D. Meekins - The CLAS Collaboration

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D. Meekins
The CLAS Collaboration

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Nuclear Experiment (48)
High Energy Physics - Experiment (13)
High Energy Physics - Phenomenology (6)
Physics - Instrumentation and Detectors (4)
Nuclear Theory (4)
Physics - Accelerator Physics (1)
Mathematical Physics (1)
Mathematics - Mathematical Physics (1)

Publications Authored By D. Meekins

$[Background]$ Measurements of the neutron charge distribution are made difficult by the fact that, with no net charge, the neutron electric form factor, $G^n_E$, is generally much smaller than the magnetic form factor, $G^n_M$. In addition, measurements of these form factors must use nuclear targets which requires accurately accounting for nuclear effects. $[Method]$ The inclusive quasi-elastic reaction $^3\overrightarrow{\rm{He}}(\overrightarrow{e},e')$ was measured at Jefferson Lab. Read More

The proton is composed of quarks and gluons, bound by the most elusive mechanism of strong interaction called confinement. In this work, the dynamics of quarks and gluons are investigated using deeply virtual Compton scattering (DVCS): produced by a multi-GeV electron, a highly virtual photon scatters off the proton which subsequently radiates a high energy photon. Similarly to holography, measuring not only the magnitude but also the phase of the DVCS amplitude allows to perform 3D images of the internal structure of the proton. Read More

Affiliations: 1The Jefferson Lab Hall A Collaboration, 2The Jefferson Lab Hall A Collaboration, 3The Jefferson Lab Hall A Collaboration, 4The Jefferson Lab Hall A Collaboration, 5The Jefferson Lab Hall A Collaboration, 6The Jefferson Lab Hall A Collaboration, 7The Jefferson Lab Hall A Collaboration, 8The Jefferson Lab Hall A Collaboration, 9The Jefferson Lab Hall A Collaboration, 10The Jefferson Lab Hall A Collaboration, 11The Jefferson Lab Hall A Collaboration, 12The Jefferson Lab Hall A Collaboration, 13The Jefferson Lab Hall A Collaboration, 14The Jefferson Lab Hall A Collaboration, 15The Jefferson Lab Hall A Collaboration, 16The Jefferson Lab Hall A Collaboration, 17The Jefferson Lab Hall A Collaboration, 18The Jefferson Lab Hall A Collaboration, 19The Jefferson Lab Hall A Collaboration, 20The Jefferson Lab Hall A Collaboration, 21The Jefferson Lab Hall A Collaboration, 22The Jefferson Lab Hall A Collaboration, 23The Jefferson Lab Hall A Collaboration, 24The Jefferson Lab Hall A Collaboration, 25The Jefferson Lab Hall A Collaboration, 26The Jefferson Lab Hall A Collaboration, 27The Jefferson Lab Hall A Collaboration, 28The Jefferson Lab Hall A Collaboration, 29The Jefferson Lab Hall A Collaboration, 30The Jefferson Lab Hall A Collaboration, 31The Jefferson Lab Hall A Collaboration, 32The Jefferson Lab Hall A Collaboration, 33The Jefferson Lab Hall A Collaboration, 34The Jefferson Lab Hall A Collaboration, 35The Jefferson Lab Hall A Collaboration, 36The Jefferson Lab Hall A Collaboration, 37The Jefferson Lab Hall A Collaboration, 38The Jefferson Lab Hall A Collaboration, 39The Jefferson Lab Hall A Collaboration, 40The Jefferson Lab Hall A Collaboration, 41The Jefferson Lab Hall A Collaboration, 42The Jefferson Lab Hall A Collaboration, 43The Jefferson Lab Hall A Collaboration, 44The Jefferson Lab Hall A Collaboration, 45The Jefferson Lab Hall A Collaboration, 46The Jefferson Lab Hall A Collaboration, 47The Jefferson Lab Hall A Collaboration, 48The Jefferson Lab Hall A Collaboration, 49The Jefferson Lab Hall A Collaboration, 50The Jefferson Lab Hall A Collaboration, 51The Jefferson Lab Hall A Collaboration, 52The Jefferson Lab Hall A Collaboration, 53The Jefferson Lab Hall A Collaboration, 54The Jefferson Lab Hall A Collaboration, 55The Jefferson Lab Hall A Collaboration, 56The Jefferson Lab Hall A Collaboration, 57The Jefferson Lab Hall A Collaboration, 58The Jefferson Lab Hall A Collaboration, 59The Jefferson Lab Hall A Collaboration, 60The Jefferson Lab Hall A Collaboration, 61The Jefferson Lab Hall A Collaboration, 62The Jefferson Lab Hall A Collaboration, 63The Jefferson Lab Hall A Collaboration, 64The Jefferson Lab Hall A Collaboration, 65The Jefferson Lab Hall A Collaboration, 66The Jefferson Lab Hall A Collaboration, 67The Jefferson Lab Hall A Collaboration, 68The Jefferson Lab Hall A Collaboration, 69The Jefferson Lab Hall A Collaboration, 70The Jefferson Lab Hall A Collaboration, 71The Jefferson Lab Hall A Collaboration, 72The Jefferson Lab Hall A Collaboration, 73The Jefferson Lab Hall A Collaboration, 74The Jefferson Lab Hall A Collaboration, 75The Jefferson Lab Hall A Collaboration, 76The Jefferson Lab Hall A Collaboration, 77The Jefferson Lab Hall A Collaboration, 78The Jefferson Lab Hall A Collaboration, 79The Jefferson Lab Hall A Collaboration, 80The Jefferson Lab Hall A Collaboration, 81The Jefferson Lab Hall A Collaboration, 82The Jefferson Lab Hall A Collaboration, 83The Jefferson Lab Hall A Collaboration, 84The Jefferson Lab Hall A Collaboration, 85The Jefferson Lab Hall A Collaboration, 86The Jefferson Lab Hall A Collaboration, 87The Jefferson Lab Hall A Collaboration, 88The Jefferson Lab Hall A Collaboration, 89The Jefferson Lab Hall A Collaboration, 90The Jefferson Lab Hall A Collaboration, 91The Jefferson Lab Hall A Collaboration, 92The Jefferson Lab Hall A Collaboration, 93The Jefferson Lab Hall A Collaboration, 94The Jefferson Lab Hall A Collaboration, 95The Jefferson Lab Hall A Collaboration, 96The Jefferson Lab Hall A Collaboration, 97The Jefferson Lab Hall A Collaboration, 98The Jefferson Lab Hall A Collaboration

