Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 32Citation - Scopus: 34The Cms Barrel Calorimeter Response To Particle Beams From 2 To 350 Gev/C(Springer Verlag, 2009) CMS HCAL/ECAL Collaborations; Sönmez, NasufThe response of the CMS barrel calorimeter (electromagnetic plus hadronic) to hadrons, electrons and muons over a wide momentum range from 2 to 350 GeV/c has been measured. To our knowledge, this is the widest range of momenta in which any calorimeter system has been studied. These tests, carried out at the H2 beam-line at CERN, provide a wealth of information, especially at low energies. The analysis of the differences in calorimeter response to charged pions, kaons, protons and antiprotons and a detailed discussion of the underlying phenomena are presented. We also show techniques that apply corrections to the signals from the considerably different electromagnetic (EB) and hadronic (HB) barrel calorimeters in reconstructing the energies of hadrons. Above 5 GeV/c, these corrections improve the energy resolution of the combined system where the stochastic term equals 84.7 ± 1.6% and the constant term is 7.4 ± 0.8%. The corrected mean response remains constant within 1.3% rms. © Springer-Verlag / Società Italiana di Fisica 2009.Article Citation - WoS: 6Citation - Scopus: 6Variation of the Light and Period of the Magnetic Cataclysmic Variable Am Her(IOP Publishing, 2008) Kalomeni, Belinda; Yakut, KadriGround-based, long-term optic variability of AM Her, covering the period between 2003-2008, has been conducted to study the features seen in both low and high states of the system. Low-state analysis shows the presence of short-term, low-amplitude light variations of about 0.02-0.03 mag with a mean power time between 16 s and 226 s. Brightness variations on the order of 0.7-2 mag, which could be due to the stellar activity of the component in the system, are also detected. A total of 30 years' times of minimum light given in the literature are combined with nine times of minima obtained in this study. We represented the (observed-calculated) diagram by a parabolic curve and also by two broken lines. Under the assumption of a parabolic variation, we estimate an increase in period, dP/dt = 7.5(1.2) x 10(-9) days yr(-1), with a mass transfer rate of. M = 8(2) x 10(-9) M(circle dot) yr(-1), in agreement with the previous findings by a different method.Article Citation - WoS: 38Citation - Scopus: 40Influences of Deposition Time and Ph on Magnetic Nife Nanowires Fabrication(Elsevier, 2009) Atalay, Funda E.; Kaya, Harun; Atalay, Selcuk; Tarı, SüleymanIn this work, NiFe nanowires were grown into highly ordered porous anodic alumina oxide (AAO) templates by dc electrodeposition at various deposition times and pH values. During the deposition process some electrochemical bath parameters such as ion content, deposition voltage, and temperature of solution were kept constant. The morphological properties of the nanowire arrays were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the chemical composition was determined by examination of the energy dispersive X-ray (EDX) spectra, and the magnetic behavior of the arrays was determined by vibrating sample magnetometer (VSM). (C) 2008 Elsevier B.V. All rights reserved.Article Citation - WoS: 150Citation - Scopus: 7Correlation of Tunneling Spectra in Bi2sr2cacu2o8+? With the Resonance Spin Excitation(American Physical Society, 2001) Zasadzinski, John F.; Özyüzer, Lütfi; Miyakawa, Nobuaki; Gray, Kenneth E.; Hinks, David G.; Kendziora, Christopher A.New break-junction tunneling data are reported in Bi2Sr2CaCu2O8+δ over a wide range of hole concentration from underdoped (Tc=74k) to optimal doped (Tc=95k) to overdoped (Tc=48k). The conductances exhibit sharp dips at a voltage, Ω/e, measured with respect to the superconducting gap. Clear trends are found such that the dip strength is maximum at optimal doping and that Ω scales as 4.9kTc over the entire doping range. These features link the dip to the resonance spin excitation and suggest quasiparticle interactions with this mode are important for superconductivity.Article Citation - WoS: 17Citation - Scopus: 18Analysis of Interface States of the Pentacene Organic Thin-Film Phototransistor by Conductance Technique(Elsevier Ltd., 2009) Okur, Salih; Yakuphanoğlu, FahrettinA pentacene thin-film transistor with a channel width of 300 μm and a channel length of 30 μm has been successfully fabricated on n-Si substrate with thermally oxidized SiO2 as a gate insulator. The photovoltaic and interface state density properties of the transistor have been investigated. A pentacene film of 200 nm thickness was deposited on the SiO2 layer with a vacuum thermal evaporator. Atomic force microscopy images of the pentacene film on SiO2 insulating layer show a homogeneous film surface with the rms roughness of 11 nm. The transistor shows p-channel characteristics, as a result of positive carriers generated in the pentacene film for the negative bias voltages applied to the gate. The photosensitivity (Iph/Idark) is measured as 1.45 at an illumination intensity of 3500 lux at the off state. This suggests that the pentacene thin-film transistor shows a phototransistor characteristic. The field-effect mobility of the pentacene OTFT was found to be 0.021 cm2/(V s). The interface state density of the transistor was determined using conductance technique and was found to be about 1.191 × 1010 eV-1 cm-2.Article Citation - WoS: 11Citation - Scopus: 11General Tensor Lagrangians From the Gravitational Higgs Mechanism(IOP Publishing Ltd., 2009) Demir, Durmuş Ali; Pak, Namık KemalThe gravitational Higgs mechanism proposed by 't Hooft in arXiv:0708.3184 involves the spacetime metric gμv as well as the induced metric ḡμν oc ηab∂μΦ a∂νφb where φ(a = 0,..., 3), as we call it, break all four diffeomorphisms