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Search Results: 1 - 10 of 31626 matches for " Wen-Tai Chiang "
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Completeness Rules for Spin Observables in Pseudoscalar Meson Photoproduction
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.
Spin Information from Vector-Meson Decay in Photoproduction
W. M. Kloet,Wen-Tai Chiang,Frank Tabakin
Physics , 1998, DOI: 10.1103/PhysRevC.58.1086
Abstract: For the photoproduction of vector mesons, all single and double spin observables involving vector meson two-body decays are defined consistently in the $\gamma N$ center of mass. These definitions yield a procedure for extracting physically meaningful single and double spin observables that are subject to known rules concerning their angle and energy evolution. As part of this analysis, we show that measuring the two-meson decay of a photoproduced $\rho$ or $\phi$ does not determine the vector meson's vector polarization, but only its tensor polarization. The vector meson decay into lepton pairs is also insensitive to the vector meson's vector polarization, unless one measures the spin of one of the leptons. Similar results are found for all double spin observables which involve observation of vector meson decay. To access the vector meson's vector polarization, one therefore needs to either measure the spin of the decay leptons, make an analysis of the background interference effects or relate the vector meson's vector polarization to other accessible spin observables.
A reggeized model for eta and eta-prime photoproduction
Wen-Tai Chiang,Shin Nan Yang,L. Tiator,M. Vanderhaeghen,D. Drechsel
Physics , 2002, DOI: 10.1103/PhysRevC.68.045202
Abstract: A reggeized model for \eta and \eta' photoproduction on the nucleon is presented. In this model, t-channel vector meson exchanges are described in terms of Regge trajectories to comply with the correct high energy behavior. We compare this reggeized model with an isobar model (\eta-MAID), where the t-channel exchanges are described by \rho and \omega poles. Both models contain the same resonance contributions, and describe current \gamma p \to \eta p data up to E_\gamma^{lab} = 2 GeV quite well, but only the reggeized model can be successfully extended to higher energies. For the \gamma p \to \eta' p reaction, the reggeized model is found to be able to give a satisfactory description. For the differential cross section data from SAPHIR, we find that the observed linear forward rise in cos(theta) near E_\gamma^{lab} = 1.6 GeV can be well described by the interference of an S11 resonance and the Regge trajectory exchanges without any need for an additional P-wave resonance.
Magnetic dipole moment of the S11(1535) from the γp \to γ ηp reaction
Wen-Tai Chiang,Shin Nan Yang,Marc Vanderhaeghen,Dieter Drechsel
Physics , 2002, DOI: 10.1016/S0375-9474(03)01160-6
Abstract: The \gamma p \to \gamma \eta p reaction in the S11(1535) resonance region is investigated as a method to access the S11(1535) magnetic dipole moment. To study the feasibility, we perform calculations of the \gamma p \to \gamma \eta p process within an effective Lagrangian approach containing both the S11 resonant mechanism and a background of non-resonant contributions. Predictions are made for the forthcoming experiments. In particular, we focus on the sensitivity of cross sections and photon asymmetries to the S11(1535) magnetic dipole moment.
An isobar model for eta photo- and electroproduction on the nucleon
Wen-Tai Chiang,Shin Nan Yang,L. Tiator,D. Drechsel
Physics , 2001,
Abstract: An isobar model containing Born terms, vector meson exchange and nucleon resonances is used to analyze recent eta photoproduction data for cross section and beam asymmetry, as well as JLab electroproduction data. Good overall description is achieved up to Q^2 = 4.0 (GeV/c)^2. Besides the dominant S11(1535) resonance, we show that the second S11 resonance, S11(1650), is also necessary to be included in order to extract S11(1535) resonance parameters properly. In addition, the beam asymmetry data allow us to extract very small (<0.1%) N* --> eta N decay branching ratios of D13(1520) and F15(1680) resonances because of the overwhelming s-wave dominance. The model is implemented as a part of the MAID program.
