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Complete sets of observables in pseudoscalar-meson photoproduction  [PDF]
Tom Vrancx,Jan Ryckebusch,Jannes Nys
Physics , 2014, DOI: 10.1051/epjconf/20147304011
Abstract: Pseudoscalar-meson photoproduction is characterized by four complex reaction amplitudes. A complete set is a minimum theoretical set of observables that allow to determine these amplitudes unambiguously. It is studied whether complete sets remain complete when experimental uncertainty is involved. To this end, data from the GRAAL Collaboration and simulated data from a realistic model, both for the $\gamma p \to K^+ \Lambda$ reaction, are analyzed in the transversity representation of the reaction amplitudes. It is found that only the moduli of the transversity amplitudes can be determined without ambiguity but not the relative phases.
Completeness Rules for Spin Observables in Pseudoscalar Meson Photoproduction  [PDF]
Wen-Tai Chiang,Frank Tabakin
Physics , 1996, DOI: 10.1103/PhysRevC.55.2054
Abstract: The number and type of measurements needed to ascertain the amplitudes for pseudoscalar meson photoproduction are analyzed in this paper. It is found that 8 carefully selected measurements can determine the four transversity amplitudes without discrete ambiguities. That number of measurements is one less than previously believed. We approach this problem in two distinct ways: (1) solving for the amplitude magnitudes and phases directly; and (2) using a bilinear helicity product formulation to map an algebra of measurements over to the well-known algebra of the $4\times 4$ Gamma matrices. It is shown that the latter method leads to an alternate proof that 8 carefully chosen experiments suffice for determining the transversity amplitudes completely. In addition, Fierz transformations of the Gamma matrices are used to develop useful linear and nonlinear relationships between the spin observables. These relationships not only help in finding complete sets of experiments, but also yield important constraints between the 16 observables for this reaction.
Polarization observables in exclusive kaon photoproduction on the deuteron  [PDF]
K. Miyagawa,T. Mart,C. Bennhold,W. Gloeckle
Physics , 2006, DOI: 10.1103/PhysRevC.74.034002
Abstract: Single and double polarization observables for kaon photoproduction on the deuteron are studied theoretically with modern hyperon-nucleon forces. The kinematical region of the kaon scattered forward with large momentum is thoroughly investigated where either the quasifree scattering leading to the kaon and hyperon or the final-state interaction between hyperon and nucleon are expected. The quasifree scatterings show characteristic peaks in the inclusive cross sections. The final-state interaction effects are significant, especially around the Lambda-N and Sigma-N thresholds. The double polarization C_z is found to be sensitive to the final-state interaction effects. Precise data would help to clarify the property of the Lambda-N--Sigma-N interaction and also help to extract the information on the elementary amplitude from the quasifree scattering region.
Ambiguities of the single spin observables in a truncated partial wave expansion for photoproduction of pseudoscalar mesons  [PDF]
Y. Wunderlich,R. Beck,L. Tiator
Physics , 2013,
Abstract: The ambiguity problem in the truncated partial wave analysis of pseudoscalar meson photoproduction with suppressed t-channel exchanges is investigated. More precisely, the focus is set to ambiguities of the four single spin observables, $\sigma_0$, $\Sigma$, $T$ and $P$. For this purpose, the approach and formalism already worked out by Omelaenko in 1981 is revisited in this work. A numerical study using multipoles of the PWA solution MAID2007 shows how, for ideal circumstances, only one additional double polarization observable can resolve all ambiguities.
