CLAS Collaboration

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Nuclear Experiment (47)
 
High Energy Physics - Experiment (23)
 
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Publications Authored By CLAS Collaboration

This paper reports new exclusive cross sections for $e p \to e' \pi^+ \pi^- p'$ using the CLAS detector at Jefferson Laboratory. These results are presented for the first time at photon virtualities 2.0 GeV^2 < Q^2 < 5. Read More

2017Mar
Authors: CLAS Collaboration, I. Bedlinskiy, V. Kubarovsky, P. Stoler, K. P. Adhikari, Z. Akbar, S. Anefalos Pereira, H. Avakian, J. Ball, N. A. Baltzell, M. Battaglieri, V. Batourine, A. S. Biselli, S. Boiarinov, W. J. Briscoe, V. D. Burkert, T. Cao, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, G. Ciullo, L. Clark, L. Colaneri, P. L. Cole, M. Contalbrigo, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, R. Dupre, A. El Alaoui, L. El Fassi, L. Elouadrhiri, P. Eugenio, E. Fanchini, G. Fedotov, R. Fersch, A. Filippi, J. A. Fleming, T. A. Forest, M. Garçon, N. Gevorgyan, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, C. Gleason, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, N. Harrison, M. Hattawy, K. Hicks, S. M. Hughes, C. E. Hyde, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, D. Jenkins, H. Jiang, H. S. Jo, K. Joo, S. Joosten, D. Keller, G. Khachatryan, M. Khachatryan, M. Khandaker, A. Kim, W. Kim, F. J. Klein, S. E. Kuhn, S. V. Kuleshov, L. Lanza, P. Lenisa, K. Livingston, I. J. D. MacGregor, N. Markov, B. McKinnon, Z. E. Meziani, M. Mirazita, V. Mokeev, R. A. Montgomery, A. Movsisyan, C. Munoz Camacho, P. Nadel-Turonski, L. A. Net, A. Ni, S. Niccolai, G. Niculescu, M. Osipenko, A. I. Ostrovidov, M. Paolone, R. Paremuzyan, K. Park, E. Pasyuk, P. Peng, W. Phelps, S. Pisano, O. Pogorelko, J. W. Price, Y. Prok, D. Protopopescu, A. J. R. Puckett, B. A. Raue, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, P. Roy, F. Sabatié, M. S. Saini, C. Salgado, R. A. Schumacher, Y. G. Sharabian, Iu. Skorodumina, G. D. Smith, D. Sokhan, N. Sparveris, S. Stepanyan, I. I. Strakovsky, S. Strauch, M. Taiuti, Ye Tian, B. Torayev, M. Turisini, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, D. P. Watts, X. Wei, L. B. Weinstein, M. H. Wood, M. Yurov, N. Zachariou, J. Zhang, I. Zonta

The cross section of the exclusive $\eta$ electroproduction reaction $ep\to e^\prime p^\prime \eta$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi_\eta$ and structure functions $\sigma_U = \sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$, as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. Read More

Quasi-elastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D-state admixture) and on the limits of the Impulse Approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Read More

Background: Measurements of polarization observables for the reactions $\vec{\gamma} p \rightarrow K^+ \Lambda$ and $\vec{\gamma} p \rightarrow K^+ \Sigma^0$ have been performed. This is part of a programme of measurements designed to study the spectrum of baryon resonances. Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits. Read More

The spectrum of nucleon excitations is dominated by broad and overlapping resonances. Polarization observables in photoproduction reactions are key in the study of these excitations. They give indispensable constraints to partial-wave analyses and help clarify the spectrum. Read More

The cross section of the exclusive $\pi^0$ and $\eta$ electroproduction reaction $ep\to e^\prime p^\prime \pi^0/\eta$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi$ and structure functions $\sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. Read More

Studying the structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The electrocouplings of $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $\pi N$, $\eta N$, and $\pi \pi N$ data. Read More

Meson photoproduction is an important tool in the study of baryon resonances. The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of polarization observables. The N* program at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) includes experimental studies with linearly and circularly polarized tagged photon beams, longitudinally and transversely polarized nucleon targets, and recoil polarizations. Read More

