Browsing by Author "Babacan, T"

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    Gamow-Teller 1+ states in 208Bi -: art. no. 037303
    Babacan, T; Salamov, DI; Kücükbursa, A
    The properties of the Gamow-Teller (GT) 1(+) states in Bi-208 have been investigated by using the Pyatov-Salamov method. The GT resonance (GTR) energy, the contribution of the GTR beta transition strength to the Ikeda sum rule, and the differential cross sections for the Pb-208(p, n)Bi-208 and Pb-208(He-3, t)Bi-208 charge exchange reactions at different energies have been calculated. Our results show good agreement with experimental values.
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    Spin-isospin transitions in chromium isotopes within the quasiparticle random phase approximation
    Cakmak, S; Nabi, JU; Babacan, T; Maras, I
    Beta decay and electron capture on isotopes of chromium are advocated to play a key role in the stellar evolution process. In this paper we endeavor to study charge-changing transitions for 24 isotopes of chromium (Cr42-65). These include neutron-rich and neutron-deficient isotopes of chromium. Three different models from the QRPA genre, namely the pn-QRPA, the Pyatov method (PM) and the Schematic model (SM), were selected to calculate and study the Gamow Teller (GT) transitions in chromium isotopes. The SM was employed separately in the particle particle (pp) and pp + particle-hole (ph) channels. To study the effect of deformation, the SM was first used assuming the nuclei to be spherical and later to be deformed. The PM was used both in pp and pp + ph channels but only for the case of spherical nuclei. The pn-QRPA calculation was done by considering both pp and ph forces and taking deformation of nucleus into consideration. A recent study proved this version of pn-QRPA to be the best for calculation of GT strength distributions amongst the QRPA models. The pn-QRPA model calculated GT distributions had low-lying centroids and small widths as compared to other QRPA models. Our calculation results were also compared with other theoretical models and measurements wherever available. Our results are in decent agreement with previous measurements and shell model calculations. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.
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    The investigation of the 2vββ decay by Pyatov method within quasiparticle random phase approximation formalism
    Unlu, S; Babacan, T; Cakmak, N; Selam, C
    The violated commutation condition between the total shell model Hamiltonian and Gamow-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 h(0) (restoration term). The influence of the h(0) effective interaction on the 2 v 3 3 decay of Ca-48, Ge-76, Se-82, Zr-96, Mo-100, Cd-116, Te-128,Te-130 and Xe-136 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 2v beta beta decay nuclear matrix elements is analysed.
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    Calculation of the log(ft) values for the allowed Gamow- Teller transitions in deformed nuclei using the basis of Woods-Saxon wave functions
    Salamov, DI; Kücükbursa, A; Maras, I; Aygör, HA; Babacan, T; Bircan, H
    The present study investigates the log(ft) values of the allowed beta(+/-) decay between odd-A deformed nuclei in the atomic mass regions of 125 less than or equal to A less than or equal to 131 and 159 less than or equal to A less than or equal to 181. Single particle energies and wave functions have been calculated with a deformed Woods-Saxon potential. Calculations have been performed within the framework of a proton-neutron quasi-particle random phase approximation (QRPA), including the schematic residual spin-isospin interaction between nucleons in the particle-hole and particle-particle channels. It has been seen that the results obtained by using the values for the fixed particle-hole and particle-particle interaction strengths, chi(GT)(ph) = 5.2/A(0.7) MeV and chi(GT)(pp) = 0.58/A(0.7) MeV, have good agreement with the experimental observations.
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    Self-consistent calculations of isospin admixtures in the ground states of the N = Z nuclei in the mass region of 50-100
    Babacan, T; Salamov, DI; Kucukbursa, A
    In the present study, based on spherical shell-model wave functions and energies with the pairing and the residual Fermi interaction treated in pn QRPA, the isospin admixture probabilities in the ground state of N = Z even-even nuclei from Z = 28 to Z = 50 are investigated. In these calculations, considering the restoration of the isotopic invariance for the nuclear part of the Hamiltonian, the residual interaction strength parameter in the quasiparticle space has been obtained in such a way that it is self-consistent with the Woods-Saxon form of the shell model potential. As a result of calculations, it has been found that the calculated isospin admixture probability is proportional to a higher power of Z than the results of other theoretical studies.
