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1. Performance of large pixelised Micromegas detectors in the COMPASS environment

Author

C Coquelet, M. Vandenbroucke, S Platchkov, F Thibaud, E. Burtin, Y. Bedfer, K Dupraz, L Capozza, Ph. Abbon, D. Desforge, R. Durand, A. Giganon, Nour Makke, A. Magnon, Q. Curiel, D. Neyret, B. Paul, C. Marchand, N d'Hose, Andrea Ferrero, M Usseglio, V Andrieux, M Anfreville, D Jourde, F. Kunne, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Département d'Electronique, des Détecteurs et d'Informatique pour la Physique (ex SEDI) (DEDIP), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and COMPASS

Subjects
Physics, Large Hadron Collider, Spectrometer, 010308 nuclear & particles physics, business.industry, Physics::Instrumentation and Detectors, Detector, MicroMegas detector, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Optics, Compass, 0103 physical sciences, Gas electron multiplier, COMPASS experiment, 010306 general physics, business, Instrumentation, Mathematical Physics, Beam (structure)
Abstract

International audience; New large-size Micromegas detectors are being developed for the future physics programof the COMPASS experiment at CERN. These detectors will have a pixelised readout in theircenter to detect particles in the beam region, where the particle flux can reach several MHz/cm2 innominal conditions, and will have to handle high intensity hadron beams (up to a few 107 hadrons/s)with a discharge rate lower than 0.01 to 0.001 discharge/s. Several prototypes with two differentdischarge rate reduction technologies (preamplification stage with a GEM foil and resistive readoutwith buried resistors) have been studied in the COMPASS beam since 2010. Four of themhave been included in the spectrometer since 2012, and have been used for the track reconstruction.Their performance (detection efficiency, space and time resolutions, and discharge rates) fordifferent beam intensities and magnetic fields environments are presented. These detectors playan important role in the track reconstruction at very small angle; their impact is presented, with aparticular emphasis on the effect of the background reduction due to an improved cluster selection.

Published
2013

2. New pixelized Micromegas detector with low discharge rate for the COMPASS experiment

Author

Damien Neyret, A. Magnon, D. Desforge, N d'Hose, Ph. Abbon, M Anfreville, Bernard Paul, F. Kunne, D Jourde, Christophe Coquelet, M Usseglio, A. Giganon, F Thibaud, Nour Makke, M. Vandenbroucke, S Platchkov, Y. Bedfer, E. Burtin, Claude Marchand, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Département d'Electronique, des Détecteurs et d'Informatique pour la Physique (ex SEDI) (DEDIP)

Subjects
Physics - Instrumentation and Detectors, Physics::Instrumentation and Detectors, FOS: Physical sciences, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), Optics, Compass, 0103 physical sciences, COMPASS experiment, Detectors and Experimental Techniques, 010306 general physics, Instrumentation, Mathematical Physics, Physics, Resistive touchscreen, Large Hadron Collider, Spectrometer, 010308 nuclear & particles physics, business.industry, Detector, MicroMegas detector, Instrumentation and Detectors (physics.ins-det), Physics::Accelerator Physics, High Energy Physics::Experiment, business, Beam (structure)
Abstract

New Micromegas (Micro-mesh gaseous detectors) are being developed in view of the future physics projects planned by the COMPASS collaboration at CERN. Several major upgrades compared to present detectors are being studied: detectors standing five times higher luminosity with hadron beams, detection of beam particles (flux up to a few hundred of kHz/mm^{2}, 10 times larger than for the present Micromegas detectors) with pixelized read-out in the central part, light and integrated electronics, and improved robustness. Two solutions of reduction of discharge impact have been studied, with Micromegas detectors using resistive layers and using an additional GEM foil. Performance of such detectors has also been measured. A large size prototypes with nominal active area and pixelized read-out has been produced and installed at COMPASS in 2010. In 2011 prototypes featuring an additional GEM foil, as well as an resistive prototype, are installed at COMPASS and preliminary results from those detectors presented very good performance. We present here the project and report on its status, in particular the performance of large size prototypes with an additional GEM foil., 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous Detectors conference (MPGD2011), 29-31 August 2011, Kobe, Japan