Unpolarized and beam-polarized four-fold cross sections $\frac{d^4 \sigma}{dQ^2 dx_B dt d\phi}$ for the $ep\to e^\prime p^\prime \gamma$ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 ($Q^2,x_B,t$) 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. Read More

2015Mar
Authors: Nicholas Zachariou, Yordanka Ilieva, Nikolay Ya. Ivanov, Misak M Sargsian, Robert Avakian, Gerald Feldman, Pawel Nadel-Turonski, K. P. Adhikari, D. Adikaram, M. D. Anderson, S. Anefalos Pereira, H. Avakian, R. A. Badui, N. A. Baltzell, M. Battaglieri, V. Baturin, I. Bedlinskiy, A. S. Biselli, W. J. Briscoe, W. K. Brooks, V. D. Burkert, T. Cao, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, L. Colaneri, P. L. Cole, N. Compton, M. Contalbrigo, O. Cortes, V. Crede, A. D'Angelo, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, L. Elouadrhiri, G. Fedotov, S. Fegan, A. Filippi, J. A. Fleming, T. A. Forest, A. Fradi, N. Gevorgyan, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, D. I. Glazier, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, K. Hafidi, C. Hanretty, N. Harrison, M. Hattawy, K. Hicks, D. Ho, M. Holtrop, S. M. Hughes, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, H. Jiang, H. S. Jo, K. Joo, D. Keller, G. Khachatryan, M. Khandaker, A. Kim, W. Kim, F. J. Klein, V. Kubarovsky, P. Lenisa, K. Livingston, H. Y. Lu, I . J . D. MacGregor, N. Markov, P. T. Mattione, B. McKinnon, T. Mineeva, M. Mirazita, V. I. Mokeeev, R. A. Montgomery, H. Moutarde, C. Munoz Camacho, L. A. Net, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, A. I. Ostrovidov, K. Park, E. Pasyuk, W. Phelps, J. J. Phillips, S. Pisano, O. Pogorelko, S. Pozdniakov, J. W. Price, S. Procureur, Y. Prok, D. Protopopescu, A. J. R. Puckett, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, P. Roy, F. Sabatié, C. Salgado, D. Schott, R. A. Schumacher, E. Seder, I. Senderovich, Y. G. Sharabian, Iu. Skorodumina, G. D. Smith, D. I. Sober, D. Sokhan, N. Sparveris, S. Stepanyan, S. Strauch, V. Sytnik, M. Taiuti, Ye Tian, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, D. Watts, X. Wei, M. H. Wood, L. Zana, J. Zhang, Z. W. Zhao, I. Zonta, for the CLAS collaboration

The beam-spin asymmetry, $\Sigma$, for the reaction $\gamma d\rightarrow pn$ has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, $\theta_{c. Read More

Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton $\vec{e}\vec{p} \to e' p'\gamma$ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ${}^{14}$NH$_3$ target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. Read More

We measured the ratios of electroproduction cross-sections from a proton target for three exclusive meson-baryon final states: $\Lambda K^+$, $p\pi^0$, and $n\pi^+$, with the CLAS detector at Jefferson Lab. Using a simple model of quark hadronization we extract q-qbar creation probabilities for the first time in exclusive two-body production, in which only a single q-qbar pair is created. We observe a sizable suppression of strange quark-antiquark pairs compared to non-strange pairs, similar to that seen in high-energy production. Read More

Differential cross sections of the exclusive process $e p \to e^\prime \pi^+ n$ were measured with good precision in the range of the photon virtuality $Q^2 = 1.8 - 4.5$ GeV$^2$, and the invariant mass range of the $\pi^+ n$ final state W = 1. Read More