We report the first longitudinal/transverse separation of the deeply virtual exclusive $\pi^0$ electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions $d\sigma_L/dt$, $d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$ and $x_B$=0. Read More

The charge and magnetic form factors, FC and FM, of 3He have been extracted in the kinematic range 25 fm-2 < Q2 < 61 fm-2 from elastic electron scattering by detecting 3He recoil nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility at Jefferson Lab. The measurements are indicative of a second diffraction minimum for the magnetic form factor, which was predicted in the Q2 range of this experiment, and of a continuing diffractive structure for the charge form factor. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the three-body nuclear problem. Read More

We propose to measure the photo-production cross section of $J/{\psi}$ near threshold, in search of the recently observed LHCb hidden-charm resonances $P_c$(4380) and $P_c$(4450) consistent with 'pentaquarks'. The observation of these resonances in photo-production will provide strong evidence of the true resonance nature of the LHCb states, distinguishing them from kinematic enhancements. A bremsstrahlung photon beam produced with an 11 GeV electron beam at CEBAF covers the energy range of $J/{\psi}$ production from the threshold photo-production energy of 8. Read More

We present deeply virtual $\pi^0$ electroproduction cross-section measurements at $x_B$=0.36 and three different $Q^2$--values ranging from 1.5 to 2 GeV$^2$, obtained from experiment E07-007 that ran in the Hall A at Jefferson Lab. Read More

Structure functions, as measured in lepton-nucleon scattering, have proven to be very useful in studying the quark dynamics within the nucleon. However, it is experimentally difficult to separately determine the longitudinal and transverse structure functions, and consequently there are substantially less data available for the longitudinal structure function in particular. Here we present separated structure functions for hydrogen and deuterium at low four--momentum transfer squared, Q^2< 1 GeV^2, and compare these with parton distribution parameterizations and a k_T factorization approach. Read More

[Background] The proton charge radius extracted from recent muonic hydrogen Lamb shift measurements is significantly smaller than that extracted from atomic hydrogen and electron scattering measurements. [Purpose] In an attempt to understand the discrepancy, we review high-precision electron scattering results from Mainz, Jefferson Lab, Saskatoon and Stanford. [Method] We make use of stepwise regression techniques using the $F$-test as well as the Akaike information criterion to systematically determine the predictive variables to use for a given set and range of electron scattering data as well as to provide multivariate error estimates. Read More

Authors: I. Senderovich, B. T. Morrison, M. Dugger, B. G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C. D. Keith, D. G. Meekins, M. L. Seely, D. R, M. D, P. Collins, K. P. Adhikari, D. Adikaram, Z. Akbar, M. D. Anderson, S. Anefalos Pereira, R. A. Badui, J. Ball, N. A. Baltzell, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, W. K. Brooks, V. D. Burkert, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, L. Colaneri, P. L. Cole, M. Contalbrigo, O. Cortes, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, A. Fradi, L. Elouadrhiri, P. Eugenio, G. Fedotov, S. Fegan, A. Filippi, J. A. Fleming, B. Garillon, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. -X. Girod, D. I. Glazier, J. T. Goetz, W. Gohn, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, M. Hattawy, K. Hicks, D. Ho, M. Holtrop, S. M. Hughes, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, D. Jenkins, H. Jiang, H. S. Jo, K. Joo, S. Joosten, D. Keller, G. Khachatryan, M. Khandaker, A. Kim, F. J. Klein, V. Kubarovsky, M. C. Kunkel, P. Lenisa, K. Livingston, H. Y. Lu, I. J. D. MacGregor, P. Mattione, B. McKinnon, C. A. Meyer, T. Mineeva, V. Mokeev, R. A. Montgomery, A. Movsisyan, C. Munoz Camacho, P. Nadel-Turonski, L. A. Net, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, K. Park, S. Park, P. Peng, W. Phelps, S. Pisano, O. Pogorelko, J. W. Price, Y. Prok, A. J. R. Puckett, M. Ripani, A. Rizzo, G. Rosner, P. Roy, F. Sabatie, C. Salgado, D. Schott, R. A. Schumacher, E. Seder, A. Simonyan, Iu. Skorodumina, G. D. Smith, D. I. Sober, D. Sokhan, N. Sparveris, S. Stepanyan, P. Stoler, I. I. Strakovsky, S. Strauch, V. Sytnik, Ye Tian, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, X. Wei, M. H. Wood, N. Zachariou, L. Zana, J. Zhang, Z. W. Zhao, I. Zonta

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the $\eta$ photoproduction reaction $\gamma p \rightarrow \eta p$. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. Read More

