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Altsybeev I.G.,Joint Institute for Nuclear Research | Zarubin A.V.,Joint Institute for Nuclear Research | Konoplyanikov V.F.,Gomel State University | Tumasyan A.R.,Alikhanyan National Science Laboratory | Shmatov S.V.,Joint Institute for Nuclear Research
Physics of Particles and Nuclei Letters | Year: 2012

The absolute scale of jet energy set in a CMS experiment using the W mass constraint in tt̄ events with W → qq̄ decay is studied. The main effects leading to systematic shifts in the jet-energy scale are identified. Estimations of these shifts are given. © 2012 Pleiades Publishing, Ltd.


Abgaryan V.S.,Joint Institute for Nuclear Research | Ananikian N.S.,Alikhanyan National Science Laboratory | Ananikyan L.N.,Alikhanyan National Science Laboratory | Hovhannisyan V.,Alikhanyan National Science Laboratory
Solid State Communications | Year: 2014

Thermal entanglement, magnetic and quadrupole moments properties of the mixed spin-12 and spin-1 Ising-Heisenberg model on a diamond chain are considered. Magnetization and quadrupole moment plateaus are observed for the antiferromagnetic couplings. Thermal negativity as a measure of quantum entanglement of the mixed spin system is calculated. Different behavior for the negativity is obtained for the various values of Heisenberg dipolar and quadrupole couplings. The intermediate plateau of the negativity has been observed at the absence of the single-ion anisotropy and quadrupole interaction term. When dipolar and quadrupole couplings are equal there is a similar behavior of negativity and quadrupole moment. © 2014 Elsevier B.V. All rights reserved.


Izmailian N.S.,Alikhanyan National Science Laboratory | Izmailian N.S.,Academia Sinica, Taiwan | Rojas O.,Federal University of Lavras | De Souza S.M.,Federal University of Lavras
Physica A: Statistical Mechanics and its Applications | Year: 2012

We propose a general method by which a spin-S is decomposed into spins less than S. We have obtained the exact mapping between spin S=pM-12 and a cluster of M spins σ=p-12, where p and M are positive integers. We have discussed the possible applications of such transformations. In particular we have shown how a general d+1 dimensional spin-p-12 model with general interactions can be reduced to a d-dimensional spin-S model with S= pM-12. © 2011 Elsevier B.V. All rights reserved.


Izmailian N.S.,Academia Sinica, Taiwan | Izmailian N.S.,Alikhanyan National Science Laboratory | Kenna R.,Coventry University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

We analyze the partition function of the dimer model on an M×N triangular lattice wrapped on a torus obtained by Fendley, Moessner, and Sondhi. From a finite-size analysis we have found that the dimer model on such a lattice can be described by a conformal field theory having a central charge c=-2. The shift exponent for the specific heat is found to depend on the parity of the number of lattice sites N along a given lattice axis: e.g., for odd N we obtain the shift exponent λ=1, while for even N it is infinite (λ=). In the former case, therefore, the finite-size specific-heat pseudocritical point is size dependent, while in the latter case it coincides with the critical point of the thermodynamic limit. © 2011 American Physical Society.


Abgaryan V.S.,Joint Institute for Nuclear Research | Ananikian N.S.,Alikhanyan National Science Laboratory | Ananikyan L.N.,Alikhanyan National Science Laboratory | Hovhannisyan V.V.,Alikhanyan National Science Laboratory
Solid State Communications | Year: 2015

We consider the quasi-one dimensional spin-1 Ising-Heisenberg model with single-ion anisotropy on a diamond chain. Due to the exact solution of the model, we constructed the ground state phases which, alongside to others, have shown capability to exhibit most interesting frustrated state. The investigation of the magnetization processes showed enrichment of possibilities to form plateaus at zero, one- and two-thirds of the saturation magnetization. Negativity as a measure of the quantum entanglement is considered at low temperatures. © 2015 Elsevier Ltd. All rights reserved.


