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Search Results: 1 - 10 of 297437 matches for " J. Hansknecht "
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Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasi-elastic Electron-Deuteron Scattering
The G0 Collaboration,D. Androi?,D. S. Armstrong,J. Arvieux,S. L. Bailey,D. H. Beck,E. J. Beise,J. Benesch,F. Benmokhtar,L. Bimbot,J. Birchall,P. Bosted,H. Breuer,C. L. Capuano,Y. -C. Chao,A. Coppens,C. A. Davis,C. Ellis,G. Flores,G. Franklin,C. Furget,D. Gaskell,M. T. W. Gericke,J. Grames,G. Guillard,J. Hansknecht,T. Horn,M. K. Jones,P. M. King,W. Korsch,S. Kox,L. Lee,J. Liu,A. Lung,J. Mammei,J. W. Martin,R. D. McKeown,A. Micherdzinska,M. Mihovilovic,H. Mkrtchyan,M. Muether,S. A. Page,V. Papavassiliou,S. F. Pate,10 S. K. Phillips,P. Pillot,M. L. Pitt,M. Poelker,B. Quinn,W. D. Ramsay,J. -S. Real,J. Roche,P. Roos,J. Schaub,T. Seva,N. Simicevic,G. R. Smith,D. T. Spayde,M. Stutzman,R. Suleiman,V. Tadevosyan,W. T. H. van Oers,M. Versteegen,E. Voutier,W. Vulcan,S. P. Wells,S. E. Williamson,S. A. Wood,B. Pasquini,M. Vanderhaeghen
Physics , 2011, DOI: 10.1103/PhysRevLett.107.022501
Abstract: We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasi-elastic scattering on the deuteron, at backward angles (lab scattering angle of 108 degrees) for Q2 = 0.22 GeV^2/c^2 and 0.63 GeV^2/c^2 at beam energies of 362 MeV and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (piN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasi-static deuterium approximation, and is also in agreement with theory.
First Measurement of the Neutral Current Excitation of the Delta Resonance on a Proton Target
G0 Collaboration,D. Androic,D. S. Armstrong,J. Arvieux,S. L. Bailey,D. H. Beck,E. J. Beise,J. Benesch,F. Benmokhtar,L. Bimbot,J. Birchall,P. Bosted,H. Breuer,C. L. Capuano,Y. -C. Chao,A. Coppens,C. A. Davis,C. Ellis,G. Flores,G. Franklin,C. Furget,D. Gaskell,J. Grames,M. T. W. Gericke,G. Guillard,J. Hansknecht,T. Horn,M. K. Jones,P. M. King,W. Korsch,S. Kox,L. Lee,J. Liu,A. Lung,J. Mammei,J. W. Martin,R. D. McKeown,A. Micherdzinska,M. Mihovilovic,H. Mkrtchyan,M. Muether,S. A. Page,V. Papavassiliou,S. F. Pate,S. K. Phillips,P. Pillot,M. L. Pitt,M. Poelker,B. Quinn,W. D. Ramsay,J. -S. Real,J. Roche,P. Roos,J. Schaub,T. Seva,N. Simicevic,G. R. Smith,D. T. Spayde,M. Stutzman,R. Suleiman,V. Tadevosyan,W. T. H. van Oers,M. Versteegen,E. Voutier,W. Vulcan,S. P. Wells,S. E. Williamson,S. A. Wood
Physics , 2012,
Abstract: The parity-violating asymmetry arising from inelastic electron-nucleon scattering at backward angle (~95 degrees) near the Delta(1232) resonance has been measured using a hydrogen target. From this asymmetry, we extracted the axial transition form factor G^A_{N\Delta}, a function of the axial Adler form factors C^A_i. Though G^A_{N\Delta} has been previously studied using charged current reactions, this is the first measurement of the weak neutral current excitation of the Delta using a proton target. For Q^2 = 0.34 (GeV/c)^2 and W = 1.18 GeV, the asymmetry was measured to be -33.4 \pm (5.3)_{stat} \pm (5.1)_{sys} ppm. The value of G^A_{N\Delta} determined from the hydrogen asymmetry was -0.05 \pm (0.35)_{stat} \pm (0.34)_{sys} \pm (0.06)_{theory}. These findings agree within errors with theoretical predictions for both the total asymmetry and the form factor. In addition to the hydrogen measurement, the asymmetry was measured at the same kinematics using a deuterium target. The asymmetry for deuterium was determined to be -43.6 \pm (14.6)_{stat} \pm (6.2)_{sys} ppm.
