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Articles 1 - 19 of 19
Full-Text Articles in Physics
Measurement Of The Helicity Asymmetry E For The 𝛾p → P𝛑⁰ Reaction In The Resonance Region, C. W. Kim, N. Zachariou, M. Bashkanov, W. J. Briscoe, S. Fegan, V. L. Kashevarov, K. Nikonov, A. Sarantsev, A. Schmidt, I. I. Strakovsky, D. P. Watts, R. L. Workman, P. Achenbach, Z. Akbar, M. J. Amaryan, G. Angelini, W. R. Armstrong, H. Atac, L. Baashen, M. Zurek, Et Al., The Clas Collaboration
Measurement Of The Helicity Asymmetry E For The 𝛾p → P𝛑⁰ Reaction In The Resonance Region, C. W. Kim, N. Zachariou, M. Bashkanov, W. J. Briscoe, S. Fegan, V. L. Kashevarov, K. Nikonov, A. Sarantsev, A. Schmidt, I. I. Strakovsky, D. P. Watts, R. L. Workman, P. Achenbach, Z. Akbar, M. J. Amaryan, G. Angelini, W. R. Armstrong, H. Atac, L. Baashen, M. Zurek, Et Al., The Clas Collaboration
Physics Faculty Publications
The double-spin-polarization observable E for 𝛾→ p→ → p𝛑⁰ has been measured with the CEBAF Large Acceptance Spectrometer (CLAS) at photon beam energies E𝛾 from 0.367 to 2.173 GeV (corresponding to center-of-mass energies from 1.240 to 2.200 GeV) for pion center-of-mass angles, cos θc.m.𝛑⁰, between - 0.86 and 0.82. These new CLAS measurements cover a broader energy range and have smaller uncertainties compared to previous CBELSA data and provide an important independent check on systematics. These measurements are compared to predictions as well as new global fits from The George Washington University, Mainz, and Bonn-Gatchina …
Measurement Of Spin-Density Matrix Elements In P(770) Production With A Linearly Polarized Photon Beam At E𝛾 = 8.2-8.8 Gev, S. Adhikari, F. Afzal, C. S. Akondi, M. Albrecht, M. Amaryan, V. Arroyave, A. Asaturyan, A. Austregesilo, Z. Baldwin, F. Barbosa, J. Barlow, E. Barriga, R. Barsotti, T. D. Beattie, V. V. Berdnikov, T. Black, W. Boeglin, W. J. Briscoe, T. Britton, B. Zihlmann, Et Al., Gluex Collaboration
Measurement Of Spin-Density Matrix Elements In P(770) Production With A Linearly Polarized Photon Beam At E𝛾 = 8.2-8.8 Gev, S. Adhikari, F. Afzal, C. S. Akondi, M. Albrecht, M. Amaryan, V. Arroyave, A. Asaturyan, A. Austregesilo, Z. Baldwin, F. Barbosa, J. Barlow, E. Barriga, R. Barsotti, T. D. Beattie, V. V. Berdnikov, T. Black, W. Boeglin, W. J. Briscoe, T. Britton, B. Zihlmann, Et Al., Gluex Collaboration
Physics Faculty Publications
The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized 8.5 GeV photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson ρ(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of s-channel helicity conservation at small squared four-momentum transfer t and are able to extract the t dependence of natural- and unnatural-parity exchange contributions to …
J/Ψ Photoproduction Near Threshold With Clas12, Joseph Newton
J/Ψ Photoproduction Near Threshold With Clas12, Joseph Newton
Physics Theses & Dissertations
The structure of the proton is comprised of quarks and a sea of gluons. A mechanism that can extract the characteristics of the hidden-color correlations of the nuclear wavefunction is the production of charm near threshold. Due to the fact that momentum transfer is large near threshold in the production of J/ψ , all three valence quarks must act coherently to ex- change energy for the reaction to occur. Models have been developed to predict the nature of J/ψ photoproduction at these specific energies. These include production mechanisms with the two-gluon and three-gluon exchanges. The transferred momentum dependence of the …
Beam-Target Helicity Asymmetry E In K 0 Λ And K 0 Σ 0 Photoproduction On The Neutron, D. H. Ho, R. A.. Schumacher, A. D' Angelo, A. Deur, J. Fleming, C. Hanretty, K. P. Adhikari, D. Adikaram, M. Khachatryan, A. Klein, M. Meyer, L. B. Weinstein, The Class Collaboration
