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1. Differential cross section measurements for γn→π-p above the first nucleon resonance region

Author

Mattione, Pt, Carman, Ds, Strakovsky, Ii, Workman, Rl, Kudryavtsev, Ae, Svarc, A, Tarasov, Ve, Adhikari, Kp, Adhikari, S, Adikaram, D, Akbar, Z, Anefalos Pereira, S, Ball, J, Baltzell, Na, Bashkanov, M, Battaglieri, M, Batourine, V, Bedlinskiy, I, Biselli, As, Boiarinov, S, Briscoe, Wj, Burkert, Vd, Cao, T, Celentano, A, Charles, G, Chetry, T, Ciullo, G, Clark, L, Cole, Pl, Contalbrigo, M, Cortes, O, Crede, V, D'Angelo, A, Dashyan, N, De Vita, R, De Sanctis, E, Defurne, M, Deur, A, Djalali, C, Dugger, M, Dupre, R, Egiyan, H, El Alaoui, A, El Fassi, L, Eugenio, P, Fedotov, G, Fersch, R, Filippi, A, Fleming, Ja, Fradi, A, Ghandilyan, Y, Gilfoyle, Gp, Giovanetti, Kl, Girod, Fx, Gleason, C, Golovatch, E, Gothe, Rw, Griffioen, Ka, Guidal, M, Hafidi, K, Hakobyan, H, Hanretty, C, Harrison, N, Hattawy, M, Heddle, D, Hicks, K, Hollis, G, Holtrop, M, Hughes, Sm, Ilieva, Y, Ireland, Dg, Ishkhanov, Bs, Isupov, El, Jenkins, D, Jiang, H, H. S., J, Joo, K, Joosten, S, Keller, D, Khachatryan, G, Khachatryan, M, Khandaker, M, Kim, A, Kim, W, Klein, A, Klein, Fj, Kubarovsky, V, Kuleshov, Sv, Lanza, L, Lenisa, P, Livingston, K, Macgregor, Ijd, Markov, N, Mckinnon, B, Meyer, Ca, Meziani, Ze, Mineeva, T, Mokeev, V, Montgomery, Ra, Movsisyan, A, Munoz Camacho, C, Murdoch, G, Nadel-Turonski, P, Net, La, Niccolai, S, Niculescu, G, Niculescu, I, Osipenko, M, Ostrovidov, Ai, Paolone, M, Paremuzyan, R, Park, K, Pasyuk, E, Phelps, W, Pisano, S, Pogorelko, O, Price, Jw, Procureur, S, Prok, Y, Protopopescu, D, Raue, Ba, Ripani, M, Ritchie, Bg, Rizzo, A, Rosner, G, Sabatie, F, Salgado, C, Schumacher, Ra, Sharabian, Yg, Simonyan, A, Skorodumina, I, Smith, Gd, Sokhan, D, Sparveris, N, Stankovic, I, Stepanyan, S, Strauch, S, Taiuti, M, Ungaro, M, Voskanyan, H, Voutier, E, Walford, Nk, Watts, D, Wei, X, Wood, Mh, Zachariou, N, Zhang, J, and Zhao, Zw

Subjects
Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2017

2. Measurements of ep→e′π+π-p′ cross sections with CLAS at 1.40 GeV<W<2.0 GeV and 2.0 GeV2<Q2<5.0 GeV2

Author

Isupov, El, Burkert, Vd, Carman, Ds, Gothe, Rw, Hicks, K, Ishkhanov, Bs, Mokeev, Vi, Adhikari, Kp, Adhikari, S, Adikaram, D, Akbar, Z, Amaryan, Mj, Anefalos Pereira, S, Avakian, H, Ball, J, Baltzell, Na, Battaglieri, M, Batourine, V, Bedlinskiy, I, Biselli, As, Briscoe, Wj, Brooks, Wk, Bultmann, S, Cao, T, Celentano, A, Charles, G, Chetry, T, Ciullo, G, Clark, L, Colaneri, L, Cole, Pl, Contalbrigo, M, Cortes, O, Crede, V, D'Angelo, A, Dashyan, N, De Vita, R, De Sanctis, E, Deur, A, Djalali, C, Dupre, R, El Alaoui, A, El Fassi, L, Elouadrhiri, L, Eugenio, P, Fedotov, G, Fersch, R, Filippi, A, Fleming, Ja, Forest, Ta, Garcon, M, Gavalian, G, Ghandilyan, Y, Gilfoyle, Gp, Giovanetti, Kl, Girod, Fx, Glazier, Di, Gleason, C, Golovatch, E, Griffioen, Ka, Guidal, M, Guo, L, Hafidi, K, Hakobyan, H, Hanretty, C, Harrison, N, Hattawy, M, Heddle, D, Holtrop, M, Hughes, Sm, Ilieva, Y, Ireland, Dg, Jenkins, D, Jiang, H, Joo, K, Joosten, S, Keller, D, Khachatryan, G, Khandaker, M, Kim, A, Kim, W, Klein, A, Klein, Fj, Kubarovsky, V, Kuleshov, Sv, Kunkel, M, Lanza, L, Lenisa, P, Livingston, K, H. Y., L, Macgregor, Ijd, Markov, N, Mckinnon, B, Mineeva, T, Mirazita, M, Montgomery, Ra, Movsisyan, A, Munevar, E, Munoz Camacho, C, Murdoch, G, Nadel-Turonski, P, Niccolai, S, Niculescu, G, Niculescu, I, Osipenko, M, Paolone, M, Paremuzyan, R, Park, K, Pasyuk, E, Phelps, W, Pogorelko, O, Price, Jw, Procureur, S, Prok, Y, Protopopescu, D, Raue, Ba, Ripani, M, Riser, D, Ritchie, Bg, Rizzo, A, Sabatie, F, Salgado, C, Schumacher, Ra, Sharabian, Yg, Simonyan, A, Skorodumina, I, Smith, Gd, Sokhan, D, Sparveris, N, Stankovic, I, Strakovsky, Ii, Strauch, S, Taiuti, M, Tian, Y, Torayev, B, Trivedi, A, Ungaro, M, Voskanyan, H, Voutier, E, Walford, Nk, Wei, X, Wood, Mh, Zachariou, N, and Zhang, J

