# D. K. Hasell - corresponding author

## Contact Details

NameD. K. Hasell |
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Affiliationcorresponding author |
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Location |
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## Pubs By Year |
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## External Links |
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## Pub CategoriesNuclear Experiment (7) Physics - Instrumentation and Detectors (3) Nuclear Theory (3) High Energy Physics - Experiment (1) |

## Publications Authored By D. K. Hasell

We review recent theoretical and experimental progress on the role of two-photon exchange (TPE) in electron-proton scattering at low to moderate momentum transfers. We make a detailed comparison and analysis of the results of competing experiments on the ratio of e+p to e-p elastic scattering cross sections, and of the theoretical calculations describing them. A summary of the current experimental situation is provided, along with an outlook for future experiments. Read More

**Authors:**B. S. Henderson, L. D. Ice, D. Khaneft, C. O'Connor, R. Russell, A. Schmidt, J. C. Bernauer, M. Kohl, N. Akopov, R. Alarcon, O. Ates, A. Avetisyan, R. Beck, S. Belostotski, J. Bessuille, F. Brinker, J. R. Calarco, V. Carassiti, E. Cisbani, G. Ciullo, M. Contalbrigo, R. De Leo, J. Diefenbach, T. W. Donnelly, K. Dow, G. Elbakian, P. D. Eversheim, S. Frullani, Ch. Funke, G. Gavrilov, B. Gläser, N. Görrissen, D. K. Hasell, J. Hauschildt, Ph. Hoffmeister, Y. Holler, E. Ihloff, A. Izotov, R. Kaiser, G. Karyan, J. Kelsey, A. Kiselev, P. Klassen, A. Krivshich, I. Lehmann, P. Lenisa, D. Lenz, S. Lumsden, Y. Ma, F. Maas, H. Marukyan, O. Miklukho, R. G. Milner, A. Movsisyan, M. Murray, Y. Naryshkin, R. Perez Benito, R. Perrino, R. P. Redwine, D. Rodríguez Piñeiro, G. Rosner, U. Schneekloth, B. Seitz, M. Statera, A. Thiel, H. Vardanyan, D. Veretennikov, C. Vidal, A. Winnebeck, V. Yeganov

**Category:**Nuclear Experiment

The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, $R_{2\gamma}$, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01~GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. Read More

Elastic scattering of relativistic electrons from the nucleon yields Lorentz invariant form factors that describe the fundamental distribution of charge and magnetism. The spatial dependence of the nucleon's charge and magnetism is typically interpreted in the Breit reference frame which is related by a Lorentz boost from the laboratory frame, where the nucleon is at rest. We construct a toy model to estimate how the charge and magnetic radii of the nucleon are modified between the Breit and lab. Read More

**Authors:**J. Balewski, J. Bernauer, J. Bessuille, R. Corliss, R. Cowan, C. Epstein, P. Fisher, D. Hasell, E. Ihloff, Y. Kahn, J. Kelsey, R. Milner, S. Steadman, J. Thaler, C. Tschalaer, C. Vidal, S. Benson, J. Boyce, D. Douglas, P. Evtushenko, C. Hernandez-Garcia, C. Keith, C. Tennant, S. Zhang, R. Alarcon, D. Blyth, R. Dipert, L. Ice, G. Randall, B. Dongwi, N. Kalantarians, M. Kohl, A. Liyanage, J. Nazeer, M. Garcon, R. Cervantes, K. Dehmelt, A. Deshpande, N. Feege, B. Surrow

We describe the current status of the DarkLight experiment at Jefferson Laboratory. DarkLight is motivated by the possibility that a dark photon in the mass range 10 to 100 MeV/c$^2$ could couple the dark sector to the Standard Model. DarkLight will precisely measure electron proton scattering using the 100 MeV electron beam of intensity 5 mA at the Jefferson Laboratory energy recovering linac incident on a windowless gas target of molecular hydrogen. Read More

**Authors:**R. Milner, D. K. Hasell, M. Kohl, U. Schneekloth, N. Akopov, R. Alarcon, V. A. Andreev, O. Ates, A. Avetisyan, D. Bayadilov, R. Beck, S. Belostotski, J. C. Bernauer, J. Bessuille, F. Brinker, B. Buck, J. R. Calarco, V. Carassiti, E. Cisbani, G. Ciullo, M. Contalbrigo, N. D'Ascenzo, R. De Leo, J. Diefenbach, T. W. Donnelly, K. Dow, G. Elbakian, D. Eversheim, S. Frullani, Ch. Funke, G. Gavrilov, B. Gläser, N. Görrissen, J. Hauschildt, B. S. Henderson, Ph. Hoffmeister, Y. Holler, L. D. Ice, A. Izotov, R. Kaiser, G. Karyan, J. Kelsey, D. Khaneft, P. Klassen, A. Kiselev, A. Krivshich, I. Lehmann, P. Lenisa, D. Lenz, S. Lumsden, Y. Ma, F. Maas, H. Marukyan, O. Miklukho, A. Movsisyan, M. Murray, Y. Naryshkin, C. O'Connor, R. Perez Benito, R. Perrino, R. P. Redwine, D. Rodríguez Piñeiro, G. Rosner, R. L. Russell, A. Schmidt, B. Seitz, M. Statera, A. Thiel, H. Vardanyan, D. Veretennikov, C. Vidal, A. Winnebeck, V. Yeganov