Beam-Target Helicity Asymmetry E In K 0 Λ And K 0 Σ 0 Photoproduction On The Neutron, D. H. Ho, R. A.. Schumacher, A. D' Angelo, A. Deur, J. Fleming, C. Hanretty, K. P. Adhikari, D. Adikaram, M. Khachatryan, A. Klein, M. Meyer, L. B. Weinstein, The Class Collaboration
Physics Faculty Publications
We report the first measurements of the E beam-target helicity asymmetry for the →γ→n→K0Λ and K0Σ0 channels in the energy range 1.70 ≤ W ≤ 2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin I=0 and I …
Measurements Of The Γv P → P'Π+Π− Cross Section With The Clas Detector For 0.4 Gev2 < Q2 < 1.0 Gev2 And 1.3 Gev < W < 1.825 Gev, G. V. Fedotov, Iu. A. Skorodumina, V. D. Burkert, R. W. Gothe, G. Charles, M. Khachatryan, A. Klein, Y. Prok, Z. W. Zhao, Clas Collaboration
Measurements Of The Γv P → P'Π+Π− Cross Section With The Clas Detector For 0.4 Gev2 < Q2 < 1.0 Gev2 And 1.3 Gev < W < 1.825 Gev, G. V. Fedotov, Iu. A. Skorodumina, V. D. Burkert, R. W. Gothe, G. Charles, M. Khachatryan, A. Klein, Y. Prok, Z. W. Zhao, Clas Collaboration
Physics Faculty Publications
New results on the single-differential and fully integrated cross sections for the process γvp → p'π+π− are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass W from 1.3 to 1.825 GeV and the photon virtuality Q2 from 0.4 to 1.0 GeV2. The cross sections were obtained in narrow Q2 bins (0.05 GeV2) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously …
First Measurement Of Ξ− Polarization In Photoproduction, J. Bono, L. Guo, K. P. Adhikari, M. J. Amaryan, G. Charles, G. Gavalian, M. Khachatryan, A. Klein, Y. Prok, J. Zhang, Z. W. Zhao
First Measurement Of Ξ− Polarization In Photoproduction, J. Bono, L. Guo, K. P. Adhikari, M. J. Amaryan, G. Charles, G. Gavalian, M. Khachatryan, A. Klein, Y. Prok, J. Zhang, Z. W. Zhao
Physics Faculty Publications
Despite decades of studies of the photoproduction of hyperons, both their production mechanisms and their spectra of excited states are still largely unknown. While the parity-violating weak decay of hyperons offers a means of measuring their polarization, which could help discern their production mechanisms and identify their excitation spectra, no such study has been possible for doubly strange baryons in photoproduction, due to low production cross sections. However, by making use of the reaction γ p → K+K+Ξ−, we have measured, for the first time, the induced polarization, P, and the transferred polarization from circularly polarized …
Photoproduction And Radiative Decay Of Ηt Meson In Clas At Jlab, Georgie Mbianda Njencheu
Photoproduction And Radiative Decay Of Ηt Meson In Clas At Jlab, Georgie Mbianda Njencheu
Physics Theses & Dissertations
In this work the η/ meson photoproduction cross sections as well as the distribution of the di-pion invariant mass, m(π+π−), in the radiative decay mode η/ → π+π−γ have been measured using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photons in the center-of-mass energy range 1.96 GeV - 2.72 GeV. The measurements are performed on a liquid hydrogen target in the reaction γp → pη/(η/ → π+π−γ). The analysis is based on the …
The Beam-Helicity Asymmetry For Two Pseudoscalar Mesons In Photoproduction And A Partial Wave Analysis For Excited Hyperons, Rafael A. Badui
The Beam-Helicity Asymmetry For Two Pseudoscalar Mesons In Photoproduction And A Partial Wave Analysis For Excited Hyperons, Rafael A. Badui
FIU Electronic Theses and Dissertations
The first-time measurement of the angular dependence of the beam-helicity asymmetry for $\gamma p \rightarrow pK^{+}K^{-}$ is shown and compared to $\gamma p \rightarrow p\pi^{+}\pi^{-}$. The data obtained were from the CLAS g12 experiment at Jefferson Lab. The experiment utilized a beam of circularly polarized photons with energies between 1.1 and 5.4 GeV incident on an unpolarized liquid hydrogen target, which produced an unprecedented number of strange hadrons in photoproduction. The production mechanism for strange hadrons is not well understood. The beam-helicity asymmetry is a polarization observable that provides information on interfering production mechanisms in the reaction. It is shown …