Subjects
Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2017

3. Beam-Target Helicity Asymmetry for γ → n → →π-p in the N∗ Resonance Region

Author

Ho, D, Peng, P, Bass, C, Collins, P, D'Angelo, A, Deur, A, Fleming, J, Hanretty, C, Kageya, T, Khandaker, M, Klein, Fj, Klempt, E, Laine, V, Lowry, Mm, Lu, H, Nepali, C, Nikonov, Va, O'Connell, T, Sandorfi, Am, Sarantsev, Av, Schumacher, Ra, Strakovsky, Ii, Svarc, A, Walford, Nk, Wei, X, Whisnant, Cs, Workman, Rl, Zonta, I, Adhikari, Kp, Adikaram, D, Akbar, Z, Amaryan, Mj, Anefalos Pereira, S, Avakian, H, Ball, J, Bashkanov, M, Battaglieri, M, Batourine, V, Bedlinskiy, I, Biselli, A, Briscoe, Wj, Burkert, Vd, Carman, Ds, Celentano, A, Charles, G, Chetry, T, Ciullo, G, Clark, L, Colaneri, L, Cole, Pl, Contalbrigo, M, Crede, V, Dashyan, N, De Sanctis, E, De Vita, R, Djalali, C, Dupre, R, El Alaoui, A, El Fassi, L, Elouadrhiri, L, Eugenio, P, Fedotov, G, Fegan, S, Fersch, R, Filippi, A, Fradi, A, Ghandilyan, Y, Gilfoyle, Gp, Girod, Fx, Glazier, Di, Gleason, C, Gohn, W, Golovatch, E, Gothe, Rw, Griffioen, Ka, Guidal, M, Guo, L, Hakobyan, H, Harrison, N, Hattawy, M, Hicks, K, Holtrop, M, Hughes, Sm, Ilieva, Y, Ireland, Dg, Ishkhanov, Bs, Isupov, El, Jenkins, D, Jiang, H, H. S., J, Joo, K, Joosten, S, Keller, D, Khachatryan, G, Kim, A, Kim, W, Klein, A, Kubarovsky, V, Kuleshov, Sv, Lanza, L, Lenisa, P, Livingston, K, Macgregor, Ijd, Markov, N, Mckinnon, B, Mineeva, T, Mokeev, V, Montgomery, Ra, Movsisyan, A, Munoz Camacho, C, Murdoch, G, Niccolai, S, Niculescu, G, Osipenko, M, Paolone, M, Paremuzyan, R, Park, K, Pasyuk, E, Phelps, W, Pogorelko, O, Price, Jw, Procureur, S, Protopopescu, D, Ripani, M, Riser, D, Ritchie, Bg, Rizzo, A, Rosner, G, Sabatie, F, Salgado, C, Sharabian, Yg, Skorodumina, I, Smith, Gd, Sober, Di, Sokhan, D, Sparveris, N, Strauch, S, Tian, Y, Torayev, B, Ungaro, M, Voskanyan, H, Voutier, E, Watts, Dp, Wood, Mh, Zachariou, N, Zhang, J, and Zhao, Zw

Subjects
Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2017

4. Determination of the proton spin structure functions for 0.05 < Q^(2) < 5 GeV^(2) using CLAS

Author

Fersch, Rg, Guler, N, Bosted, P, Deur, A, Griffioen, K, Keith, C, Kuhn, Se, Minehart, R, Prok, Y, Adhikari, Kp, Adhikari, S, Akbar, Z, Amaryan, Mj, Anefalos Pereira, S, Asryan, G, Avakian, H, Ball, J, Balossino, I, Baltzell, Na, Battaglieri, M, Bedlinskiy, I, Biselli, As, Briscoe, Wj, Brooks, Wk, Bultmann, S, Burkert, Vd, Thanh Cao, F, Carman, Ds, Careccia, S, Celentano, A, Chandavar, S, Charles, G, Chetry, T, Ciullo, G, Clark, L, Colaneri, L, Cole, Pl, Compton, N, Contalbrigo, M, Cortes, O, Crede, V, D'Angelo, A, Dashyan, N, De Vita, R, De Sanctis, E, Djalali, C, Dodge, Ge, Dupre, R, Egiyan, H, El Alaoui, A, El Fassi, L, Elouadrhiri, L, Eugenio, P, Fanchini, E, Fedotov, G, Filippi, A, Fleming, Ja, Forest, Ta, Garcon, M, Gavalian, G, Ghandilyan, Y, Gilfoyle, Gp, Giovanetti, Kl, Girod, Fx, Gleason, C, Golovatch, E, Gothe, Rw, Guidal, M, Guo, L, Hafidi, K, Hakobyan, H, Hanretty, C, Harrison, N, Hattawy, M, Heddle, D, Hicks, K, Holtrop, M, Hughes, Sm, Ilieva, Y, Ireland, Dg, Ishkhanov, Bs, Isupov, El, Jenkins, D, Joo, K, Keller, D, Khachatryan, G, Khachatryan, M, Khandaker, M, Kim, A, Kim, W, Klein, A, Klein, Fj, Kubarovsky, V, Lagerquist, Vg, Lanza, L, Lenisa, P, Livingston, K, H. Y., L, Mckinnon, B, Meyer, Ca, Mirazita, M, Mokeev, V, Montgomery, Ra, Movsisyan, A, Munoz Camacho, C, Murdoch, G, Nadel-Turonski, P, Niccolai, S, Niculescu, G, Niculescu, I, Osipenko, M, Ostrovidov, Ai, Paolone, M, Paremuzyan, R, Park, K, Pasyuk, E, Phelps, W, Pierce, J, Pisano, S, Pogorelko, O, Price, Jw, Protopopescu, D, Raue, Ba, Ripani, M, Riser, D, Rizzo, A, Rosner, G, Rossi, P, Roy, P, Sabatie, F, Salgado, C, Schumacher, Ra, Sharabian, Yg, Simonyan, A, Skorodumina, I, Smith, Gd, Sokhan, D, Sparveris, N, Stankovic, I, Stepanyan, S, Strakovsky, Ii, Strauch, S, Taiuti, M, Tian, Y, Torayev, B, Ungaro, M, Voskanyan, H, Voutier, E, Walford, Nk, Watts, Dp, Wei, X, Weinstein, Lb, Zachariou, N, and Zhang, J