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    An investigation of the influence of the pairing correlations on the properties of the isobar analog resonances in A=208 nuclei
    Kücükbursa, A; Salamov, DI; Babacan, T; Aygör, HA
    Within the quasi-particle random phase approximation (QRPA), the method of the self-consistent determination of the isovector effective interaction which restores a broken isotopic symmetry for the nuclear part of the Hamiltonian is given. The effect of the pairing correlations between nucleons on the following quantities were investigated for the A = 208 nuclei: energies of the isobar analog 0(+) states, the isospin admixtures in the ground state of the even-even nuclei, and the differential cross-section for the Pb-208(He-3,t)Bi-208 reaction at E(He-3) = 450 MeV. Both couplings of the excitation branches with T-z = T-o +/- 1, and the analog state with isovector monopole resonance (IVMR) in the quasi-particle representation were taken into account in our calculations. As a result of these calculations, it was seen that the pairing correlations between nucleons have no considerable effect on the T = 23 isospin admixture in the ground state of the Pb-208 nucleus, and they cause partially an increase in the isospin impurity of the isobar analog resonance (IAR). It was also established that these correlations have changed the isospin structure of the IAR states, and shifted the energies of the IVMR states to the higher values.
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    Calculation of two neutrino double beta decay nuclear matrix elements for 128,130Te
    Ünlu, S; Salamov, D; Babacan, T; Küçükbursa, A
    Based on Pyatov-Salamov method, spin-isospin (Gamow-Teller) effective interaction strength parameter has been found self-consistently. Then, the problem has been solved within the framework of QRPA. Gamow-Teller matrix elements for both beta(-) and beta(+) transitions and two neutrino double beta decay nuclear matrix elements have been calculated for Te-128,Te-130 -> Xe-128,Xe-130 transitions. The obtained results have been compared with the corresponding experimental data and other theoretical results.
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    Study of Gamow-Teller transitions in isotopes of titanium within the quasi particle random phase approximation
    Cakmak, S; Nabi, JU; Babacan, T; Selam, C
    The Gamow-Teller (GT) transition is inarguably one of the most important nuclear weak transitions of the spin-isospin sigma tau type. It has many applications in nuclear and astrophysics. These include, but are not limited to, r-process beta-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 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.
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    The isospin admixture of the ground state and the properties of the isobar analog resonances in medium and heavy mass nuclei
    Salamov, DI; Babacan, T; Kücükbursa, A; Ünlü, S; Maras, I
    Within the framework of quasiparticle random phase approximation (QRPA), Pyatov-Salamov method [23] 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 were investigated with the inclusion of the pairing correlations between nucleons for the medium and heavy mass regions: 80 < A < 90, 102 < A < 124, and 204 < A < 214. It was determined that the influence of the pairing interaction between nucleons on the isospin admixtures in the ground state and the isospin structure of the IAR state is more pronounced for the light isotopes (N approximate to Z) of the investigated nuclei.
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    Investigation of Gamow Teller transition properties in 56-64Ni isotopes using QRPA methods
    Cakmak, S; Nabi, JU; Babacan, T
    Weak rates in nickel isotopes play an integral role in the dynamics of supernovae. Electron capture and beta-decay of nickel isotopes, dictated by Gamow-Teller transitions, significantly alter the lepton fraction of the stellar matter. In this paper we calculate Gamow-Teller (GT) transitions for isotopes of nickel, Ni56-64, using QRPA methods. The GT strength distributions were calculated using four different QRPA models. Our results are also compared with previous theoretical calculations and measured strength distributions wherever available. Our investigation concluded that amongst all RPA models, the pn-QRPA(C) model best described the measured GT distributions (including total GT strength and centroid placement). It is hoped that the current investigation of GT properties would prove handy and may lead to a better understanding of the presupernova evolution of massive stars. (C) 2017 Elsevier B.V. All rights reserved.
