A Feynman graph selection tool in GRACE system

We present a Feynman graph selection tool {\tt grcsel}, which is an interpreter written in C language. In the framework of {\tt GRACE}, it enables us to get a subset of Feynman graphs according to given conditions.Comment: 3 pages, 2 figures, Latex, ACAT200

Neutrino Oscillations in Intermediate States.II -- Wave Packets

We analyze oscillations of intermediate neutrinos in terms of the scattering of particles described by Gaussian wave packets. We study a scalar model as in a previous paper (I) but in realistic situations, where the two particles of the initial state and final state are wave packets and neutrinos are in the intermediate state. The oscillation of the intermediate neutrino is found from the time evolution of the total transition probability between the initial state and final state. The effect of a finite lifetime and a finite relaxation time are also studied. We find that the oscillation pattern depends on the magnitude of wave packet sizes of particles in the initial state and final state and the lifetime of the initial particle. For $\Delta m^2_{21}=3\times 10^{-2}$ eV$^2$, the oscillation probability deviates from that of the standard formula if the wave packet sizes are around $10^{-13}$ m for 0.4 MeV neutrino.Comment: 29 pages, 11 figures. typos corrected, appendix adde

Evidence for Narrow S=+1 Baryon Resonance in Photo-production from Neutron

The gamma n -> K+ K- n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54 +- 0.01 GeV with a width smaller than 25 MeV and a Gaussian significance of 4.6 sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic 5-quark state (uudd{s_bar}) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an anti-decuplet of baryons predicted by the chiral soliton model.Comment: 12 pages, 3 encapsulated postscript figure

Operation of Faddeev-Kernel in Configuration Space

We present a practical method to solve Faddeev three-body equations at energies above three-body breakup threshold as integral equations in coordinate space. This is an extension of previously used method for bound states and scattering states below three-body breakup threshold energy. We show that breakup components in three-body reactions produce long-range effects on Faddeev integral kernels in coordinate space, and propose numerical procedures to treat these effects. Using these techniques, we solve Faddeev equations for neutron-deuteron scattering to compare with benchmark solutions.Comment: 20 pages, 8 figures, to be published in Few-Body System