The OLYMPUS experiment was designed to measure the ratio between the positron-proton and electron-proton elastic scattering cross sections, with the goal of determining the contribution of two-photon exchange to the elastic cross section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, $\mu_p G^p_E/G^p_M$, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2. Read More

**Authors:**C. Crawford, T. Akdogan, R. Alarcon, W. Bertozzi, E. Booth, T. Botto, J. R. Calarco, B. Clasie, A. DeGrush, T. W. Donnelly, K. Dow, M. Farkhondeh, R. Fatemi, O. Filoti, W. Franklin, H. Gao, E. Geis, S. Gilad, D. Hasell, P. Karpius, M. Kohl, H. Kolster, T. Lee, E. Lomon, A. Maschinot, J. Matthews, K. McIlhany, N. Meitanis, R. Milner, J. Rapaport, R. Redwine, J. Seely, A. Shinozaki, A. Sindile, S. Sirca, E. Six, T. Smith, B. Tonguc, C. Tschalaer, E. Tsentalovich, W. Turchinetz, Y. Xiao, W. Xu, C. Zhang, Z. Zhou, V. Ziskin, T. Zwart

The roles played by mesons in the electromagnetic form factors of the nucleon are explored using as a basis a model containing vector mesons with coupling to the continuum together with the asymptotic $Q^2$ behavior of perturbative QCD. Specifically, the vector dominance model (GKex) developed by Lomon is employed, as it is known to be very successful in representing the existing high-quality data published to date. An analysis is made of the experimental uncertainties present when the differences between the GKex model and the data are expanded in orthonormal basis functions. Read More

The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is in the process of designing and constructing a forward tracking system based on triple GEM technology. This upgrade is necessary to give STAR the capability to reconstruct and identify the charge sign of W bosons over an extended rapidity range through their leptonic decay mode into an electron (positron) and a neutrino. This will allow a detailed study of the flavor-separated spin structure of the proton in polarized p + p collisions uniquely available at RHIC. Read More

**Authors:**E. Geis

^{1}, V. Ziskin

^{2}, T. Akdogan

^{3}, H. Arenhoevel

^{4}, R. Alarcon

^{5}, W. Bertozzi

^{6}, E. Booth

^{7}, T. Botto

^{8}, J. Calarco

^{9}, B. Clasie

^{10}, C. B. Crawford

^{11}, A. DeGrush

^{12}, T. W. Donnelly

^{13}, K. Dow

^{14}, M. Farkhondeh

^{15}, R. Fatemi

^{16}, O. Filoti

^{17}, W. Franklin

^{18}, H. Gao

^{19}, S. Gilad

^{20}, D. Hasell

^{21}, P. Karpius

^{22}, M. Kohl

^{23}, H. Kolster, T. Lee, A. Maschinot, J. Matthews, K. McIlhany, N. Meitanis, R. G. Milner, J. Rapaport, R. P. Redwine, J. Seely, A. Shinozaki, S. Sirca, A. Sindile, E. Six, T. Smith, M. Steadman, B. Tonguc, C. Tschalaer, E. Tsentalovich, W. Turchinetz, Y. Xiao, W. Xu, C. Zhang, Z. Zhou, T. Zwart

**Affiliations:**

^{1}corresponding author,

^{2}corresponding author,

^{3}corresponding author,

^{4}corresponding author,

^{5}corresponding author,

^{6}corresponding author,

^{7}corresponding author,

^{8}corresponding author,

^{9}corresponding author,

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^{13}corresponding author,

^{14}corresponding author,

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^{16}corresponding author,

^{17}corresponding author,

^{18}corresponding author,

^{19}corresponding author,

^{20}corresponding author,

^{21}corresponding author,

^{22}corresponding author,

^{23}corresponding author

**Category:**Nuclear Experiment

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. Read More

**Authors:**C. B. Crawford, A. Sindile, T. Akdogan, R. Alarcon, W. Bertozzi, E. Booth, T. Botto, J. Calarco, B. Clasie, A. DeGrush, T. W. Donnelly, K. Dow, D. Dutta, M. Farkhondeh, R. Fatemi, O. Filoti, W. Franklin, H. Gao, E. Geis, S. Gilad, W. Haeberli, D. Hasell, W. Hersman, M. Holtrop, P. Karpius, M. Kohl, H. Kolster, T. Lee, A. Maschinot, J. Matthews, K. McIlhany, N. Meitanis, R. G. Milner, J. Rapaport, R. P. Redwine, J. Seely, A. Shinozaki, S. Sirca, E. Six, T. Smith, B. Tonguc, C. Tschalaer, E. Tsentalovich, W. Turchinetz, J. F. J. van den Brand, J. van der Laan, F. Wang, T. Wise, Y. Xiao, W. Xu, C. Zhang, Z. Zhou, V. Ziskin, T. Zwart

**Category:**Nuclear Experiment

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared $Q^2$ from 0.15 to 0. Read More