Subjects
Nuclear and High Energy Physics, Lepton Induced Nuclear Reactions, Polarized Phenomena, Socio-culturale, Proton Quark Model, Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2017

5. Measurements of ep→e′π+nat1.6<W<2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS

Author

Park, K, Aznauryan, Ig, Burkert, Vd, Adhikari, Kp, Amaryan, Mj, Pereira, Sa, Avakian, H, Battaglieri, M, Badui, R, Bedlinskiy, I, Biselli, As, Bono, J, Briscoe, Wj, Brooks, Wk, Carman, Ds, Celentano, A, Chandavar, S, Charles, G, Colaneri, L, Cole, Pl, Contalbrigo, M, Cortes, O, Crede, V, D'Angelo, A, Dashyan, N, De Vita, R, De Sanctis, E, Deur, A, Djalali, C, Doughty, D, Dupre, R, Egiyan, H, Alaoui, Ae, Elouadrhiri, L, Fassi, Le, Eugenio, P, Fedotov, G, Fegan, S, Fersch, R, Filippi, A, Fleming, Ja, Garillon, B, Garçon, M, Gevorgyan, N, Gilfoyle, Gp, Giovanetti, Kl, Girod, Fx, Joo, Hs, Goetz, Jt, Golovatch, E, Gothe, Rw, Griffioen, Ka, Guegan, B, Guidal, M, Guo, L, Hakobyan, H, Hanretty, C, Hattawy, M, Hicks, K, Holtrop, M, Hughes, Sm, Hyde, Ce, Ilieva, Y, Ireland, Dg, Ishkhanov, Bs, Isupov, El, Jenkins, D, Jiang, H, H. S., J, Joo, K, Joosten, S, Keller, D, Khandaker, M, Kim, A, Kim, W, Klein, A, Klein, Fj, Kubarovsky, V, Kuhn, Se, Kuleshov, Sv, Lenisa, P, Livingston, K, H. Y., L, Macgregor, Ijd, Markov, N, Martinez, D, Mckinnon, B, Mokeev, V, Montgomery, Ra, Moutarde, H, Camacho, Cm, Nadel-Turonski, P, Niccolai, S, Niculescu, G, Niculescu, I, Osipenko, M, Ostrovidov, Ai, Paolone, M, Pasyuk, E, Peng, P, Phelps, W, Phillips, Jj, Pisano, S, Pogorelko, O, Price, Jw, Procureur, S, Prok, Y, Protopopescu, D, Puckett, Ajr, Raue, Ba, Ripani, M, Rizzo, A, Rosner, G, Rossi, P, Roy, P, Sabatié, F, Salgado, C, Schott, D, Schumacher, Ra, Seder, E, Sharabian, Yg, Simonyan, A, Skorodumina, I, Smith, Es, Smith, Gd, Sparveris, N, Stoler, P, Strakovsky, Ii, Strauch, S, Sytnik, V, Taiuti, M, Tang, W, Taylor, Ce, Tian, Y, Trivedi, A, Ungaro, M, Voskanyan, H, Voutier, E, Walford, Nk, Watts, Dp, Wei, X, Weinstein, Lb, Wood, Mh, Zachariou, N, Zana, L, Zhang, J, Zhao, Zw, and Zonta, I

Subjects
RELATIVISTIC QUARK-MODEL, TRANSITION FORM-FACTORS, MESON PRODUCTION, GAMMA-ASTERISK, ELECTROPRODUCTION, PHOTOPRODUCTION, REGION, Settore FIS/04 - Fisica Nucleare e Subnucleare
Published
2015

6. First Measurement Using Elliptically Polarized Photons of the Double-Polarization Observable E for γp→pπ^{0} and γp→nπ^{+}.

Author

Afzal F, Spieker K, Hurck P, Abt S, Achenbach P, Adlarson P, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Drexler P, Fegan S, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Kashevarov VL, Kay SJD, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Macrae RG, Manley DM, Martel PP, Miskimen R, Mocanu M, Mornacchi E, Mullen C, Neganov A, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Powell A, Reicherz G, Rostomyan T, Sfienti C, Sokhoyan V, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, and Zachariou N

Abstract

We report the measurement of the helicity asymmetry E for the pπ^{0} and nπ^{+} final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g., G) and circularly polarized photons (e.g., E) and a longitudinally polarized target. The new data cover a photon energy range 270-1400 MeV for the pπ^{0} final state (230-842 MeV for the nπ^{+} final state) and the full range of pion polar angles, θ, providing the most precise measurement of the observable E. A moment analysis gives a clear observation of the pη cusp in the pπ^{0} final state.

Published
2024
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7. Single π 0 production off neutrons bound in deuteron with linearly polarized photons.

Author

Mullen C, Gardner S, Glazier DI, Kay SJD, Livingston K, Strakovsky II, Workman RL, Abt S, Achenbach P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Bashkanov M, Beck R, Biroth M, Borisov NS, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Drexler P, Fegan S, Ferretti-Bondy MI, Ghosal D, Gorodnov I, Gradl W, Günther M, Gurevic G, Heijkenskjöld L, Hornidge D, Huber GM, Jermann N, Kaeser A, Korolija M, Kashevarov VL, Krusche B, Kulikov VV, Lazarev A, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Martemianov MA, Meier C, Miskimen R, Mocanu M, Mornacchi E, Neganov A, Oberle M, Ostrick M, Otte P, Paudyal D, Pedroni P, Powell A, Prakhov SN, Reicherz G, Ron G, Rostomyan T, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, and Zachariou N

Abstract

The quasifree γ → d → π 0 n ( p ) photon beam asymmetry, Σ , has been measured at photon energies, E γ , from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49 ∘ to 148 ∘ . In this kinematic region, polarization observables are sensitive to contributions from the Δ ( 1232 ) and N (1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn-Gatchina analyses; while a revised SAID fit, including the new Σ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict π 0 n photoproduction observables, based on fits to published data in the channels π 0 p , π + n and π - p ., (© The Author(s) 2021.)