The Gluex Start Counter & Beam Asymmetry $\Sigma$ In Single $\Pi^{0}$ Photoproduction, Eric J. Pooser
The Gluex Start Counter & Beam Asymmetry $\Sigma$ In Single $\Pi^{0}$ Photoproduction, Eric J. Pooser
FIU Electronic Theses and Dissertations
The GlueX experiment aims to study meson photoproduction while utilizing the coherent bremsstrahlung technique to produce a 9 GeV linearly polarized photon beam incident on a liquid $\mathrm{H_{2}}$ target. A Start Counter detector was fabricated to properly identify the accelerator electron beam buckets and to provide accurate timing information. The Start Counter detector was designed to operate at photon intensities of up to $\mathrm{10^{8}\gamma/s}$ in the coherent peak and provides a timing resolution $\mathrm{\sim 300\ ps}$ so as to provide successful identification of the electron beam buckets to within 99\% accuracy. Furthermore, the Start Counter detector provides excellent solid angle …
Separated Response Functions In Exclusive, Forward Π± Electroproduction On Deuterium, G. M. Huber, H. P. Blok, A. Klein, L. M. Qin, K. Vansyoc, Jefferson Lab, Fπ Collaboration
Separated Response Functions In Exclusive, Forward Π± Electroproduction On Deuterium, G. M. Huber, H. P. Blok, A. Klein, L. M. Qin, K. Vansyoc, Jefferson Lab, Fπ Collaboration
Physics Faculty Publications
Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q2, and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π- and π+ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form …
Photoproduction Of Π0 On Hydrogen With Clas From 1.1 Gev - 5.45 Gev Using E+E –Γ Decay, Michael C. Kunkel
Photoproduction Of Π0 On Hydrogen With Clas From 1.1 Gev - 5.45 Gev Using E+E –Γ Decay, Michael C. Kunkel
Physics Theses & Dissertations
Photoproduction of the π0 meson was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photon energies spanning the range Eγ = 1.1 GeV - 5.45 GeV. The measurement is performed on a liquid hydrogen target in the reaction γp → pe +e–(γ). The final state of the reaction is the sum of two subprocesses for π0 decay, the Dalitz decay mode of π0 → e +e–γ and conversion mode where one photon from π0 → γγ decay is converted into a …
Separated Response Function Ratios In Exclusive, Forward Π± Electroproduction, G. M. Huber, H. P. Blok, C. Butuceanu, D. Gaskell, T. Horn, D. J. Mack, D. Abbott, A. Klein, L. M. Qin, K. Vansyoc
Separated Response Function Ratios In Exclusive, Forward Π± Electroproduction, G. M. Huber, H. P. Blok, C. Butuceanu, D. Gaskell, T. Horn, D. J. Mack, D. Abbott, A. Klein, L. M. Qin, K. Vansyoc
Physics Faculty Publications
The study of exclusive π± electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio R-L=sigma(pi-)(L) / sigma(pi+)(L) is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of R-T=sigma(pi-)(L) / sigma(pi+)(L) from unity at small -t, to 1/4 at large -t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier …
Photoproduction Of The Φ(1020) Meson In Neutral Decay Mode Γp → Φp → K(S)K(L)P, Heghine Seraydaryan
Photoproduction Of The Φ(1020) Meson In Neutral Decay Mode Γp → Φp → K(S)K(L)P, Heghine Seraydaryan
Physics Theses & Dissertations
The Φ(1020) meson photoproduction cross sections in the neutral decay mode Φ → KSKL are measured for the first time. This work presents measurements of differential cross sections, dσ/dt, dσ/d cos θΦc.m.; Φ decay angular distributions, W(cos θ) and W(Φ), and spin-density matrix elements, ρ0, in the Helicity and Gottfried-Jackson frames, in the energy range 1.6 GeV < Eγ < 2.6 GeV. We analyzed the photoproduction data of the g11a experiment collected on an LH2 target using the CLAS detectector at Hall B, TJNAF. The measured cross sections show some differences from the charged decay mode Φ → K+ K−.