Authors: S. Strauch1, W. J. Briscoe2, M. Döring3, E. Klempt4, V. A. Nikonov5, E. Pasyuk6, D. Rönchen7, A. V. Sarantsev8, I. Strakovsky9, R. Workman10, K. P. Adhikari11, D. Adikaram12, M. D. Anderson13, S. Anefalos Pereira14, A. V. Anisovich15, R. A. Badui16, J. Ball17, V. Batourine18, M. Battaglieri19, I. Bedlinskiy20, N. Benmouna21, A. S. Biselli22, J. Brock23, W. K. Brooks24, V. D. Burkert25, T. Cao26, C. Carlin27, D. S. Carman28, A. Celentano29, S. Chandavar30, G. Charles31, L. Colaneri32, P. L. Cole33, N. Compton34, M. Contalbrigo35, O. Cortes36, V. Crede37, N. Dashyan38, A. D'Angelo39, R. De Vita40, E. De Sanctis41, A. Deur42, C. Djalali43, M. Dugger44, R. Dupre45, H. Egiyan46, A. El Alaoui47, L. El Fassi48, L. Elouadrhiri49, P. Eugenio50, G. Fedotov51, S. Fegan52, A. Filippi53, J. A. Fleming54, T. A. Forest55, A. Fradi56, N. Gevorgyan57, Y. Ghandilyan58, K. L. Giovanetti59, F. X. Girod60, D. I. Glazier61, W. Gohn62, E. Golovatch63, R. W. Gothe64, K. A. Griffioen65, M. Guidal66, L. Guo67, K. Hafidi68, H. Hakobyan69, C. Hanretty70, N. Harrison71, M. Hattawy72, K. Hicks73, D. Ho74, M. Holtrop75, S. M. Hughes76, Y. Ilieva77, D. G. Ireland78, B. S. Ishkhanov79, E. L. Isupov80, D. Jenkins81, H. Jiang82, H. S. Jo83, K. Joo84, S. Joosten85, C. D. Keith86, D. Keller87, G. Khachatryan88, M. Khandaker89, A. Kim90, W. Kim91, A. Klein92, F. J. Klein93, V. Kubarovsky94, S. E. Kuhn95, P. Lenisa96, K. Livingston97, H. Y. Lu98, I . J . D. MacGregor99, N. Markov100, B. McKinnon101, D. G. Meekins102, C. A. Meyer103, V. Mokeev104, R. A. Montgomery105, C. I. Moody106, H. Moutarde107, A Movsisyan108, E. Munevar109, C. Munoz Camacho110, P. Nadel-Turonski111, L. A. Net112, S. Niccolai113, G. Niculescu114, I. Niculescu115, M. Osipenko116, A. I. Ostrovidov117, K. Park118, P. Peng119, W. Phelps120, J. J. Phillips121, S. Pisano122, O. Pogorelko123, S. Pozdniakov124, J. W. Price125, S. Procureur126, Y. Prok127, D. Protopopescu128, A. J. R. Puckett129, B. A. Raue130, M. Ripani131, B. G. Ritchie132, A. Rizzo133, G. Rosner134, P. Roy135, F. Sabatié136, C. Salgado137, D. Schott138, R. A. Schumacher139, E. Seder140, M. L. Seely141, I Senderovich142, Y. G. Sharabian143, A. Simonyan144, Iu. Skorodumina145, G. D. Smith146, D. I. Sober147, D. Sokhan148, N. Sparveris149, P. Stoler150, S. Stepanyan151, V. Sytnik152, M. Taiuti153, Ye Tian154, A. Trivedi155, R. Tucker156, M. Ungaro157, H. Voskanyan158, E. Voutier159, N. K. Walford160, D. P. Watts161, X. Wei162, M. H. Wood163, N. Zachariou164, L. Zana165, J. Zhang166, Z. W. Zhao167, I. Zonta168
Affiliations: 1The CLAS Collaboration, 2The CLAS Collaboration, 3The CLAS Collaboration, 4The CLAS Collaboration, 5The CLAS Collaboration, 6The CLAS Collaboration, 7The CLAS Collaboration, 8The CLAS Collaboration, 9The CLAS Collaboration, 10The CLAS Collaboration, 11The CLAS Collaboration, 12The CLAS Collaboration, 13The CLAS Collaboration, 14The CLAS Collaboration, 15The CLAS Collaboration, 16The CLAS Collaboration, 17The CLAS Collaboration, 18The CLAS Collaboration, 19The CLAS Collaboration, 20The CLAS Collaboration, 21The CLAS Collaboration, 22The CLAS Collaboration, 23The CLAS Collaboration, 24The CLAS Collaboration, 25The CLAS Collaboration, 26The CLAS Collaboration, 27The CLAS Collaboration, 28The CLAS Collaboration, 29The CLAS Collaboration, 30The CLAS Collaboration, 31The CLAS Collaboration, 32The CLAS Collaboration, 33The CLAS Collaboration, 34The CLAS Collaboration, 35The CLAS Collaboration, 36The CLAS Collaboration, 37The CLAS Collaboration, 38The CLAS Collaboration, 39The CLAS Collaboration, 40The CLAS Collaboration, 41The CLAS Collaboration, 42The CLAS Collaboration, 43The CLAS Collaboration, 44The CLAS Collaboration, 45The CLAS Collaboration, 46The CLAS Collaboration, 47The CLAS Collaboration, 48The CLAS Collaboration, 49The CLAS Collaboration, 50The CLAS Collaboration, 51The CLAS Collaboration, 52The CLAS Collaboration, 53The CLAS Collaboration, 54The CLAS Collaboration, 55The CLAS Collaboration, 56The CLAS Collaboration, 57The CLAS Collaboration, 58The CLAS Collaboration, 59The CLAS Collaboration, 60The CLAS Collaboration, 61The CLAS Collaboration, 62The CLAS Collaboration, 63The CLAS Collaboration, 64The CLAS Collaboration, 65The CLAS Collaboration, 66The CLAS Collaboration, 67The CLAS Collaboration, 68The CLAS Collaboration, 69The CLAS Collaboration, 70The CLAS Collaboration, 71The CLAS Collaboration, 72The CLAS Collaboration, 73The CLAS Collaboration, 74The CLAS Collaboration, 75The CLAS Collaboration, 76The CLAS Collaboration, 77The CLAS Collaboration, 78The CLAS Collaboration, 79The CLAS Collaboration, 80The CLAS Collaboration, 81The CLAS Collaboration, 82The CLAS Collaboration, 83The CLAS Collaboration, 84The CLAS Collaboration, 85The CLAS Collaboration, 86The CLAS Collaboration, 87The CLAS Collaboration, 88The CLAS Collaboration, 89The CLAS Collaboration, 90The CLAS Collaboration, 91The CLAS Collaboration, 92The CLAS Collaboration, 93The CLAS Collaboration, 94The CLAS Collaboration, 95The CLAS Collaboration, 96The CLAS Collaboration, 97The CLAS Collaboration, 98The CLAS Collaboration, 99The CLAS Collaboration, 100The CLAS Collaboration, 101The CLAS Collaboration, 102The CLAS Collaboration, 103The CLAS Collaboration, 104The CLAS Collaboration, 105The CLAS Collaboration, 106The CLAS Collaboration, 107The CLAS Collaboration, 108The CLAS Collaboration, 109The CLAS Collaboration, 110The CLAS Collaboration, 111The CLAS Collaboration, 112The CLAS Collaboration, 113The CLAS Collaboration, 114The CLAS Collaboration, 115The CLAS Collaboration, 116The CLAS Collaboration, 117The CLAS Collaboration, 118The CLAS Collaboration, 119The CLAS Collaboration, 120The CLAS Collaboration, 121The CLAS Collaboration, 122The CLAS Collaboration, 123The CLAS Collaboration, 124The CLAS Collaboration, 125The CLAS Collaboration, 126The CLAS Collaboration, 127The CLAS Collaboration, 128The CLAS Collaboration, 129The CLAS Collaboration, 130The CLAS Collaboration, 131The CLAS Collaboration, 132The CLAS Collaboration, 133The CLAS Collaboration, 134The CLAS Collaboration, 135The CLAS Collaboration, 136The CLAS Collaboration, 137The CLAS Collaboration, 138The CLAS Collaboration, 139The CLAS Collaboration, 140The CLAS Collaboration, 141The CLAS Collaboration, 142The CLAS Collaboration, 143The CLAS Collaboration, 144The CLAS Collaboration, 145The CLAS Collaboration, 146The CLAS Collaboration, 147The CLAS Collaboration, 148The CLAS Collaboration, 149The CLAS Collaboration, 150The CLAS Collaboration, 151The CLAS Collaboration, 152The CLAS Collaboration, 153The CLAS Collaboration, 154The CLAS Collaboration, 155The CLAS Collaboration, 156The CLAS Collaboration, 157The CLAS Collaboration, 158The CLAS Collaboration, 159The CLAS Collaboration, 160The CLAS Collaboration, 161The CLAS Collaboration, 162The CLAS Collaboration, 163The CLAS Collaboration, 164The CLAS Collaboration, 165The CLAS Collaboration, 166The CLAS Collaboration, 167The CLAS Collaboration, 168The CLAS Collaboration