Photoproduction of Pseudoscalar Mesons  [PDF]
R. A. Arndt,W. J. Briscoe,G. V. O'Rielly,I. I. Strakovsky,R. L. Workman
Physics , 2002, DOI: 10.1016/S0375-9474(03)01177-1
Abstract: Experiments that study the photoproduction of pseudoscalar mesons; pions, etas and kaons, have the potential to increase our knowledge of baryon and hyperon resonance properties. Recent experiments at JLab, Mainz, GRAAL, and Bonn are beginning to produce results in the form of polarization and asymmetry measurements and determinations of the differential and integrated cross sections. These new data are essential to the performance of Partial-Wave Analyses that are less model dependent and coupled-channels calculations that incorporate unitarity dynamically,combining hadronic reaction channels together with electromagnetic processes. This approach is necessary to extract resonance properties and may lead to the identification of missing, but predicted, resonances. Some recent experimental and phenomenological results for single and double pseudoscalar meson photoproduction are discussed.
Multipole analysis of spin observables in vector meson photoproduction  [PDF]
Cetin Savkli,Frank Tabakin,Shin Nan Yang
Physics , 1995, DOI: 10.1103/PhysRevC.53.1132
Abstract: A multipole analysis of vector meson photoproduction is formulated as a generalization of the pseudoscalar meson case. Expansion of spin observables in the multipole basis and behavior of these observables near threshold and resonances are examined.
Amplitude ambiguities in pseudoscalar meson photoproduction  [PDF]
Greg Keaton,Ron Workman
Physics , 1995, DOI: 10.1103/PhysRevC.53.1434
Abstract: We consider the problem of determining amplitudes from observables for the case of pseudoscalar meson photoproduction. We find a number of surprisingly simple constraints which give necessary conditions for a complete set of measurements. These results contradict one of the selection rules derived previously.
Measurement of the polarization observables T, P, H in pseudoscalar meson photoproduction with the CBELSA/TAPS experiment  [PDF]
Jan Hartmann,for the CBELSA/TAPS collaboration
Physics , 2011, DOI: 10.1063/1.3701230
Abstract: The CBELSA/TAPS experiment with a longitudinally or transversely polarized target and an energy tagged, linearly or circularly polarized photon beam allows the measurement of a large set of polarization observables. Due to its good energy resolution and high detection efficiency for photons, as well as the nearly complete solid angle coverage, it is ideally suited for the measurement of neutral mesons decaying into photons. Preliminary results for the target asymmetry T, the recoil polarization P, and the double polarization observable H are shown for \pi^0 and \eta photoproduction off the proton.
Photoproduction of Pseudoscalar Mesons from Nuclei  [PDF]
Laith Abu-Raddad
Physics , 2000,
Abstract: The subject of this doctoral study is the pseudoscalar meson photoproduction from nuclei. Two types of processes are investigated in this regard: coherent and quasifree processes. In the case of the coherent process, we study it for the photoproduction of pion and eta mesons. We place special emphasis on the various sources that put into question earlier nonrelativistic-impulse-approximation calculations. These include: final-state interactions, relativistic effects, off-shell ambiguities, and violations to the impulse approximation. By far the largest uncertainty emerges from the ambiguity in extending the many on-shell-equivalent representations of the elementary amplitude off the mass shell. In the case of the quasifree process, we study it for the photoproduction of the kaon meson. We compute the recoil polarization of the lambda-hyperon and the photon asymmetry as well as the differential cross section. By introducing the notion of a ``bound-nucleon propagator'' we exploit Feynman's trace techniques to develop closed-form, analytic expressions for all photoproduction observables. Our results indicate that polarization observables are sensitive only to the fundamental physics, making them ideal tools for the study of modifications to the elementary process in the nuclear medium.
Nuclear exclusive vector meson photoproduction  [PDF]
V. P. Goncalves,M. V. T. Machado
Physics , 2004, DOI: 10.1140/epjc/s2004-02044-7
Abstract: We calculate the nuclear cross section for vector meson exclusive photoproduction within the QCD color dipole picture and in the Regge approach. For the former approach, we have considered the phenomenological saturation model, whereas for the latter we use a model based on the dipole Pomeron framework. Theoretical estimates for scattering on both light and heavy nuclei are given for a large range on energy.
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