Measurement of the parity-violating asymmetry in inclusive electroproduction of $π^-$ near the $Δ^0$ resonance
G0 Collaboration,D. Androi?,D. S. Armstrong,J. Arvieux,S. L. Bailey,D. H. Beck,E. J. Beise,J. Benesch,F. Benmokhtar,L. Bimbot,J. Birchall,P. Bosted,H. Breuer,C. L. Capuano,Y. -C. Chao,A. Coppens,C. A. Davis,C. Ellis,G. Flores,G. Franklin,C. Furget,D. Gaskell,M. T. W. Gericke,J. Grames,G. Guillard,J. Hansknecht,T. Horn,M. K. Jones,P. M. King,W. Korsch,S. Kox,L. Lee,J. Liu,A. Lung,J. Mammei,J. W. Martin,R. D. McKeown,A. Micherdzinska,M. Mihovilovic,H. Mkrtchyan,M. Muether,S. A. Page,V. Papavassiliou,S. F. Pate,S. K. Phillips,P. Pillot,M. L. Pitt,M. Poelker,B. Quinn,W. D. Ramsay,J. -S. Real,J. Roche,P. Roos,J. Schaub,T. Seva,N. Simicevic,G. R. Smith,D. T. Spayde,M. Stutzman,R. Suleiman,V. Tadevosyan,W. T. H. van Oers,M. Versteegen,E. Voutier,W. Vulcan,S. P. Wells,S. E. Williamson,S. A. Wood
Physics , 2011, DOI: 10.1103/PhysRevLett.108.122002
Abstract: The parity-violating (PV) asymmetry of inclusive $\pi^-$ production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasi-free photoproduction off the neutron via the $\Delta^0$ resonance. In the context of heavy-baryon chiral perturbation theory (HB$\chi$PT), this asymmetry is related to a low energy constant $d_\Delta^-$ that characterizes the parity-violating $\gamma$N$\Delta$ coupling. Zhu et al. calculated $d_\Delta^-$ in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from $A_\gamma^-=-5.2$ to $+5.2$ ppm. The measurement performed in this work leads to $A_\gamma^-=-0.36\pm 1.06\pm 0.37\pm 0.03$ ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to $V_{ud}/V_{us}$. The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the $N-\Delta$ axial transition form-factors using PV electron scattering.
