Browsing by Author "Selam C."

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    Nuclear matrix elements of double beta decay in deformed nuclei
    (2003) Selam C.; Küçükbursa A.; Bircan H.; Aygör H.A.; Babacan T.; Maraş I.; Kökçe A.
    Nuclear matrix elements (MGT for two-neutrino double beta transitions of selected nuclei were calculated via a QRPA approach by considering the charge-exchange spin-spin interactions in the particle-hole channel among nucleons. Calculations were performed for both spherical and deformed cases of nuclei. As a result of these calculations, it has been seen that, although the value of the nuclear matrix elements in deformation case are 2-4 times smaller when compared with that of the spherical case, it is still 2-8 times greater than the experimental values.
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    The investigation of the log(ft) values for the allowed Gamow-Teller transitions of some deformed nuclei
    (Association for Scientific Research, 2004) Selam C.; Babacan T.; Aygör H.A.; Bircan H.; Küçükbursa A.; Maraş I.
    The log(ft) values of allowed β± decay between odd-A nuclei for 125≤A≤180 mass region are investigated. Single particle energies and wave functions are calculated by making use of a deformed Woods-Saxon potential. The calculations are performed in the framework of proton-neutron quasi particle random phase approximation (QRPA) including the schematic residual spin-isospin interaction among the nucleons in the particle hole channel. The calculations indicated that the results obtained through using the ΧGT=5.2/A0.7 are more in agreement with experimental observations.
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    The isospin admixture of the ground state and the properties of the isobar analog resonances in deformed nuclei
    (American Institute of Physics Inc., 2008) Aygor H.A.; Cakmak N.; Maras I.; Selam C.
    Within quasiparticle random phase approximation (QRPA), Pyatov-Salamov method for the self-consistent determination of the isovector effective interaction strength parameter, restoring a broken isotopic symmetry for the nuclear part of the Hamiltonian, is used. The isospin admixtures in the ground state of the parent nucleus, and the isospin structure of the isobar analog resonance (IAR) state are investigated by including the pairing correlations between nucleons for 72-80Kr isotopes. Our results are compared with the spherical case and with other theoretical results. © 2008 American Institute of Physics.
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    The investigation of the 2νββ decay by Pyatov method within quasiparticle random phase approximation formalism
    (2008) Unlu S.; Babacan T.; Cakmak N.; Selam C.
    The violated commutation condition between the total shell model Hamiltonian and Garnow-Teller operator (GT) has been restored by Pyatov method (PM). The considered nuclear model Hamiltonian in PM includes the separable GT residual interaction in ph and pp channels and is differentiated from the traditional schematic model by ho (restoration term). The influence of the ho effective interaction on the 2νββ decay of 48Ca, 70Ge, 82Se, 96Zr, 100Mo, 116Cd, 128,130Te and 136Xe is investigated. All the calculations have been done within the framework of standard QRPA. The results obtained by PM are compared with those of other approaches and experimental data. The influence of the restoration term on the stability of the 2νββ decay nuclear matrix elements is analysed. © Indian Academy of Sciences.
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    Study of Gamow-Teller transitions in isotopes of titanium within the quasi particle random phase approximation
    (Kluwer Academic Publishers, 2014) Cakmak S.; Nabi J.-U.; Babacan T.; Selam C.
    The Gamow-Teller (GT) transition is inarguably one of the most important nuclear weak transitions of the spin-isospin στ type. It has many applications in nuclear and astrophysics. These include, but are not limited to, r-process β-decays, stellar electron captures, neutrino cooling rates, neutrino absorption and inelastic scattering on nuclei. The quasiparticle random phase approximation (QRPA) is an efficient way to generate GT strength distribution. In order to better understand both theoretical systematics and uncertainties, we compare the GT strength distributions, centroid and width calculations for 40-60Ts isotopes, using the pn-QRPA, Pyatov method (PM) and the Schematic model (SM). The pn-QRPA and SM are further sub-divided into three categories in order to highlight the role of particle-particle (pp) force and deformation of the nucleus in the GT strength calculations. In PM, we study only the influence of the pp force in the calculation. We also compare with experimental results and other calculations where available. We found that the inclusion of pp force and deformation significantly improves the performance of SM and pn-QRPA models. Incorporation of pp force leads to pinning down the centroid value in the PM. The calculated GT strength functions using the pn-QRPA (C) and SM (C) models are in reasonable agreement with measured data. © 2014 Springer Science+Business Media Dordrecht.