arXiv subjects

R. Kaminski

Publications and source records attributed to R. Kaminski.

60 records · Page 4Linked to original sources

arXiv1997

New Solutions for Scalar-Isoscalar pi-pi Phase Shifts

The scalar-isoscalar pi-pi phase shifts are calculated in the pi-pi energy range from 600 MeV to 1600 MeV. We use results of the CERN-Cracow-Munich collaboration for the reaction pi^- p --> pi^+ pi^- n on a transversely polarized target at 17.2 GeV/c pi^- momentum. Energy-independent separation of the S-wave pseudoscalar amplitude (pi exchange) from the pseudovector amplitude (a_1 exchange) is carried out. Below the KK threshold we find two solutions for the pi-pi phase shifts, for which the phases increase slower with the effective pi-pi mass than the P-wave phases ("flat" solutions) and two solutions for which the phases increase faster than the P-wave phases ("steep" solutions). Above 1420 MeV both sets of phase shifts increase with energy faster than in the experiment on an unpolarized target. This fact can be related to a presence of the scalar resonance f_0(1500).

hep-ph↗

arXiv1997

Analysis of New Results For Scalar-Isoscalar pi-pi Phase Shifts

The scalar -- isoscalar pi-pi phase shifts are analysed using a separable potential model of three coupled channels (pipi, KK and an effective 2pi2pi system). Model parameters are fitted to two sets of solutions obtained in a recent analysis of the CERN-Cracow-Munich measurements of the pi^- p --> pi^+ pi^- n reaction on a polarized target. A relatively narrow (90 -- 180 MeV) scalar resonance f_0(1400-1460) is found, together with a wide f_0(500) (Gamma = 500 MeV) and the narrow f_0(980) state.

hep-ph↗

arXiv1997

Three channel model of meson-meson scattering and scalar meson spectroscopy

New solutions on the scalar -- isoscalar $ππ$ phase shifts are analysed together with previous $K\bar{K}$ results using a separable potential model of three coupled channels ($ππ$, $K\bar{K}$ and an effective $2π2π$ system). Model parameters are fitted to two sets of solutions obtained in a recent analysis of the CERN-Cracow-Munich measurements of the $π^- p_{\uparrow} \to π^+ π^- n$ reaction on a polarized target. A relatively narrow (90 -- 180 MeV) scalar resonance $f_0(1400-1460)$ is found, in contrast to a much broader ($Γ\approx 500$ MeV) state emerging from the analysis of previous unpolarized target data.

hep-ph↗

arXiv1997

Separation of S- wave pseudoscalar and pseudovector amplitudes in pi^- p---> pi^+ pi^- n reaction on polarized target

A new analysis of S-wave production amplitudes for the reaction $π^- p_{\uparrow} \rightarrow π^+ π^- n$ on a transversely polarized target is performed. It is based on the results obtained by the CERN-Cracow -Munich collaboration in the pion-pion energy range from 600 MeV to 1600 MeV at 17.2 GeV/c $π^-$ momentum. Energy-independent separation of the S-wave pseudoscalar amplitude ($π$ exchange) from the pseudovector amplitude ($a_{1}$ exchange) is carried out using assumptions much weaker than those in all previous analyses. We show that, especially around 1000 MeV and around 1500 MeV, the $a_{1}$ exchange amplitude cannot be neglected. The scalar-isoscalar $ππ$ phase shifts are calculated using fairly weak assumptions. Below the $K\overline{K}$ threshold we find two solutions for the $π-π$ phase shifts, for which the phases increase slower with the effective $π-π$ mass than the P-wave phases. Both solutions are consistent with a broad $f_{0}(500)$ but only one is similar to the well-known "down" solution. We find also the third solution (with a somewhat puzzling behavior of inelasticity) which exhibits a narrow $f_{0}(750)$ claimed by Svec. All the solutions undergo a rapid change at the $K\overline{K}$ threshold. Above 1420 MeV the phase shifts increase with energy faster than those obtained without the polarized-target data. This phase behavior as well as an increase of the modulus of the $a_{1}$-exchange amplitude can be due to the presence of the $f_{0}(1500)$.

hep-ph↗

arXiv1994

Low Energy Parameters of the KK and Pipi Scalar-Isoscalar Interactions

Threshold expansions of the $ππ$ and $K\overline{K}$ spin 0 and isospin 0 scattering amplitudes are performed. Scattering lengths, effective ranges and so--called volume parameters are evaluated. Good agreement with the existing experimental data for the $ππ$ scalar--isoscalar amplitude is found. An importance of future accurate measurements of the $K\overline{K}$ threshold parameters is stressed. New data are needed to understand the basic features of the scalar mesons.

hep-ph↗

arXiv1994

Relativistic Effects in the Scalar Meson Dynamics

A separable potential formalism is used to describe the $ππ$ and $K\overline{K}$ interactions in the scalar-isoscalar states in the energy range from the $ππ$ threshold up to 1.4 GeV. Introduction of relativistic propagators into a system of Lippmann-Schwinger equations leads to a very good description of the data ($χ^{2}=0.93$ per one degree of freedom). Three poles are found in this energy region: fo(500) ($M=506\pm 10$ MeV, $Γ=494\pm 5$ MeV), fo(975) ($M=973\pm 2$ MeV, $Γ=29\pm 2$ MeV) and fo(1400) ($M=1430\pm 5$ MeV, $Γ=145\pm 25$ MeV). The fo(975) state can be interpreted as a $K\overline{K}$ bound state. The fo(500) state may be associated with the often postulated very broad scalar resonance under the $K\overline{K}$ threshold (sometimes called $σ$ or $ε$ meson). The scattering lengths in the $ππ$ and $K\overline{K}$ channels have also been obtained. The relativistic approach provides qualitatively new results (e.g. the appearance of the fo(500)) in comparison with previously used nonrelativistic approach.

hep-ph↗