Toshihiko Komada

Effect of Light .SIGMA.-Meson Production in pp .RAR. 3.PI.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.

The σ‐Meson Production in Excited Υ Decay Processes

We analyze the ππ production amplitudes in the excited Υ decay processes, Υ(2S) → Υ(1S)π+π−, Υ(3S) → Υ(1S)π+π− and Υ(3S) → Υ(2S)π+π−, and the ππ and KK production amplitudes in the charmonium decay processes, ψ(2S) → J/ψπ+π− and J/ψ → φπ+π−, φK+K−, including the possible effect of light σ production. The amplitudes are parametrized by the sum of Breit‐Wigner amplitudes for the σ and the other relevant particles and of the direct 2π‐production amplitude, following the VMW method. All the ππ (and KK) mass spectra are reproduced well with the obtained values of σ‐parameters, mσ = 526−37+48MeV and Γσ = 301−100+145MeV, which is almost consistent with the values in our previous phase shift analyses.

Indications for the Existence of Chiral Particles: the Axial-Vector D1χ and the Scalar B0χ

In a covariant level-classification scheme of hadrons proposed recently, the existence of “chiral particles”, scalar and axial-vector mesons as the partners of the ground-state pseudo-scalar and vector mesons, respectively, were predicted in D and B meson systems, realizing a linear representation of chiral symmetry concerning the light quark. In this work we reanalyze the D^*π mass spectra obtained through Υ(4S) and Z^0 decay and the Bπ spectra obtained through Z^0 decay to show the possibility of the existence of D_1^χ and B_0^χ, respectively.

An extra vector state at a lower mass, ω(1250) in a re-analysis of e+e− annihilation data

The combined data of cross section of the process, e+ e− → π+ π− π0 obtained by SND and BaBar in the energy region s from the threshold to 2 GeV are analyzed to study I=0 vector states in the energy region s between 1 and 2 GeV. Two ω states, ω(1) and ω(2) between 1 and 2 GeV and a direct decay amplitude as well as ω and ϕ are considered to contribute to the process. We carefully searched for the solution not only below 180° of a relative phase between ω and ϕ amplitudes, θϕ but also above 180°. We have obtained solutions for mass and width values of two ω states, one around 1200 MeV with width 700 MeV, and the other around 1600 MeV with width 125 MeV, respectively, in the region of θϕ above 180°. The state around 1200 MeV seems to be different from the ω(1420) listed in the PDG tables.

Indication of Existence of Low Mass Extra Vector Mesons, ω(1250) and ρ(1250), expected in the Ũ(12)‐Classification Scheme of Hadrons

Mass distributions of π+π−π0 and ωπ0 systems obtained by several experiments are analyzed. We obtain indication of extra vector mesons ω(1250) and ρ(1250) in lower mass region. Those state are expected to exist in the Ũ(12)‐classification scheme.

Possible Evidence for a Chiral Axial‐Vector State in the D Meson System

We reanalyze the D^{*+} pi^- mass spectrum from CLEO II by the VMW method in order to examine the existence of a chiral axial-vector state, which is predicted in a covariant level-classification scheme recently proposed, other than normal orbitally-excited P-wave states in the D meson system. A result of the present analysis seems to suggest that there exists an extra axial-vector meson, in addition to the two normal ones, in a similar mass region.

Confirmation of σ(450–600)‐Meson in Υ′ → Υππ & Other ππ‐Production Processes

Applying the effective amplitude, which is evidently consistent with general constraints from chiral symmetry, the ππ spectra in the relevant processes are analyzed, leading to a strong evidence for existence of the light σ meson. It is also pointed out that the ππ scattering process, which had been one of the main sources for PDG table for these many years, is, in principle, exceptionally difficult to investigate the property of σ‐meson.Applying the effective amplitude, which is evidently consistent with general constraints from chiral symmetry, the pipi spectra in the relevant processes are analyzed, leading to a strong evidence for existence of the light sigma meson. It is also pointed out that the pipi scattering process, which had been one of the main sources for PDG table for these many years, is, in principle, exceptionally difficult to investigate the property of sigma-meson.

Effect of σ(600)-production in pp → 3π0 at rest

The pi0 pi0 mass spectra and angular distributions around KK_bar-threshold and at 1.5 GeV in pp_bar(at rest) to 3pi0 in the Crystal Barrel experiment are reanalyzed by applying the new method, which is consistent with unitarity of S-matrix and expressed directly by resonance parameters. The effects of light sigma-meson production are clearly seen to improve the fit with sigma, in comparing with the fit without sigma.

Effect of sigma(600)-Production in pp_bar to 3pi0 at rest

The pi0 pi0 mass spectra and angular distributions around KK_bar-threshold and at 1.5 GeV in pp_bar(at rest) to 3pi0 in the Crystal Barrel experiment are reanalyzed by applying the new method, which is consistent with unitarity of S-matrix and expressed directly by resonance parameters. The effects of light sigma-meson production are clearly seen to improve the fit with sigma, in comparing with the fit without sigma.