2014Nov
Authors: D. Adikaram, D. Rimal, L. B. Weinstein, B. Raue, P. Khetarpal, R. P. Bennett, J. Arrington, W. K. Brooks, K. P. Adhikari, A. V. Afanasev, M. J. Amaryan, M. D. Anderson, J. Ball, M. Battaglieri, I. Bedlinskiy, A. S. Biselli, J. Bono, S. Boiarinov, W. J. Briscoe, V. D. Burkert, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, L. Colaneri, P. L. Cole, M. Contalbrigo, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, G. E. Dodge, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, P. Eugenio, G. Fedotov, S. Fegan, A. Filippi, J. A. Fleming, A. Fradi, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, J. T. Goetz, W. Gohn, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, N. Harrison, M. Hattawy, K. Hicks, M. Holtrop, S. M. Hughes, C. E. Hyde, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, D. Jenkins, H. Jiang, K. Joo, S. Joosten, M. Khandaker, W. Kim, A. Klein, F. J. Klein, S. Koirala, V. Kubarovsky, S. E. Kuhn, H. Y. Lu, I . J . D. MacGregor, N. Markov, M. Mayer, B. McKinnon, M. D. Mestayer, C. A. Meyer, M. Mirazita, V. Mokeev, R. A. Montgomery, C. I. Moody, H. Moutarde, A Movsisyan, C. Munoz Camacho, P. Nadel-Turonski, S. Niccolai, G. Niculescu, M. Osipenko, A. I. Ostrovidov, K. Park, E. Pasyuk, S. Pisano, O. Pogorelko, S. Procureur, Y. Prok, D. Protopopescu, A. J. R. Puckett, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, F. Sabatié, D. Schott, R. A. Schumacher, Y. G. Sharabian, A. Simonyan, I. Skorodumina, E. S. Smith, G. D. Smith, D. I. Sober, N. Sparveris, S. Stepanyan, S. Strauch, V. Sytnik, M. Taiuti, Ye Tian, A. Trivedi, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, D. P. Watts, X. Wei, M. H. Wood, N. Zachariou, L. Zana, J. Zhang, Z. W. Zhao, I. Zonta, The CLAS Collaboration

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. Read More

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 $ep\to e'p'\gamma$ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in $Q^2$, $x_B$, $t$ and $\phi$, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the $t$ dependence of these asymmetries provides insight on the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. Read More

