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Articles 361 - 390 of 434

Full-Text Articles in Elementary Particles and Fields and String Theory

Quark Contribution To The Small-š” Evolution Of Color Dipole, Ian Balitsky Jan 2007

Quark Contribution To The Small-š” Evolution Of Color Dipole, Ian Balitsky

Physics Faculty Publications

The small-š” deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov (BK) equation for the evolution of color dipoles. In the next-to-leading order (NLO) the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-š” evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop levelā€”just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, ā€¦

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Erratum: Cross Sections For The š›¾p -> K*ā° Ī£āŗ Reaction At Eš›¾ = 1.7-3.0 Gev (Physical Review C. 75, 042201), M. Amarian, H. Bagdasaryan, S. BĆ¼ltmann, G. E. Dodge, G. Gavalian, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, F. SabatiĆ©, L. B. Weinstein, Et. Al., The Clas Collaboration Jan 2007

Erratum: Cross Sections For The š›¾p -> K*ā° Ī£āŗ Reaction At Eš›¾ = 1.7-3.0 Gev (Physical Review C. 75, 042201), M. Amarian, H. Bagdasaryan, S. BĆ¼ltmann, G. E. Dodge, G. Gavalian, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, F. SabatiĆ©, L. B. Weinstein, Et. Al., The Clas Collaboration

Physics Faculty Publications

No abstract provided.

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First Measurement Of Beam-Recoil Observables CX And CZ In Hyperon Photoproduction, M. J. Amaryan, H. Bagdasaryan, H. Bektasoglu, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2007

First Measurement Of Beam-Recoil Observables CX And CZ In Hyperon Photoproduction, M. J. Amaryan, H. Bagdasaryan, H. Bektasoglu, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions ā†’Ī³ + p ā†’ K+ + ā†’Ī› and ā†’Ī³+p ā†’ K+ + ā†’Ī£0. The data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS) detector at the Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for -0.85 < cos Īøc.m.K+ < +0.95. For the Ī›, the polarization transfer coefficient along the photon momentum axis, Cz, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient Cx is smaller than Cz by a roughly ā€¦

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Measurement Of Coherent Éø-Meson Photoproduction From The Deuteron At Low Energies, M. J. Amaryan, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, Et. Al., Clas Collaboration Jan 2007

Measurement Of Coherent Éø-Meson Photoproduction From The Deuteron At Low Energies, M. J. Amaryan, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, Et. Al., Clas Collaboration

Physics Faculty Publications

The cross section and decay angular distributions for the coherent Éø-meson photoproduction on the deuteron have been measured for the first time up to a squared four-momentum transfer t = (pįµ§ - pÉø)2 =-2 GeV2/c2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are compared with predictions from a rescattering model. In a framework of vector meson dominance, the data are consistent with the total Éø-N cross section ĻƒÉøN at about 10 mb. If vector meson dominance is violated, a larger ĻƒÉøN is possible by introducing a ā€¦

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Form Factors And Wave Functions Of Vector Mesons In Holographic Qcd, Hovhannes R. Grigoryan, Anatoly V. Radyushkin Jan 2007

Form Factors And Wave Functions Of Vector Mesons In Holographic Qcd, Hovhannes R. Grigoryan, Anatoly V. Radyushkin

Physics Faculty Publications

Within the framework of a holographic dual model of QCD, we develop a formalism for calculating form factors of vector mesons. We show that the holographic bound states can be described not only in terms of eigenfunctions of the equation of motion, but also in terms of conjugate wave functions that are close analogues of quantum-mechanical bound state wave functions. We derive a generalized VMD representation for form factors, and find a very specific VMD pattern, in which form factors are essentially given by contributions due to the first two bound states in the Q2 -channel. We calculate electric ā€¦

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Cascade Production In The Reactions š›¾p ā†’ Kāŗ Kāŗ(X) And š›¾p ā†’ KāŗKāŗ Ī ā»ā»(X), M. J. Amaryan, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration Jan 2007