Published
2021
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8. Helicity-Dependent Cross Sections for the Photoproduction of π^{0} Pairs from Nucleons.

Author

Dieterle M, Witthauer L, Fix A, Abt S, Achenbach P, Adlarson P, Afzal F, Aguar Bartolome P, Ahmed Z, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dolzhikov AS, Downie EJ, Drexler P, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Metag V, Meyer W, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neganov A, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Polonski A, Powell A, Prakhov SN, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zana LA

Abstract

The double-polarization observable E and helicity-dependent cross sections σ&#95;{1/2}, σ&#95;{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.

Published
2020
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9. Signatures of the d^{*}(2380) Hexaquark in d(γ,pn[over →]).

Author

Bashkanov M, Watts DP, Kay SJD, Abt S, Achenbach P, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Downie EJ, Drexler P, Fegan S, Fix A, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Miskimen R, Mornacchi E, Mullen C, Neganov A, Neiser A, Ostrick M, Otte PB, Paudyal D, Pedroni P, Powell A, Prakhov SN, Ron G, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Usov YA, Wagner S, Walford NK, Werthmüller D, Wettig J, Wolfes M, Zachariou N, and Zana LA

Abstract

We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E&#95;{γ}∼570  MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.

Published
2020
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10. First Measurements of the Double-Polarization Observables F, P, and H in ω Photoproduction off Transversely Polarized Protons in the N^{*} Resonance Region.

Author

Roy P, Park S, Crede V, Anisovich AV, Klempt E, Nikonov VA, Sarantsev AV, Wei NC, Huang F, Nakayama K, Adhikari KP, Adhikari S, Angelini G, Avakian H, Barion L, Battaglieri M, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brock J, Brooks WK, Burkert VD, Cao F, Carlin C, Carman DS, Celentano A, Chatagnon P, Chetry T, Ciullo G, Cole PL, Contalbrigo M, Cortes O, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Diehl S, Djalali C, Dugger M, Dupre R, Duran B, Egiyan H, Ehrhart M, El Alaoui A, El Fassi L, Eugenio P, Fegan S, Filippi A, Fradi A, Gilfoyle GP, Girod FX, Golovatch E, Gothe RW, Griffioen KA, Guidal M, Guo L, Hafidi K, Hanretty C, Harrison N, Hattawy M, Hayward TB, Heddle D, Hicks K, Holtrop M, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Jo HS, Johnston S, Joosten S, Kabir ML, Keith CD, Keller D, Khachatryan G, Khachatryan M, Khanal A, Khandaker M, Kim A, Kim W, Klein FJ, Kubarovsky V, Kuleshov SV, Kunkel MC, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Marchand D, McKinnon B, Meekins DG, Meyer CA, Mineeva T, Mokeev V, Montgomery RA, Movsisyan A, Munoz Camacho C, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidov AI, Paolone M, Pappalardo LL, Paremuzyan R, Pasyuk E, Payette D, Phelps W, Pierce J, Pogorelko O, Prok Y, Protopopescu D, Raue BA, Ripani M, Riser D, Ritchie BG, Rizzo A, Rosner G, Sabatié F, Salgado C, Schumacher RA, Seely ML, Sharabian YG, Shrestha U, Skorodumina I, Sokhan D, Soto O, Sparveris N, Strakovsky II, Strauch S, Taiuti M, Tan JA, Torayev B, Tyler N, Ungaro M, Voskanyan H, Voutier E, Walford NK, Wang R, Watts DP, Wei X, Wood MH, Zachariou N, Zhang J, and Zhao ZW

Abstract

First measurements of double-polarization observables in ω photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry F has been measured using circularly polarized, tagged photons in the energy range 1200-2700 MeV, and the beam-target asymmetries H and P have been measured using linearly polarized, tagged photons in the energy range 1200-2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon (N^{*}) resonances. In particular, contributions from new N^{*} resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum.

Published
2019
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11. First Exclusive Measurement of Deeply Virtual Compton Scattering off ^{4}He: Toward the 3D Tomography of Nuclei.

Author

Hattawy M, Baltzell NA, Dupré R, Hafidi K, Stepanyan S, Bültmann S, De Vita R, El Alaoui A, El Fassi L, Egiyan H, Girod FX, Guidal M, Jenkins D, Liuti S, Perrin Y, Torayev B, Voutier E, Adhikari KP, Adhikari S, Adikaram D, Akbar Z, Amaryan MJ, Anefalos Pereira S, Armstrong WR, Avakian H, Ball J, Bashkanov M, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Burkert VD, Thanh Cao F, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Colaneri L, Cole PL, Contalbrigo M, Cortes O, Crede V, D'Angelo A, Dashyan N, De Sanctis E, Deur A, Djalali C, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Fersch R, Filippi A, Fleming JA, Forest TA, Fradi A, Garçon M, Gevorgyan N, Ghandilyan Y, Gilfoyle GP, Giovanetti KL, Gleason C, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guo L, Hakobyan H, Hanretty C, Harrison N, Heddle D, Hicks K, Holtrop M, Hughes SM, Ireland DG, Ishkhanov BS, Isupov EL, Jiang H, Joo K, Joosten S, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Kubarovsky V, Kuhn SE, Kuleshov SV, Lanza L, Lenisa P, Livingston K, Lu HY, MacGregor IJD, Markov N, Mayer M, McCracken ME, McKinnon B, Meyer CA, Meziani ZE, Mineeva T, Mirazita M, Mokeev V, Montgomery RA, Moutarde H, Movsisyan A, Munoz Camacho C, Nadel-Turonski P, Net LA, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Paolone M, Paremuzyan R, Park K, Pasyuk E, Phelps E, Phelps W, Pisano S, Pogorelko O, Price JW, Prok Y, Protopopescu D, Ripani M, Ritchie BG, Rizzo A, Rosner G, Rossi P, Sabatié F, Salgado C, Schumacher RA, Seder E, Sharabian YG, Simonyan A, Skorodumina I, Smith GD, Sokhan D, Sparveris N, Strauch S, Taiuti M, Ungaro M, Voskanyan H, Walford NK, Watts DP, Wei X, Weinstein LB, Wood MH, Zachariou N, Zana L, Zhang J, and Zhao ZW