First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction $\vec \gamma \vec p \to \pi^+n$, has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2. Read More

Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, $Q^2$, and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in $\pi^-$ and $\pi^+$ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data. Read More

Authors: MOLLER Collaboration, J. Benesch, P. Brindza, R. D. Carlini, J-P. Chen, E. Chudakov, S. Covrig, M. M. Dalton, A. Deur, D. Gaskell, A. Gavalya, J. Gomez, D. W. Higinbotham, C. Keppel, D. Meekins, R. Michaels, B. Moffit, Y. Roblin, R. Suleiman, R. Wines, B. Wojtsekhowski, G. Cates, D. Crabb, D. Day, K. Gnanvo, D. Keller, N. Liyanage, V. V. Nelyubin, H. Nguyen, B. Norum, K. Paschke, V. Sulkosky, J. Zhang, X. Zheng, J. Birchall, P. Blunden, M. T. W. Gericke, W. R. Falk, L. Lee, J. Mammei, S. A. Page, W. T. H. van Oers, K. Dehmelt, A. Deshpande, N. Feege, T. K. Hemmick, K. S. Kumar, T. Kutz, R. Miskimen, M. J. Ramsey-Musolf, S. Riordan, N. Hirlinger Saylor, J. Bessuille, E. Ihloff, J. Kelsey, S. Kowalski, R. Silwal, G. De Cataldo, R. De Leo, D. Di Bari, L. Lagamba, E. NappiV. Bellini, F. Mammoliti, F. Noto, M. L. Sperduto, C. M. Sutera, P. Cole, T. A. Forest, M. Khandekar, D. McNulty, K. Aulenbacher, S. Baunack, F. Maas, V. Tioukine, R. Gilman, K. Myers, R. Ransome, A. Tadepalli, R. Beniniwattha, R. Holmes, P. Souder, D. S. Armstrong, T. D. Averett, W. Deconinck, W. Duvall, A. Lee, M. L. Pitt, J. A. Dunne, D. Dutta, L. El Fassi, F. De Persio, F. Meddi, G. M. Urciuoli, E. Cisbani, C. Fanelli, F. Garibaldi, K. Johnston, N. Simicevic, S. Wells, P. M. King, J. Roche, J. Arrington, P. E. Reimer, G. Franklin, B. Quinn, A. Ahmidouch, S. Danagoulian, O. Glamazdin, R. Pomatsalyuk, R. Mammei, J. W. Martin, T. Holmstrom, J. Erler, Yu. G. Kolomensky, J. Napolitano, K. A. Aniol, W. D. Ramsay, E. Korkmaz, D. T. Spayde, F. Benmokhtar, A. Del Dotto, R. Perrino, S. Barkanova, A. Aleksejevs, J. Singh

The physics case and an experimental overview of the MOLLER (Measurement Of a Lepton Lepton Electroweak Reaction) experiment at the 12 GeV upgraded Jefferson Lab are presented. A highlight of the Fundamental Symmetries subfield of the 2007 NSAC Long Range Plan was the SLAC E158 measurement of the parity-violating asymmetry $A_{PV}$ in polarized electron-electron (M{\o}ller) scattering. The proposed MOLLER experiment will improve on this result by a factor of five, yielding the most precise measurement of the weak mixing angle at low or high energy anticipated over the next decade. Read More

The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. Read More

Authors: Qweak Collaboration, T. Allison, M. Anderson, D. Androic, D. S. Armstrong, A. Asaturyan, T. D. Averett, R. Averill, J. Balewski, J. Beaufait, R. S. Beminiwattha, J. Benesch, F. Benmokhtar, J. Bessuille, J. Birchall, E. Bonnell, J. Bowman, P. Brindza, D. B. Brown, R. D. Carlini, G. D. Cates, B. Cavness, G. Clark, J. C. Cornejo, S. Covrig Dusa, M. M. Dalton, C. A. Davis, D. C. Dean, W. Deconinck, J. Diefenbach, K. Dow, J. F. Dowd, J. A. Dunne, D. Dutta, W. S. Duvall, J. R. Echols, M. Elaasar, W. R. Falk, K. D. Finelli, J. M. Finn, D. Gaskell, M. T. W. Gericke, J. Grames, V. M. Gray, K. Grimm, F. Guo, J. Hansknecht, D. J. Harrison, E. Henderson, J. R. Hoskins, E. Ihloff, K. Johnston, D. Jones, M. Jones, R. Jones, M. Kargiantoulakis, J. Kelsey, N. Khan, P. M. King, E. Korkmaz, S. Kowalski, A. Kubera, J. Leacock, J. P. Leckey, A. R. Lee, J. H. Lee, L. Lee, Y. Liang, S. MacEwan, D. Mack, J. A. Magee, R. Mahurin, J. Mammei, J. W. Martin, A. McCreary, M. H. McDonald, M. J. McHugh, P. Medeiros, D. Meekins, J. Mei, R. Michaels, A. Micherdzinska, A. Mkrtchyan, H. Mkrtchyan, N. Morgan, J. Musson, K. E. Mesick, A. Narayan, L. Z. Ndukum, V. Nelyubin, Nuruzzaman, W. T. H. van Oers, A. K. Opper, S. A. Page, J. Pan, K. D. Paschke, S. K. Phillips, M. L. Pitt, M. Poelker, J. F. Rajotte, W. D. Ramsay, W. R. Roberts, J. Roche, P. W. Rose, B. Sawatzky, T. Seva, M. H. Shabestari, R. Silwal, N. Simicevic, G. R. Smith, S. Sobczynski, P. Solvignon, D. T. Spayde, B. Stokes, D. W. Storey, A. Subedi, R. Subedi, R. Suleiman, V. Tadevosyan, W. A. Tobias, V. Tvaskis, E. Urban, B. Waidyawansa, P. Wang, S. P. Wells, S. A. Wood, S. Yang, S. Zhamkochyan, R. B. Zielinski