Cascade Production In The Reactions š›¾p ā†’ Kāŗ Kāŗ(X) And š›¾p ā†’ KāŗKāŗ Ī ā»ā»(X), M. J. Amaryan, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

Photoproduction of the cascade resonances has been investigated in the reactions Ī³p ā†’ K + K +(X) and Ī³p ā†’ K + K + Ļ€ āˆ’(X). The mass splitting of the ground state (Īžāˆ’,Īž0) doublet is measured to be 5.4 Ā± 1.8 MeV/c2, consistent with existing measurements. The differential (total) cross sections for the Īžāˆ’ have been determined for photon beam energies from 2.75 to 3.85 (4.75) GeV and are consistent with a production mechanism of Yāˆ—ā†’K+Īžāˆ’ through a t-channel process. The reaction Ī³pā†’K+K+Ļ€āˆ’[Īž0] has also been investigated to ā€¦

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Cross Sections For The š›¾p -> K*ā° Ī£āŗ Reaction At Eš›¾ = 1.7-3.0 Gev, M. Amarian, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., The Clas Collaboration Jan 2007

Cross Sections For The š›¾p -> K*ā° Ī£āŗ Reaction At Eš›¾ = 1.7-3.0 Gev, M. Amarian, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., The Clas Collaboration

Physics Faculty Publications

Differential cross sections for the reaction š›¾pā†’ K*0Ī£+ are presented in the photon energy range of 1.7 to 3.0 GeV. The K*0 was detected by its decay products, K+Ļ€āˆ’, in the Continuous Electron Beam Accelerator Facility's large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility. These data are the first K*0 photoproduction cross sections ever published over a broad range of angles. Comparison with a theoretical model based on the vector and tensor Kāˆ—-quark couplings shows good agreement with the data, except at forward angles, suggesting that ā€¦

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Running Coupling Constant And Transition From Low To High Energies In Quantum Chromodynamics, Alexander Babansky Apr 2006

Running Coupling Constant And Transition From Low To High Energies In Quantum Chromodynamics, Alexander Babansky

Physics Theses & Dissertations

The remarkable feature of QCD is that the coupling constant (the strength of the interaction) depends on the energy of the interacting particles. At high energies, the coupling constant vanishes and QCD becomes asymptotically free. However, at lower energy, the running coupling constant increases, leading to the confining strong-coupling theory at energies of the order of hadron masses. We study the essential effects of the running coupling constant and analyze the transition from high to low energies in different processes.

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Constraints On The Nucleon Strange Form Factors At Q2 āˆ¼ 0.1 Gev2, K. A. Aniol, D. S. Armstrong, T. Averett, H. Benaoum, P. Y. Bertin, E. Burtin, J. Cahoon, G. D. Cates, C. C. Chang, Y.-C. Chao, D. Deepa, H. Ibrahim Jan 2006

Constraints On The Nucleon Strange Form Factors At Q2 āˆ¼ 0.1 Gev2, K. A. Aniol, D. S. Armstrong, T. Averett, H. Benaoum, P. Y. Bertin, E. Burtin, J. Cahoon, G. D. Cates, C. C. Chang, Y.-C. Chao, D. Deepa, H. Ibrahim

Mechanical & Aerospace Engineering Faculty Publications

We report the most precise measurement to date of a parity-violating asymmetry in elastic electronā€“proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle (Īølab) = 6.0ā—‹ , with the result A PV = ( āˆ’ 1.14 Ā± 0.24 ( stat ) Ā± 0.06 ( syst ) ) Ɨ 10āˆ’6 . From this we extract, at Q2 = 0.099 GeV2 , the strange form factor combination GsE + 0.080 GsM = 0.030 Ā± 0.025 ( stat ) Ā± 0.006 ( syst ) Ā± ā€¦

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High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky Jan 2006

High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky

Physics Faculty Publications

At high energies, the relevant degrees of freedom are Wilson lines--infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops

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Plasma Treatment Of Bulk Niobium Surfaces For Srf Cavities, M. RaÅ”ković, L. VuÅ”kovic, S. Popović, L. Phillips, A. -M. Valente-Feliciano, S. B. Radovanov, L. Godet Jan 2006