Abstract

We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized ^{4}He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling ^{4}He nuclei. We measure beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we are able to extract, in a model-independent way, the real and imaginary parts of the only ^{4}He Compton form factor, H&#95;{A}. This first measurement of coherent deeply virtual Compton scattering on the ^{4}He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.

Published
2017
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12. Beam-Target Helicity Asymmetry for γ[over →]n[over →]→π^{-}p in the N^{*} Resonance Region.

Author

Ho D, Peng P, Bass C, Collins P, D'Angelo A, Deur A, Fleming J, Hanretty C, Kageya T, Khandaker M, Klein FJ, Klempt E, Laine V, Lowry MM, Lu H, Nepali C, Nikonov VA, O'Connell T, Sandorfi AM, Sarantsev AV, Schumacher RA, Strakovsky II, Švarc A, Walford NK, Wei X, Whisnant CS, Workman RL, Zonta I, Adhikari KP, Adikaram D, Akbar Z, Amaryan MJ, Anefalos Pereira S, Avakian H, Ball J, Bashkanov M, Battaglieri M, Batourine V, Bedlinskiy I, Biselli A, Briscoe WJ, Burkert VD, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Colaneri L, Cole PL, Contalbrigo M, Crede V, Dashyan N, De Sanctis E, De Vita R, Djalali C, Dupre R, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Fersch R, Filippi A, Fradi A, Ghandilyan Y, Gilfoyle GP, Girod FX, Glazier DI, Gleason C, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guidal M, Guo L, Hakobyan H, Harrison N, Hattawy M, Hicks K, Holtrop M, Hughes SM, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Jiang H, Jo HS, Joo K, Joosten S, Keller D, Khachatryan G, Kim A, Kim W, Klein A, Kubarovsky V, Kuleshov SV, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Markov N, McKinnon B, Mineeva T, Mokeev V, Montgomery RA, Movsisyan A, Munoz Camacho C, Murdoch G, Niccolai S, Niculescu G, Osipenko M, Paolone M, Paremuzyan R, Park K, Pasyuk E, Phelps W, Pogorelko O, Price JW, Procureur S, Protopopescu D, Ripani M, Riser D, Ritchie BG, Rizzo A, Rosner G, Sabatié F, Salgado C, Sharabian YG, Skorodumina I, Smith GD, Sober DI, Sokhan D, Sparveris N, Strauch S, Tian Y, Torayev B, Ungaro M, Voskanyan H, Voutier E, Watts DP, Wood MH, Zachariou N, Zhang J, and Zhao ZW

Abstract

We report the first beam-target double-polarization asymmetries in the γ+n(p)→π^{-}+p(p) reaction spanning the nucleon resonance region from invariant mass W=1500 to 2300 MeV. Circularly polarized photons and longitudinally polarized deuterons in solid hydrogen deuteride (HD) have been used with the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The exclusive final state has been extracted using three very different analyses that show excellent agreement, and these have been used to deduce the E polarization observable for an effective neutron target. These results have been incorporated into new partial wave analyses and have led to significant revisions for several γnN^{*} resonance photocouplings.

Published
2017
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13. Insight into the Narrow Structure in η Photoproduction on the Neutron from Helicity-Dependent Cross Sections.

Author

Witthauer L, Dieterle M, Abt S, Achenbach P, Afzal F, Ahmed Z, Annand JR, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov NS, Braghieri A, Briscoe WJ, Cividini F, Costanza S, Collicott C, Denig A, Downie EJ, Drexler P, Ferretti-Bondy MI, Gardner S, Garni S, Glazier DI, Glowa D, Gradl W, Günther M, Gurevich GM, Hamilton D, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev AB, Linturi JM, Lisin V, Livingston K, Lutterer S, MacGregor IJ, Mancell J, Manley DM, Martel PP, Metag V, Meyer W, Miskimen R, Mornacchi E, Mushkarenkov A, Neganov AB, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Polonski A, Prakhov SN, Rajabi A, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sikora MH, Sokhoyan V, Spieker K, Steffen O, Strakovski II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zana L

Abstract

The double polarization observable E and the helicity dependent cross sections σ&#95;{1/2} and σ&#95;{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ&#95;{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S&#95;{11}) and N 1/2^{+} (P&#95;{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ&#95;{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P&#95;{11} wave as the origin of this structure.

Published
2016
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14. Cross Sections for the Exclusive Photon Electroproduction on the Proton and Generalized Parton Distributions.

