WoS (Web of Science) İndeksli Yayınlar

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Value of the ξ parameter in Kl3 decay from the pion-gauge condition
(1972) Aydın, Zeki Zekeriya; Fen Fakültesi
It is shown with the help of the pion-gauge condition that the divergence of the most general boson current in K l 3 decay vanishes in the limit of zero four-momentum of the pion. This in turn implies ξ = − 1 at the (unphysical) point t = m 2 K . Inasmuch as ξ does not seem, experimentally, to vary much with t , the result is significant in the physical region and agrees with experiment.
Kl3 and πe3 decays in terms of the Kemmer β current
(1973) Aydın, Zeki Zekeriya; Fen Fakültesi
It is shown with the help of the pion-gauge condition that the divergence of the most general boson current in K l 3 decay vanishes in the limit of zero four-momentum of the pion. This in turn implies ξ = − 1 at the (unphysical) point t = m 2 K . Inasmuch as ξ does not seem, experimentally, to vary much with t , the result is significant in the physical region and agrees with experiment
Relativistic composite systems and minimal coupling
(1974) Duru, İsamil Hakkı; Fen Fakültesi
The problem of minimal coupling of relativistic composite systems having internal degrees of freedom is investigated. The ambiguity in the introduction of various internal coordinates with the same mass spectrum can be solved by probing the system with external electromagnetic interactions. For the generalized Majorana equation this procedure shows that the charged constituent of the system performs a two-dimensional Kepler motion in the Klein-Gordon approximation and not an oscillator motion.
Space motions of galactic G- and K-type stars
(1977) Aslan, S; Fen Fakültesi
Spectra of 912 G- and K -type stars in six galactic directions (⁠lII=90∘,bII=±20∘;lII=180∘,bII=±20∘;lII=90∘,bII=+45∘;bII=+90∘⁠) have been secured. The relevant space motions of the stars, subdivided into distance groups have been derived and these show no significant departures from the mean motion of nearby stars. The velocity dispersions, in general, indicate that these (mainly giant) stars are moderately old. The dispersion in u, however, is lower than that for nearby stars and the significance of this result is discussed.
Internal structure of composite systems described by infinite-component wave equations
(1977) Duru, İsmail Hakkı; Fen Fakültesi
It is shown that the boson representation of infinite-component SO(4,2) wave equations represents a system of four oscillators as well as three-dimensional Kepler dynamics. These two pictures are complementary to each other; that is, the Kepler dynamics is adequate for small distances, while the oscillator dynamics is more relevant for infinitely large distances, and both pictures are equivalently possible for finite distances. This is interpreted as a sort of constituent confinement.
On the K-term and dispersion ratios of semi-regular variables
(1981) Aslan, Zeki; Fen Fakültesi
Optical velocities of semi-regular (SR) and irregular (Lb) variables are analysed for a K-term. There is evidence for a dependence upon stellar period. Absorption lines in shorter period non-emission SR variables are blue-shifted relative to the centre-of-mass velocity by about 6±3 km s−1. Emission-line SR variables give a non-negative absorption K-term and Lb variables give no K-terms other than zero. Comparison is made with the K-terms implied by the OH velocity pattern in long-period variables. Dispersion ratios are also calculated. They are σv/σu=0.69±0.16 for non-emission, and 0.74±0.20 for emission variables (from absorption lines). Kinematics suggest that the sequence Lb–SR (non-emission)–SR (emission)–Mira is a sequence of increasing age. It is suggested that this sequence may also be the sequence indicating the direction of evolution.
Upper limit on the magnetic moment of the neutrino
(1982) Aydın, Zeki Zekeriya; Duru, İsmail Hakkı; Fen Fakültesi
We have recalculated the processes e ν → e ν and e + e − → ν ¯ ν due to an assumed magnetic moment κ of the neutrino (correcting some errors in the previous calculations). Comparing the results with the Fermi and electroweak models we set a suggestive limit κ ≲ ( gm e M Z ) 2 μ 0 , where m is the electron mass and μ 0 = e 2 m . A very sensitive method to set a good upper limit would be to measure the angular distribution of e ν → e ν near the forward direction.