Plasma Treatment Of Bulk Niobium Surfaces For Srf Cavities, M. RaÅ”ković, L. VuÅ”kovic, S. Popović, L. Phillips, A. -M. Valente-Feliciano, S. B. Radovanov, L. Godet

Physics Faculty Publications

Two types of electric discharges were used to demonstrate the validity of plasma surface treatment for superconducting radio-frequency (SRF) cavities. The experiments were performed on disc-shaped Nb samples and compared with identical samples treated with buffer chemical polishing (BCP) techniques. Surface analysis indicates comparable or superior properties of plasma-treated samples. These promising results are still preliminary and additional work is in progress.

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Measurement Of The X- And Q2 -Dependence Of The Asymmetry A1 On The Nucleon, K. V. Dharmawardane, S. E. Kuhn, P. Bosted, Y. Prok, G. Adams, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, M. Bektasoglu, S. BĆ¼ltmann, S. L. Careccia, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Zhang Jan 2006

Measurement Of The X- And Q2 -Dependence Of The Asymmetry A1 On The Nucleon, K. V. Dharmawardane, S. E. Kuhn, P. Bosted, Y. Prok, G. Adams, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, M. Bektasoglu, S. BĆ¼ltmann, S. L. Careccia, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Zhang

Physics Faculty Publications

We report results for the virtual photon asymmetry A1 on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton (15NH3) and deuteron (15ND3) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present Letter, we concentrate on our results for A1 ( x , Q2 ) and the related ratio g1 / F1 ( x , Q2 ) in the resonance and the deep inelastic ā€¦

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Differential Cross Sections For š›¾ + P ā†’ Kāŗ + Y For Ī› And Ī£ā° Hyperons, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, S. BĆ¼ltmann, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration Jan 2006

Differential Cross Sections For š›¾ + P ā†’ Kāŗ + Y For Ī› And Ī£ā° Hyperons, H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, S. BĆ¼ltmann, G. E. Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. V. Klimenko, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

High-statistics cross sections for the reactions š›¾ + p ā†’ Kāŗ + Ī› and š›¾ + p ā†’ Kāŗ + Ī£ā° have been measured using CLAS at Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for -0.85 < cos Īø Kc.m. < +0.95. In the Kāŗ + Ī› channel we confirm a resonance-like structure near W=1.9 GeV at backward kaon angles. The position and width of this structure change with angle, indicating that more than one resonance is likely playing a role. The Kāŗ + Ī› channel at forward angles and all energies is well described by a t-channel scaling characteristic of Regge exchange, whereas the same scaling applied to the Kāŗ + Ī£ā° channel is less successful. Several existing theoretical models are compared to the data, but none provide a good representation of the results.

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Electron Scattering From High-Momentum Neutrons In Deuterium, A.V. Klimenko, S. E. Kuhn, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, Gail Dodge, G. Gavalian, N. Guler, C.E. Hyde-Wright, A. Klein, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, Et Al., Clas Collaboration Jan 2006

Electron Scattering From High-Momentum Neutrons In Deuterium, A.V. Klimenko, S. E. Kuhn, H. Bagdasaryan, S. BĆ¼ltmann, S. L. Careccia, K. V. Dharmawardane, Gail Dodge, G. Gavalian, N. Guler, C.E. Hyde-Wright, A. Klein, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, Et Al., Clas Collaboration

Physics Faculty Publications

We report results from an experiment measuring the semiinclusive reaction 2H(e,eā€²ps) in which the proton ps is moving at a large angle relative to the momentum transfer. If we assume that the proton was a spectator to the reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred. This method, known as spectator tagging, can be used to study electron scattering from high-momentum (off-shell) neutrons in deuterium. The data were taken with a 5.765 GeV electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CEBAF ā€¦

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Ī—ā€™ Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev, M. Bektasoglu, S.L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, A. V. Klimenko, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration Jan 2006

Ī—ā€™ Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev, M. Bektasoglu, S.L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, A. V. Klimenko, L. M. Qin, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

Differential cross sections for the reaction Ī³pā†’Ī·ā€²p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data suggest for the first time the coupling of the Ī·ā€²N channel to both the S11(1535) and P11(1710) resonances, known to couple strongly to the Ī·N channel in photoproduction on the proton, and the importance of J=3/2 resonances in the process.