Dynamical coupled-channel model of kaon-hyperon interactions
Wen-Tai Chiang,B. Saghai,F. Tabakin,T. -S. H. Lee
Physics , 2004, DOI: 10.1103/PhysRevC.69.065208
Abstract: The pi N --> KY and KY --> KY reactions are studied using a dynamical coupled-channel model of meson-baryon interactions at energies where the baryon resonances are strongly excited. The channels included are: pi N, K \Lambda, and K\Sigma. The resonances considered are: N^* [S_{11}(1650), P_{11}(1710), P_{13}(1720),D_{13}(1700)]; \Delta^* [S_{31}(1900), P_{31}(1910), P_{33}(1920)]; \Lambda ^* [S_{01}(1670), P_{01}(1810)] \Sigma^* [P_{11}(1660), D_{13}(1670)]; and K^*(892). The basic non-resonant \pi N --> KY and KY --> KY transition potentials are derived from effective Lagrangians using a unitary transformation method. The dynamical coupled-channel equations are simplified by parametrizing the pi N -->pi N amplitudes in terms of empirical pi N partial-wave amplitudes and a phenomenological off-shell function. Two models have been constructed. Model A is built by fixing all coupling constants and resonance parameters using SU(3) symmetry, the Particle Data Group values, and results from a constituent quark model. Model B is obtained by allowing most of the parameters to vary around the values of model A in fitting the data. Good fits to the available data for pi^- p to K^0 \Lambda, K^0 \Sigma^0 have been achieved. The investigated kinematics region in the center-of-mass frame goes from threshold to 2.5 GeV. The constructed models can be imbedded into associated dynamical coupled-channel studies of kaon photo- and electro-production reactions.
An isobar model for eta photo- and electroproduction on the nucleon
Wen-Tai Chiang,Shin Nan Yang,Lothar Tiator,Dieter Drechsel
Physics , 2001, DOI: 10.1016/S0375-9474(01)01325-2
Abstract: Eta photo- and electroproduction on the nucleon is studied using an isobar model. The model contains Born terms, and contributions from vector meson exchanges and nucleon resonances. Our results are compared with recent eta photoproduction data for differential and total cross sections, beam asymmetry, and target asymmetry, as well as electroproduction data. Besides the dominant S11(1535) resonance, we show that the second S11 resonance, S11(1650), is also necessary to be included in order to extract S11(1535) resonance parameters properly. In addition, the beam asymmetry data allow us to extract very small (<0.1%) N* --> eta N decay branching ratios of the D13(1520) and F15(1680) resonances because of the overwhelming s-wave dominance. This model (ETA-MAID) is implemented as a part of the MAID program.
Coupled-channel study of gamma p --> K+ Lambda
Wen-Tai Chiang,F. Tabakin,T. -S. H. Lee,B. Saghai
Physics , 2001, DOI: 10.1016/S0370-2693(01)00945-5
Abstract: A coupled-channel (CC) approach has been developed to investigate kaon photoproduction on the nucleon. In addition to direct K+ Lambda production, our CC approach accounts for strangeness production including K+ Lambda final state interactions with both pi0 p and pi+ n intermediate states. Calculations for the gamma p --> K+ Lambda reaction have been performed, and compared with the recent data from SAPHIR, with emphasis on the CC effects. We show that the CC effects are significant at the level of inducing 20% changes on total cross sections; thereby, demonstrating the need to include pi N channels to correctly describe the gamma p --> K+ Lambda reaction.
Optimal Nonadditive Quantum Error-Detecting Code
Wen-Tai Yen,Li-Yi Hsu
Physics , 2009,
Abstract: In this paper, we investigate the optimal nonadditive quantum error-detecting codes with distance two. The the numerical simulation shows that, with n being can be 5, 6, 7, 8, 10 and 12, such the n-qubit quantum error-detecting codes with maximal number of codewords can be found. Therein, except the n=7 case, the n-vertex loop graphs help find the optimal quantum codes.
2-Chloro-N-[(4-chlorophenyl)(phenyl)methyl]-N-[2-(4-nitro-1H-imidazol-1-yl)ethyl]ethanamine
Wen-Tai Zhang,Cheng-He Zhou,Qing-Gang Ji
Acta Crystallographica Section E , 2011, DOI: 10.1107/s160053681100256x
Abstract: In the title compound, C20H20Cl2N4O2, the nitroimidazole ring makes dihedral angles of 17.00 (1) and 60.45 (11)° with the phenyl and chlorophenyl rings, respectively. The three-coordinate N atom connected to two methylene and one methine C atoms shows pyramidal coordination.
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