spontaneously via the vacuum expectation values (φa) ∝ xa. In this framework, we construct and analyze the most general action density in terms of various invariants involving the curvature tensors, connexion coefficients, and the contractions and the determinants of the two metric fields. We show that this action admits a consistent expansion about the flat background such that the resulting Lagrangian possesses several novel features not found in the linearized Einstein-Hilbert Lagrangian with FierzPauli mass term (LEHL-FP): (i) its kinetic part generalizes that of LELHL-FP by weighing the corresponding structures with certain coefficients generated by invariants, (ii) the entire Lagrangian is ghost- and tachyon-free for mass terms not necessarily in the Fierz-Pauli form, and, (iii) a consistent mass term is generated with no apparent need to higher derivative couplings.Article Citation - WoS: 2Citation - Scopus: 4Signal Performance of Dc-Squids With Respect To Ybco Thin Film Deposition Rate(Elsevier Ltd., 2009) Avcı, İlbeyi; Algül, Berrin Pınar; Akram, Rizwan; Bozbey, Ali; Tepe, Mustafa; Abukay, DoğanThe signal performances of YBa2Cu3O7-δ (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) have been investigated as a function of the thin film structure affected by the growth process. YBCO thin films of 200 nm thicknesses were deposited by DC magnetron sputtering using different deposition rates between 1.0 nm/min and 2.0 nm/min onto 24° bicrystal SrTiO3 (STO) substrates. The thin film samples were subsequently analyzed by XRD and AFM in order to determine their crystalline structures and surface morphologies respectively. The 67 pH directly coupled DC-SQUIDs with 4 μm-wide bicrystal Josephson junctions were fabricated, and characterized with respect to their device performances. The variations in the critical current (Ic), the voltage modulation depth (ΔV) and the noise performance of DC-SQUIDs were reported. The SQUIDs having relatively low deposition rate of 1.0 nm/min was observed to have larger voltage modulation depth as well as higher critical current than that of the samples having larger rate of 2.0 nm/min. The better noise performances were observed as the film deposition rate decreases. The results were associated with the thin film structure and the SQUID characteristics.Article Citation - WoS: 38Citation - Scopus: 37Close Binary and Other Variable Stars in the Solar-Age Galactic Open Cluster M67(EDP Sciences, 2009) Yakut, Kadri; Zima, W.; Kalomeni, Belinda; Van Winckel, H.; Wealkens, C.; De Cat, P.; Bauwens, E.; Vuckovic, M.; Saesen, S.; Le Guillou, L.; Parmaksızoğlu, M.; Uluç, K.; Khamitov, I.; Raskin, G.; Aerts, C.We present multi-colour time-series CCD photometry of the solar-age galactic open cluster M67 (NGC 2682). About 3600 frames spread over 28 nights were obtained with the 1.5 m Russian-Turkish and 1.2 m Mercator telescopes. High-precision observations of the close binary stars AH Cnc, EV Cnc, ES Cnc, the δ Scuti type systems EX Cnc and EW Cnc, and some long-period variables belonging to M67 are presented. Three full multi-colour light curves of the overcontact binary AH Cnc were obtained during three observing seasons. Likewise we gathered three light curves of EV Cnc, an EB-type binary, and two light curves of ES Cnc, a blue straggler binary. Parts of the light change of long-term variables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained. Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done using all times of mid-eclipse available in the literature and those obtained in this study. In addition, we analyzed multi-colour light curves of the close binaries and also determined new frequencies for the δ Scuti systems. The physical parameters of the close binary stars were determined with simultaneous solutions of multicolour light and radial velocity curves. Finally we determined the distance of M67 as 857(33) pc via binary star parameters, which is consistent with an independent method from earlier studies.Article Citation - WoS: 15Citation - Scopus: 17Influence of Crystallographic Orientation on Hydration of Mgo Single Crystals(Elsevier Ltd., 2009) Sütçü, Mücahit; Akkurt, Sedat; Okur, SalihThis study has been performed in order to find out the influence of crystallographic orientation on hydration of MgO single crystal substrates with (1 0 0)-, (1 1 0)-, and (1 1 1)-orientations. The samples were left in a hydration chamber with an 88% relative humidity for 18 h at room temperature. The effect of humidity on the samples was examined by scanning probe microscope (SPM) and scanning electron microscope (SEM) which showed that the degree of hydration was noticeably influenced by the crystallographic orientation. It was found that the MgO with (1 1 1)-orientation has the highest tendency to hydrate than the other orientations. Second most affected sample was (1 1 0) crystal. Loss of MgO on the surface by hydration is most severe when the crystal is oriented in (1 1 1) plane with the maximum hydrate layer thickness of 174 nm after 18 h of exposure.Article Citation - WoS: 35Citation - Scopus: 37Dirac Neutrino Masses From Generalized Supersymmetry Breaking(American Physical Society, 2008) Demir, Durmuş Ali; Everett, Lisa L.; Langacker, PaulWe demonstrate that Dirac neutrino masses in the experimentally preferred range are generated within supersymmetric gauge extensions of the standard model with a generalized supersymmetry breaking sector. If the superpotential neutrino Yukawa terms are forbidden by the gauge symmetry [such as a U(1)′], sub-eV scale effective Dirac mass terms can arise at tree level from hard supersymmetry breaking Yukawa couplings, or at one loop due to nonanalytic soft supersymmetry breaking trilinear scalar couplings. The radiative neutrino magnetic and electric dipole moments vanish at one-loop order.