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Erratum: Ī—' Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev (Phys. Rev. Lett. 96, Pg 062001, 2006), H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, F. SabatiĆ©, L. B. Weinstein, Et Al., Clas Collaboration Jan 2006

Erratum: Ī—' Photoproduction On The Proton For Photon Energies From 1.527 To 2.227 Gev (Phys. Rev. Lett. 96, Pg 062001, 2006), H. Bagdasaryan, M. Bektasoglu, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, F. SabatiĆ©, L. B. Weinstein, Et Al., Clas Collaboration

Physics Faculty Publications

No abstract provided.

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Measurement Of The Deuteron Structure Function Fā‚‚ In The Resonance Region And Evaluation Of Its Moments, H. Bagdasaryan, S. BĆ¼ltmann, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, S. E. Kuhn, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2006

Measurement Of The Deuteron Structure Function Fā‚‚ In The Resonance Region And Evaluation Of Its Moments, H. Bagdasaryan, S. BĆ¼ltmann, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, S. E. Kuhn, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasielastic peak up to the invariant mass of the final-state hadronic system W similar or equal to 2.7 GeV with four-momentum transfers Q2 from 0.4 to 6 (GeV/c)2. These data are complementary to previous measurements of the proton structure function F2 and cover a similar two-dimensional region of Q2 and Bjorken variable x. Determination of ā€¦

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The Ā²H(E, E'P)N Reaction At High Four-Momentum Transfer, Hassan F. Ibrahim Jan 2006

The Ā²H(E, E'P)N Reaction At High Four-Momentum Transfer, Hassan F. Ibrahim

Physics Theses & Dissertations

This dissertation presents the highest four-momentum transfer, Q2, quasielastic (xBj = 1) results from Experiment E01-020 which systematically explored the 2H(e, e'p)n reaction ("Electro-disintegration" of the deuteron) at three different four-momentum transfers, Q2 = 0.8, 2.1, and 3.5 GeV2 and missing momenta, pmiss = 0, 100, 200, 300, 400, and 500 GeV including separations of the longitudinal-transverse interference response function, RLT, and extraction of the longitudinal-transverse asymmetry, ALT. This systematic approach will help to understand the reaction mechanism and the deuteron structure down to the short ā€¦

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Predicted Properties Of Microhollow Cathode Discharges In Xenon, J. P. Boeuf, L. C. Pitchford, K. H. Schoenbach Jan 2005

Predicted Properties Of Microhollow Cathode Discharges In Xenon, J. P. Boeuf, L. C. Pitchford, K. H. Schoenbach

Bioelectrics Publications

A fluid model has been developed and used to help clarify the physical mechanisms occurring in microhollow cathode discharges (MHCD). Calculated current-voltage (I-V) characteristics and gas temperatures in xenon at 100 Torr are presented. Consistent with previous experimental results in similar conditions, we find a voltage maximum in the I-V characteristic. We show that this structure reflects a transition between a low-current, abnormal discharge localized inside the cylindrical hollow cathode to a higher-current, normal glow discharge sustained by electron emission from the outer surface of the cathode. This transition, due to the geometry of ā€¦

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High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky Jan 2005

High-Energy Effective Action From Scattering Of Qcd Shock Waves, Ian Balitsky

Physics Faculty Publications

At high energies, the relevant degrees of freedom are Wilson linesā€”infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops.

