arXiv subjects

O. Yilmaz

Publications and source records attributed to O. Yilmaz.

At least 37 records · Page 2Linked to original sources

arXiv2008

Quantal Effects on Spinodal Instabilities in Charge Asymmetric Nuclear Matter

Quantal effects on growth of spinodal instabilities in charge asymmetric nuclear matter are investigated in the framework of a stochastic mean field approach. Due to quantal effects, in both symmetric and asymmetric matter, dominant unstable modes shift towards longer wavelengths and modes with wave numbers larger than the Fermi momentum are strongly suppressed. As a result of quantum statistical effects, in particular at lower temperatures, magnitude of density fluctuations grows larger than those calculated in semi-classical approximation.

nucl-th↗

arXiv2007

Scalar mesons in radiative ϕ\to K^0\bar{K}^0γdecay

We study the radiative $ϕ\to K^0\bar{K}^0γ$ decay within a phenomenological framework by considering the contributions of the $f_{0}(980)$ and $a_{0}(980)$ scalar resonances. We calculate the branching ratio $B(ϕ\to K^0\bar{K}^0γ)$ by employing the coupling constants $g_{f_0K^{+}K^{-}}$ and $g_{a_0K^{+}K^{-}}$ as determined by different experimental groups.

hep-ph↗

arXiv2006

Spin-Dependent Quantized Magnetic Flux Through The Electronic Orbits of Dirac Hydrogen Atom

We investigate the quantized magnetic flux through the electronic orbits of Dirac hydrogen atom in the absence of an external magnetic field. The sources of the magnetic fields are taken to be that of proton's magnetic moment $μ_{p}$ and electron's magnetic moment $μ_{e}$ (or $μ_{j}$) which has two components namely the orbital part $μ_{l}$ and the spinning part $μ_{s}$ >.We show that the quantized magnetic fluxes through the electronic orbits corresponding to the ($n,l=n-1,m_{j}$) eigenstates of Dirac hydrogen atom take the forms: $Φ(n,l,m_{j})=[ n-l-m_{j}] Φ_{0}$, where $Φ_{0}=\frac{h}{| e|}$ is the flux quanta. The application of the present result to the selection rules for the optical transitions of hydrogen atom gives access to the spin flip-floppings. The present result is believed to serve a significant help for understanding the recent observations of spin relaxation in excitonic transitions (such as 1s -> 2p or 2p -> 3d) in nanostructures.

physics.atom-ph↗

arXiv2005

Quantum Statistical Effects on Fusion Dynamics of Heavy-Ions

In order to describe the fusion of two very heavy nuclei at near barrier energies, a generalized Langevin approach is proposed, which incorporates the quantum statistical fluctuations in accordance with the fluctuation and dissipation theorem. It is illustrated that the quantum statistical effects introduce an enhancement of the formation of compound nucleus, though the quantum enhancement is somewhat less pronounced as indicated in the previous calculations.

nucl-th↗

arXiv2004

An analysis of f_0-sigma mixing in light cone QCD sum rules

We investigate f_0-sigma mixing in the framework of light cone QCD sum rules and by employing the experimental results about the decay widths and the masses of these scalar mesons we estimate the scalar mixing angle by using sigma meson data and f_0 meson data. The two values we thus obtain of the scalar mixing angle are not entirely consistent with each other, possibly indicating that the structure of these mesons cannot be simple quark-antiquark states.

hep-ph↗

arXiv2003

The $a_0K^+K^-$-vertex in light cone QCD sum rules

We investigate the $a_0K^+K^-$-vertex in the framework of light cone QCD sum rules. We estimate the coupling constant g$_{a_0K^+K^-}$ which is an essential ingredient in the analysis of physical processes involving $a_0(980)$ meson. Our result is somewhat larger than the previous determinations of this coupling constant.

hep-ph↗

arXiv2003

Sigma-meson and omega-rho mixing effects in omega --> pi^+ pi^- gamma decay

We calculate the branching ratio of omega --> pi^+ pi^- gamma decay in a phenomenological framework in which the contributions of VMD, chiral loops, sigma-meson intermediate state amplitudes and the effects of omega-rho mixing are considered. We conclude that the sigma-meson intermediate state amplitude and omega-rho mixing make substantial contribution to the branching ratio.

hep-ph↗

arXiv2003

VMD, chiral loops, sigma-meson, and omega-rho mixing in omega-->pi^0 pi^0 gamma decay

In an attempt to explain the latest experimental result about the branching ratio of $ω\to π^0π^0γ$ decay we reexamine the decay mechanism of this decay in a phenomenological framework in which the contributions of VMD, chiral loops, $σ$-meson intermediate state amplitudes and the effects of $ω-ρ$ mixing are considered. We conclude that in order to obtain the experimental value of the branching ratio $B(ω\to π^0π^0γ)$ $σ$-meson amplitude which makes a substantial contribution should be included into the reaction mechanism and the effects of $ω-ρ$ mixing should be taken into account. We also estimate the coupling constant $g_{ωσγ}$ as $g_{ωσγ}=0.11$ which is much smaller than the values suggested by light cone QCD sum rules calculations.

