Amplitude determination for MM -> MM, M= pi, K and cross-sections for gamma gamma -> pi^+pi^-, pi^0 pi^0 in a chiral model

Recently Dai and Pennington have performed a comprehensive analysis of essentially all pion and kaon pair production data from two-photon collisions below 1.5 GeV, including all high statistics results from Belle, as well as the older data from Mark II at SLAC, CELLO at DESY, and Crystal Ball at SLAC. Imposing the basic constraints required by analyticity, unitarity, and crossing symmetry and making use of Low's low energy theorem for QED, they are able to extract the final-state strong-interaction scattering amplitudes for the intermediate pi pi->pi pi and pi pi-> K\bar K reactions in a model-independent fashion. In addition, they provide good fits to the respective gamma gamma-> pi pi cross-sections that are known in the low-energy sector in the restricted angular range, | cos theta|< 0.6-0.8. Using the parameters obtained in this fashion, these authors contruct the \gamma\gamma->pi pi cross-sections integrated over the full angular range. In this work, we use a version of chiral perturbation theory developed by Oller and Oset to evaluate the final-state strong-interaction amplitudes directly theoretically and we compare our thus obtained low-energy QCD-based results directly with the amplitudes extracted by Dai and Pennington. We also calculate the gamma gamma -> pi pi cross-sections (integrated over the full angular range) and compare these with those obtained by Dai and Pennington. This calculation thus gives a more detailed insight into the fit of chiral perturbation theory, not just to the measured gamma gamma-> pi pi cross-sections, as is usually presented, but rather to a higher level of detail through the available analysis of the experimental data for the underlying final-state strong-interaction meson-meson scattering amplitudes pi pi-> pi pi and pi pi-> K\bar K themselves. The fits appear to be reasonable over the energy range considered.Comment: 17 pages, 5 figure

Lifetime of Kaonium

The kaon--antikaon system is studied in both the atomic and the strongly interacting sector. We discuss the influence of the structures of the $f_0(980)$ and the $a_0(980)$ mesons on the lifetime of kaonium. The strong interactions are generated by vector meson exchange within the framework of the standard $SU(3)_V\times SU(3)_A$ invariant effective Lagrangian. In the atomic sector, the energy levels and decay widths of kaonium are determined by an eigenvalue equation of the Kudryavtsev--Popov type, with the strong interaction effects entering through the complex scattering length for $K\bar K$ scattering and annihilation. The presence of two scalar mesons, $f_0(980)$ and $a_0(980)$, leads to a ground state energy for the kaonium atom that is shifted above the point Coulomb value by a few hundred eV. The effect on the lifetime for the kaonium decay into two pions is much more dramatic. This lifetime is reduced by two orders of magnitude from $0.8\times 10^{-16}$ sec for annihilation in a pure Coulomb field down to $3.1\times 10^{-18}$ sec when the strong interactions are included. The analysis of the two photon decay width of the $f_0(980)$ suggests a generalization of the molecular picture which reduces the lifetime of kaonium still further to $1.1\times 10^{-18}\textrm{sec}$.Comment: 33 pages, 12 figures;3 new figures and new comment concerning the a

A multifarious understanding of eschatology in Ephesians: A possible solution to a vexing issue

Although an almost forgotten debate, the issue of eschatology in Ephesians remains unresolved and possibly insoluble. However, presuppositions inevitably determine the final outcome of investigations. This latter datum is characterized, indicating the outcome of the investigations of both those who would endorse and those who would deny the premises of the Early Catholicism Hypothesis. By postulating that differences from so-called authentic Pauline letters in Ephesians are merely as a result of addressing a different contingent situation, as well as by accepting that the composite eschatological profile in Ephesians is merely an adaptation of Pauline eschatology to that specific contingent situation, it is argued that it is possible to retain futuristic eschatological dimensions in Ephesians

Umbilical Hernia Incarceration: A Complication of Medical Therapy of Ascites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73352/1/j.1572-0241.1983.tb01875.x.pd

Shape-memory polymers as flexible resonator substrates for continuously tunable organic DFB lasers

We introduce shape-memory polymers (SMP) as substrate material for active optical devices. As an exemplary application we build a tunable organic semiconductor distributed feedback (DFB) laser. Hence, we transfer a second order Bragg grating with a period of 400 nm into SMP foils by hot embossing. The composite organic gain medium Alq3:DCM evaporated on the SMP substrate serves as laser active material. Mechanical stretching of the substrate increases the grating period temporarily and triggering the shape-memory effect afterwards reduces the period on demand. In this way, we can adjust the grating period to achieve a broad continuously tuning of the laser emission wavelength by 30 nm

Defects of the Broad Ligament of the Uterus

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74780/1/j.1572-0241.1986.tb01505.x.pd

KKbar molecules with momentum-dependent interactions

It is shown that the momentum-dependent kaon-antikaon interactions generated via vector meson exchange from the standard SU_V(3) x SU_A(3) interaction Lagrangian lead to a non-local potential in coordinate space that can be incorporated without approximation into a non-relativistic version of the Bethe-Salpeter wave equation containing a radial-dependent effective kaon mass appearing in a fully symmetrized kinetic energy operator, in addition to a local potential. Estimates of the mass and decay widths of f_0(980) and a_0(980), considered as KKbar molecules of isospin 0 and 1, as well as for K^+K^- atomic bound states (kaonium) are presented, and compared with previous studies of a similar nature. It is argued that without a better knowledge of hadronic form factors it is not possible to distinguish between the molecular versus elementary particle models for the structure of the light scalar mesons.Comment: 14 pages, 2 tables, 5 figures. Added subsection on s-channel exchange, additional remarks on the possible effect of gluon exchange, and 1 additional figur