Polarization Observables in Strangeness Photoproduction with CLAS at Jefferson Lab PDF Download

Author: Craig Alexander Paterson
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Category : Photons
Languages : en
Pages : 202

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Author: Stuart Fegan
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Category : Mesons
Languages : en
Pages : 169

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Languages : en
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An extensive program of strange particle productian off the proton is currently underway with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at Jefferson Laboratory. Precision measurements of ground-state and low-lying excited-state hyperons are being carried out with both electron and real photon beams, both of which are available with high polarization at energies up to 6 GeV. This talk will focus an selected aspects of our strangeness physics program regarding electroproduction measurements of single and double-polarization observables.

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Languages : en
Pages : 167

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The preliminary results discussed in this theses have been carried out with the Nuclear Physics group of the Department of Physics at the University of Rome Tor Vergata, under the supervision of Prof. A. D'Angelo. On March 2012 I joined the CLAS collaboration at the Thomas Jefferson National Laboratory, in Virginia, USA, and became a term member after a probation period of 9 months. As a member I could participate to the g14 data taking, started on November 18th 2011 and finished on May 18th 2012. In that period I was in charge of the timing calibration of the CLAS forward electromagnetic spectrometer. For the duration of the experiment, I was also responsible of the Raman laboratory located at the University of Rome Tor Vergata, where the Raman measurements were performed. The Raman measurements were crucial for determining the relative concentrations of H2 and D2 in the Hydrogen-Deuteride gas which was used for the target of the g14 experiment.

Author: Kazushige Maeda
Publisher: World Scientific
ISBN: 9814483273
Category : Science
Languages : en
Pages : 475

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This book contains important papers on the strangeness production processes and strangeness nuclear physics resulting from electromagnetic interaction. Both experimentalists and theorists in the field present information on recent activities and discuss the prospects of related fields.

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Languages : en
Pages : 5

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The set of experiments forming the g8a run took place in the summer of 2001 in Hall B of Jefferson Lab. The g8a run was the commissioning experiment for the linearly-polarized photon beam at CLAS. The aim of these experiments is to improve the understanding of the underlying symmetry of the quark degrees of freedom in the nucleon, the nature of the parity exchange between the incident photon and the target nucleon, and the mechanism of associated strangeness production in electromagnetic reactions. A beam of tagged and collimated linearly polarized photons (energy range 1.8-2.2 GeV) in conjunction with the large solid angle coverage of CLAS make possible the extraction of the differential cross-sections and polarization observables for the photoproduction of vector mesons and kaons. The reaction channels are under investigation to search for possibly missing nucleon resonances. An overview of the experiment and preliminary results on the measurement of the photon asymmetries of the aforementioned reactions will be presented in this paper.

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Languages : en
Pages : 7

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A very brief overview is presented of varied strangeness-physics studies that have been conducted with the CLAS system in the era of 6 GeV beam at Jefferson Lab. A full bibliography of articles related to open strangeness production is given, together with some physics context for each work. One natural place where these studies could be continued, using a K L beam and the GlueX detector, is in the further investigation of the [Lambda](1405) baryon. The line shapes and cross sections of this state were found, using photoproduction at CLAS, to differ markedly in the three possible [Sigma][pi] final states. The analogous strong-interaction reactions using a K L beam could further bring this phenomenon into focus. 1. The CLAS program ran from 1998 to 2012, during the time when the maximum Jefferson Lab beam energy was 6 GeV. An important thrust of this program was to investigate the spectrum of N * and [Delta] * (non-strange) baryon resonances using photo-and electro-production reactions. To this end, final states containing strange particles (K mesons and low-mass hyperons) played a significant role. The reason for this is partly due to favorable kinemat-ics. When the total invariant energy W (= √ s) of a baryonic system exceeds 1.6 GeV it becomes possible to create the lightest strangeness-containing final state, K + [Lambda]. This is a two-body final state that is straightforward to reconstruct in the CLAS detector system [1], and theoretically it is easier to deal with two-body reaction amplitudes than with three-and higher-body reaction amplitudes. In the mass range W > 1.6 GeV the decay modes of excited nucleons tend to not to favor two-body [pi]-nucleon final states but rather multi-pion states. As input to partial-wave decompositions and resonance-extraction models, therefore, the strangeness-containing final states of high-mass nucleon excitations have had importance. Excited baryons decay through all possible channels simultaneously, constrained by unitarity of course, and channel-coupling is crucial to determining the spectrum of excita-tions. Within this mix of amplitudes, however, the KY decay modes have proven useful. The end result has been, as summarized in the recent edition of the Review of Particle Properties [2], clearer definition of the spectrum of baryonic excitations, with definite contributions from the strangeness sector channels. To this end, strangeness photoproduction cross sections measurements at CLAS for the K + [Lambda], K + [Sigma] 0 and K 0 [Sigma] + channels on a proton target were published [3-6]. Cross sections are not enough, in general, to define the reaction mechanism, including the underlying N * excitation spectrum. Photoproduction of pseudo-scalar mesons is described by four complex amplitudes, leading to fifteen spin observables in addition to the cross section. Full knowledge of these spin observables would exhaust the information that can be gleaned experimentally about any given reaction channel. Here the hyperonic channels offer another advantage when compared with the non-strange reaction channels: the polarization of most hyperons can be measured directly through their parity-violating weak decay asymmetries. Unlike 163.

