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Title: Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

Abstract

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE 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 (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.

Authors:
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Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); Instituto Nazionale di Fisica Nucleare (INFN); Centre National de la Recherche Scientifique (CNRS); National Science Foundation (NSF)
Contributing Org.:
CLAS Collaboration
OSTI Identifier:
1169688
Alternate Identifier(s):
OSTI ID: 1180924; OSTI ID: 1251618
Report Number(s):
JLAB-PHY-14-1960; DOE/OR/23177-3300; arXiv:1411.6908
Journal ID: ISSN 0031-9007; PRLTAO; ArticleNumber: 062003
Grant/Contract Number:
AC05-06OR23177; FG02-96ER40960; AC02-06CH11357; AC05-060R23177
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 114; Journal Issue: 6; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Adikaram, D., Rimal, D., Weinstein, L. B., Raue, B., Khetarpal, P., Bennett, R., Arrington, J., Brooks, W., Adhikari, K., Afanasev, A., Amaryan, M., Anderson, M., Anefalos Pereira, S., Avakian, H., Ball, J., Battaglieri, M., Bedlinskiy, I., Biselli, A., Bono, J., Boiarinov, S., Briscoe, W., Burkert, V., Carman, D., Careccia, S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P., Contalbrigo, M., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dodge, G., Dupre, R., Egiyan, H., El Alaoui, A., El Fassi, L., Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fleming, J., Fradi, A., Garillon, B., Gilfoyle, G., Giovanetti, K., Girod, F., Goetz, J., Gohn, W., Golovatch, E., Gothe, R., Griffioen, K., Guegan, B., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Hicks, K., Holtrop, M., Hughes, S., Hyde, C. E., Ilieva, Y., Ireland, D., Ishkhanov, B., Jenkins, D., Jiang, H., Jo, H., Joo, K., Joosten, S., Kalantarians, N., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F., Koirala, S., Kubarovsky, V., Kuhn, S., Livingston, K., Lu, H., MacGregor, I., Markov, N., Mattione, P., Mayer, M., McKinnon, B., Mestayer, M., Meyer, C., Mirazita, M., Mokeev, V., Montgomery, R., Moody, C., Moutarde, H., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A., Park, K., Pasyuk, E., Pisano, S., Pogorelko, O., Price, J., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A., Ripani, M., Rizzo, A., Rosner, G., Rossi, P., Roy, P., Sabati, F., Salgado, C., Schott, D., Schumacher, R., Seder, E., Sharabian, Y., Simonyan, A., Skorodumina, I., Smith, E., Smith, G., Sober, D., Sokhan, D., Sparveris, N., Stepanyan, S., Stoler, P., Strauch, S., Sytnik, V., Taiuti, M., Tian, Ye, Trivedi, A., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N., Watts, D., Wei, X., Wood, M., Zachariou, N., Zana, L., Zhang, J., Zhao, Z., and Zonta, I.. Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data. United States: N. p., 2015. Web. doi:10.1103/PhysRevLett.114.062003.
Adikaram, D., Rimal, D., Weinstein, L. B., Raue, B., Khetarpal, P., Bennett, R., Arrington, J., Brooks, W., Adhikari, K., Afanasev, A., Amaryan, M., Anderson, M., Anefalos Pereira, S., Avakian, H., Ball, J., Battaglieri, M., Bedlinskiy, I., Biselli, A., Bono, J., Boiarinov, S., Briscoe, W., Burkert, V., Carman, D., Careccia, S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P., Contalbrigo, M., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dodge, G., Dupre, R., Egiyan, H., El Alaoui, A., El Fassi, L., Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fleming, J., Fradi, A., Garillon, B., Gilfoyle, G., Giovanetti, K., Girod, F., Goetz, J., Gohn, W., Golovatch, E., Gothe, R., Griffioen, K., Guegan, B., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Hicks, K., Holtrop, M., Hughes, S., Hyde, C. E., Ilieva, Y., Ireland, D., Ishkhanov, B., Jenkins, D., Jiang, H., Jo, H., Joo, K., Joosten, S., Kalantarians, N., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F., Koirala, S., Kubarovsky, V., Kuhn, S., Livingston, K., Lu, H., MacGregor, I., Markov, N., Mattione, P., Mayer, M., McKinnon, B., Mestayer, M., Meyer, C., Mirazita, M., Mokeev, V., Montgomery, R., Moody, C., Moutarde, H., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A., Park, K., Pasyuk, E., Pisano, S., Pogorelko, O., Price, J., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A., Ripani, M., Rizzo, A., Rosner, G., Rossi, P., Roy, P., Sabati, F., Salgado, C., Schott, D., Schumacher, R., Seder, E., Sharabian, Y., Simonyan, A., Skorodumina, I., Smith, E., Smith, G., Sober, D., Sokhan, D., Sparveris, N., Stepanyan, S., Stoler, P., Strauch, S., Sytnik, V., Taiuti, M., Tian, Ye, Trivedi, A., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N., Watts, D., Wei, X., Wood, M., Zachariou, N., Zana, L., Zhang, J., Zhao, Z., & Zonta, I.. Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data. United States. doi:10.1103/PhysRevLett.114.062003.