The Jefferson Lab Q_weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ${\vec{e}}$p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. Read More

Authors: Y. Prok, P. Bosted, N. Kvaltine, K. P. Adhikari, D. Adikaram, M. Aghasyan, M. J. Amaryan, M. D. Anderson, S. Anefalos Pereira, H. Avakian, H. Baghdasaryan, J. Ball, N. A. Baltzell, M. Battaglieri, A. S. Biselli, J. Bono, W. J. Briscoe, J. Brock, W. K. Brooks, S. Bültmann, V. D. Burkert, C. Carlin, D. S. Carman, A. Celentano, S. Chandavar, L. Colaneri, P. L. Cole, M. Contalbrigo, O. Cortes, D. Crabb, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, G. E. Dodge, D. Doughty, R. Dupre, A. El Alaoui, L. El Fassi, L. Elouadrhiri, G. Fedotov, S. Fegan, R. Fersch, J. A. Fleming, T. A. Forest, M. Garcon, N. Gevorgyan, Y. Ghandilyan, G. P. Gilfoyle, F. X. Girod, K. L. Giovanetti, J. T. Goetz, W. Gohn, R. W. Gothe, K. A. Griffioen, B. Guegan, N. Guler, K. Haffidi, C. Hanretty, N. Harrison, M. Hattawy, K. Hicks, D. Ho, M. Holtrop, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, S. Jawalkar, X. Jiang, H. S. Jo, K. Joo, N. Kalantarians, C. Keith, D. Keller, M. Khandaker, A. Kim, W. Kim, A. Klein, F. J. Klein, S. Koirala, V. Kubarovsky, S. E. Kuhn, S. V. Kuleshov, P. Lenisa, K. Livingston, H. Y. Lu, I . J. D. MacGregor, N. Markov, M. Mayee, B. McKinnon, D. Meekins, T. Mineeva, M. Mirazita, V. Mokeev, R. A. Montgomery, H. Moutarde, A Movsisyan, E. Munevar, C. Munoz Camacho, P. Nadel-Turonski, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, A. I. Ostrovidov, L. L. Pappalardo, R. Paremuzyan, K. Park, P. Peng, J. J. Phillips, J. Pierce, S. Pisano, O. Pogorelko, S. Pozdniakov, J. W. Price, S. Procureur, D. Protopopescu, A. J. R. Puckett, B. A. Raue, D. Rimal, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, P. Roy, F. Sabatié, M. S. Saini, C. Salgado, D. Schott, R. A. Schumacher, E. Seder, Y. G. Sharabian, A. Simonyan, C. Smith, G. Smith, D. I. Sober, D. Sokhan, S. S. Stepanyan, S. Stepanyan, I. I. Strakovsky, S. Strauch, V. Sytnik, M. Taiuti, W. Tang, S. Tkachenko, M. Ungaro, B . Vernarsky, A. V. Vlassov, H. Voskanyan, E. Voutier, N. K. Walford, D . P. Watts, L. B. Weinstein, N. Zachariou, L. Zana, J. Zhang, B. Zhao, Z. W. Zhao, I. Zonta, for the CLAS collaboration

The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Read More

Affiliations: 1The Jefferson Lab Fpi Collaboration, 2The Jefferson Lab Fpi Collaboration, 3The Jefferson Lab Fpi Collaboration, 4The Jefferson Lab Fpi Collaboration, 5The Jefferson Lab Fpi Collaboration, 6The Jefferson Lab Fpi Collaboration, 7The Jefferson Lab Fpi Collaboration, 8The Jefferson Lab Fpi Collaboration, 9The Jefferson Lab Fpi Collaboration, 10The Jefferson Lab Fpi Collaboration, 11The Jefferson Lab Fpi Collaboration, 12The Jefferson Lab Fpi Collaboration, 13The Jefferson Lab Fpi Collaboration, 14The Jefferson Lab Fpi Collaboration, 15The Jefferson Lab Fpi Collaboration, 16The Jefferson Lab Fpi Collaboration, 17The Jefferson Lab Fpi Collaboration, 18The Jefferson Lab Fpi Collaboration, 19The Jefferson Lab Fpi Collaboration, 20The Jefferson Lab Fpi Collaboration, 21The Jefferson Lab Fpi Collaboration, 22The Jefferson Lab Fpi Collaboration, 23The Jefferson Lab Fpi Collaboration, 24The Jefferson Lab Fpi Collaboration, 25The Jefferson Lab Fpi Collaboration, 26The Jefferson Lab Fpi Collaboration, 27The Jefferson Lab Fpi Collaboration, 28The Jefferson Lab Fpi Collaboration, 29The Jefferson Lab Fpi Collaboration, 30The Jefferson Lab Fpi Collaboration, 31The Jefferson Lab Fpi Collaboration, 32The Jefferson Lab Fpi Collaboration, 33The Jefferson Lab Fpi Collaboration, 34The Jefferson Lab Fpi Collaboration, 35The Jefferson Lab Fpi Collaboration, 36The Jefferson Lab Fpi Collaboration, 37The Jefferson Lab Fpi Collaboration, 38The Jefferson Lab Fpi Collaboration, 39The Jefferson Lab Fpi Collaboration, 40The Jefferson Lab Fpi Collaboration, 41The Jefferson Lab Fpi Collaboration, 42The Jefferson Lab Fpi Collaboration, 43The Jefferson Lab Fpi Collaboration, 44The Jefferson Lab Fpi Collaboration, 45The Jefferson Lab Fpi Collaboration, 46The Jefferson Lab Fpi Collaboration, 47The Jefferson Lab Fpi Collaboration, 48The Jefferson Lab Fpi Collaboration, 49The Jefferson Lab Fpi Collaboration, 50The Jefferson Lab Fpi Collaboration, 51The Jefferson Lab Fpi Collaboration, 52The Jefferson Lab Fpi Collaboration, 53The Jefferson Lab Fpi Collaboration, 54The Jefferson Lab Fpi Collaboration, 55The Jefferson Lab Fpi Collaboration, 56The Jefferson Lab Fpi Collaboration, 57The Jefferson Lab Fpi Collaboration, 58The Jefferson Lab Fpi Collaboration, 59The Jefferson Lab Fpi Collaboration, 60The Jefferson Lab Fpi Collaboration, 61The Jefferson Lab Fpi Collaboration, 62The Jefferson Lab Fpi Collaboration, 63The Jefferson Lab Fpi Collaboration, 64The Jefferson Lab Fpi Collaboration, 65The Jefferson Lab Fpi Collaboration, 66The Jefferson Lab Fpi Collaboration, 67The Jefferson Lab Fpi Collaboration, 68The Jefferson Lab Fpi Collaboration, 69The Jefferson Lab Fpi Collaboration, 70The Jefferson Lab Fpi Collaboration, 71The Jefferson Lab Fpi Collaboration, 72The Jefferson Lab Fpi Collaboration, 73The Jefferson Lab Fpi Collaboration, 74The Jefferson Lab Fpi Collaboration, 75The Jefferson Lab Fpi Collaboration, 76The Jefferson Lab Fpi Collaboration, 77The Jefferson Lab Fpi Collaboration, 78The Jefferson Lab Fpi Collaboration, 79The Jefferson Lab Fpi Collaboration, 80The Jefferson Lab Fpi Collaboration, 81The Jefferson Lab Fpi Collaboration, 82The Jefferson Lab Fpi Collaboration, 83The Jefferson Lab Fpi Collaboration, 84The Jefferson Lab Fpi Collaboration, 85The Jefferson Lab Fpi Collaboration, 86The Jefferson Lab Fpi Collaboration, 87The Jefferson Lab Fpi Collaboration, 88The Jefferson Lab Fpi Collaboration

