Differential Cross Sections and Spin Density Matrix Elements for the Reaction Gamma P -] P Omega PDF Download

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Languages : en
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High-statistics differential cross sections and spin density matrix elements for the reaction gamma p -> p omega have been measured using the CLAS at Jefferson Lab for center-of-mass (CM) energies from threshold up to 2.84 GeV. Results are reported in 112 10-MeV wide CM energy bins, each subdivided into cos(theta_CM) bins of width 0.1. These are the most precise and extensive omega photoproduction measurements to date. A number of prominent structures are clearly present in the data. Many of these have not previously been observed due to limited statistics in earlier measurements.

Author: Tianqi Hu
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Category : Physics
Languages : en
Pages : 0

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Meson photoproduction off the nucleon has long been serving as a tool for understanding the properties of hadrons. At lower energy scales, the production mechanisms are dominated by the $s$-channel inelastic scattering process, where the proton absorbs the photon, gets excited to the resonance state, and then decays. Nucleon resonances have been extensively studied in this energy regime using techniques such as partial wave analysis. When the energy scale increases, the production mechanism gradually transitions from the formation of nucleon resonances to the pure scattering process, corresponding to the $t$- and $u$-channel exchange. However, the scarcity of cross section and polarization data over the photon energy range 3-6 GeV have thus far hindered our understanding of the mechanism transition from nucleon resonance to the $t$-channel Pomeron and Reggeon exchange. This work presents differential cross sections for the reaction $\\\\gamma p\\\\rightarrow p\\\\eta$ with energy-tagged photon energies between 1.2 and 4.7 GeV using the CLAS spectrometer at Jefferson Laboratory. The $\\\\eta$ meson is reconstructed in its dominant charged decay channel $\\\\eta\\\\rightarrow \\\\pi^{+}\\\\pi^{-}\\\\pi^{0}$. The energy scale extends from the nucleon resonance regime to the Regge regime, allowing for studying the $t$-channel exchange mechanisms. The d$\\\\sigma/$d$\\\\Omega$ differential cross sections are compared with predictions of $\\\\eta$-MAID 2018 and the latest solution of the Bonn-Gatchina coupled-channel analysis. In the energy regime $W>2.5$ GeV, the d$\\\\sigma/$d$t$ differential cross sections are presented in comparison with the Regge model from the Joint Physics Analysis Center. The data confirm the expected dominance of $\\\\rho$, $\\\\omega$ vector-meson exchange. Differential cross sections and spin density matrix elements (SDMEs) are also measured for the reaction $\\\\gamma p\\\\rightarrow p\\\\omega$ in the energy range $1.6E_{\\\\gamma}

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Languages : en
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This work presents measurements of differential cross sections, do/d cos$wCM, and spin density matrix elements, PsMM', for the reaction ypâ pw in the energy range 1.72 GeV

Author: Mike Williams
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Languages : en
Pages : 0

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Languages : en
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High-statistics differential cross sections and spin density matrix elements for the reaction [gamma]p --> p[omega] have been measured using the CLAS at Jefferson Lab for center-of-mass energies, W, from threshold up to 2.84 GeV. An event-based partial wave analysis (PWA) has also been performed on the data. This analysis benefits from access to the world's first high precision spin density matrix element measurements, available to the event-based PWA through the decay distribution of omega-->pi+pi-pi0. Strong evidence has been found for nucleon resonance contributions.

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Languages : en
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High-statistics measurements of differential cross sections and spin density matrix elements for the reaction ? p → ?p have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.97 to 2.84 GeV, with an extensive coverage in the ? production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the ? natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- (? → K+K−) and neutral- (? → K0SK0L) $Kar{K}$ decay modes of the ?. Further, for the charged mode, we differentiate between the cases where the final K− track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed ? mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide √s bins for the charged- and the neutral-mode, respectively. Possible effects from K+?* channels with p$Kar{K}$ final-states are discussed. These present results constitute the most precise and extensive ? photoproduction measurements to date and in conjunction with the ? photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.

Author: David Christopher Langs
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Languages : en
Pages : 382

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Languages : en
Pages : 229

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This work presents measurements of differential cross sections, d?/dcos?$?top{CW}$, and spin density matrix elements, P$0top{MM'}$, for the reaction ?p → p? in the energy range 1.72 GeV

Author: Brigitte Weßels-Wagini
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Category :
Languages : de
Pages : 32

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Author: Brigitte Wessels-Wagini
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Category :
Languages : de
Pages : 32

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