2014May
Authors: I. Bedlinskiy1, V. Kubarovsky2, S. Niccolai3, P. Stoler4, K. P. Adhikari5, M. D. Anderson6, S. Anefalos Pereira7, H. Avakian8, J. Ball9, N. A. Baltzell10, M. Battaglieri11, V. Batourine12, A. S. Biselli13, S. Boiarinov14, J. Bono15, W. J. Briscoe16, W. K. Brooks17, V. D. Burkert18, D. S. Carman19, A. Celentano20, S. Chandavar21, L. Colaneri22, P. L. Cole23, M. Contalbrigo24, O. Cortes25, V. Crede26, A. D'Angelo27, N. Dashyan28, R. De Vita29, E. De Sanctis30, A. Deur31, C. Djalali32, D. Doughty33, R. Dupre34, H. Egiyan35, A. El Alaoui36, L. El Fassi37, L. Elouadrhiri38, P. Eugenio39, G. Fedotov40, S. Fegan41, J. A. Fleming42, T. A. Forest43, B. Garillon44, M. Garçon45, G. Gavalian46, N. Gevorgyan47, Y. Ghandilyan48, G. P. Gilfoyle49, K. L. Giovanetti50, F. X. Girod51, E. Golovatch52, R. W. Gothe53, K. A. Griffioen54, B. Guegan55, L. Guo56, K. Hafidi57, H. Hakobyan58, N. Harrison59, M. Hattawy60, K. Hicks61, M. Holtrop62, D. G. Ireland63, B. S. Ishkhanov64, E. L. Isupov65, D. Jenkins66, H. S. Jo67, K. Joo68, D. Keller69, M. Khandaker70, A. Kim71, W. Kim72, A. Klein73, F. J. Klein74, S. Koirala75, S. E. Kuhn76, S. V. Kuleshov77, P. Lenisa78, W. I. Levine79, K. Livingston80, H. Y. Lu81, I . J . D. MacGregor82, N. Markov83, M. Mayer84, B. McKinnon85, M. Mirazita86, V. Mokeev87, R. A. Montgomery88, C. I. Moody89, H. Moutarde90, A Movsisyan91, C. Munoz Camacho92, P. Nadel-Turonski93, I. Niculescu94, M. Osipenko95, A. I. Ostrovidov96, L. L. Pappalardo97, K. Park98, S. Park99, E. Pasyuk100, E. Phelps101, W. Phelps102, J. J. Phillips103, S. Pisano104, O. Pogorelko105, J. W. Price106, Y. Prok107, D. Protopopescu108, S. Procureur109, A. J. R. Puckett110, B. A. Raue111, M. Ripani112, B. G. Ritchie113, A. Rizzo114, P. Rossi115, P. Roy116, F. Sabatié117, C. Salgado118, D. Schott119, R. A. Schumacher120, E. Seder121, I. Senderovich122, Y. G. Sharabian123, A. Simonyan124, G. D. Smith125, D. I. Sober126, D. Sokhan127, S. S. Stepanyan128, S. Strauch129, V. Sytnik130, W. Tang131, Ye Tian132, M. Ungaro133, A. V. Vlassov134, H. Voskanyan135, E. Voutier136, N. K. Walford137, D. Watts138, X. Wei139, L. B. Weinstein140, M. Yurov141, N. Zachariou142, L. Zana143, J. Zhang144, Z. W. Zhao145, I. Zonta146, for the CLAS Collaboration
Affiliations: 1Institute of Theoretical and Experimental Physics, 2Thomas Jefferson National Accelerator Facility, 3Institut de Physique Nucléaire ORSAY, 4Rensselaer Polytechnic Institute, 5Old Dominion University, 6University of Glasgow, 7INFN, 8Thomas Jefferson National Accelerator Facility, 9CEA, 10Argonne National Laboratory, 11INFN, 12Thomas Jefferson National Accelerator Facility, 13Thomas Jefferson National Accelerator Facility, 14Thomas Jefferson National Accelerator Facility, 15Florida International University, 16The George Washington University, 17Universidad Técnica Federico Santa María, 18Thomas Jefferson National Accelerator Facility, 19Thomas Jefferson National Accelerator Facility, 20INFN, 21Ohio University, 22INFN, 23Idaho State University, 24INFN, 25Idaho State University, 26Florida State University, 27INFN, 28Yerevan Physics Institute, 29INFN, 30INFN, 31Thomas Jefferson National Accelerator Facility, 32University of South Carolina, 33Christopher Newport University, 34Institut de Physique Nucléaire ORSAY, 35Thomas Jefferson National Accelerator Facility, 36Argonne National Laboratory, 37Old Dominion University, 38Thomas Jefferson National Accelerator Facility, 39Florida State University, 40University of South Carolina, 41INFN, 42Edinburgh University, 43Idaho State University, 44Institut de Physique Nucléaire ORSAY, 45CEA, 46Old Dominion University, 47Yerevan Physics Institute, 48Yerevan Physics Institute, 49University of Richmond, 50James Madison University, 51Thomas Jefferson National Accelerator Facility, 52Skobeltsyn Institute of Nuclear Physics, 53University of South Carolina, 54Institut de Physique Nucléaire ORSAY, 55Institut de Physique Nucléaire ORSAY, 56Florida International University, 57Argonne National Laboratory, 58Universidad Técnica Federico Santa María, 59University of Connecticut, 60Institut de Physique Nucléaire ORSAY, 61Ohio University, 62University of New Hampshire, 63University of Glasgow, 64Skobeltsyn Institute of Nuclear Physics, 65Skobeltsyn Institute of Nuclear Physics, 66Institut de Physique Nucléaire ORSAY, 67Institut de Physique Nucléaire ORSAY, 68University of Connecticut, 69University of Virginia, 70Idaho State University, 71University of Connecticut, 72Kyungpook National University, 73Old Dominion University, 74Catholic University of America, 75Old Dominion University, 76Old Dominion University, 77Universidad Técnica Federico Santa María, 78INFN, 79Carnegie Mellon University, 80University of Glasgow, 81University of South Carolina, 82University of Glasgow, 83University of Connecticut, 84Old Dominion University, 85University of Glasgow, 86INFN, 87Thomas Jefferson National Accelerator Facility, 88INFN, 89Argonne National Laboratory, 90CEA, 91INFN, 92Institut de Physique Nucléaire ORSAY, 93Thomas Jefferson National Accelerator Facility, 94James Madison University, 95INFN, 96Florida State University, 97INFN, 98Thomas Jefferson National Accelerator Facility, 99Florida State University, 100Thomas Jefferson National Accelerator Facility, 101University of South Carolina, 102Florida International University, 103University of Glasgow, 104INFN, 105Institute of Theoretical and Experimental Physics, 106California State University, 107Old Dominion University, 108University of Glasgow, 109CEA, 110University of Connecticut, 111Florida International University, 112INFN, 113Arizona State University, 114INFN, 115INFN, 116Florida State University, 117CEA, 118Norfolk State University, 119The George Washington University, 120Carnegie Mellon University, 121University of Connecticut, 122Arizona State University, 123Thomas Jefferson National Accelerator Facility, 124Yerevan Physics Institute, 125Edinburgh University, 126Catholic University of America, 127University of Glasgow, 128Kyungpook National University, 129University of South Carolina, 130Universidad Técnica Federico Santa María, 131Ohio University, 132University of South Carolina, 133Thomas Jefferson National Accelerator Facility, 134Institute of Theoretical and Experimental Physics, 135Yerevan Physics Institute, 136LPSC, 137Catholic University of America, 138University of Glasgow, 139Thomas Jefferson National Accelerator Facility, 140Old Dominion University, 141University of Virginia, 142University of South Carolina, 143Edinburgh University, 144Thomas Jefferson National Accelerator Facility, 145University of Virginia, 146INFN

