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Search Results: 1 - 10 of 297457 matches for " J. Lachniet "
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Precise Determination of the Neutron Magnetic Form Factor to Higher $Q^2$
W. K. Brooks,J. D. Lachniet
Physics , 2005, DOI: 10.1016/j.nuclphysa.2005.03.138
Abstract: The neutron elastic magnetic form factor $G_M^n$ has been extracted from quasielastic scattering from deuterium in the CEBAF Large Acceptance Spectrometer, CLAS. The kinematic coverage of the measurement is continuous over a broad range, extending from below 1 $GeV^2$ to nearly 5 $GeV^2$ in four-momentum transfer squared. High precision is achieved by employing a ratio technique in which most uncertainties cancel, and by a simultaneous in-situ calibration of the neutron detection efficiency, the largest correction to the data. Preliminary results are shown with statistical errors only.
A Precise Measurement of the Neutron Magnetic Form Factor GMn in the Few-GeV2 Region
J. Lachniet,A. Afanasev,H. Arenh?vel,W. K. Brooks,G. P. Gilfoyle,S. Jeschonnek,B. Quinn,M. F. Vineyard
Physics , 2008, DOI: 10.1103/PhysRevLett.102.192001
Abstract: The neutron elastic magnetic form factor GMn has been extracted from quasielastic electron scattering data on deuterium with the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic coverage of the measurement is continuous from Q2=1 GeV2 to 4.8 GeV2. High precision was achieved by employing a ratio technique in which many uncertainties cancel, and by a simultaneous in-situ calibration of the neutron detection efficiency, the largest correction to the data. Neutrons were detected using the CLAS electromagnetic calorimeters and the time-of-flight scintillators. Data were taken at two different electron beam energies, allowing up to four semi-independent measurements of GMn to be made at each value of Q2. The dipole parameterization is found to provide a good description of the data over the measured Q2 range.
G$^0$ Electronics and Data Acquisition (Forward-Angle Measurements)
D. Marchand,J. Arvieux,L. Bimbot,A. Biselli,J. Bouvier,H. Breuer,R. Clark,J. -C. Cuzon,M. Engrand,R. Foglio,C. Furget,X. Grave,B. Guillon,H. Guler,P. M. King,S. Kox,J. Kuhn,Y. Ky,J. Lachniet,J. Lenoble,E. Liatard,J. Liu,E. Munoz,J. Pouxe,G. Quéméner,B. Quinn,J. -S. Réal,O. Rossetto,R. Sellem
Physics , 2007, DOI: 10.1016/j.nima.2007.11.028
Abstract: The G$^0$ parity-violation experiment at Jefferson Lab (Newport News, VA) is designed to determine the contribution of strange/anti-strange quark pairs to the intrinsic properties of the proton. In the forward-angle part of the experiment, the asymmetry in the cross section was measured for $\vec{e}p$ elastic scattering by counting the recoil protons corresponding to the two beam-helicity states. Due to the high accuracy required on the asymmetry, the G$^0$ experiment was based on a custom experimental setup with its own associated electronics and data acquisition (DAQ) system. Highly specialized time-encoding electronics provided time-of-flight spectra for each detector for each helicity state. More conventional electronics was used for monitoring (mainly FastBus). The time-encoding electronics and the DAQ system have been designed to handle events at a mean rate of 2 MHz per detector with low deadtime and to minimize helicity-correlated systematic errors. In this paper, we outline the general architecture and the main features of the electronics and the DAQ system dedicated to G$^0$ forward-angle measurements.
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.
