Relation between Scattering and Production Amplitude - Case of Intermediate \sigma-Particle in \pi\pi-System

The relation between scattering and production amplitudes are investigated, using a simple field theoretical model, from the general viewpoint of unitarity and the applicability of final state interaction(FSI-) theorem. The IA-method and VMW-method, which are applied to our phenomenological analyses suggesting the \sigma-existence, are obtained as the physical state representations of scattering and production amplitudes, respectively. Moreover, the VMW-method is shown to be an effective method to obtain the resonance properties from general production processes, while the conventional analyses based on the ``universality'' of \pi\pi-scattering amplitude are powerless for this purpose.Comment: Talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL, August 1997. 4 pages with no figur

Re-analysis of \pi\pi / K\pi Phase Shift and Existence of \sigma$(600) / \kappa(900)-Particle

Re-analyzing the old phase shift data of I=0, \pi\pi (I=1/2, K\pi) scattering, we show an evidence for existence of the \sigma-particle (\kappa-particle) with a comparatively light mass, which has been missing for a long time: In the analysis we have applied a new method of interfering Breit-Wigner amplitudes, which makes the scattering amplitude parametrized in terms of only physical quantities, mass and width of resonant particles, in conformity with unitarity. We have introduced phenomenologically a background phase shift \delta_{BG} of repulsive core type. The \chi^2-fits of the both \pi\pi- and K\pi- phase shifts are improved greatly with the \delta_{BG} over the conventional fits without it.Comment: Talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL, August 1997. 4 pages with 3 eps figure

Further Analysis on \sigma-particle Properties

In a previous work, we have reanalyzed the I=0 S-wave \pi\pi-scattering phase-shift through a new method of Interfering Breit-Wigner amplitudes, and have shown the existence of a light scalar, \sigma particle, accompanied by a negative "repulsive core"-type background phase-shift, whose origin may have some correspondence to a ``compensating'' \pi\pi contact interaction. In this work we make further analysis on the phase shift under KKbar threshold from the same standpoint, to determine precise values of \sigma mass and width, so far as present experimental data are concerned.Comment: Updated with recent progres

The First Results of K2K long-baseline Neutrino Oscillation Experiment

The first results of the K2K(KEK to Kamioka) long-baseline neutrino oscillation experiment are presented in this talk. In 1999 7.2x10^18 protons on target were delivered to the experiment. During this period of running there were 3 events fully contained in the Super-Kamiokande inner detector fiducial area which occurred during the beam spill timing window. In the case of no oscillations the expected number of events during this period was 12.3+1.7-1.9. The near detectors located at KEK also have begun detailed measurements of neutrino interactions in water at around 1 GeV.Comment: 5 pages, 5 figures, Talk at the 7th Conference On Intersections Between Particle And Nuclear Physics (CIPANP2000), 25-28 May 2000, Quebec, Canad

Relation between Scattering and Production Amplitudes - concerning sigma Particle in pi pi System -

In a series of previous papers the present authors and collaborators have shown strong evidence for existence of the long-sought sigma-particle by analyzing the pi pi-scattering and pi pi-production processes, applying, respectively, the IA method and the VMW method. In this paper we examine the relation between the scattering amplitude T and the production amplitude F from the viewpoint of the unitarity and the final state interaction (FSI) theorem by using a simple field theoretical model. As a result it is shown that the amplitudes in the physical state representation are directly represented through the Breit-Wigner amplitudes of the relevant resonances, and the respective forms of T and F coincide with those in the IA and VMW methods, justifying our methods of analyses.Comment: 14 pages, 5 eps figures, uses ptptex.sty. To be published in Progress of Theoretical Physic

\sigma-Particle in Production Processes

A S-wave \pi\pi resonance below 1 GeV/c^2, sigma has been observed in analyses of the phase shift data of \pi\pi scatterings. It is important to observe it in production processes. A huge events of \pi^0\pi^0 below 1 GeV/c^2 is seen in the central production of the GAMS experiment. Its mass spectrum is well described by the variant mass and width method (VMW) including f_0(980), f_2(1270) and a S-wave resonance which might be assigned to be a sigma. We report here that the angular distributions of the \pi^0\pi^0 system are also described with the S-wave resonance interfering with f_0(980) and the tail of f_2(1270) by VMW. The same method is applied to the \pi^+\pi^- data of J/\psi \to \omega\pi\pi decay, and is shown that not only \pi^+\pi^- mass spectrum but also its cos\theta_\pi distributions are described well.Comment: Talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL, August 1997. 4 pages with 2 eps figure