Author

Jo HS, Girod FX, Avakian H, Burkert VD, Garçon M, Guidal M, Kubarovsky V, Niccolai S, Stoler P, Adhikari KP, Adikaram D, Amaryan MJ, Anderson MD, Anefalos Pereira S, Ball J, Baltzell NA, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Carman DS, Celentano A, Chandavar S, Charles G, Colaneri L, Cole PL, Compton N, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Djalali C, Dupre R, Alaoui AE, Fassi LE, Elouadrhiri L, Fedotov G, Fegan S, Filippi A, Fleming JA, Garillon B, Gevorgyan N, Ghandilyan Y, Gilfoyle GP, Giovanetti KL, Goetz JT, Golovatch E, Gothe RW, Griffioen KA, Guegan B, Guler N, Guo L, Hafidi K, Hakobyan H, Harrison N, Hattawy M, Hicks K, Hirlinger Saylor N, Ho D, Holtrop M, Hughes SM, Ilieva Y, Ireland DG, Ishkhanov BS, Jenkins D, Joo K, Joosten S, Keller D, Khachatryan G, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Kuhn SE, Kuleshov SV, Lenisa P, Livingston K, Lu HY, MacGregor IJ, McKinnon B, Meziani ZE, Mirazita M, Mokeev V, Montgomery RA, Moutarde H, Movsisyan A, Munevar E, Munoz Camacho C, Nadel-Turonski P, Net LA, Niculescu G, Osipenko M, Ostrovidov AI, Paolone M, Park K, Pasyuk E, Phillips JJ, Pisano S, Pogorelko O, Price JW, Procureur S, Prok Y, Puckett AJ, Raue BA, Ripani M, Rizzo A, Rosner G, Rossi P, Roy P, Sabatié F, Salgado C, Schott D, Schumacher RA, Seder E, Simonyan A, Skorodumina Iu, Smith GD, Sokhan D, Sparveris N, Stepanyan S, Strakovsky II, Strauch S, Sytnik V, Tian Y, Tkachenko S, Ungaro M, Voskanyan H, Voutier E, Walford NK, Watts DP, Wei X, Weinstein LB, Wood MH, Zachariou N, Zana L, Zhang J, Zhao ZW, and Zonta I

Abstract

Unpolarized and beam-polarized fourfold cross sections (d^{4}σ/dQ^{2}dx&#95;{B}dtdϕ) for the ep→e^{'}p^{'}γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q^{2},x&#95;{B},t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist extraction of Compton form factors, these results support the model predictions of a larger nucleon size at lower quark-momentum fraction x&#95;{B}.

Published
2015
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15. Towards a resolution of the proton form factor problem: new electron and positron scattering data.

Author

Adikaram D, Rimal D, Weinstein LB, Raue B, Khetarpal P, Bennett RP, Arrington J, Brooks WK, Adhikari KP, Afanasev AV, Amaryan MJ, Anderson MD, Anefalos Pereira S, Avakian H, Ball J, Battaglieri M, Bedlinskiy I, Biselli AS, Bono J, Boiarinov S, Briscoe WJ, Burkert VD, Carman DS, Careccia S, Celentano A, Chandavar S, Charles G, Colaneri L, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Djalali C, Dodge GE, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Filippi A, Fleming JA, Fradi A, Garillon B, Gilfoyle GP, Giovanetti KL, Girod FX, Goetz JT, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guegan B, Guidal M, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Hicks K, Holtrop M, Hughes SM, Hyde CE, Ilieva Y, Ireland DG, Ishkhanov BS, Jenkins D, Jiang H, Jo HS, Joo K, Joosten S, Kalantarians N, Keller D, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Koirala S, Kubarovsky V, Kuhn SE, Livingston K, Lu HY, MacGregor IJ, Markov N, Mattione P, Mayer M, McKinnon B, Mestayer MD, Meyer CA, Mirazita M, Mokeev V, Montgomery RA, Moody CI, Moutarde H, Movsisyan A, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidov AI, Park K, Pasyuk E, Peña C, Pisano S, Pogorelko O, Price JW, Procureur S, Prok Y, Protopopescu D, Puckett AJ, Ripani M, Rizzo A, Rosner G, Rossi P, Roy P, Sabatié F, Salgado C, Schott D, Schumacher RA, Seder E, Sharabian YG, Simonyan A, Skorodumina I, Smith ES, Smith GD, Sober DI, Sokhan D, Sparveris N, Stepanyan S, Stoler P, Strauch S, Sytnik V, Taiuti M, Tian Y, Trivedi A, Ungaro M, Voskanyan H, Voutier E, Walford NK, Watts DP, Wei X, Wood MH, Zachariou N, Zana L, Zhang J, Zhao ZW, and Zonta I

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 (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45  GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75  GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3  GeV(2).

Published
2015
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16. Longitudinal target-spin asymmetries for deeply virtual compton scattering.

Author

Seder E, Biselli A, Pisano S, Niccolai S, Smith GD, Joo K, Adhikari K, Amaryan MJ, Anderson MD, Anefalos Pereira S, Avakian H, Battaglieri M, Bedlinskiy I, Bono J, Boiarinov S, Bosted P, Briscoe W, Brock J, Brooks WK, Bültmann S, Burkert VD, Carman DS, Carlin C, Celentano A, Chandavar S, Charles G, Colaneri L, Cole PL, Contalbrigo M, Crabb D, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Djalali C, Doughty D, Dupre R, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Filippi A, Fleming JA, Fradi A, Garillon B, Garçon M, Gevorgyan N, Ghandilyan Y, Giovanetti KL, Girod FX, Goetz JT, Gohn W, Gothe RW, Griffioen KA, Guegan B, Guidal M, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Hirlinger Saylor N, Holtrop M, Hughes SM, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jo HS, Joosten S, Keith CD, Keller D, Khachatryan G, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Koirala S, Kubarovsky V, Kuhn SE, Lenisa P, Livingston K, Lu HY, MacGregor IJ, Markov N, Mayer M, McKinnon B, Meekins DG, Mineeva T, Mirazita M, Mokeev V, Montgomery R, Moody CI, Moutarde H, Movsisyan A, Munoz Camacho C, Nadel-Turonski P, Niculescu I, Osipenko M, Ostrovidov AI, Paolone M, Pappalardo LL, Park K, Park S, Pasyuk E, Peng P, Phelps W, Pogorelko O, Price JW, Prok Y, Protopopescu D, Puckett AJ, Ripani M, Rizzo A, Rosner G, Rossi P, Roy P, Sabatié F, Salgado C, Schott D, Schumacher RA, Senderovich I, Simonyan A, Skorodumina I, Sokhan D, Sparveris N, Stepanyan S, Stoler P, Strakovsky II, Strauch S, Sytnik V, Taiuti M, Tang W, Tian Y, Ungaro M, Voskanyan H, Voutier E, Walford NK, Watts DP, Wei X, Weinstein LB, Wood MH, Zachariou N, Zana L, Zhang J, and Zonta I

Abstract

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep→e^{'}p^{'}γ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q^{2}, x&#95;{B}, t, and ϕ, for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even generalized parton distributions.