The study of exclusive $\pi^{\pm}$ electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio $R_L=\sigma_L^{\pi^-}/\sigma_L^{\pi^+}$ is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of $R_T=\sigma_T^{\pi^-}/\sigma_T^{\pi^+}$ from unity at small $-t$, to 1/4 at large $-t$, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Read More


We studied simultaneously the 4He(e,e'p), 4He(e,e'pp), and 4He(e,e'pn) reactions at Q^2=2 [GeV/c]2 and x_B>1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Read More

A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ep scattering to provide the first determination of the protons weak charge Qweak(p). The experiment employed a 180 uA longitudinally polarized 1. Read More

The charge form factor of $^$4He has been extracted in the range 29 fm$^{-2}$ $\le Q^2 \le 77$ fm$^{-2}$ from elastic electron scattering, detecting $^4$He nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility of Jefferson Lab. The results are in qualitative agreement with realistic meson-nucleon theoretical calculations. The data have uncovered a second diffraction minimum, which was predicted in the $Q^2$ range of this experiment, and rule out conclusively long-standing predictions of dimensional scaling of high-energy amplitudes using quark counting. Read More

The Qweak experiment has measured the parity-violating asymmetry in polarized e-p elastic scattering at Q^2 = 0.025(GeV/c)^2, employing 145 microamps of 89% longitudinally polarized electrons on a 34.4cm long liquid hydrogen target at Jefferson Lab. Read More

We describe a dynamically polarized target that has been utilized for two electron scattering experiments in Hall A at Jefferson Lab. The primary components of the target are a new, high cooling power 4He evaporation refrigerator, and a re-purposed, superconducting split-coil magnet. It has been used to polarize protons in irradiated NH3 at a temperature of 1 K and at fields of 2. Read More

We report on parity-violating asymmetries in the nucleon resonance region measured using $5 - 6$ GeV longitudinally polarized electrons scattering off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the $\Delta(1232)$, and provide a verification of quark-hadron duality in the nucleon electroweak $\gamma Z$ interference structure functions at the (10-15)% level. The results are of particular interest to models relevant for calculating the $\gamma Z$ box-diagram corrections to elastic parity-violating electron scattering measurements. Read More