Exclusive neutral-pion electroproduction ($ep\to e^\prime p^\prime \pi^0$) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi_\pi$ and structure functions $\sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. Read More

2014Apr
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

We have measured the moment $A_{LU}^{\sin\phi}$ corresponding to the polarized electron beam-spin asymmetry in SIDIS. $A_{LU}^{\sin\phi}$ is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5. Read More

We report the first measurement of the photoproduction cross section of the $\phi$ meson in its neutral decay mode in the reaction $\gamma p \to p\phi(K_SK_L)$. The experiment was performed with a tagged photon beam of energy $1.6 \le E_\gamma \le 3. Read More

We report the first observation of the line shape of the $\Lambda(1405)$ from electroproduction, and show that it is not a simple Breit-Wigner resonance. Electroproduction of $K^+ \Lambda(1405)$ off the proton was studied by using data from CLAS at Jefferson Lab in the range $1.0Read More

We report the exclusive photoproduction cross sections for the Sigma(1385), Lambda(1405), and Lambda(1520) in the reactions gamma + p -> K+ + Y* using the CLAS detector for energies from near the respective production thresholds up to a center-of-mass energy W of 2.85 GeV. The differential cross sections are integrated to give the total exclusive cross sections for each hyperon. Read More

Nuclear transparency, Tp(A), is a measure of the average probability for a struck proton to escape the nucleus without significant re-interaction. Previously, nuclear transparencies were extructed for quasi-elastic A(e,e'p) knockout of protons with momentum below the Fermi momentum, where the spectral functions are well known. In this paper we extract a novel observable, the transparency ratio, Tp(A)/T_p(12C), for knockout of high-missing-momentum protons from the breakup of short range correlated pairs (2N-SRC) in Al, Fe and Pb nuclei relative to C. Read More

We report measurements of the exclusive electroproduction of $K^+\Lambda$ and $K^+\Sigma^0$ final states from an unpolarized proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions $\sigma_U$, $\sigma_{LT}$, $\sigma_{TT}$, and $\sigma_{LT'}$ were extracted from the $\Phi$-dependent differential cross sections acquired with a longitudinally polarized 5.499 GeV electron beam. Read More