Author: Kazushige Maeda
Publisher: World Scientific
ISBN: 981427786X
Category : Science
Languages : en
Pages : 469

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Importance of strange quarks in hadrons, nuclei and dense matter / A.W. Thomas -- Overview of strangeness nuclear physics / A. Gal -- Experimental overview and challenge in strangeness nuclear physics / K. Imai -- Recent QCD results on the strange hadron systems / M. Oka -- Strangeness physics with CLAS / V.D. Burkert -- Progress and issues in the electromagnetic production of kaon on the nucleon / T. Mart -- Neutral kaon photoproduction at LNS, Tohoku University / M. Kaneta et al. for the NKS/NKS2 collaboration -- Photoproduction of the [symbol] resonance from the neutron / K.H. Hicks and D. Keller for the LEPS collaboration -- Photo- and electroproduction of kaons / P. Bydz̮ouský -- Strangeness pproduction at ELSA / V. Kleber for the CBELSA/TAB collaboration -- Low Q[symbol] kaon electroproduction / P. Markowitz and A. Acha for the JLab E94-107 and Hall A collaborations -- Results on strangeness production from HADES / A. Schmah for the HADES collaboration -- [symbol] photo-production on the deuteron at LNS, Tohoku University / T. Ishikawa -- Current status of the GO parity violation experiment carried out at Jefferson Laboratory / L. Bimbot for the GO collaboration -- Production and searches for cascade baryons with CLAS / E.S. Smith for the CLAS collaboration -- Nijmegen Baryon-Baryon interactions S = -1,-2 systems / Th. A. Rijken, M.M. Nagels and Y. Yamamoto -- Hyperon-nucleus systems in G-matrix approach / Y. Yamamoto -- [symbol]C(O[symbol]) and [symbol]O potentials derived from the SU[symbol] quark-model Baryon-Baryon interaction / Y. Fujiwara, M. Kohno and Y. Suzuki

Author: Steven A Dytman
Publisher: World Scientific
ISBN: 9814485659
Category : Science
Languages : en
Pages : 413

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This book covers recent advances in the physics of nucleon resonances, including new experimental results from laboratories in the USA, Europe, and Asia, and new developments in effective field theories, quark models, and lattice gauge theory.

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Languages : en
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The work presented in this thesis describes the first experimental measurement of the photon asymmetry of the exclusive [rvec [gamma]] [yields] [rho][sup 0]p [yields] [pi][sup +][pi][sup -]p reaction. The data were gathered during the summer of 2001 as a proof of principle study using a polarized beam of photons with the CLAS detector in Hall B of Jefferson Lab for the first time. The aim of the g8a set of experiments is to improve the understanding of the underlying symmetry of the quark degrees of freedom in the nucleon, the nature of the parity exchange between the incident photon and the target nucleon, the mechanism of associated strangeness production in electromagnetic reactions, and to search for evidence for the existence of the so called missing resonances. A beam of tagged and collimated linearly polarized photons (energy range 1.8-2.2 GeV) in conjunction with the large solid angle coverage of CLAS make possible the extraction of polarization observables for the photoproduction of vector mesons. For example, the azimuthal distribution of the [rho][sup 0] as a function of its polar angle in the ([rvec [gamma]], p) c.m. system enables the measurement of the photon asymmetry parameter, [Sigma]. This has been measured for [theta][sub c.m.] [le] 65[sup o], the results of which are compared with the prediction of the quark model of Zhao for the [omega] vector meson. It has been found that the tensor coupling for the [rho][sup 0] is quite different than that of the [omega]. The experimental technique of using a beam of linear polarized photons with the CLAS detector has been shown to be viable. By the end of the second phase of these experiments they expect to have a high quality data set which will allow the measurement of the spin density matrix elements for the [rho][sup 0] and provide evidence relating to the existence of the missing resonances.