Related papers: Effect of light sigma-meson Production in ppbar --…
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…
We adopt a novel formalism for the low-energy analysis of the $\gamma p \to K^{+}\pi\Sigma$ photoproduction reaction to calculate the $\pi\Sigma$ invariant mass distributions in the $\Lambda(1405)$ resonance region. The approach adheres to…
Photoproduction of pi0 mesons was studied with the Crystal-Barrel detector at ELSA for incident energies from 300 MeV to 3 GeV. Differential cross sections d sigma /d Omega, d sigma/d t, and the total cross section are presented. For…
The analysis of the poles of the $\pi\pi$ scattering amplitude is shown to favour a dynamical origin of the sigma meson: it is created by a strongly attractive $\pi\pi$ interaction in the $J^{PC}=0^{++}I=0$ channel. In the limit…
We analyze the pi pi production amplitudes in the excited Upsilon decay processes, Upsilon(2S)-->Upsilon(1S)pi+pi-, Upsilon(3S)-->Upsilon(1S)pi+pi- and Upsilon(3S)-->Upsilon(2S)pi+pi-, and the pi pi and KKbar production amplitudes in the…
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…
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…
The results of analyses obtained in Part I are examined from the viewpoint of chiral symmetry. The mass spectra of pi pi system are widely believed to be suppressed generally near the threshold, because of the derivative coupling property…
Our method of analysis, which led to existence of sigma and kappa mesons, is reviewed and examined from a viewpoint of general S-matrix. It is shown that the method is consistent with the constraints from chiral symmetry and unitarity.…
For the study of the $\Sigma$ resonances, we analyze the differential cross sections and $\Lambda$ polarizations for the reactions $K^-n\to\pi^-\Lambda$ and $K^-p\to\pi^0\Lambda$ with an effective Lagrangian approach. Data of an early…
On the basis of a simultaneous description of the isoscalar s-wave channel of the $\pi\pi$ scattering (from the threshold up to 1.9 GeV) and of the $\pi\pi\to K\bar{K}$ process (from the threshold to $\sim$ 1.4 GeV) in the model-independent…
The Crystal Ball Collaboration has recently reported the differential cross sections and $\Lambda$ polarization for the reaction $K^-p\rightarrow \pi^0\Lambda$ using an incident $K^-$ beam with momenta between 514 and 750 MeV/$c$. We make a…
The light scalar meson sigma(600) is known to appear at low excitation energy with very large width on top of continuum states. We investigate it in the QCD sum rule as an example of resonance structures appearing above the corresponding…
Photo- and electroproduction of $K\Sigma$ have been investigated near their production thresholds by using an effective Lagrangian approach. For this purpose, the background amplitude is constructed from suitable Feynman diagrams, whereas…
The sigma meson mass and width are studied at finite baryonic density in the framework of a chiral unitary approach which successfully reproduces the meson meson phase shifts and generates the f0 and sigma resonances in vacuum.
The recent experimental data of both pipi / Kpi scattering and production processes, suggesting the existence of scalar sigma and kappa mesons, are reviewed. In many pipi /Kpi production processes the direct effects of their productions are…
The meson meson interaction in the scalar isoscalar channel at finite baryonic density is studied in the framework of a chiral unitary approach which generates the f0 and sigma resonances and reproduces well the meson meson phase shifts in…
New Crystal Barrel data are reported for pbar-p -> omega-eta and pbar-p -> omega-pizero-pizero with omega decaying to piplus-piminus-pizero. The omega-eta data confirm angular distributions obtained earlier from data where omega ->…
Photoproduction of pi0-eta on protons in the energy range from threshold to 1.4 GeV is discussed. The data for representative angular distributions recently obtained at MAMI C are analyzed using an isobar model. The isobars considered are…
The $s-$wave meson-baryon scattering is analyzed for the isospin-strangeness $I=1/2, S=0$ and $I=0,S=-1$ sectors, in a Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry. For both sectors, four channels have been…