This paper focuses on a measurement of deeply virtual Compton scattering (DVCS) performed at Jefferson Lab using a nearly-6-GeV polarized electron beam, two longitudinally polarized (via DNP) solid targets of protons (NH3) and deuterons (ND3) and the CEBAF Large Acceptance Spectrometer. Here, preliminary results for target-spin asymmetries and double (beam-target) asymmetries for proton DVCS, as well as a very preliminary extraction of beam-spin asymmetry for neutron DVCS, are presented and linked to Generalized Parton Distributions. Read More

2012Jun
Authors: CLAS Collaboration, I. Bedlinskiy, V. Kubarovsky, S. Niccolai, P. Stoler, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, H. Avakian, H. Baghdasaryan, J. Ball, N. A. Baltzell, M. Battaglieri, R. P. Bennett, A. S. Biselli, C. Bookwalter, S. Boiarinov, W. J. Briscoe, W. K. Brooks, V. D. Burkert, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, M. Contalbrigo, V. Crede, A. D'Angelo, A. Daniel, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, D. Doughty, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, L. Elouadrhiri, P. Eugenio, G. Fedotov, S. Fegan, J. A. Fleming, T. A. Forest, M. Garçon, N. Gevorgyan, K. L. Giovanetti, F. X. Girod, W. Gohn, R. W. Gothe, L. Graham, K. A. Griffioen, B. Guegan, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, D. Heddle, K. Hicks, M. Holtrop, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, H. S. Jo, K. Joo, D. Keller, M. Khandaker, P. Khetarpal, A. Kim, W. Kim, F. J. Klein, S. Koirala, A. Kubarovsky, S. E. Kuhn, S. V. Kuleshov, N. D. Kvaltine, K. Livingston, H. Y. Lu, I. J. D. MacGregor, Y. Mao, N. Markov, D. Martinez, M. Mayer, B. McKinnon, C. A. Meyer, T. Mineeva, M. Mirazita, V. Mokeev, H. Moutarde, E. Munevar, C. Munoz Camacho, P. Nadel-Turonski, G. Niculescu, I. Niculescu, M. Osipenko, A. I. Ostrovidov, L. L. Pappalardo, R. Paremuzyan, K. Park, S. Park, E. Pasyuk, S. Anefalos Pereira, E. Phelps, S. Pisano, O. Pogorelko, S. Pozdniakov, J. W. Price, S. Procureur, Y. Prok, D. Protopopescu, A. J. R. Puckett, B. A. Raue, G. Ricco, D. Rimal, M. Ripani, G. Rosner, P. Rossi, F. Sabatié, M. S. Saini, C. Salgado, N. Saylor, D. Schott, R. A. Schumacher, E. Seder, H. Seraydaryan, Y. G. Sharabian, G. D. Smith, D. I. Sober, D. Sokhan, S. S. Stepanyan, S. Stepanyan, S. Strauch, M. Taiuti, W. Tang, C. E. Taylor, Ye Tian, S. Tkachenko, M. Ungaro, M. F. Vineyard, A. Vlassov, H. Voskanyan, E. Voutier, N. K. Walford, D. P. Watts, L. B. Weinstein, D. P. Weygand, M. H. Wood, N. Zachariou, J. Zhang, Z. W. Zhao, I. Zonta

Exclusive $\pi^0$ 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 $\phi_\pi$, in the $Q^2$ range from 1. Read More

The transition helicity amplitudes from the proton ground state to the $P_{11}(1440)$ and $D_{13}(1520)$ excited states ($\gamma_{v}pN^*$ electrocouplings) were determined from the analysis of nine independent one-fold differential $\pi^{+} \pi^{-} p$ electroproduction cross sections off a proton target, taken with CLAS at photon virtualities 0.25\enskip {\rm GeV$^{2}$} $<$ $Q^{2}$ $<$ 0.60 \enskip {\rm GeV$^{2}$}. Read More

Measuring nucleon-nucleon Short Range Correlations (SRC) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wavefunction, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. Read More

