arXiv subjects
Publications and source records attributed to O. Yilmaz.
We employ QCD sum rules to calculate the coupling constants g$_{ρπγ}$ and g$_{ωπγ}$ by studying the three point ${ρπγ}$- and ${ωπγ}$-correlation functions. Our results for the decay widths $Γ(ρ^0\to π^0γ)$ and $Γ(ω\to π^0γ)$ calculated using the obtained coupling constants are in good agreement with the experimental values of these decay widths.
Collisional damping widths of giant monopole and quadrupole excitations for $^{120}$Sn and $^{208}$Pb at zero and finite temperatures are calculated within Thomas-Fermi approximation by employing the microscopic in-medium cross-sections of Li and Machleidt and the phenomenological Skyrme and Gogny forces, and are compared with each other. The results for the collisional widths of giant monopole and quadrupole vibrations at zero temperature as a function of the mass number show that the collisional damping of giant monopole vibrations accounts for about 30-40% of the observed widths at zero temperature, while for giant quadrupole vibrations it accounts for only 20-30% of the observed widths of zero temperature.
We study the radiative decay $ρ^{0}\toπ^{0}π^{0}γ$ within the framework of a phenomenological approach in which the contributions of $σ$-meson and $ω$-meson intermediate states and of the pion-loops are considered. We conclude that the $σ$-meson amplitude provides the dominant contribution.
We study the $ω\toππγ$ decays by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of $σ$-meson intermediate state. We estimate the coupling constant $g_{ωσγ}$ utilizing the experimental value of the $ω\toπ^{0}π^{0}γ$ decay rate.
Production of supersymmetric particles in TeV scale polarized photon-proton collisions is discussed. Polarizations of both photon and proton beams are considered. Associated productions of squark-chargino and squark-gluino, and production of squark pairs have been examined. Although the cross sections for different initial beam polarizations do not differ much, the polarization asymmetry is sensitive to the sparticle mass. We conclude that the capacity of future linac-ring type TeV scale photon-proton colliders is quite promising in the search for SUSY particles.
The experimental branching ratio for the radiative decay $ρ^{0}\toπ^{+}+π^{-}+γ$ is used to estimate the coupling constant $g_{ρσγ}$ for a set of values of $σ$-meson parameters M$_σ$ and $Γ_σ$. Our results are quite different than the values of this constant used in the literature.
The associated production of squarks and charginos in high energy collisions of the polarized real photons and protons is discussed. We give the cross sections for different initial beam polarizations and the polarization asymmetries which can be used to anticipate the masses of squarks and charginos.
We employ the light cone QCD sum rules to calculate $ΔπN$ coupling constant by studying the two point correlation function between the vacuum and the pion state. Our result is consistent with the traditional QCD sum rules calculations and it is in agreement with the experimental value.
A detailed derivation of the collisional widths of collective vibrations is presented in both quantal and semi-classical frameworks by considering the linearized limits of the extended TDHF and the BUU model with a non-Markovian binary collision term. Damping widths of giant dipole and giant quadrupole excitations are calculated by employing an effective Skyrme force, and the results are compared with GDR measurements in Lead and Tin nuclei at finite temperature.