The Q_weak Experimental Apparatus
Qweak Collaboration,T. Allison,M. Anderson,D. Androic,D. S. Armstrong,A. Asaturyan,T. D. Averett,R. Averill,J. Balewski,J. Beaufait,R. S. Beminiwattha,J. Benesch,F. Benmokhtar,J. Bessuille,J. Birchall,E. Bonnell,J. Bowman,P. Brindza,D. B. Brown,R. D. Carlini,G. D. Cates,B. Cavness,G. Clark,J. C. Cornejo,S. Covrig Dusa,M. M. Dalton,C. A. Davis,D. C. Dean,W. Deconinck,J. Diefenbach,K. Dow,J. F. Dowd,J. A. Dunne,D. Dutta,W. S. Duvall,J. R. Echols,M. Elaasar,W. R. Falk,K. D. Finelli,J. M. Finn,D. Gaskell,M. T. W. Gericke,J. Grames,V. M. Gray,K. Grimm,F. Guo,J. Hansknecht,D. J. Harrison,E. Henderson,J. R. Hoskins,E. Ihloff,K. Johnston,D. Jones,M. Jones,R. Jones,M. Kargiantoulakis,J. Kelsey,N. Khan,P. M. King,E. Korkmaz,S. Kowalski,A. Kubera,J. Leacock,J. P. Leckey,A. R. Lee,J. H. Lee,L. Lee,Y. Liang,S. MacEwan,D. Mack,J. A. Magee,R. Mahurin,J. Mammei,J. W. Martin,A. McCreary,M. H. McDonald,M. J. McHugh,P. Medeiros,D. Meekins,J. Mei,R. Michaels,A. Micherdzinska,A. Mkrtchyan,H. Mkrtchyan,N. Morgan,J. Musson,K. E. Mesick,A. Narayan,L. Z. Ndukum,V. Nelyubin,Nuruzzaman,W. T. H. van Oers,A. K. Opper,S. A. Page,J. Pan,K. D. Paschke,S. K. Phillips,M. L. Pitt,M. Poelker,J. F. Rajotte,W. D. Ramsay,W. R. Roberts,J. Roche,P. W. Rose,B. Sawatzky,T. Seva,M. H. Shabestari,R. Silwal,N. Simicevic,G. R. Smith,S. Sobczynski,P. Solvignon,D. T. Spayde,B. Stokes,D. W. Storey,A. Subedi,R. Subedi,R. Suleiman,V. Tadevosyan,W. A. Tobias,V. Tvaskis,E. Urban,B. Waidyawansa,P. Wang,S. P. Wells,S. A. Wood
Physics , 2014,
Abstract: The Jefferson Lab Q_weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ${\vec{e}}$p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 microA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicity-correlated beam properties that can induce false asymmetries. Moller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8 degrees and 11.6 degrees were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silica Cerenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q^2 = 0.025 GeV^2 was determined using dedicated low-current (~100 pA) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.
New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei
The HAPPEX,PREX Collaborations,:,S. Abrahamyan,A. Acha,A. Afanasev,Z. Ahmed,H. Albataineh,K. Aniol,D. S. Armstrong,W. Armstrong,J. Arrington,T. Averett,B. Babineau,S. L. Bailey,J. Barber,A. Barbieri,A. Beck,V. Bellini,R. Beminiwattha,H. Benaoum,J. Benesch,F. Benmokhtar,P. Bertin,T. Bielarski,W. Boeglin,P. Bosted,F. Butaru,E. Burtin,J. Cahoon,A. Camsonne,M. Canan,P. Carter,C. C. Chang,G. D. Cates,Y. C. Chao,C. Chen,J. P. Chen,Seonho Choi,E. Chudakov,E. Cisbani,B. Craver,F. Cusanno,M. M. Dalton,R. De Leo,K. de Jager,W. Deconinck,P. Decowski,D. Deepa,X. Deng,A. Deur,D. Dutta,A. Etile,C. Ferdi,R. J. Feuerbach,J. M. Finn,D. Flay,G. B. Franklin,M. Friend,S. Frullani,E. Fuchey,S. A. Fuchs,K. Fuoti,F. Garibaldi,E. Gasser,R. Gilman,A. Giusa,A. Glamazdin,L. E. Glesener,J. Gomez,M. Gorchtein,J. Grames,K. Grimm,C. Gu,O. Hansen,J. Hansknecht,O. Hen,D. W. Higinbotham,R. S. Holmes,T. Holmstrom,C. J. Horowitz,J. Hoskins,J. Huang,T. B. Humensky,C. E. Hyde,H. Ibrahim,F. Itard,C. M. Jen,E. Jensen,X. Jiang,G. Jin,S. Johnston,J. Katich,L. J. Kaufman,A. Kelleher,K. Kliakhandler,P. M. King,A. Kolarkar,S. Kowalski,E. Kuchina,K. S. Kumar,L. Lagamba,D. Lambert,P. LaViolette,J. Leacock,J. Leckey IV,J. H. Lee,J. J. LeRose,D. Lhuillier,R. Lindgren,N. Liyanage,N. Lubinsky,J. Mammei,F. Mammoliti,D. J. Margaziotis,P. Markowitz,M. Mazouz,K. McCormick,A. McCreary,D. McNulty,D. G. Meekins,L. Mercado,Z. E. Meziani,R. W. Michaels,M. Mihovilovic,B. Moffit,P. Monaghan,N. Muangma,C. Munoz-Camacho,S. Nanda
Physics , 2012, DOI: 10.1103/PhysRevLett.109.192501
Abstract: We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1-3 GeV transversely polarized electrons from $^1$H and for the first time from $^4$He, $^{12}$C, and $^{208}$Pb. For $^1$H, $^4$He and $^{12}$C, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}$Pb result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new $A_n$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.