Virtual Compton Scattering And Neutral Pion Electroproduction In The Resonance Region Up To The Deep Inelastic Region At Backward Angles, G. Laveissiere, N. Degrande, S. Jaminion, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein, Jefferson Lab Hall A Collaboration
Virtual Compton Scattering And Neutral Pion Electroproduction In The Resonance Region Up To The Deep Inelastic Region At Backward Angles, G. Laveissiere, N. Degrande, S. Jaminion, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein, Jefferson Lab Hall A Collaboration
Physics Faculty Publications
We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e′p)γ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q2=1 GeV2 and for the Q2 dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q2 dependence is smooth. The measured ratio of H(e, e′p)γ to H(e, e′p)π0 cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared …
Three- And Four-Jet Final States In Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, M. Jechow, N. Pavel, A. G. Yagües Molina, S. Antonelli, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, M. Bindi, D. Boscherini, A. Bruni, G. Bruni, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, G. Iacobucci, A. Margotti, R. Nania, A. Polini, G. Sartorelli, A. Zichichi
Three- And Four-Jet Final States In Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, M. Jechow, N. Pavel, A. G. Yagües Molina, S. Antonelli, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, M. Bindi, D. Boscherini, A. Bruni, G. Bruni, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, G. Iacobucci, A. Margotti, R. Nania, A. Polini, G. Sartorelli, A. Zichichi
Faculty Publications
Three- and four-jet final states have been measured in photoproduction at HERA using the ZEUS detector with an integrated luminosity of 121 pb -1. The results are presented for jets with transverse energy E Tjet > 6 GeV and pseudorapidity | η jet | < 2.4, in the kinematic region given by the virtuality of the photon Q 2 < 1 GeV 2 and the inelasticity 0.2 ≤ y ≤ 0.85 and in two mass regions defined as 25 ≤ M n j < 50 GeV and M n j ≥ 50 GeV, where M n j is the invariant mass of the n-jet system. The four-jet photoproduction cross section has been measured for the first time and represents the highest-order process studied at HERA. Both the three- and four-jet cross sections have been compared with leading-logarithmic parton-shower Monte Carlo models, with and without multi-parton interactions. The three-jet cross sections have been compared to an O (α α s2) perturbative QCD calculation. © 2007 Elsevier B.V. All rights reserved.
First Measurement Of Transferred Polarization In The Exclusive →E P → E'K+ →Λ, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, L. B. Weinstein, J. Yun
First Measurement Of Transferred Polarization In The Exclusive →E P → E'K+ →Λ, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, L. M. Qin, L. B. Weinstein, J. Yun
Physics Faculty Publications
The first measurements of the transferred polarization for the exclusive →ep → e'K+ →Λ over right arrow reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q2 from 0.3 to 1.5 (GeV/c)2, W from 1.6 to 2.15 GeV, and over the full K+ center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the s -s quark pair is produced with spins predominantly …
Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, S. Stepanyan, J. Yun, Et Al., Clas Collaboration
Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, S. Stepanyan, J. Yun, Et Al., Clas Collaboration
Physics Faculty Publications
Differential cross sections for γp→ηp have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W = 1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass ∼1.8 GeV couples to the ηN channel.
Corrected Article: Exclusive Electroproduction Of ᵠ Mesons At 4.2 Gev [Physical. Rev. C 63, 065205, (2001)], M. Bektasoglu, L. Ciciani, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., The Clas Collaboration
Corrected Article: Exclusive Electroproduction Of ᵠ Mesons At 4.2 Gev [Physical. Rev. C 63, 065205, (2001)], M. Bektasoglu, L. Ciciani, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., The Clas Collaboration
Physics Faculty Publications
We studied the exclusive reaction ep → e' p' ᵠ using the ᵠ →K+K- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in Q2 from 0.7 to 2.2 GeV2and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of ᵠ production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time c Δ t …
Phenomenological Description Of Double-Pion Photoproduction, Andry M. Rakotovao
Phenomenological Description Of Double-Pion Photoproduction, Andry M. Rakotovao
Physics Theses & Dissertations
Double pion photoproduction off proton targets is studied, in the framework of an Effective Lagrangian approach at tree level, based on the coupling of photons and pions to nucleons and resonances. We consider N, Δ(1232), N(1440), N(1520) and N(1535) as intermediate baryonic states and ρ-meson as the intermediate 2π resonance. The general form of the amplitude is presented and total cross sections of the γp → π+π− p, γp → π0π0p and γp → π +π0n processes are evaluated up to Eγ …