hep-ph↗

arXiv2003

Scalar sigma meson effects in radiative rho^0-meson decays

We study the radiative $ρ^0\to π^+π^-γ$ and $ρ^0\to π^0π^0γ$ decays and we calculate their branching ratios using a phenomenological approach by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of $σ$-meson intermediate state. Our results for the branching ratios are in good agreement with the experimental values.

hep-ph↗

arXiv2002

Scalar $a_0(980)$ meson in $ϕ\to π^{0}ηγ$ decay

We study the radiative decay $ϕ\toπ^{0}ηγ$ within the framework of a phenomenological approach in which the contributions of $ρ$-meson, chiral loop and $a_0$-meson are considered. We analyze the interference effects between different contributions and utilizing the experimental branching ratio and invariant $π^0η$ mass spectrum for $ϕ\toπ^{0}ηγ$ decay we estimate the branching ratio of $ϕ\to a_0γ$ decay.

hep-ph↗

arXiv2002

Collisional Effects in Isovector Response Function of Nuclear Matter at Finite Temperature

The dipole response function of nuclear matter at zero and finite temperatures is investigated by employing the linearized version of the extended TDHF theory with a non-Markovian binary collision term. Calculations are carried out for nuclear dipole vibrations by employing the Steinwedel-Jensen model and compared with experimental results for $^{120}Sn$ and $^{208}Pb$.

nucl-th↗

arXiv2002

The $ωσγ$-vertex in light cone QCD sum rules

We investigate the $ωσγ$-vertex and estimate the coupling constant g$_{ωσγ}$ in the framework of the light cone QCD sum rules. We compare our result with the values of this coupling constant deduced from a phenomenological analysis of $ω\toππγ$ decays.

hep-ph↗

arXiv2001

The $ϕa_0γ$- and $ϕσγ$-vertices in light cone QCD

We study $ϕa_0γ$- and $ϕσγ$-vertices in the framework of the light cone QCD sum rules and we estimate the coupling constants g$_{ϕa_0γ}$ and g$_{ϕσγ}$ utilizing $ωϕ$-mixing. We compare our results with the previous estimations of these coupling constants in the literature obtained from phenomenological considerations.

hep-ph↗

arXiv2001

$ω$-Meson Photoproduction on Nucleons In the Near Threshold Region

The $ω$-meson photoproduction, $γ+p\to p+ω$, is studied in the framework of a model, containing $π$-meson exchange in t-channel and nucleon-exchange in s- and u-channels. Considering both $ωNN$-coupling constants in the region of time-like meson four momenta as the free parameters, we find different sets of solutions for these constants from the existing data on the t-dependence of the differential cross sections, $dσ(γ+p\to p+ω)/dt$, in the near threshold region $E_γ\leq 2$ GeV. These sets of $ωNN$-coupling constants, corresponding to destructive and constructive $π\bigotimes N$-interference contributions to $dσ/dt$ can be well distinguished by measurements of beam asymmetry, induced by linear photon polarization.

nucl-th↗

arXiv2001

A Theoretical Study of $ρ^{0}$-Photoproduction on Nucleons near Threshold

We investigate the possibility that the process of $ρ^{0}$-meson photoproduction on proton, $γ+p\to p+ρ^{0}$, in the near threshold region $E_γ< 2$ GeV, can be considered in the framework of model with $π$-, $σ$- and N-exchanges. This suggestion is based on a study of the t-dependence of differential cross section, $dσ(γp \to p ρ^{0})/dt$, which has been measured by SAPHIR Collaboration. We find that the suggested model provides a good description of the experimental data with new values of $ρNN$-coupling constants in the region of the time-like $ρ^{0}$-meson momentum. Our results suggest that such model can be considered as a suitable nonresonant background mechanism for the future discussion of possible role of nucleon resonance contributions. Our predictions for $ρ^{0}$-meson photoproduction on neutron target and for beam asymmetry on both proton and neutron targets are presented.

nucl-th↗

arXiv2001

Coupling constants g$_{a_0ωγ}$ and g$_{a_0ργ}$ as derived from QCD sum rules

We consider the two point correlation function of scalar current in QCD sum rules approach to estimate the overlap amplitude of $a_0$ meson. We then employ QCD sum rules to calculate the coupling constants g$_{ωa_0γ}$ and g$_{ρa_0γ}$ by studying the three point ${a_0ωγ}$- and ${a_0ργ}$-correlation functions.

hep-ph↗

arXiv2001

Interference effects in the decay ϕ\to π^{0}π^{0}γand the coupling constant g_{ϕσγ}

We study the radiative decay $ϕ\toπ^{0}π^{0}γ$ within the framework of a phenomenological approach in which the contributions of $σ$-meson, $ρ$-meson and $f_0$-meson are considered. We analyze the interference effects between different contributions and utilizing the experimental branching ratio for this decay we estimate the coupling constant $g_{ϕσγ}$.

hep-ph↗

arXiv2001

The coupling constant g$_{ρσγ}$ as derived from QCD sum rules

We employ QCD sum rules to calculate the coupling constant g$_{ρσγ}$ by studying the three point ${ρσγ}$-correlation function. Our results is consistent with the value of this coupling constant obtained using vector meson dominance of the electromagnetic current and the experimental $ρ^0$-photoproduction data.

hep-ph↗