Gevorgyan A.H.,Yerevan State University | Oganesyan K.B.,Alikhanyan National Science Laboratory
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2011

Specific features of the defect modes of cholesteric liquid crystals (CLCs) with an isotropic defect, as well as their photonic density of states, Q factor, and emission, have been investigated. The effect of the thicknesses of the defect layer and the system as a whole, the position of the defect layer, and the dielectric boundaries on the features of the defect modes have been analyzed. It is shown that when the CLC layer is thin the density of states and emission intensity are maximum for the defect mode, whereas when the CLC layer is thick, these peaks are observed at the edges of the photonic band gap. Similarly, when the gain is low, the density of states and emission intensity are maximum for the defect mode, whereas at high gains these peaks are also observed at the edges of the photonic band gap. The possibilities of low-threshold lasing and obtaining high-Q microcavities have been investigated. © 2011 Pleiades Publishing, Ltd.


Grabski V.,National Autonomous University of Mexico | Nellen L.,National Autonomous University of Mexico | Chilingarian A.,Alikhanyan National Science Laboratory | Vardanian A.,Alikhanyan National Science Laboratory
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

The High Altitude Water Cherenkov (HAWC) is a high duty cycle, wide field of view gamma-ray observatory that will be located in Mexico at an elevation of 4100m (lat. 19° and long. 97°). The gamma/hadron separation study is performed on the base of the non parametric methods for different probability density estimators, using a multidimensional feature space. Data from full detector simulations of the HAWC observatory are used to estimate the features. The gamma/hadron separation study is performed using different methods of multivariate analysis. A study of sensitive parameters for gamma/hadron separation versus signal efficiency, obtained by the use of different cuts on the classifier outputs, is presented. The results show a significant reduction of the background contamination in the region of high signal efficiency uaing multivariate analysis, compared to the default procedure proposed for HAWC.


Abgaryan V.S.,Alikhanyan National Science Laboratory | Ananikian N.S.,Alikhanyan National Science Laboratory | Ananikyan L.N.,Alikhanyan National Science Laboratory | Kocharian A.N.,Alikhanyan National Science Laboratory | Kocharian A.N.,California State University, Los Angeles
Physica Scripta | Year: 2011

The incipient quantum phase transitions of relevance to nonzero fluctuations and entanglement in Heisenberg clusters are studied in this paper by exploiting negativity as a measure in bipartite and frustrated spin-1 anisotropic Heisenberg clusters with bilinear-biquadratic exchange, single-ion anisotropy and magnetic field. Using the exact diagonalization technique, it is shown that quantum critical points signaled by qualitative changes in behavior of magnetization and particle number are ultimately related to microscopic entanglement and collective excitations. The plateaus and peaks in spin and particle susceptibilities define the conditions for a high/low-density quantum entanglement and various ordered phases with different spin (particle) concentrations. © 2011 The Royal Swedish Academy of Sciences.


Gabrielyan L.A.,Alikhanyan National Science Laboratory | Hovhannisyan M.K.,Alikhanyan National Science Laboratory | Petrosyan M.L.,Alikhanyan National Science Laboratory
Journal of Contemporary Physics | Year: 2014

Experimental study of magnetic characteristics of planar magnet undulator for terahertz FEL has been carried out with use of pulsed-wire method. Special attention was given to the procedure of measurement of the second integral of undulator magnetic field, which shows variation of the beam position at passing the undulator magnetic system. © 2014 Allerton Press, Inc.


Karyan G.,Alikhanyan National Science Laboratory
EPJ Web of Conferences | Year: 2014

The HERMES collaboration has measured charge-separated pion and kaon multiplicities in semi-inclusive deep-inelastic scattering using a 27.6? GeV electron or positron beam scattering off a hydrogen or deuterium target. The results are presented as functions of the Bjorken variable xB, the negative squared four-momentum transfer Q2, a hadron fractional energy z and the hadron's transverse momentum. These data will be very useful to understand the quark-fragmentation process in deep-inelastic hadron electro-production and will serve as crucial input in the understanding of charge and flavour separated fragmentation functions. Furthermore, it provides important information on the transverse-momentum dependence of hadron production. © Owned by the authors, published by EDP Sciences, 2014.

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