur
C. Djalali
  • Function : Author
G. E. Dodge
  • Function : Author
R. Dupre
H. Egiyan
A. El Alaoui
  • Function : Author
L. El Fassi
  • Function : Author
P. Eugenio
  • Function : Author
G. Fedotov
  • Function : Author
S. Fegan
  • Function : Author
A. Filippi
  • Function : Author
J. A. Fleming
  • Function : Author
A. Fradi
  • Function : Author
G. P. Gilfoyle
  • Function : Author
K. L. Giovanetti
  • Function : Author
F. X. Girod
  • Function : Author
J. T. Goetz
  • Function : Author
W. Gohn
  • Function : Author
E. Golovatch
  • Function : Author
R. W. Gothe
  • Function : Author
K. A. Griffioen
  • Function : Author
L. Guo
  • Function : Author
K. Hafidi
  • Function : Author
H. Hakobyan
  • Function : Author
N. Harrison
  • Function : Author
K. Hicks
  • Function : Author
M. Holtrop
S. M. Hughes
  • Function : Author
C. E. Hyde
  • Function : Author
Y. Ilieva
  • Function : Author
D. G. Ireland
  • Function : Author
B. S. Ishkhanov
  • Function : Author
D. Jenkins
  • Function : Author
H. Jiang
  • Function : Author
K. Joo
  • Function : Author
S. Joosten
M. Khandaker
W. Kim
  • Function : Author
A. Klein
  • Function : Author
F. J. Klein
  • Function : Author
S. Koirala
  • Function : Author
V. Kubarovsky
  • Function : Author
S. E. Kuhn
  • Function : Author
H. Y. Lu
  • Function : Author
I . J . D. Macgregor
  • Function : Author
N. Markov
  • Function : Author
M. Mayer
  • Function : Author
B. Mckinnon
  • Function : Author
M. D. Mestayer
  • Function : Author
C. A. Meyer
  • Function : Author
M. Mirazita
  • Function : Author
V. Mokeev
R. A. Montgomery
  • Function : Author
C. I. Moody
  • Function : Author
H. Moutarde
  • Function : Author
A Movsisyan
  • Function : Author
P. Nadel-Turonski
  • Function : Author
G. Niculescu
  • Function : Author
M. Osipenko
A. I. Ostrovidov
  • Function : Author
K. Park
  • Function : Author
E. Pasyuk
O. Pogorelko
  • Function : Author
Y. Prok
  • Function : Author
D. Protopopescu
A. J. R. Puckett
  • Function : Author
M. Ripani
A. Rizzo
  • Function : Author
G. Rosner
  • Function : Author
P. Rossi
  • Function : Author
D. Schott
  • Function : Author
R. A. Schumacher
  • Function : Author
Y. G. Sharabian
  • Function : Author
A. Simonyan
  • Function : Author
I. Skorodumina
  • Function : Author
E. S. Smith
  • Function : Author
G. D. Smith
  • Function : Author
D. I. Sober
  • Function : Author
N. Sparveris
S. Stepanyan
  • Function : Author
S. Strauch
  • Function : Author
V. Sytnik
  • Function : Author
M. Taiuti
  • Function : Author
Ye Tian
A. Trivedi
  • Function : Author
M. Ungaro
  • Function : Author
H. Voskanyan
  • Function : Author
N. K. Walford
  • Function : Author
D. P. Watts
  • Function : Author
X. Wei
  • Function : Author
M. H. Wood
  • Function : Author
N. Zachariou
L. Zana
J. Zhang
  • Function : Author
Z. W. Zhao
  • Function : Author
I. Zonta
  • Function : Author

Abstract

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 ($\varepsilon$) and momentum transfer ($Q^2$) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing $\varepsilon$ at $Q^2 = 1.45 \text{ GeV}^2$. This measurement is consistent with the size of the form factor discrepancy at $Q^2\approx 1.75$ GeV$^2$ and with hadronic calculations including nucleon and $\Delta$ intermediate states, which have been shown to resolve the discrepancy up to $2-3$ GeV$^2$.
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Dates and versions

in2p3-01088523 , version 1 (30-10-2024)

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D. Adikaram, D. Rimal, L. B. Weinstein, B. Raue, P. Khetarpal, et al.. Towards a resolution of the proton form factor problem: new electron and positron scattering data. Physical Review Letters, 2015, 114, pp.062003. ⟨10.1103/PhysRevLett.114.062003⟩. ⟨in2p3-01088523⟩
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