The CLAS detector was used to obtain the first ever measurement of the electromagnetic decay of the $\Sigma^{*+}(1385)$ from the reaction $\gamma p \to K^0 \Sigma^{*+}(1385)$. A real photon beam with a maximum energy of 3.8 GeV was incident on a liquid-hydrogen target, resulting in the photoproduction of the kaon and $\Sigma^*$ hyperon. Read More

The influence of cold nuclear matter on lepto-production of hadrons in semi-inclusive deep inelastic scattering is measured using the CLAS detector in Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the $K_s^0$ multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a function of the fractional virtual photon energy $z$ transferred to the $K_s^0$ and the transverse momentum squared $p_{T}^2$ of the $K_s^0$. Read More

The nature of the Lambda(1405), and its place in the baryon spectrum has remained uncertain for decades. Theoretical studies have shown that it may possess strong dynamical components which are not seen in other well-known baryons. Using the CLAS detector system in Hall B at Jefferson Lab, we have measured the photoproduction reaction gamma+p->K+ Lambda(1405) with high statistics and over different Sigma pi decay channels. Read More

We searched for the Phi--(1860) pentaquark in the photoproduction process off the deuteron in the Xi- pi- decay channel using CLAS. The invariant mass spectrum of the Xi- pi- system does not indicate any statistically significant enhancement near the reported mass M = 1.860 GeV. Read More

Baryons are complex systems of confined quarks and gluons and exhibit the characteristic spectra of excited states. The systematics of the baryon excitation spectrum is important to our understanding of the effective degrees of freedom underlying nucleon matter. High-energy electrons and photons are a remarkably clean probe of hadronic matter, providing a microscope for examining the nucleon and the strong nuclear force. Read More

The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction gamma p to pi+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0. Read More

The electromagnetic decay $\Sigma^0(1385) \to \Lambda \gamma$ was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility. A real photon beam with a maximum energy of 3.8 GeV was incident on a proton target, producing an exclusive final state of $K^+\Sigma^{*0}$. Read More

We have measured the differential cross section for the $\gamma$$^3$He$\rightarrow \pi^+ t$ reaction. This reaction was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0. Read More

Due to their long lifetimes, the $\omega$ and $\phi$ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas Jefferson National Accelerator Facility, the mesons were photoproduced from $^{2}$H, C, Ti, Fe, and Pb targets. This paper reports the first measurement of the ratio of nuclear transparencies for the $e^{+}e^{-}$ channel. Read More

High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\gamma p \rightarrow K^+ \Sigma^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2. Read More

2010Mar
Authors: The CLAS Collaboration, H. Avakian, P. Bosted, V. D. Burkert, L. Elouadrhiri, K. P. Adhikari, M. Aghasyan, M. Amaryan, M. Anghinolfi, H. Baghdasaryan, J. Ball, M. Battaglieri, I. Bedlinskiy, A. S. Biselli, D. Branford, W. J. Briscoe, W. Brooks, D. S. Carman, L. Casey, P. L. Cole, P. Collins, D. Crabb, V. Crede, A. D'Angelo, A. Daniel, N. Dashyan, R. DeVita, E. DeSanctis, A. Deur, B. Dey, S. Dhamija, R. Dickson, C. Djalali, G. Dodge, D. Doughty, R. Dupre, A. ElAlaoui, P. Eugenio, S. Fegan, R. Fersch, T. A. Forest, A. Fradi, M. Y. Gabrielyan, G. Gavalian, N. Gevorgyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, W. Gohn, R. W. Gothe, K. A. Griffioen, M. Guidal, N. Guler, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, N. Hassall, D. Heddle, K. Hicks, M. Holtrop, Y. Ilieva, D. G. Ireland, E. L. Isupov, S. S. Jawalkar, H. S. Jo, K. Joo, D. Keller, M. Khandaker, P. Khetarpal, W. Kim, A. Klein, F. J. Klein, P. Konczykowski, V. Kubarovsky, S. E. Kuhn, S. V. Kuleshov, V. Kuznetsov, K. Livingston, H. Y. Lu, N. Markov, M. Mayer, J. McAndrew, M. E. McCracken, B. McKinnon, C. A. Meyer, T. Mineeva, M. Mirazita, V. Mokeev, B. Moreno, K. Moriya, B. Morrison, H. Moutarde, E. Munevar, P. Nadel-Turonski, R. Nasseripour, S. Niccolai, G. Niculescu, I. Niculescu, M. R. Niroula, M. Osipenko, A. I. Ostrovidov, R. Paremuzyan, K. Park, S. Park, E. Pasyuk, S. Anefalos Pereira, Y. Perrin, S. Pisano, O. Pogorelko, J. W. Price, S. Procureur, Y. Prok, D. Protopopescu, B. A. Raue, G. Ricco, M. Ripani, G. Rosner, P. Rossi, F. Sabatié, M. S. Saini, J. Salamanca, C. Salgado, R. A. Schumacher, E. Seder, H. Seraydaryan, Y. G. Sharabian, D. I. Sober, D. Sokhan, S. S. Stepanyan, S. Stepanyan, P. Stoler, S. Strauch, R. Suleiman, M. Taiuti, D. J. Tedeschi, S. Tkachenko, M. Ungaro, B . Vernarsky, M. F. Vineyard, E. Voutier, D. P. Watts, L. B. Weinstein, D. P. Weygand, M. H. Wood, J. Zhang, B. Zhao, Z. W. Zhao