Published
2015
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17. Nuclear physics. Momentum sharing in imbalanced Fermi systems.

Author

Hen O, Sargsian M, Weinstein LB, Piasetzky E, Hakobyan H, Higinbotham DW, Braverman M, Brooks WK, Gilad S, Adhikari KP, Arrington J, Asryan G, Avakian H, Ball J, Baltzell NA, Battaglieri M, Beck A, May-Tal Beck S, Bedlinskiy I, Bertozzi W, Biselli A, Burkert VD, Cao T, Carman DS, Celentano A, Chandavar S, Colaneri L, Cole PL, Crede V, D'Angelo A, De Vita R, Deur A, Djalali C, Doughty D, Dugger M, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Fedotov G, Fegan S, Forest T, Garillon B, Garcon M, Gevorgyan N, Ghandilyan Y, Gilfoyle GP, Girod FX, Goetz JT, Gothe RW, Griffioen KA, Guidal M, Guo L, Hafidi K, Hanretty C, Hattawy M, Hicks K, Holtrop M, Hyde CE, Ilieva Y, Ireland DG, Ishkanov BI, Isupov EL, Jiang H, Jo HS, Joo K, Keller D, Khandaker M, Kim A, Kim W, Klein FJ, Koirala S, Korover I, Kuhn SE, Kubarovsky V, Lenisa P, Levine WI, Livingston K, Lowry M, Lu HY, MacGregor IJ, Markov N, Mayer M, McKinnon B, Mineeva T, Mokeev V, Movsisyan A, Munoz Camacho C, Mustapha B, Nadel-Turonski P, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Pappalardo LL, Paremuzyan R, Park K, Pasyuk E, Phelps W, Pisano S, Pogorelko O, Price JW, Procureur S, Prok Y, Protopopescu D, Puckett AJ, Rimal D, Ripani M, Ritchie BG, Rizzo A, Rosner G, Roy P, Rossi P, Sabatié F, Schott D, Schumacher RA, Sharabian YG, Smith GD, Shneor R, Sokhan D, Stepanyan SS, Stepanyan S, Stoler P, Strauch S, Sytnik V, Taiuti M, Tkachenko S, Ungaro M, Vlassov AV, Voutier E, Walford NK, Wei X, Wood MH, Wood SA, Zachariou N, Zana L, Zhao ZW, Zheng X, and Zonta I

Abstract

The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems., (Copyright © 2014, American Association for the Advancement of Science.)

Published
2014
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18. Strangeness suppression of qq creation observed in exclusive reactions.

Author

Mestayer MD, Park K, Adhikari KP, Aghasyan M, Pereira SA, Ball J, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Burkert VD, Carman DS, Celentano A, Chandavar S, Charles G, Colaneri L, Cole PL, Contalbrigo M, Cortes O, Crede V, D'Angelo A, Dashyan N, De Vita R, Deur A, Djalali C, Doughty D, Dupre R, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fleming JA, Forest TA, Garillon B, Garçon M, Ghandilyan Y, Gilfoyle GP, Giovanetti KL, Girod FX, Goetz JT, Golovatch E, Gothe RW, Griffioen KA, Guegan B, Guidal M, Hakobyan H, Hanretty C, Hattawy M, Holtrop M, Hughes SM, Hyde CE, Ilieva Y, Ireland DG, Jiang H, Jo HS, Joo K, Keller D, Khandaker M, Kim A, Kim W, Koirala S, Kubarovsky V, Kuleshov SV, Lenisa P, Levine WI, Livingston K, Lu HY, MacGregor IJ, Mayer M, McKinnon B, Meyer CA, Mirazita M, Mokeev V, Montgomery RA, Moody CI, Moutarde H, Movsisyan A, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Pappalardo LL, Paremuzyan R, Peng P, Phelps W, Pisano S, Pogorelko O, Pozdniakov S, Price JW, Protopopescu D, Puckett AJ, Raue BA, Rimal D, Ripani M, Rizzo A, Rosner G, Roy P, Sabatié F, Saini MS, Schott D, Schumacher RA, Simonyan A, Sokhan D, Strauch S, Sytnik V, Tang W, Tian Y, Ungaro M, Vernarsky B, Vlassov AV, Voskanyan H, Voutier E, Walford NK, Watts DP, Wei X, Weinstein LB, Wood MH, Zachariou N, Zhang J, Zhao ZW, and Zonta I

Abstract

We measured the ratios of electroproduction cross sections from a proton target for three exclusive meson-baryon final states: ΛK(+), pπ(0), and nπ(+), with the CLAS detector at Jefferson Lab. Using a simple model of quark hadronization, we extract qq creation probabilities for the first time in exclusive two-body production, in which only a single qq pair is created. We observe a sizable suppression of strange quark-antiquark pairs compared to nonstrange pairs, similar to that seen in high-energy production.

Published
2014
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19. Hard two-body photodisintegration of 3He.