Authors: I. Pomerantz1, Y. Ilieva2, R. Gilman3, D. W. Higinbotham4, E. Piasetzky5, S. Strauch6, K. P. Adhikari7, M. Aghasyan8, K. Allada9, M. J. Amaryan10, S. Anefalos Pereira11, M. Anghinolfi12, H. Baghdasaryan13, J. Ball14, N. A. Baltzell15, M. Battaglieri16, V. Batourine17, A. Beck18, S. Beck19, I. Bedlinskiy20, B. L. Berman21, A. S. Biselli22, W. Boeglin23, J. Bono24, C. Bookwalter25, S. Boiarinov26, W. J. Briscoe27, W. K. Brooks28, N. Bubis29, V. Burkert30, A. Camsonne31, M. Canan32, D. S. Carman33, A. Celentano34, S. Chandavar35, G. Charles36, K. Chirapatpimol37, E. Cisbani38, P. L. Cole39, M. Contalbrigo40, V. Crede41, F. Cusanno42, A. D'Angelo43, A. Daniel44, N. Dashyan45, C. W. de Jager46, R. De Vita47, E. De Sanctis48, A. Deur49, C. Djalali50, G. E. Dodge51, D. Doughty52, R. Dupre53, C. Dutta54, H. Egiyan55, A. El Alaoui56, L. El Fassi57, P. Eugenio58, G. Fedotov59, S. Fegan60, J. A. Fleming61, A. Fradi62, F. Garibaldi63, O. Geagla64, N. Gevorgyan65, K. L. Giovanetti66, F. X. Girod67, J. Glister68, J. T. Goetz69, W. Gohn70, E. Golovatch71, R. W. Gothe72, K. A. Griffioen73, B. Guegan74, M. Guidal75, L. Guo76, K. Hafidi77, H. Hakobyan78, N. Harrison79, D. Heddle80, K. Hicks81, D. Ho82, M. Holtrop83, C. E. Hyde84, D. G. Ireland85, B. S. Ishkhanov86, E. L. Isupov87, X. Jiang88, H. S. Jo89, K. Joo90, A. T. Katramatou91, D. Keller92, M. Khandaker93, P. Khetarpal94, E. Khrosinkova95, A. Kim96, W. Kim97, F. J. Klein98, S. Koirala99, A. Kubarovsky100, V. Kubarovsky101, S. V. Kuleshov102, N. D. Kvaltine103, B. Lee104, J. J. LeRose105, S. Lewis106, R. Lindgren107, K. Livingston108, H. Y. Lu109, I. J. D. MacGregor110, Y. Mao111, D. Martinez112, M. Mayer113, E. McCullough114, B. McKinnon115, D. Meekins116, C. A. Meyer117, R. Michaels118, T. Mineeva119, M. Mirazita120, B. Moffit121, V. Mokeev122, R. A. Montgomery123, H. Moutarde124, E. Munevar125, C. Munoz Camacho126, P. Nadel-Turonski127, R. Nasseripour128, C. S. Nepali129, S. Niccolai130, G. Niculescu131, I. Niculescu132, M. Osipenko133, A. I. Ostrovidov134, L. L. Pappalardo135, R. Paremuzyan136, K. Park137, S. Park138, G. G. Petratos139, E. Phelps140, S. Pisano141, O. Pogorelko142, S. Pozdniakov143, S. Procureur144, D. Protopopescu145, A. J. R. Puckett146, X. Qian147, Y. Qiang148, G. Ricco149, D. Rimal150, M. Ripani151, B. G. Ritchie152, I. Rodriguez153, G. Ron154, G. Rosner155, P. Rossi156, F. Sabatie157, A. Saha158, M. S. Saini159, A. J. Sarty160, B. Sawatzky161, N. A. Saylor162, D. Schott163, E. Schulte164, R. A. Schumacher165, E. Seder166, H. Seraydaryan167, R. Shneor168, G. D. Smith169, D. Sokhan170, N. Sparveris171, S. S. Stepanyan172, S. Stepanyan173, P. Stoler174, R. Subedi175, V. Sulkosky176, M. Taiuti177, W. Tang178, C. E. Taylor179, S. Tkachenko180, M. Ungaro181, B. Vernarsky182, M. F. Vineyard183, H. Voskanyan184, E. Voutier185, N. K. Walford186, Y. Wang187, D. P. Watts188, L. B. Weinstein189, D. P. Weygand190, B. Wojtsekhowski191, M. H. Wood192, X. Yan193, H. Yao194, N. Zachariou195, X. Zhan196, J. Zhang197, Z. W. Zhao198, X. Zheng199, I. Zonta200
Affiliations: 1The CLAS and Hall-A Collaborations, 2The CLAS and Hall-A Collaborations, 3The CLAS and Hall-A Collaborations, 4The CLAS and Hall-A Collaborations, 5The CLAS and Hall-A Collaborations, 6The CLAS and Hall-A Collaborations, 7The CLAS and Hall-A Collaborations, 8The CLAS and Hall-A Collaborations, 9The CLAS and Hall-A Collaborations, 10The CLAS and Hall-A Collaborations, 11The CLAS and Hall-A Collaborations, 12The CLAS and Hall-A Collaborations, 13The CLAS and Hall-A Collaborations, 14The CLAS and Hall-A Collaborations, 15The CLAS and Hall-A Collaborations, 16The CLAS and Hall-A Collaborations, 17The CLAS and Hall-A Collaborations, 18The CLAS and Hall-A Collaborations, 19The CLAS and Hall-A Collaborations, 20The CLAS and Hall-A Collaborations, 21The CLAS and Hall-A Collaborations, 22The CLAS and Hall-A Collaborations, 23The CLAS and Hall-A Collaborations, 24The CLAS and Hall-A Collaborations, 25The CLAS and Hall-A Collaborations, 26The CLAS and Hall-A Collaborations, 27The 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We have measured cross sections for the gamma+3He->p+d reaction at photon energies of 0.4 - 1.4 GeV and a center-of-mass angle of 90 deg. Read More

The five-fold differential cross section for the 12C(e,e'p)11B reaction was determined over a missing momentum range of 200-400 MeV/c, in a kinematics regime with Bjorken x > 1 and Q2 = 2.0 (GeV/c)2. A comparison of the results and theoretical models and previous lower missing momentum data is shown. Read More

Authors: The HAPPEX, PREX Collaborations, :, S. Abrahamyan, A. Acha, A. Afanasev, Z. Ahmed, H. Albataineh, K. Aniol, D. S. Armstrong, W. Armstrong, J. Arrington, T. Averett, B. Babineau, S. L. Bailey, J. Barber, A. Barbieri, A. Beck, V. Bellini, R. Beminiwattha, H. Benaoum, J. Benesch, F. Benmokhtar, P. Bertin, T. Bielarski, W. Boeglin, P. Bosted, F. Butaru, E. Burtin, J. Cahoon, A. Camsonne, M. Canan, P. Carter, C. C. Chang, G. D. Cates, Y. C. Chao, C. Chen, J. P. Chen, Seonho Choi, E. Chudakov, E. Cisbani, B. Craver, F. Cusanno, M. M. Dalton, R. De Leo, K. de Jager, W. Deconinck, P. Decowski, D. Deepa, X. Deng, A. Deur, D. Dutta, A. Etile, C. Ferdi, R. J. Feuerbach, J. M. Finn, D. Flay, G. B. Franklin, M. Friend, S. Frullani, E. Fuchey, S. A. Fuchs, K. Fuoti, F. Garibaldi, E. Gasser, R. Gilman, A. Giusa, A. Glamazdin, L. E. Glesener, J. Gomez, M. Gorchtein, J. Grames, K. Grimm, C. Gu, O. Hansen, J. Hansknecht, O. Hen, D. W. Higinbotham, R. S. Holmes, T. Holmstrom, C. J. Horowitz, J. Hoskins, J. Huang, T. B. Humensky, C. E. Hyde, H. Ibrahim, F. Itard, C. M. Jen, E. Jensen, X. Jiang, G. Jin, S. Johnston, J. Katich, L. J. Kaufman, A. Kelleher, K. Kliakhandler, P. M. King, A. Kolarkar, S. Kowalski, E. Kuchina, K. S. Kumar, L. Lagamba, D. Lambert, P. LaViolette, J. Leacock, J. Leckey IV, J. H. Lee, J. J. LeRose, D. Lhuillier, R. Lindgren, N. Liyanage, N. Lubinsky, J. Mammei, F. Mammoliti, D. J. Margaziotis, P. Markowitz, M. Mazouz, K. McCormick, A. McCreary, D. McNulty, D. G. Meekins, L. Mercado, Z. E. Meziani, R. W. Michaels, M. Mihovilovic, B. Moffit, P. Monaghan, N. Muangma, C. Munoz-Camacho, S. Nanda, V. Nelyubin, D. Neyret, Nuruzzaman, Y. Oh, K. Otis, A. Palmer, D. Parno, K. D. Paschke, S. K. Phillips, M. Poelker, R. Pomatsalyuk, M. Posik, M. Potokar, K. Prok, A. J. R. Puckett, X. Qian, Y. Qiang, B. Quinn, A. Rakhman, P. E. Reimer, B. Reitz, S. Riordan, J. Roche, P. Rogan, G. Ron, G. Russo, K. Saenboonruang, A. Saha, B. Sawatzky, A. Shahinyan, R. Silwal, J. Singh, S. Sirca, K. Slifer, R. Snyder, P. Solvignon, P. A. Souder, M. L. Sperduto, R. Subedi, M. L. Stutzman, R. Suleiman, V. Sulkosky, C. M. Sutera, W. A. Tobias, W. Troth, G. M. Urciuoli, P. Ulmer, A. Vacheret, E. Voutier, B. Waidyawansa, D. Wang, K. Wang, J. Wexler, A. Whitbeck, R. Wilson, B. Wojtsekhowski, X. Yan, H. Yao, Y. Ye, Z. Ye, V. Yim, L. Zana, X. Zhan, J. Zhang, Y. Zhang, X. Zheng, V. Ziskin, P. Zhu