Neutrino and antineutrino elastic scattering and photoneutrino reactions
(1983) Aydın, Zeki Zekeriya; Fen Fakültesi
The processes ν ν → ν ν , ν ¯ ν → ν ¯ ν , ν ¯ ν → 2 γ , and ν γ → ν γ , which are of astrophysical interest, are calculated both in the electroweak model and in the magnetic model when the neutrino has a small magnetic moment κ . Received 31 January 1983
Euler-form actions and the vanishing of the cosmological constant
(1989) Dereli, T; Fen Fakültesi
We investigate the conditions of the vanishing cosmological constant and the presence of gravity and vector gauge fields in a D -dimensional non-Abelian Kaluza-Klein theory based on a dimensionally continued 2 N -dimensional Euler-form action. It is shown that these conditions can be satisfied only for D = 2 N + 3 .
A physical realisation of the super-sine algebra
(1992) Verçin, Abdullah; http://orcid.org/0000-0002-0608-6648; Fen Fakültesi
An explicit physical realisation of the supersymmetric extension of the sine algebra generated by the symmetries of a spinless Bloch electron in a constant uniform magnetic field is given in terms of the symmetry operators of a spin- 1 2 Bloch electron.
Two anyons with Coulomb interaction in a magnetic field
(1992) Verçin, Abdullah; http://orcid.org/0000-0002-0608-6648; Fen Fakültesi
We have computed numerically the energy spectrum of two anyons with Coulomb (1/r) interaction in a uniform magnetic field. Both non-singular and singular energy eigenfunctions are considered. We solve a second order difference equation with boundary conditions by a new, simple and efficient numerical method.
Scalar leptoquark production at TeV energy γp colliders
(1994) Çelikel, Ayşegül; Atağ, Satılmış; Fen Fakültesi
Single scalar leptoquark production in the collisions of high energy γ and proton beams has been investigated. It is shown that future γp colliders will be sensitive to scalar leptoquark masses up to few
Light-curve and period changes of AB-Andromedae
(1994) Selam, Selim; Derman, Ethem; Müyesseroğlu, Zekeriya; Akalın, Aynur; Demircan, Osman; Fen Fakültesi
New photoelectric observations of AB And obtained between 1989 and 1992 have been used, together with all available light curves from the literature, to study the light-curve variation of the system and its probable connection with the orbital period variation. A long-term brightness variation in the light levels is detected. The maximum brightness occurred in 1970 (+/- 3 yr). A period study based on all available times of minimum light (of which 22 are newly determined) reveals that the photometric period of the system oscillates around a mean value (P0 almost-equal-to 0.331 890 d) with an oscillation period of almost-equal-to 88.0 +/- 0.2 yr and a half-amplitude of 0.000 003 76 d. Such a variation can be caused by either (i) a period modulation due to the magnetic activity cycle of the active primary component, or (ii) a light-traveltime effect due to a third body in the system. It is shown that the third body, if it exists, can only be a white dwarf; this can be checked by ultraviolet spectroscopy. The rms light variation of the system predicted by Applegate's theory of the magnetic activity modulation of the orbital period is found to be comparable with the observed amplitude of long-term brightness variations of the system. However, the brightness variation is found to be 90-degrees out of phase with the O - C curve. Such a phase shift can be explained in terms of the damping effect of the convective zone. The theory predicts a subsurface magnetic field of 7.4 kG for the primary component of AB And.