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    The effect of the pairing interaction on the energies of isobar analogue resonances in 112-124Sb and isospin admixture in 100-124Sn isotopes
    Babacan, T; Salamov, D; Kücükbursa, A; Babacan, H; Maras, I; Aygör, HA; Ünal, A
    In the present study, the effect of the pairing interaction and the isovector correlation between nucleons on the properties of the isobar analogue resonances (IAR) in Sb112-124 isotopes and the isospin admixture in Sn100-124 isotopes is investigated within the framework of the proton-neutron quasi-particle random phase approximation (pnQRPA). The form of the interaction strength parameter is related to the shell-model potential by restoring the isotopic invariance of the nuclear part of the total Hamiltonian. In this respect, the isospin admixtures in the Sn100-124 isotopes are calculated, and the dependence of the differential cross section and the volume integral J(F) for the Sn(He-3,t)Sb reactions at E(He-3) = 200 MeV occurring by the excitation of IAR on mass number A is examined. Our results show that the calculated value for the isospin mixing in the Sn-100 isotope is in good agreement with Colo et al's estimates (4-5%), and the obtained values for the volume integral change within the error range of the value reported by Fujiwara et al (53 +/- 5 MeV fm(3)). Moreover, it is concluded that although the differential cross section of the isobar analogue resonance for the (He-3,t) reactions is not sensitive to pairing correlations between nucleons, a considerable effect on the isospin admixtures in N approximate to Z isotopes can be seen with the presence of these correlations.
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    Associative photoproduction of Roper resonance and ω meson -: art. no. 055208
    Babacan, H; Babacan, T
    Associative photoproduction of omega meson and N-*(1440) on nucleons, gamma+N-->omega+N-*(1440), in the near threshold region is investigated in a framework employing effective Lagrangians. Besides pi exchange in the t channel, baryon exchanges, i.e., N and N-* exchanges, in the s and u channels are also taken into account in calculations of differential cross section and beam asymmetry. Important inputs of this model are the vector and tensor coupling constants of omegaNN(*)(1440) vertex, which are assumed to be equal to the values of these couplings for omegaNN vertex. Using our previous estimation of omegaNN coupling constants obtained from a fit to available experimental data on photoproduction of omega meson in the near threshold region, we produce the necessary numerical predictions for different observables in gamma+N-->omega+N-*(1440). Numerical results show that at low parallel totparallel to dominant contribution comes from t channel pi exchange while the effects of nucleon and N-*(1440) pole terms can be seen at large parallel totparallel to. Our predictions for the differential cross section and beam asymmetry for the processes gamma+N-->omega+N-*(1440), where N is proton and neutron, at E-gamma=2.5 GeV are presented with zero width approximation and also with the inclusion of width effects of N-*(1440).
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    Investigation of tribological properties of polypropylene (PP)- Acrylonitrile butadiene styrene (ABS) blends reinforced with graphene nano-platelets (GNPs)
    Karteri, I; Öge, M; Küçük, Y; Öge, TÖ; Özdemir, FB; Karatasli, M; Çulha, MA; Babacan, T
    The tribological response of PP-ABS/GNPs nanocomposites fabricated via extrusion and injection molding with varying wt% GNPs fractions were examined under varying normal load and sliding speed wear test parameters. The specimens with 3% GNPs and 11% GNPs respectively exhibited the lowest and highest specific wear rates and COF under all test conditions. Increased load led to significantly reduced COF values, whereas increased sliding speed led to a slight reduction in COF by contributing to the formation of a continuous transfer layer. Addition of GNPs helped to retain the worn material on the contact surface and led to improved wear resistance up to the weight fraction of 3% after which non-homogeneous dispersion of GNPs occurred.