Demonstration of a novel technique to measure two-photon exchange effects in elastic $e^\pm p$ scattering
M. Moteabbed,M. Niroula,B. A. Raue,L. B. Weinstein,D. Adikaram,J. Arrington,W. K. Brooks,J. Lachniet,Dipak Rimal,M. Ungaro,K. P. Adhikari,M. Aghasyan,M. J. Amaryan,S. Anefalos Pereira,H. Avakian,J. Ball,N. A. Baltzell,M. Battaglieri,V. Batourine,I. Bedlinskiy,R. P. Bennett,A. S. Biselli,J. Bono,S. Boiarinov,W. J. Briscoe,V. D. Burkert,D. S. Carman,A. Celentano,S. Chandavar,P. L. Cole,P. Collins,M. Contalbrigo,O. Cortes,V. Crede,A. D'Angelo,N. Dashyan,R. De Vita,E. De Sanctis,A. Deur,C. Djalali,D. Doughty,R. Dupre,H. Egiyan,L. El Fassi,P. Eugenio,G. Fedotov,S. Fegan,R. Fersch,J. A. Fleming,N. Gevorgyan,G. P. Gilfoyle,K. L. Giovanetti,F. X. Girod,J. T. Goetz,W. Gohn,E. Golovatch,R. W. Gothe,K. A. Griffioen,M. Guidal,N. Guler,L. Guo,K. Hafidi,H. Hakobyan,C. Hanretty,N. Harrison,D. Heddle,K. Hicks,D. Ho,M. Holtrop,C. E. Hyde,Y. Ilieva,D. G. Ireland,B. S. Ishkhanov,E. L. Isupov,H. S. Jo,K. Joo,D. Keller,M. Khandaker,A. Kim,F. J. Klein,S. Koirala,A. Kubarovsky,V. Kubarovsky,S. E. Kuhn,S. V. Kuleshov,S. Lewis,H. Y. Lu,M. MacCormick,I . J . D. MacGregor,D. Martinez,M. Mayer,B. McKinnon,T. Mineeva,M. Mirazita,V. Mokeev,R. A. Montgomery,K. Moriya,H. Moutarde,E. Munevar,C. Munoz Camacho,P. Nadel-Turonski,R. Nasseripour,S. Niccolai,G. Niculescu,I. Niculescu,M. Osipenko,A. I. Ostrovidov,L. L. Pappalardo,R. Paremuzyan,K. Park,S. Park,E. Phelps,J. J. Phillips,S. Pisano,O. Pogorelko,S. Pozdniakov,J. W. Price,S. Procureur,D. Protopopescu,A. J. R. Puckett,M. Ripani,G. Rosner,P. Rossi
Physics , 2013, DOI: 10.1103/PhysRevC.88.025210
Abstract: The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections. We present the results of a new experimental technique for making direct $e^\pm p$ comparisons, which has the potential to make precise measurements over a broad range in $Q^2$ and scattering angles. We use the Jefferson Lab electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton. The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of $Q^2$ and scattering angle. Nonetheless, this measurement yields a data sample for $e^\pm p$ with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. The final ratio of positron to electron scattering: $R=1.027\pm0.005\pm0.05$ for $=0.206$ GeV$^2$ and $0.830\leq \epsilon\leq 0.943$.
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.
On the augmented density of a spherical anisotropic dynamic system
J. An
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18324.x
Abstract: This paper presents a set of new conditions on the augmented density of a spherical anisotropic system that is necessary for the underlying two-integral phase-space distribution function to be non-negative. In particular, it is shown that the partial derivatives of the Abel transformations of the augmented density must be non-negative. Applied for the separable augmented densities, this recovers the result of van Hese et al. (2011).
Fractional calculus, completely monotonic functions, a generalized Mittag-Leffler function and phase-space consistency of separable augmented densities
J. An
Physics , 2012,
Abstract: Under the separability assumption on the augmented density, a distribution function can be always constructed for a spherical population with the specified density and anisotropy profile. Then, a question arises, under what conditions the distribution constructed as such is non-negative everywhere in the entire accessible subvolume of the phase-space. We rediscover necessary conditions on the augmented density expressed with fractional calculus. The condition on the radius part R(r^2) -- whose logarithmic derivative is the anisotropy parameter -- is equivalent to R(1/w)/w being a completely monotonic function whereas the condition on the potential part is stated as its derivative up to the order not greater than 3/2-b being non-negative (where b is the central limiting value for the anisotropy parameter). We also derive the set of sufficient conditions on the separable augmented density for the non-negativity of the distribution, which generalizes the condition derived for the generalized Cuddeford system by Ciotti & Morganti to arbitrary separable systems. This is applied for the case when the anisotropy is parameterized by a monotonic function of the radius of Baes & Van Hese. The resulting criteria are found based on the complete monotonicity of generalized Mittag-Leffler functions.
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