Published
2011

3. Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles

Author

Seigo Kato, H. Ueno, K. Wijesooriya, R. Di Salvo, L. C. Alexa, G. W. Miller, H. Voskanyan, C. Jutier, J. Jardillier, E. Voutier, J. A. Templon, G. Rutledge, B. Frois, D. G. Zainea, C. C. Chang, E. Chudakov, David L. Prout, G. Laveissière, T. Terasawa, Vincent Breton, Mauro Iodice, Bogdan Wojtsekhowski, K. S. Kumar, Latifa Elouadrhiri, J. O. Hansen, A. Gasparian, K. Arundell, Pavel Sorokin, Sebastien Incerti, Larry Weinstein, P. Grenier, R. W. Lourie, W. Kahl, J. Berthot, G. Audit, L. B. Auerbach, T. Pussieux, G. Fournier, William Bertozzi, A. Deur, P. Vernin, Pierre A.M. Guichon, Ronald Ransome, Kazushige Maeda, K. Kino, N. Degrande, Pete Markowitz, D. Rowntree, Z. Papandreou, R. L.J. van der Meer, A. T. Katramatou, T. Saito, Richard Madey, Paul Souder, P. M. Rutt, S. K. Nanda, Roberto Perrino, R. De Leo, D. S. Dale, S. Mehrabyan, S. Kerhoas, J. M. Finn, W. U. Boeglin, D. J. Margaziotis, R. I. Pomatsalyuk, A. Ketikyan, L. Todor, A. Leone, M. Baylac, S. Jaminion, Nilanga Liyanage, S. Malov, E. Burtin, M. Holtrop, Thomas E. Smith, Richard Wilson, G. E. Dodge, R. Holmes, J. Marroncle, D. Marchand, E. Tomasi-Gustaffson, S. Platchkov, J. S. Real, J. Martino, Raphael Noel Tieulent, G.I. Smirnov, J. P. Chen, R. Van de Vyver, G. M. Urciuoli, Branislav Vlahovic, R. A. Lindgren, J. J. LeRose, C. R. Howell, Justin I. McIntyre, J. R. Calarco, L. Tiator, L. Bimbot, Arijit Saha, K. Soldi, O. Ravel, Hiroaki Tsubota, A. Serdarevic, C. E. Hyde, Y. Roblin, J. Y. Mougey, G. M. Huber, F. Garibaldi, E. Cisbani, J. Gomez, V. Gorbenko, J. W. Watson, F. Renard, L. Cardman, B. D. Anderson, G. J. Lolos, M. B. Epstein, F. T. Baker, F. Merchez, P. Y. Bertin, Haiyan Gao, M. Liang, G. Quéméner, D. Neyret, N. d'Hose, S. Frullani, Charles Glashausser, M. Khayat, H. Breuer, D. M. Manley, J. Gao, L. Van Hoorebeke, G. G. Petratos, Z. E. Meziani, V. A. Punjabi, L. A. Ewell, Ronald Gilman, K. McCormick, H. Fonvieille, Z. L. Zhou, A. V. Glamazdin, S. Kox, Jing Zhao, C. F. Perdrisat, R. Michaels, C. Marchand, M. K. Jones, C. Furget, P. E. Ulmer, Kevin Fissum, M. Kuss, James J. Kelly, E. J. Brash, Laird Kramer, Shalev Gilad, C. W. de Jager, K. A. Aniol, E. A.J.M. Offermann, C. Cavata, S.S. Kamalov, G. J. Kumbartzki, A. J. Sarty, W. M. Zhang, R. Suleiman, J. Domingo, Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), HALL A, Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)

Subjects
Elastic scattering, Physics, Nuclear and High Energy Physics, Particle physics, 010308 nuclear & particles physics, Scattering, Compton scattering, Resonance, FOS: Physical sciences, Inelastic scattering, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Deep inelastic scattering, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), Pion, 0103 physical sciences, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Nuclear Experiment (nucl-ex), 010306 general physics, Nucleon, Nuclear Experiment
Abstract

