Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Publisher: search.filters.publisher.Springer VerlagSubject: search.filters.subject.Monte Carlo method

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  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Electronic Structure and Correlations of Vitamin B12 Studied Within the Haldane-Anderson Impurity Model
    (Springer Verlag, 2016) Kandemir, Zafer; Mayda, Selma; Bulut, Nejat
    We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Co (3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 18
    Forward Energy Flow, Central Charged-Particle Multiplicities, and Pseudorapidity Gaps in W and Z Boson Events From Pp Collisions at ?s = 7 Tev
    (Springer Verlag, 2012) Demir, Durmuş Ali; Karapınar, Güler
    A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 pb-1, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1. 9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the W(Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (pompyt) and non-diffractive (pythia) Monte Carlo simulations, the diffractive component is determined to be (50. 0 ± 9. 3 (stat.) ± 5. 2 (syst.))%. © 2012 CERN for the benefit of the CMS collaboration.