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

被引：78

作者：

Adikaram, D. ^{[1
]}

Rimal, D. ^{[2
]}

Weinstein, L. B. ^{[1
]}

Raue, B. ^{[2
]}

Khetarpal, P. ^{[2
]}

Bennett, R. P. ^{[1
]}

Arrington, J. ^{[3
]}

Brooks, W. K. ^{[4
]}

Adhikari, K. P. ^{[1
]}

Afanasev, A. V. ^{[15
]}

Amaryan, M. J. ^{[1
]}

Anderson, M. D. ^{[39
]}

Pereira, S. Anefalos ^{[18
]}

Avakian, H. ^{[37
]}

Ball, J. ^{[9
]}

Battaglieri, M. ^{[19
]}

Bedlinskiy, I. ^{[24
]}

Biselli, A. S. ^{[12
]}

Bono, J. ^{[2
]}

Boiarinov, S. ^{[37
]}

Briscoe, W. J. ^{[15
]}

Burkert, V. D. ^{[37
]}

Carman, D. S. ^{[37
]}

Careccia, S. ^{[1
]}

Celentano, A. ^{[19
]}

Chandavar, S. ^{[30
]}

Charles, G. ^{[22
,23
]}

Colaneri, L. ^{[20
,33
]}

Cole, P. L. ^{[16
]}

Contalbrigo, M. ^{[17
]}

Crede, V. ^{[13
]}

D'Angelo, A. ^{[20
,33
]}

Dashyan, N. ^{[43
]}

De Vita, R. ^{[19
]}

De Sanetis, E. ^{[18
]}

Deur, A. ^{[37
]}

Djalali, C. ^{[35
]}

Dodge, G. E. ^{[1
]}

Dupre, R. ^{[3
,22
,23
]}

Egiyan, H. ^{[37
]}

El Alaoui, A. ^{[3
,4
]}

El Fassi, L. ^{[1
,3
]}

Elouadrhiri, L. ^{[37
]}

Eugenio, P. ^{[13
]}

Fedotov, G. ^{[34
,35
]}

Fegan, S. ^{[19
,39
]}

Filippi, A. ^{[21
]}

Fleming, J. A. ^{[38
]}

Fradi, A. ^{[22
,23
]}

Garillon, B. ^{[22
,23
]}

机构：

[1] Old Dominion Univ, Norfolk, VA 23529 USA

[2] Florida Int Univ, Miami, FL 33199 USA

[3] Argonne Natl Lab, Argonne, IL 60439 USA

[4] Univ Tecn Federico Santa Maria, Valparaiso, Chile

[5] Calif State Univ Dominguez Hills, Carson, CA 90747 USA

[6] Canisius Coll, Buffalo, NY 14208 USA

[7] Carnegie Mellon Univ, Pittsburgh, PA 15213 USA

[8] Catholic Univ Amer, Washington, DC 20064 USA

[9] CEA, Ctr Saclay, Irfu Serv Phys Nucl, F-91191 Gif Sur Yvette, France

[10] Christopher Newport Univ, Newport News, VA 23606 USA

[11] Univ Connecticut, Storrs, CT 06269 USA

[12] Fairfield Univ, Fairfield, CT 06824 USA

[13] Florida State Univ, Tallahassee, FL 32306 USA

[14] Univ Genoa, I-16146 Genoa, Italy

[15] George Washington Univ, Washington, DC 20052 USA

[16] Idaho State Univ, Pocatello, ID 83209 USA

[17] Ist Nazl Fis Nucl, Sez Ferrara, I-44100 Ferrara, Italy

[18] Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy

[19] Ist Nazl Fis Nucl, Sez Genova, I-16146 Genoa, Italy

[20] Ist Nazl Fis Nucl, Sez Roma Tor Vergata, I-00133 Rome, Italy

[21] Ist Nazl Fis Nucl, Sez Torino, I-10125 Turin, Italy

[22] CNRS, Inst Phys Nucl, IN2P3, F-91405 Orsay, France

[23] Univ Paris 11, Orsay, France

[24] Inst Theoret & Expt Phys, Moscow 117259, Russia

[25] James Madison Univ, Harrisonburg, VA 22807 USA

[26] Kyungpook Natl Univ, Taegu 702701, South Korea

[27] Univ Grenoble Alpes, LPSC, CNRS, IN2P3, Grenoble, France

[28] Univ New Hampshire, Durham, NH 03824 USA

[29] Norfolk State Univ, Norfolk, VA 23504 USA

[30] Ohio Univ, Athens, OH 45701 USA

[31] Rensselaer Polytech Inst, Troy, NY 12180 USA

[32] Univ Richmond, Richmond, VA 23173 USA

[33] Univ Roma Tor Vergata, I-00133 Rome, Italy

[34] Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow 119234, Russia

[35] Univ S Carolina, Columbia, SC 29208 USA

[36] Temple Univ, Philadelphia, PA 19122 USA

[37] Thomas Jefferson Natl Accelerator Facil, Newport News, VA 23606 USA

[38] Univ Edinburgh, Edinburgh EH9 3JZ, Midlothian, Scotland

[39] Univ Glasgow, Glasgow G12 8QQ, Lanark, Scotland

[40] Virginia Tech, Blacksburg, VA 24061 USA

[41] Univ Virginia, Charlottesville, VA 22901 USA

[42] Coll William & Mary, Williamsburg, VA 23187 USA

[43] Yerevan Phys Inst, Yerevan 375036, Armenia

来源：

PHYSICAL REVIEW LETTERS | 2015年 / 114卷 / 06期

基金：

美国国家科学基金会; 新加坡国家研究基金会; 英国科学技术设施理事会; 美国能源部;

关键词：

ELASTIC-SCATTERING; NUCLEON; 2-PHOTON-EXCHANGE; TRANSFERS; CLAS; EP;

D O I：

10.1103/PhysRevLett.114.062003

中图分类号：

O4 [物理学];

学科分类号：

0702 ;

摘要：

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 (epsilon) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing epsilon at Q(2) = 1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q(2) approximate to 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.

引用

页数：6

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