We have made the first measurements of the virtual Compton scattering (VCS) process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the $W$-dependence at fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed $Q^2$-dependence is smooth. The measured ratio of H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data at the highest $W$ (1.8-1.9 GeV) show a striking $Q^2$- independence, which may suggest a transition to a perturbative scattering mechanism at the quark level., Comment: 20 pages, 8 figures. To appear in Phys.Rev.C

Published
2009

4. Accurate measurement of the electron beam polarization in JLab Hall A using Compton polarimetry

Author

John C. Mitchell, P.Y. Bertin, A. Delbart, D. Lhuillier, E. Burtin, M. Brossard, C. W. de Jager, C. Cavata, N. Colombel, F. Marie, T. Pussieux, S. Escoffier, D. Neyret, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and HALL A

Subjects
Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, Polarimetry, FOS: Physical sciences, 7. Clean energy, 01 natural sciences, law.invention, polarized beams, Optics, law, 0103 physical sciences, Compton polarimeter, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010306 general physics, Instrumentation, Physics, 010308 nuclear & particles physics, business.industry, Amplifier, Compton scattering, Polarimeter, Particle accelerator, Instrumentation and Detectors (physics.ins-det), 07.60.Fs, 42.60.-v, 29.27.Hj, Polarization (waves), 3. Good health, optical cavity, Optical cavity, Cathode ray, Physics::Accelerator Physics, business
Abstract

A major advance in accurate electron beam polarization measurement has been achieved at Jlab Hall A with a Compton polarimeter based on a Fabry-Perot cavity photon beam amplifier. At an electron energy of 4.6 GeV and a beam current of 40 uA, a total relative uncertainty of 1.5% is typically achieved within 40 min of data taking. Under the same conditions monitoring of the polarization is accurate at a level of 1%. These unprecedented results make Compton polarimetry an essential tool for modern parity-violation experiments, which require very accurate electron beam polarization measurements., Comment: 21 pages, 10 figures, 4 tables, submitted to Nucl. Instr. Meth. A