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Beam-Helicity Asymmetries In Double-Charged-Pion Photoproduction On The Proton, H. Bagdasaryan, M. Bektasoglu, S. BĆ¼ltmann, Gail Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, L. M. Qin, W. Roberts, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration Jan 2005

Beam-Helicity Asymmetries In Double-Charged-Pion Photoproduction On The Proton, H. Bagdasaryan, M. Bektasoglu, S. BĆ¼ltmann, Gail Dodge, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, S. E. Kuhn, L. M. Qin, W. Roberts, F. SabatiĆ©, S. Tkachenko, L. B. Weinstein, J. Yun, J. Zhang, Et Al., Clas Collaboration

Physics Faculty Publications

Beam-helicity asymmetries for the two-pion-photoproduction reaction š›¾āƒ—p ā†’ p Ļ€+Ļ€- have been studied for the first time in the resonance region for center-of-mass energies between 1.35 and 2.30 GeV. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized tagged photons incident on an unpolarized hydrogen target. Beam-helicity-dependent angular distributions of the final-state particles were measured. The large cross-section asymmetries exhibit strong sensitivity to the kinematics and dynamics of the reaction. The data are compared with the results of various phenomenological model calculations, and show that these models currently do not ā€¦

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Higher Twist Analysis Of The Proton Gā‚ Structure Function, M. Osipenko, W. Melnitchouk, S. Simula, P. Bosted, V. Burkert, M. E. Christy, K. Griffioen, C. Keppel, S. E. Kuhn Jan 2005

Higher Twist Analysis Of The Proton Gā‚ Structure Function, M. Osipenko, W. Melnitchouk, S. Simula, P. Bosted, V. Burkert, M. E. Christy, K. Griffioen, C. Keppel, S. E. Kuhn

Physics Faculty Publications

We perform a global analysis of all available spin-dependent proton structure function data, covering a large range of Q2, 1 ā©½ Q2 ā©½ 30 GeV2, and calculate the lowest moment of the g1 structure function as a function of Q2. From the Q2 dependence of the lowest moment we extract matrix elements of twist-4 operators, and determine the color electric and magnetic polarizabilities of the proton to be XE= 0.026 Ā± 0.015(stat) Ā± 0.0210.024 (sys) and XB= -0.013 āˆ“ 0.007(stat) āˆ“ 0.010 0.012(sys), respectively.

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Exclusive Ī”0 Meson Electroproduction From Hydrogen At Clas, C. Hadjidakis, M. Guidal, M. GarƧon, J.-M. Laget, E. S. Smith, M. Vanderhaeghen, G. Adams, P. Ambrozewicz, E. Anciant, M. Anghinolfi, H. Bagdasaryan, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, M. Guler, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, F. Sabatie, L. B. Weinstein, J. Yun Jan 2005

Exclusive Ī”0 Meson Electroproduction From Hydrogen At Clas, C. Hadjidakis, M. Guidal, M. GarƧon, J.-M. Laget, E. S. Smith, M. Vanderhaeghen, G. Adams, P. Ambrozewicz, E. Anciant, M. Anghinolfi, H. Bagdasaryan, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, M. Guler, C. E. Hyde-Wright, A. Klein, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, F. Sabatie, L. B. Weinstein, J. Yun

Physics Faculty Publications

The longitudinal and transverse components of the cross section for the ep ā†’ eā€² pĻ0 reaction were measured in Hall B at Jefferson Laboratory using the CLAS detector. The data were taken with a 4.247 GeV electron beam and were analyzed in a range of xB from 0.2 to 0.6 and of Q2 from 1.5 to 3.0 GeV2. The data are compared to a Regge model based on effective hadronic degrees of freedom and to a calculation based on Generalized Parton Distributions. It is found that, at our lowest xB values, the transverse part of the ā€¦

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Exclusive Photoproduction Of The Cascade Īž Hyperons, H. Bagdasaryan, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, L. M. Qin, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration Jan 2005

Exclusive Photoproduction Of The Cascade Īž Hyperons, H. Bagdasaryan, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, L. M. Qin, L. B. Weinstein, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

We report on the first measurement of exclusive Īž-(1321) hyperon photoproduction in š›¾p ā†’ K+K+Īž- for 3.2 < Eš›¾ < 3.9 GeV. The final state is identified by the missing mass in p(š›¾,K+K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground state Īž-(1321)1/2+ and have estimated the total cross section for its production. We also have strong evidence for the first excited state Īž-(1530)3/2+. Photoproduction provides a copious source of Īž's. We discuss the possibilities of a search for the recently proposed Īž5- and Īž5+ ā€¦