The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles
G0 Collaboration,D. Androic,D. S. Armstrong,J. Arvieux,R. Asaturyan,T. D. Averett,S. L. Bailey,G. Batigne,D. H. Beck,E. J. Beise,J. Benesch,F. Benmokhtar,L. Bimbot,J. Birchall,A. Biselli,P. Bosted,H. Breuer,P. Brindza,C. L. Capuano,R. D. Carlini,R. Carr,N. Chant,Y. -C. Chao,R. Clark,A. Coppens,S. D. Covrig,A. Cowley,D. Dale,C. A. Davis,C. Ellis,W. R. Falk,H. Fenker,J. M. Finn,T. Forest,G. Franklin,R. Frascaria,C. Furget,D. Gaskell,M. T. W. Gericke,J. Grames,K. A. Griffioen,K. Grimm,G. Guillard,B. Guillon,H. Guler,K. Gustafsson,L. Hannelius,J. Hansknecht,R. D. Hasty,A. M. Hawthorne Allen,T. Horn,T. M. Ito,K. Johnston,M. Jones,P. Kammel,R. Kazimi,P. M. King,A. Kolarkar,E. Korkmaz,W. Korsch,S. Kox,J. Kuhn,J. Lachniet,R. Laszewski,L. Lee,J. Lenoble,E. Liatard,J. Liu,A. Lung,G. A. MacLachlan,J. Mammei,D. Marchand,J. W. Martin,D. J. Mack,K. W. McFarlane,D. W. McKee,R. D. McKeown,F. Merchez,M. Mihovilovic,A. Micherdzinska,H. Mkrtchyan,B. Moffit,M. Morlet,M. Muether,J. Musson,K. Nakahara,R. Neveling,S. Niccolai,D. Nilsson,S. Ong,S. A. Page,V. Papavassiliou,S. F. Pate,S. K. Phillips,P. Pillot,M. L. Pitt,M. Poelker,T. A. Porcelli,G. Quemener,B. P. Quinn,W. D. Ramsay,A. W. Rauf,J. -S. Real,T. Ries,J. Roche P. Roos,G. A. Rutledge,J. Schaub,J. Secrest,T. Seva,N. Simicevic,G. R. Smith,D. T. Spayde,S. Stepanyan,M. Stutzman,R. Suleiman,V. Tadevosyan,R. Tieulent,J. van de Wiele,W. T. H. van Oers,M. Versteegen,E. Voutier,W. F. Vulcan,S. P. Wells,G. Warren,S. E. Williamson,R. J. Woo,S. A. Wood
Physics , 2011, DOI: 10.1016/j.nima.2011.04.031
Abstract: In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, as well as fast readout electronics for the measurement of individual events. The overall design and performance of this experimental system is discussed.
Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering
S. Abrahamyan,Z. Ahmed,H. Albataineh,K. Aniol,D. S. Armstrong,W. Armstrong,T. Averett,B. Babineau,A. Barbieri,V. Bellini,R. Beminiwattha,J. Benesch,F. Benmokhtar,T. Bielarski,W. Boeglin,A. Camsonne,M. Canan,P. Carter,G. D. Cates,C. Chen,J. -P. Chen,O. Hen,F. Cusanno,M. M. Dalton,R. De Leo,K. de Jager,W. Deconinck,P. Decowski,X. Deng,A. Deur,D. Dutta,A. Etile,D. Flay,G. B. Franklin,M. Friend,S. Frullani,E. Fuchey,F. Garibaldi,E. Gasser,R. Gilman,A. Giusa,A. Glamazdin,J. Gomez,J. Grames,C. Gu,O. Hansen,J. Hansknecht,D. W. Higinbotham,R. S. Holmes,T. Holmstrom,C. J. Horowitz,J. Hoskins,J. Huang,C. E. Hyde,F. Itard,C. -M. Jen,E. Jensen,G. Jin,S. Johnston,A. Kelleher,K. Kliakhandler,P. M. King,S. Kowalski,K. S. Kumar,J. Leacock,J. Leckey IV,J. H. Lee,J. J. LeRose,R. Lindgren,N. Liyanage,N. Lubinsky,J. Mammei,F. Mammoliti,D. J. Margaziotis,P. Markowitz,A. McCreary,D. McNulty,L. Mercado,Z. -E. Meziani,R. W. Michaels,M. Mihovilovic,N. Muangma,C. Mu?oz-Camacho,S. Nanda,V. Nelyubin,N. Nuruzzaman,Y. Oh,A. Palmer,D. Parno,K. D. Paschke,S. K. Phillips,B. Poelker,R. Pomatsalyuk,M. Posik,A. J. R. Puckett,B. Quinn,A. Rakhman,P. E. Reimer,S. Riordan,P. Rogan,G. Ron,G. Russo,K. Saenboonruang,A. Saha,B. Sawatzky,A. Shahinyan,R. Silwal,S. Sirca,K. Slifer,P. Solvignon,P. A. Souder,M. L. Sperduto,R. Subedi,R. Suleiman,V. Sulkosky,C. M. Sutera,W. A. Tobias,W. Troth,G. M. Urciuoli,B. Waidyawansa,D. Wang,J. Wexler,R. Wilson,B. Wojtsekhowski,X. Yan,H. Yao,Y. Ye,Z. Ye,V. Yim,L. Zana,X. Zhan,J. Zhang
Statistics , 2012, DOI: 10.1103/PhysRevLett.108.112502
Abstract: We report the first measurement of the parity-violating asymmetry A_PV in the elastic scattering of polarized electrons from 208Pb. A_PV is sensitive to the radius of the neutron distribution (Rn). The result A_PV = 0.656 \pm 0.060 (stat) \pm 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions Rn - Rp = 0.33 +0.16 -0.18 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.
New components of the mercury’s perihelion precession  [PDF]
J. J. Smulsky
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.34034
Abstract: The velocity of perihelion rotation of Mercury's orbit relatively motionless space is computed. It is prove that it coincides with that calculated by the Newtonian interaction of the planets and of the compound model of the Sun’s rotation.
Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens  [PDF]
J. Lopes, J. Rocha
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33014
Abstract: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavém, Portugal (CTN).
Constraints on velocity anisotropy of spherical systems with separable augmented densities
J. An
Physics , 2011, DOI: 10.1088/0004-637X/736/2/151
Abstract: If the augmented density of a spherical anisotropic system is assumed to be multiplicatively separable to functions of the potential and the radius, the radial function, which can be completely specified by the behavior of the anisotropy parameter alone, also fixes the anisotropic ratios of every higher-order velocity moment. It is inferred from this that the non-negativity of the distribution function necessarily limits the allowed behaviors of the radial function. This restriction is translated into the constraints on the behavior of the anisotropy parameter. We find that not all radial variations of the anisotropy parameter satisfy these constraints and thus that there exist anisotropy profiles that cannot be consistent with any separable augmented density.
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