We report the first measurement of the transverse momentum dependence of double spin asymmetries in semi-inclusive production of pions in deep inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). Read More

We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2. Read More

Differential cross sections of the reaction gamma d to K+ Sigma- (p) have been measured with the CLAS detector at Jefferson Lab using incident photons with energies between 1.1 and 3.6 GeV. Read More

We present measurements of the differential cross section and Lambda recoil polarization for the gamma p to K+ Lambda reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2. Read More

We present results on the electroexcitation of the low mass resonances Delta(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of JLab-CLAS data on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for pion electroproduction off the proton. The data were analysed using two conceptually different approaches, fixed-t dispersion relations and a unitary isobar model, allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. Read More

High-statistics differential cross sections for the reactions gamma p -> p eta and gamma p -> p eta-prime have been measured using the CLAS at Jefferson Lab for center-of-mass energies from near threshold up to 2.84 GeV. The eta-prime results are the most precise to date and provide the largest energy and angular coverage. Read More

Recent measurements with CLAS at Jefferson Lab of nucleon resonance transition form factors for several lower mass states are discussed. Read More

High-statistics differential cross sections and spin density matrix elements for the reaction gamma p -> p omega have been measured using the CLAS at Jefferson Lab for center-of-mass (CM) energies from threshold up to 2.84 GeV. Results are reported in 112 10-MeV wide CM energy bins, each subdivided into cos(theta_CM) bins of width 0. Read More

An event-based partial wave analysis (PWA) of the reaction gamma p -> p omega has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world's first high precision spin density matrix element measurements, available to the event-based PWA through the decay distribution of omega-> pi+ pi - pi0. Read More

The hadronization of $K^0$ particles was measured in semi-inclusive deep inelastic scattering (SIDIS) kinematics for several nuclear targets using the CLAS detector. Multiplicity ratios and $\Delta p_T^2$ values were extracted from the data. These results may be compared with similar values for $\pi^+$ hadronization from CLAS (at the same kinematics) and $K^+$ hadronization from HERMES (at higher energy transfer). Read More

The exclusive reaction $\gamma p \to p \pi^+ \pi^-$ was studied in the photon energy range 3.0 - 3.8 GeV and momentum transfer range $0. Read More

A large part of the experimental program in Hall B of the Jefferson Lab is dedicated to baryon spectroscopy. Photoproduction experiments are essential part of this program. CEBAF Large Acceptance Spectrometer (CLAS) and availability of circularly and linearly polarized tagged photon beams provide unique conditions for this type of experiments. Read More

Beam-recoil transferred polarizations for the exclusive $\vec{e}p \to e'K^+ \vec{\Lambda},\vec{\Sigma}^0$ reactions have been measured using the CLAS spectrometer at Jefferson Laboratory. New measurements have been completed at beam energies of 4.261 and 5. Read More