Adikaram, D., Rimal, D., Weinstein, L. B., Raue, B., Khetarpal, P., Bennett, R., Arrington, J., Brooks, W., Adhikari, K., Afanasev, A., Amaryan, M., Anderson, M., Anefalos Pereira, S., Avakian, H., Ball, J., Battaglieri, M., Bedlinskiy, I., Biselli, A., Bono, J., Boiarinov, S., Briscoe, W., Burkert, V., Carman, D., Careccia, S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P., Contalbrigo, M., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dodge, G., Dupre, R., Egiyan, H., El Alaoui, A., El Fassi, L., Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fleming, J., Fradi, A., Garillon, B., Gilfoyle, G., Giovanetti, K., Girod, F., Goetz, J., Gohn, W., Golovatch, E., Gothe, R., Griffioen, K., Guegan, B., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Hicks, K., Holtrop, M., Hughes, S., Hyde, C. E., Ilieva, Y., Ireland, D., Ishkhanov, B., Jenkins, D., Jiang, H., Jo, H., Joo, K., Joosten, S., Kalantarians, N., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F., Koirala, S., Kubarovsky, V., Kuhn, S., Livingston, K., Lu, H., MacGregor, I., Markov, N., Mattione, P., Mayer, M., McKinnon, B., Mestayer, M., Meyer, C., Mirazita, M., Mokeev, V., Montgomery, R., Moody, C., Moutarde, H., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A., Park, K., Pasyuk, E., Pisano, S., Pogorelko, O., Price, J., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A., Ripani, M., Rizzo, A., Rosner, G., Rossi, P., Roy, P., Sabati, F., Salgado, C., Schott, D., Schumacher, R., Seder, E., Sharabian, Y., Simonyan, A., Skorodumina, I., Smith, E., Smith, G., Sober, D., Sokhan, D., Sparveris, N., Stepanyan, S., Stoler, P., Strauch, S., Sytnik, V., Taiuti, M., Tian, Ye, Trivedi, A., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N., Watts, D., Wei, X., Wood, M., Zachariou, N., Zana, L., Zhang, J., Zhao, Z., and Zonta, I.. Tue . "Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data". United States. doi:10.1103/PhysRevLett.114.062003. https://www.osti.gov/servlets/purl/1169688.
@article{osti_1169688,
title = {Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data},
author = {Adikaram, D. and Rimal, D. and Weinstein, L. B. and Raue, B. and Khetarpal, P. and Bennett, R. and Arrington, J. and Brooks, W. and Adhikari, K. and Afanasev, A. and Amaryan, M. and Anderson, M. and Anefalos Pereira, S. and Avakian, H. and Ball, J. and Battaglieri, M. and Bedlinskiy, I. and Biselli, A. and Bono, J. and Boiarinov, S. and Briscoe, W. and Burkert, V. and Carman, D. and Careccia, S. and Celentano, A. and Chandavar, S. and Charles, G. and Colaneri, L. and Cole, P. and Contalbrigo, M. and Crede, V. and D'Angelo, A. and Dashyan, N. and De Vita, R. and De Sanctis, E. and Deur, A. and Djalali, C. and Dodge, G. and Dupre, R. and Egiyan, H. and El Alaoui, A. and El Fassi, L. and Elouadrhiri, L. and Eugenio, P. and Fedotov, G. and Fegan, S. and Filippi, A. and Fleming, J. and Fradi, A. and Garillon, B. and Gilfoyle, G. and Giovanetti, K. and Girod, F. and Goetz, J. and Gohn, W. and Golovatch, E. and Gothe, R. and Griffioen, K. and Guegan, B. and Guidal, M. and Guo, L. and Hafidi, K. and Hakobyan, H. and Hanretty, C. and Harrison, N. and Hattawy, M. and Hicks, K. and Holtrop, M. and Hughes, S. and Hyde, C. E. and Ilieva, Y. and Ireland, D. and Ishkhanov, B. and Jenkins, D. and Jiang, H. and Jo, H. and Joo, K. and Joosten, S. and Kalantarians, N. and Keller, D. and Khandaker, M. and Kim, A. and Kim, W. and Klein, A. and Klein, F. and Koirala, S. and Kubarovsky, V. and Kuhn, S. and Livingston, K. and Lu, H. and MacGregor, I. and Markov, N. and Mattione, P. and Mayer, M. and McKinnon, B. and Mestayer, M. and Meyer, C. and Mirazita, M. and Mokeev, V. and Montgomery, R. and Moody, C. and Moutarde, H. and Movsisyan, A. and Camacho, C. Munoz and Nadel-Turonski, P. and Niccolai, S. and Niculescu, G. and Osipenko, M. and Ostrovidov, A. and Park, K. and Pasyuk, E. and Pisano, S. and Pogorelko, O. and Price, J. and Procureur, S. and Prok, Y. and Protopopescu, D. and Puckett, A. and Ripani, M. and Rizzo, A. and Rosner, G. and Rossi, P. and Roy, P. and Sabati, F. and Salgado, C. and Schott, D. and Schumacher, R. and Seder, E. and Sharabian, Y. and Simonyan, A. and Skorodumina, I. and Smith, E. and Smith, G. and Sober, D. and Sokhan, D. and Sparveris, N. and Stepanyan, S. and Stoler, P. and Strauch, S. and Sytnik, V. and Taiuti, M. and Tian, Ye and Trivedi, A. and Ungaro, M. and Voskanyan, H. and Voutier, E. and Walford, N. and Watts, D. and Wei, X. and Wood, M. and Zachariou, N. and Zana, L. and Zhang, J. and Zhao, Z. and Zonta, I.},
abstractNote = {There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE 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 (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.},
doi = {10.1103/PhysRevLett.114.062003},
journal = {Physical Review Letters},
number = 6,
volume = 114,
place = {United States},
year = {Tue Feb 10 00:00:00 EST 2015},
month = {Tue Feb 10 00:00:00 EST 2015}
}

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