Completeness Rules for Spin Observables in Pseudoscalar Meson Photoproduction

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.Comment: 32 pages, no figures, LaTeX/REVTeX, submitted to Phys. Rev. C, typos correcte

A comparison of 3D gait models based on the Helen Hayes Hospital marker set

Bibliography: leaves 108-112.This study compares three commercial gait analysis packages, Vicon Clinical Manager (VCM), GaitLab 2.0 (GL) and Peak Motus 2000 (PM) with a standard model developed using the Vicon BodyBuilder (BB) software package. All these packages use the same modified Helen Hayes Hospital marker set for external marker placement

Coupled channel study of K+ΛK^+\Lambda photoproduction

A coupled channel model with $\gamma N$, $KY$ and $\pi N$ channels has been used to analyze the recent data of $\gamma p \to K^+ \Lambda$. The non-resonant interactions within the subspace $KY \oplus \pi N$ are derived from effective Lagrangians using a unitary transformation method. The direct photoproduction reaction is obtained from a chiral constituent quark model with $SU(6)\otimes O(3)$ breaking. Missing baryon resonances issues are briefly discussed.Comment: Part of the proceedings of the International Workshop on the Physics of Excited Baryons NSTAR05, 12-15 October 2005, Tallahassee, Florida, US

Amplitude ambiguities in pseudoscalar meson photoproduction

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.Comment: 7 page

Coupled-channel study of gamma p --> K+ Lambda

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.Comment: 12 pages, 6 eps figures, uses elsart.cls, submitted to Phys.Lett.B; v2: added paragraph in section