Author

Pomerantz I, Ilieva Y, Gilman R, Higinbotham DW, Piasetzky E, Strauch S, Adhikari KP, Aghasyan M, Allada K, Amaryan MJ, Anefalos Pereira S, Anghinolfi M, Baghdasaryan H, Ball J, Baltzell NA, Battaglieri M, Batourine V, Beck A, Beck S, Bedlinskiy I, Berman BL, Biselli AS, Boeglin W, Bono J, Bookwalter C, Boiarinov S, Briscoe WJ, Brooks WK, Bubis N, Burkert V, Camsonne A, Canan M, Carman DS, Celentano A, Chandavar S, Charles G, Chirapatpimol K, Cisbani E, Cole PL, Contalbrigo M, Crede V, Cusanno F, D'Angelo A, Daniel A, Dashyan N, de Jager CW, De Vita R, De Sanctis E, Deur A, Djalali C, Dodge GE, Doughty D, Dupre R, Dutta C, Egiyan H, El Alaoui A, El Fassi L, Eugenio P, Fedotov G, Fegan S, Fleming JA, Fradi A, Garibaldi F, Geagla O, Gevorgyan N, Giovanetti KL, Girod FX, Glister J, Goetz JT, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guegan B, Guidal M, Guo L, Hafidi K, Hakobyan H, Harrison N, Heddle D, Hicks K, Ho D, Holtrop M, Hyde CE, Ireland DG, Ishkhanov BS, Isupov EL, Jiang X, Jo HS, Joo K, Katramatou AT, Keller D, Khandaker M, Khetarpal P, Khrosinkova E, Kim A, Kim W, Klein FJ, Koirala S, Kubarovsky A, Kubarovsky V, Kuleshov SV, Kvaltine ND, Lee B, LeRose JJ, Lewis S, Lindgren R, Livingston K, Lu HY, MacGregor IJ, Mao Y, Martinez D, Mayer M, McCullough E, McKinnon B, Meekins D, Meyer CA, Michaels R, Mineeva T, Mirazita M, Moffit B, Mokeev V, Montgomery RA, Moutarde H, Munevar E, Munoz Camacho C, Nadel-Turonski P, Nasseripour R, Nepali CS, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Pappalardo LL, Paremuzyan R, Park K, Park S, Petratos GG, Phelps E, Pisano S, Pogorelko O, Pozdniakov S, Procureur S, Protopopescu D, Puckett AJ, Qian X, Qiang Y, Ricco G, Rimal D, Ripani M, Ritchie BG, Rodriguez I, Ron G, Rosner G, Rossi P, Sabatié F, Saha A, Saini MS, Sarty AJ, Sawatzky B, Saylor NA, Schott D, Schulte E, Schumacher RA, Seder E, Seraydaryan H, Shneor R, Smith GD, Sokhan D, Sparveris N, Stepanyan SS, Stepanyan S, Stoler P, Subedi R, Sulkosky V, Taiuti M, Tang W, Taylor CE, Tkachenko S, Ungaro M, Vernarsky B, Vineyard MF, Voskanyan H, Voutier E, Walford NK, Wang Y, Watts DP, Weinstein LB, Weygand DP, Wojtsekhowski B, Wood MH, Yan X, Yao H, Zachariou N, Zhan X, Zhang J, Zhao ZW, Zheng X, and Zonta I

Abstract

We have measured cross sections for the γ(3)He → pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Published
2013
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20. Measurement of exclusive π(0) electroproduction structure functions and their relationship to transverse generalized parton distributions.

Author

Bedlinskiy I, Kubarovsky V, Niccolai S, Stoler P, Adhikari KP, Aghasyan M, Amaryan MJ, Anghinolfi M, Avakian H, Baghdasaryan H, Ball J, Baltzell NA, Battaglieri M, Bennett RP, Biselli AS, Bookwalter C, Boiarinov S, Briscoe WJ, Brooks WK, Burkert VD, Carman DS, Celentano A, Chandavar S, Charles G, Contalbrigo M, Crede V, D'Angelo A, Daniel A, Dashyan N, De Vita R, De Sanctis E, Deur A, Djalali C, Doughty D, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Fleming JA, Forest TA, Fradi A, Garçon M, Gevorgyan N, Giovanetti KL, Girod FX, Gohn W, Gothe RW, Graham L, Griffioen KA, Guegan B, Guidal M, Guo L, Hafidi K, Hakobyan H, Hanretty C, Heddle D, Hicks K, Holtrop M, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jo HS, Joo K, Keller D, Khandaker M, Khetarpal P, Kim A, Kim W, Klein FJ, Koirala S, Kubarovsky A, Kuhn SE, Kuleshov SV, Kvaltine ND, Livingston K, Lu HY, MacGregor IJ, Mao Y, Markov N, Martinez D, Mayer M, McKinnon B, Meyer CA, Mineeva T, Mirazita M, Mokeev V, Moutarde H, Munevar E, Munoz Camacho C, Nadel-Turonski P, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Pappalardo LL, Paremuzyan R, Park K, Park S, Pasyuk E, Anefalos Pereira S, Phelps E, Pisano S, Pogorelko O, Pozdniakov S, Price JW, Procureur S, Prok Y, Protopopescu D, Puckett AJ, Raue BA, Ricco G, Rimal D, Ripani M, Rosner G, Rossi P, Sabatié F, Saini MS, Salgado C, Saylor N, Schott D, Schumacher RA, Seder E, Seraydaryan H, Sharabian YG, Smith GD, Sober DI, Sokhan D, Stepanyan SS, Stepanyan S, Strauch S, Taiuti M, Tang W, Taylor CE, Tian Y, Tkachenko S, Ungaro M, Vineyard MF, Vlassov A, Voskanyan H, Voutier E, Walford NK, Watts DP, Weinstein LB, Weygand DP, Wood MH, Zachariou N, Zhang J, Zhao ZW, and Zonta I

Abstract

Exclusive π(0) electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q(2), x(B), t, and ϕ(π), in the Q(2) range from 1.0 to 4.6  GeV(2), -t up to 2  GeV(2), and x(B) from 0.1 to 0.58. Structure functions σ(T)+ϵσ(L), σ(TT), and σ(LT) were extracted as functions of t for each of 17 combinations of Q(2) and x(B). The data were compared directly with two handbag-based calculations including both longitudinal and transversity generalized parton distributions (GPDs). Inclusion of only longitudinal GPDs very strongly underestimates σ(T)+ϵσ(L) and fails to account for σ(TT) and σ(LT), while inclusion of transversity GPDs brings the calculations into substantially better agreement with the data. There is very strong sensitivity to the relative contributions of nucleon helicity-flip and helicity nonflip processes. The results confirm that exclusive π(0) electroproduction offers direct experimental access to the transversity GPDs.

Published
2012
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