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Global Analysis Of Data On The Proton Structure Function Gā‚ And The Extraction Of Its Moments, M. Osipenko, S. Simula, W. Melnitchouk, P. Bosted, V. Burkert, E. Christy, K. Griffioen, C. Keppel, S. Kuhn, G. Ricco Jan 2005

Global Analysis Of Data On The Proton Structure Function Gā‚ And The Extraction Of Its Moments, M. Osipenko, S. Simula, W. Melnitchouk, P. Bosted, V. Burkert, E. Christy, K. Griffioen, C. Keppel, S. Kuhn, G. Ricco

Physics Faculty Publications

Inspired by recent measurements with the CLAS detector at Jefferson Lab, we perform a self-consistent analysis of world data on the proton structure function g1 in the range 0.17 < Q2 < 30 (GeV/c)2. We compute for the first time low-order moments of g, and study their evolution from small to large values of Q2. The analysis includes the latest data on both the unpolarized inclusive cross sections and the ratio R = Ļƒ L/ĻƒT from Jefferson Lab, as well as a new model for the transverse asymmetry A2 in the resonance region. The contributions of ā€¦

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Inclusive And Exclusive Compton Processes In Quantum Chromodynamics, A. Psaker Jan 2005

Inclusive And Exclusive Compton Processes In Quantum Chromodynamics, A. Psaker

Physics Theses & Dissertations

In our work, we describe two types of Compton processes. As an example of an inclusive process, we consider the high-energy photoproduction of massive muon pairs off the nucleon. We analyze the process in the framework of the QCD parton model, in which the usual parton distributions emerge as a tool to describe the nucleon in terms of quark and gluonic degrees of freedom. To study its exclusive version, a new class of phenomenological functions is required, namely, generalized parton distributions. They can be considered as a generalization of the usual parton distributions measured in deeply inelastic lepton-nucleon scattering. Generalized ā€¦

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Some Aspects Of Deeply Virtual Compton Scattering, Elena Kuchina Apr 2004

Some Aspects Of Deeply Virtual Compton Scattering, Elena Kuchina

Physics Theses & Dissertations

We consider different aspects of the virtual Compton amplitude in QCD on two examples: small-x physics accessible in the Regge regime and twist-3 approximation in the description of DVCS through the general parton distributions. Using this model, we give an estimate for the cross section of deeply virtual Compton scattering for the kinematics of CEBAF at Jefferson Lab.

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Scattering Of Shock Waves In Qcd, Ian Balitsky Jan 2004

Scattering Of Shock Waves In Qcd, Ian Balitsky

Physics Faculty Publications

The cross section of heavy-ion collisions is represented as a double functional integral with the saddle point being the classical solution of the Yang-Mills equations with boundary conditions/sources in the form of two shock waves corresponding to the two colliding ions. I develop the expansion of this classical solution in powers of the commutator of the Wilson lines describing the colliding particles and calculate the first two terms of the expansion.

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Inclusive Photoproduction Of Lepton Pairs In The Parton Model, A. Psaker Jan 2004

Inclusive Photoproduction Of Lepton Pairs In The Parton Model, A. Psaker

Physics Faculty Publications

In the framework of the QCD parton model, we study unpolarized scattering of high energy real photons from a proton target into lepton pairs and a system of hadrons. For a given parametrization of parton distributions in the proton, we calculate the cross section of this process and show the cancellation of the interference terms.

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Complete Measurement Of Three-Body Photodisintegration Of 3He For Photon Energies Between 0.35 And 1.55 Gev, H. Bagdasaryan, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., The Clas Collaboration Jan 2004

Complete Measurement Of Three-Body Photodisintegration Of 3He For Photon Energies Between 0.35 And 1.55 Gev, H. Bagdasaryan, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, L. M. Qin, S. Stepanyan, L. B. Weinstein, J. Yun, Et Al., The Clas Collaboration

Physics Faculty Publications

The three-body photodisintegration of 3He has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.

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