Published
2005

5. Basic instrumentation for Hall A at Jefferson Lab

Author

T. Pussieux, Paul Souder, J. H. Mitchell, Y. Roblin, O. Ravel, E. Chudakov, K. A. Griffioen, C. Cavata, J. A. Templon, H. F. Ibrahim, J. S. McCarthy, M. A. Stevens, D. P. Watts, B. Frois, W. J. Schneider, Dipangkar Dutta, R. Di Salvo, R. I. Pomatsalyuk, A. Soldi, G. J. Kumbartzki, Arijit Saha, N. Colombel, J. Berthot, Jing Zhao, A. J. Sarty, B. D. Anderson, J. Martine, M. Coman, R. Michaels, M. B. Epstein, R. W. Lourie, J. O. Hansen, N. Degrande, J. Mclntyre, John Arrington, L. Zhu, W. Kahl, Bogdan Wojtsekhowski, P. Djawotho, M. Leuschner, William Bertozzi, K. A. Aniol, A. Gasparian, Karl Slifer, Jrm Annand, C. F. Perdrisat, D. Pripstein, M. Baylac, S. Kox, X. Jiang, K. Kramer, H. Breuer, David Hamilton, Jian-Ping Chen, T. Averett, L. B. Auerbach, G. A. Rutledge, G. Quéméner, Stephanie Escoffier, P.Y. Bertin, R. Suleiman, R. Carr, Pete Markowitz, A. Deur, Z. Papandreou, R. L. Walter, R. D. McKeown, T. P. Gorringe, M. Rvachev, R. Holmes, S. Churchwell, J. Marroncle, S. Platchkov, M. Khandaker, M. Liang, L. Pierangeli, K. Kino, A. Ketikyan, Kevin Fissum, F. W. Hersman, J. LeRose, F. Giuliani, P. E. Ulmer, Roberto Perrino, R. De Leo, J. Gao, L. A. Ewell, S. Jensen, R. Crateri, Shalev Gilad, C. W. de Jager, D. Lhuillier, J.E. Ducret, M. Gricia, R. Iommi, F. Sabatavenere, P. A. Zolnierczuk, K. Wijesooriya, Alan M. Nathan, D. Rowntree, E. Voutier, H. Holmgren, S. K. Nanda, D. G. Meekins, K. S. Egiyan, C. R. Howell, A. Serdarevic-Offermann, Hiroaki Tsubota, D. G. Zainea, J. R. Calarco, S. Esp, T. Terasawa, Vincent Breton, C. C. Chang, J. Domingo, T. Black, A. T. Katramatou, S. Kerhoas, F. Santavenere, J. Y. Mougey, R. Van de Vyver, G. M. Urciuoli, Seigo Kato, G. M. Huber, B. Reitz, E. J. Beise, K. S. Kumar, F. Garibaldi, Pavel Sorokin, G. J. Lolos, M. Lucentini, J. Segal, H. Xiang, D. V. Boykin, W. U. Boeglin, C. Glashausser, E. Cisbani, A. Leone, R. D. Ransomez, Gordon D. Cates, Sonja Dieterich, H. Voskanyan, C. Jutier, R. L.J. van der Meer, Olivier Gayou, James A. Miller, L. Van Hoorebeke, Sebastien Incerti, J. Jardillier, L. Cardman, James J. Kelly, F. Xiong, S. Jaminion, I. K. Kominis, K. McCormick, P. Vernin, P. M. Rutt, A. Petrosyan, David L. Prout, Nilanga Liyanage, L. Lagamba, X. Zheng, S. L. Spiegel, Branislav Vlahovic, Leonid Levchuk, Mauro Iodice, Larry Weinstein, F. Marie, D. G. Ireland, N. S. Chant, David Manley, V. A. Punjabi, C. E. Jones, J. Gomez, Wolfgang Korsch, W. Xu, J. W. Watson, M. Roedelbronn, F. T. Baker, Z. E. Meziani, T. Saito, S. Frullani, H. Ueno, E. J. Brash, R. Roche, E. Hovhannisyan, C. E. Hyde-Wright, N. d'Hose, L. Bimbot, G. Laveissière, R. Madey, Kazushige Maeda, A. Gavalya, W. Miller, D. Neyret, T. P. Smith, B. Diederich, E. Burtin, M. Holtrop, L. Todor, G. Dezern, Z. L. Zhou, K. Livingston, D. S. Dale, V. Zeps, S. Mayilyan, E. Folts, B. D. Milbrath, Haiyan Gao, J. M. Finn, O. Rondon-Aramayo, R. A. Lindgren, V. Gorbenko, A. V. Glamazdin, Z. Chai, E. A.J.M. Offermann, S. Malov, J. Alcorn, S. Strauch, A. Shahinyan, G. Rosner, H. Fonvieille, P. G. Roos, E. W. Hughes, K. Joo, D. S. Brown, P. Brindza, G. G. Petratos, S. van Verst, M. Khayat, S. Colilli, Douglas Higinbotham, M. K. Jones, D. J. Margaziotis, M. Kuss, Seonho Choi, Ronald Gilman, Thomas Jefferson National Accelerator Facility (Jefferson Lab), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS), HALL A, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Nuclear and High Energy Physics, Spectrometer, 010308 nuclear & particles physics, Cryogenics, Scintillator, 7. Clean energy, 01 natural sciences, Particle identification, Magnetic field, Nuclear physics, Cardinal point, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Nuclear Experiment, 010306 general physics, Nucleon, Instrumentation, Cherenkov radiation
Abstract

The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.

Published
2004

6. Precision Measurement of the Neutron Spin Asymmetries and Spin-dependent Structure Functions in the Valence Quark Region

