Shin Ishida

Analysis of a Kπ-Scattering Phase Shift and Evidence for the κ(900) Meson

Recently we have shown an evidence for existence of sigma-particle in the previous works; where the pipi S-wave phase shift is reanalyzed, by introducing a repulsive background suggested by the chiral symmetry, and by applying a new method of Interfering Breit-Wigner Amplitudes. In this work we also show, reanalyzing the Kpi S-wave phase shift from a similar standpoint, an evidence for existence of kappa(900), possibly to be a member of sigma-nonet.

π0π0 scattering amplitudes and phase shifts obtained by the π−p charge exchange process

Abstract The results of the analysis of the π0π0 scattering amplitudes obtained with π−p charge exchange reaction, π−p → π0π0n, data at 9 GeV/c are presented. The π0π0 scattering amplitudes show clear f0(1370) and f2(1270) signals in the S and D waves, respectively. The π0π0 scattering phase shifts have been obtained below K K threshold and been analyzed by the Interfering Amplitude method with introduction of negative background phases. The results show a S wave resonance, σ. Its Breit-Wigner parameters are in good agreement with those of our previous analysis on the π+π− phase shift data.

Re-analysis of ππ/Kπ phase shift and existence of σ(600)/κ(900)-particle

Re-analyzing the old phase shift data of I=0, pipi (I=1/2, Kpi) 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 pipi- and Kpi- phase shifts are improved greatly with the delta_{BG} over the conventional fits without it.

D[sub s1]∗](2710) and [sub D[sub sj]]∗](2860) in the Ũ(12)×O(3,1)-scheme

In order to classify the charmed‐strange mesons, including puzzling Ds0*(2317) and Ds1(2460), and recently observed Ds1*(2710) ans Dsj*(2860), we employ the Ũ(12)×O(3,1) level‐classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2)ρ, which leads to a number of extra states out of conventional SU(6)‐scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S‐ and P‐wave cs mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that Ds0*(2317) and Ds1(2460) are described as 1S0χ and 3S1χ chiralons, forming the SU(2)ρ doublet with the ground‐state Ds and Ds*, respectively. Furthermore, the observed decay properties of Ds1*(2710) is consistently explained as the vector chiralon 1P1χ. On the other hand, it is also found that the controversial narrow state, Dsj*(2860), does not fit as predicted properties of our P‐wave vector chiralon.In order to classify the charmed-strange mesons, including puzzling D{sub s0}*(2317) and D{sub s1}(2460), and recently observed D{sub s1}*(2710) ans D{sub sj}*(2860), we employ the U-tilde(12)xO(3,1) level-classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2){sub {rho}}, which leads to a number of extra states out of conventional SU(6)-scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S- and P-wave cs-bar mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that D{sub s0}*(2317) and D{sub s1}(2460) are described as {sup 1}S{sub 0}{sup {chi}}and {sup 3}S{sub 1}{sup {chi}}chiralons, forming the SU(2){sub {rho}}doublet with the ground-state D{sub s} and D{sub s}*, respectively. Furthermore, the observed decay properties of D{sub s1}*(2710) is consistently explained as the vector chiralon {sup 1}P{sub 1}{sup {chi}}. On the other hand, it is also found that the controversial narrow state, D{sub sj}*(2860), does not fit as predicted properties of our P-wave vector chiralon.

Effect of Light -Meson Production in pp-> 3 0 at Rest

The ππ mass spectra and angular distributions around the KK-threshold and at 1.5 GeV in pp (at rest) → 3π in the Crystal Barrel experiment are reanalyzed by applying a new method, which is consistent with the unitarity of the S-matrix and is expressed directly in terms of resonance parameters. The effects of light σ-meson production are clearly seen to improve the fit with σ in comparison with the fit without σ.

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, pipi (I=1/2, Kpi) 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 pipi- and Kpi- phase shifts are improved greatly with the delta_{BG} over the conventional fits without it.

Further Analysis on bcy Particle Properties

In a previous work, we have reanalyzed the I=0 S-wave pipi-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 pipi 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.