We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1-3 GeV transversely polarized electrons from $^1$H and for the first time from $^4$He, $^{12}$C, and $^{208}$Pb. For $^1$H, $^4$He and $^{12}$C, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}$Pb result is significantly smaller than the corresponding prediction using the same formalism. Read More

A frozen spin polarized target, constructed at Jefferson Lab for use inside a large acceptance spectrometer, is described. The target has been utilized for photoproduction measurements with polarized tagged photons of both longitudinal and circular polarization. Protons in TEMPO-doped butanol were dynamically polarized to approximately 90% outside the spectrometer at 5 T and 200--300 mK. Read More

We propose a new precision measurement of parity-violating electron scattering on the proton at very low Q^2 and forward angles to challenge predictions of the Standard Model and search for new physics. A unique opportunity exists to carry out the first precision measurement of the proton's weak charge, $Q_W =1 - 4\sin^2\theta_W$. A 2200 hour measurement of the parity violating asymmetry in elastic ep scattering at Q^2=0. Read More

We present new data for the polarization observables of the final state proton in the $^{1}H(\vec{\gamma},\vec{p})\pi^{0}$ reaction. These data can be used to test predictions based on hadron helicity conservation (HHC) and perturbative QCD (pQCD). These data have both small statistical and systematic uncertainties, and were obtained with beam energies between 1. Read More

The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV and beam energy E =3.48 GeV to be A_PV = -23. Read More

A large set of cross sections for semi-inclusive electroproduction of charged pions ($\pi^\pm$) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared $W^2$ > 4 GeV$^2$ and range in four-momentum transfer squared $2 < Q^2 < 4$ (GeV/c)$^2$, and cover a range in the Bjorken scaling variable 0.2 < x < 0. Read More


Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $G_{E}/G_{M}$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $H(\vec{e},e'\vec{p})$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2. Read More

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for $x>1$, which is sensitive to short range contributions to the nuclear wave-function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the `super-fast' quarks probed at x>1. Read More


Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6. Read More

High precision measurements of induced and transferred recoil proton polarization in d(polarized gamma, polarized p})n have been performed for photon energies of 277--357 MeV and theta_cm = 20 degrees -- 120 degrees. The measurements were motivated by a longstanding discrepancy between meson-baryon model calculations and data at higher energies. At the low energies of this experiment, theory continues to fail to reproduce the data, indicating that either something is missing in the calculations and/or there is a problem with the accuracy of the nucleon-nucleon potential being used. Read More

The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, where a proton is knocked-out of the nucleus with high momentum transfer and high missing momentum, show that in 12C the neutron-proton pairs are nearly twenty times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars. Read More

Affiliations: 1nee Rohe, 2nee Rohe, 3nee Rohe, 4nee Rohe, 5nee Rohe, 6nee Rohe, 7nee Rohe, 8nee Rohe, 9nee Rohe, 10nee Rohe, 11nee Rohe, 12nee Rohe, 13nee Rohe, 14nee Rohe, 15nee Rohe, 16nee Rohe, 17nee Rohe, 18nee Rohe, 19nee Rohe, 20nee Rohe, 21nee Rohe, 22nee Rohe, 23nee Rohe, 24nee Rohe, 25nee Rohe, 26nee Rohe, 27nee Rohe, 28nee Rohe, 29nee Rohe, 30nee Rohe, 31nee Rohe, 32nee Rohe, 33nee Rohe, 34nee Rohe, 35nee Rohe, 36nee Rohe, 37nee Rohe, 38nee Rohe, 39nee Rohe, 40nee Rohe, 41nee Rohe, 42nee Rohe, 43nee Rohe, 44nee Rohe, 45nee Rohe, 46nee Rohe, 47nee Rohe, 48nee Rohe, 49nee Rohe, 50nee Rohe, 51nee Rohe, 52nee Rohe

We have extracted QCD matrix elements from our data on double polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix element \tilde{d_2}, which arises strictly from quark- gluon interactions, to be unambiguously non zero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. Read More

Cross sections for the reaction ${^1}$H($e,e'\pi^+$)$n$ were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF high-intensity, continous electron beam in order to determine the charged pion form factor. Data were taken for central four-momentum transfers ranging from $Q^2$=0.60 to 2. Read More

The charged pion form factor, Fpi(Q^2), is an important quantity which can be used to advance our knowledge of hadronic structure. However, the extraction of Fpi from data requires a model of the 1H(e,e'pi+)n reaction, and thus is inherently model dependent. Therefore, a detailed description of the extraction of the charged pion form factor from electroproduction data obtained recently at Jefferson Lab is presented, with particular focus given to the dominant uncertainties in this procedure. Read More

Affiliations: 1nee Rohe, 2nee Rohe, 3nee Rohe, 4nee Rohe, 5nee Rohe, 6nee Rohe, 7nee Rohe, 8nee Rohe, 9nee Rohe, 10nee Rohe, 11nee Rohe, 12nee Rohe, 13nee Rohe, 14nee Rohe, 15nee Rohe, 16nee Rohe, 17nee Rohe, 18nee Rohe, 19nee Rohe, 20nee Rohe, 21nee Rohe, 22nee Rohe, 23nee Rohe, 24nee Rohe, 25nee Rohe, 26nee Rohe, 27nee Rohe

A search was made for sub-threshold $J/\psi$ production from a carbon target using a mixed real and quasi-real Bremsstrahlung photon beam with an endpoint energy of 5.76 GeV. No events were observed, which is consistent with predictions assuming quasi-free production. Read More