Light-curve and period changes of AB Andromedae
(1994) Derman, Ethem; Akalın, A; Selam, Salim O; Müyesseroğlu, Zekeriya; Demirçan, Osman; Fen Fakültesi
New photoelectric observations of AB And obtained between 1989 and 1992 have been used, together with all available light curves from the literature, to study the light-curve variation of the system and its probable connection with the orbital period variation. A long-term brightness variation in the light levels is detected. The maximum brightness occurred in 1970 (±3 yr). A period study based on all available times of minimum light (of which 22 are newly determined) reveals that the photometric period of the system oscillates around a mean value (⁠P0≈0.331890d⁠) with an oscillation period of ≈88.0\textpm0.2 yr and a half-amplitude of 0.000 003 76 d. Such a variation can be caused by either (i) a period modulation due to the magnetic activity cycle of the active primary component, or (ii) a light-traveltime effect due to a third body in the system. It is shown that the third body, if it exists, can only be a white dwarf; this can be checked by ultraviolet spectroscopy. The rms light variation of the system predicted by Applegate's theory of the magnetic activity modulation of the orbital period is found to be comparable with the observed amplitude of long-term brightness variations of the system. However, the brightness variation is found to be 90° out of phase with the O–C curve. Such a phase shift can be explained in terms of the damping effect of the convective zone. The theory predicts a subsurface magnetic field of 7.4 kG for the primary component of AB And.
Pair production of scalar leptoquarks at TeV energy γp colliders
(1994) Çakır, Orhan; Ata, S; Fen Fakültesi
Scalar leptoquark pair production in high energy γ -proton collisions is investigated. We show that future TeV energy γ p colliders are convenient places for searching for scalar leptoquarks up to the masses of a few TeV.
A search for the fourth SM family
(1995) Çelikel, A; Çiftçi, Abbas K; Sultansoy, Saleh F; Fen Fakültesi
Arguments favouring the existence of a fourth fermion family in the framework of the Standard Model are given. The masses of the fourth family neutrino, charged lepton and down quark are close to each other within an accuracy of the order of a few GeV and lie between 300–700 GeV. Experiments on the search for these particles are discussed.
Compensation of lepton charge of matter with relic anti-sneutrinos
(1995) Çiftçi, Abbas K; Sultansoy, Saleh F; Tütköz, Shemsettin; Fen Fakültesi
We reconsider the idea of the leptonic photon by taking into account the possible compensation of the lepton charge of matter with relic anti-sneutrinos. As a consequence of this compensation we have shown that the available experimental data admit the range of the leptonic interaction constant to be 10−38 < αl < 10−14.
Pair production of squarks in TeV scale polarized γp collisions
(1996) Kandemir, Ayfer; Yılmazer, Ali Ulvi; Fen Fakültesi
The production of squarks in the high energy collisions of the real photons off the protons is discussed. The polarizations of both photon and proton beams are considered. Although the cross sections for different initial beam polarizations do not differ much, the polarization asymmetry is sensitive to the squark mass. We conclude that the capacity of the future TeV scale ~JJ colliders is quite promising in the search for SUSY particles.
Crystal structure of bis[4-(5-methyl-2-oxyphenyl-kappa O,2 kappa O)-4-imino-2-penten-2-olato-O,O ' N ']copper(II)
(1997) Atakol, Orhan; Fen Fakültesi
Crystal Structure of [1-{(2-Oxyphenyl)iminomethyl}benzen- 2-oxy-N,O,O′]cyclopropylamine-Nnickel(II) Complex
(1997) Atakol, Orhan; Eriş, Figen Z; Fen Fakültesi
The structures of monomeric Ni complexes in the presence of a tridentate ONO or ONS Schiff-base ligand and different monodentate ligands (piperidinel, pyrrolidine2 and cyclohexylamine3) were reported previously. In those complexes the Ni ion has either a square or distorted square-planar coordination. Here, we report on the structure of a new Ni complex, which has as a monodentate ligand the cyclopropylamine molecule (Fig. 1). As can be seen from Fig. 2, the coordination around the Ni ion in the title complex is also distorted square planar. The Ni-0 and Ni-N bond lengths are [1.814(5) -1.866(5)A] and [1.846(6) -1.929(5)A],

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