Author

Z. Chai, Douglas Higinbotham, G. M. Urciuoli, J. R. Calarco, L. J. Kaufman, D. J. Margaziotis, T. Averett, V. Sulkosky, Baile Zhang, S. K. Nanda, W. Hinton, Haiyan Gao, B. Reitz, Dipangkar Dutta, Bogdan Wojtsekhowski, E. Chudakov, Paul Souder, Nilanga Liyanage, Jaideep Singh, J. O. Hansen, Sonja Dieterich, L. Zhu, F. Garibaldi, D. S. Armstrong, F. Cusanno, F. Marie, Karl Slifer, C. Butuceanu, William Bertozzi, Z. E. Meziani, A. Deur, Jiansong Gao, D. J. Steiner, A. Powell, Seonho Choi, Jian-Ping Chen, K. McCormick, Pete Markowitz, J. Gomez, P. Solvignon, E. Burtin, J. LeRose, Ronald Gilman, R. De Leo, A. Camsonne, Arijit Saha, S. Frullani, J. M. Finn, X. Zheng, D. Lhuillier, Xiaofeng Zhu, Guy Ron, F. Xiong, S. Širca, S. Strauch, D. Neyret, Antonin Vacheret, T. Horn, S. Binet, Wolfgang Korsch, Hua Xiang, M. Roedelbronn, R. Roche, T. Pussieux, X. Jiang, M. Rvachev, Y. Xiao, Emmanuel Busato, Gordon D. Cates, S. K. Phillips, Shalev Gilad, C. W. de Jager, K. A. Aniol, R. Michaels, Bryan J. Moffit, J. Roche, P. A. Zolnierczuk, James J. Kelly, N. Savvinov, K. Kramer, Adam M. Tobias, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and HALL A

Subjects
Nuclear and High Energy Physics, Particle physics, Hadron, Constituent quark, FOS: Physical sciences, Parton, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, High Energy Physics - Experiment, 13.60.Hb, 24.85.+p, 25.30.-c, Nuclear physics, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Quantum chromodynamics, Physics, 010308 nuclear & particles physics, Perturbative QCD, Deep inelastic scattering, Baryon, High Energy Physics - Phenomenology, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], High Energy Physics::Experiment, Nucleon
Abstract

We report on measurements of the neutron spin asymmetries $A_{1,2}^n$ and polarized structure functions $g_{1,2}^n$ at three kinematics in the deep inelastic region, with $x=0.33$, 0.47 and 0.60 and $Q^2=2.7$, 3.5 and 4.8 (GeV/c)$^2$, respectively. These measurements were performed using a 5.7 GeV longitudinally-polarized electron beam and a polarized $^3$He target. The results for $A_1^n$ and $g_1^n$ at $x=0.33$ are consistent with previous world data and, at the two higher $x$ points, have improved the precision of the world data by about an order of magnitude. The new $A_1^n$ data show a zero crossing around $x=0.47$ and the value at $x=0.60$ is significantly positive. These results agree with a next-to-leading order QCD analysis of previous world data. The trend of data at high $x$ agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (pQCD) assuming hadron helicity conservation. Results for $A_2^n$ and $g_2^n$ have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment $d_2^n$ was evaluated and the new result has improved the precision of this quantity by about a factor of two. When combined with the world proton data, polarized quark distribution functions were extracted from the new $g_1^n/F_1^n$ values based on the quark parton model. While results for $\Delta u/u$ agree well with predictions from various models, results for $\Delta d/d$ disagree with the leading-order pQCD prediction when hadron helicity conservation is imposed., Comment: A typing error in A_\parallel(3He) at x=0.47 in Table VII of Phys. Rev. C has been noticed and corrected

Published
2004

7. First electron beam polarization measurements with a Compton polarimeter at Jefferson Laboratory

Author

D. Neyret, E. Burtin, C. W. de Jager, B. Frois, Stephanie Escoffier, D. Lhuillier, J. Martino, C. Cavata, M. Baylac, T. Pussieux, Pierre Bertin, J. H. Mitchell, F. Marie, Laboratoire de Physique Corpusculaire - Clermont-Ferrand (LPC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and HALL A

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Electron energy, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Compton scattering, FOS: Physical sciences, Polarimeter, Astrophysics::Cosmology and Extragalactic Astrophysics, Polarization (waves), 01 natural sciences, Total error, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, Cathode ray, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Physics::Accelerator Physics, Average current, 010306 general physics
Abstract

A Compton polarimeter has been installed in Hall A at Jefferson Laboratory. This letter reports on the first electron beam polarization measurements performed during the HAPPEX experiment at an electron energy of 3.3 GeV and an average current of 40 $\mu$A. The heart of this device is a Fabry-Perot cavity which increased the luminosity for Compton scattering in the interaction region so much that a 1.4% statistical accuracy could be obtained within one hour, with a 3.3% total error.

Published
2002

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