Browsing by Author "Alexandrou, Constantia"

Now showing items 21-40 of 155

    • Article  

      Determination of Δ-resonance parameters from lattice QCD 

      Petschlies, Marcus; Alexandrou, Constantia; Negele, J. W.; Strelchenko, A.; Tsapalis, Antonios (2013)
      A method suitable for extracting resonance parameters of unstable baryons in lattice QCD is examined. The method is applied to the strong decay of the Δ to a pion-nucleon state, extracting the πNΔ coupling constant and Δ ...
    • Article  

      Direct Evaluation of the Quark Content of Nucleons from Lattice QCD at the Physical Point 

      Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V. (2016)
      We evaluate the light, strange, and charm scalar content of the nucleon using one lattice QCD ensemble generated with two degenerate light quarks with mass fixed to their physical value. We use improved techniques to ...
    • Conference Object  

      Disconnected diagrams with twisted-mass fermions 

      Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Finkenrath, J.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V.; Volmer, J. (Proceedings of Science (PoS), 2016)
      The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction, ...
    • Article  

      Disconnected quark loop contributions to nucleon observables in lattice QCD 

      Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Vaquero, A. (2014)
      We perform a high statistics calculation of disconnected fermion loops on graphics processing units for a range of nucleon matrix elements extracted using lattice QCD. The isoscalar electromagnetic and axial vector form ...
    • Conference Object  

      Disconnected quark loop contributions to nucleon observables using Nf = 2 twisted clover fermions at the physical value of the light quark mass 

      Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V. (Proceedings of Science (PoS), 2015)
      We compute the disconnected quark loops contributions entering the determination of nucleon observables, by using a Nf = 2 ensemble of twisted mass fermions with a clover term at a pION mass mπ = 133 MeV. We employ exact ...
    • Article  

      Effects of short range N interaction on observables of the NN system. 

      Alexandrou, Constantia; Blankleider, B. (1990)
      The inadequacy of standard few-body approaches in describing the NN system has motivated searches for the responsible missing mechanism. In the case of d scattering, it has recently been asserted that an additional short ...
    • Article  

      Efficiency of the UV-filtered multiboson algorithm 

      Alexandrou, Constantia; De Forcrand, P.; D'Elia, M.; Panagopoulos, Haralambos G. (2000)
      We study the efficiency of an improved multiboson algorithm with two flavors of Wilson fermions in a realistic physical situation (β=5.60,κ=0.156 on a 163X24 lattice). The performance of this exact algorithm is compared ...
    • Conference Object  

      The electric dipole moment of the neutron from Nf = 2+1+1 twisted mass fermions 

      Petschlies, Marcus; Alexandrou, Constantia; Athenodorou, A.; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Ottnad, K. (Proceedings of Science (PoS), 2015)
      We extract the neutron electric dipole moment (nEDM) dn on configurations produced with Nf = 2+1+1 twisted mass fermions with lattice spacing of a ≃ 0.082fm and a light quark mass that correpsonds to Mπ ≃ 373 MeV. We do ...
    • Article  

      Electromagnetic form factors of the Ω- In lattice QCD 

      Alexandrou, Constantia; Korzec, T.; Koutsou, Giannis; Negele, J. W.; Proestos, Y. (2010)
      We present results on the omega baryon (Ω-) electromagnetic form factors using Nf=2+1 domain-wall fermion configurations for three pion masses in the range of about 350 to 300 MeV. We compare results obtained using domain-wall ...
    • Article  

      Erratum: Axial nucleon and nucleon to Δ form factors and the Goldberger-Treiman relations from lattice QCD (Phys. Rev. D (2007) 76 (094511)) 

      Alexandrou, Constantia; Koutsou, Giannis; Leontiou, Theodoros; Negele, J. W.; Tsapalis, Antonios (2009)
    • Article  

      Erratum: Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass (Physical Review D - Particles, Fields, Gravitation and Cosmology (2015) 92 (114513)) 

      Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Dimopoulos, Petros; Frezzotti, R.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Kostrzewa, B.; Koutsou, Giannis; Mangin-Brinet, M.; Oehm, M.; Rossi, G. C.; Urbach, C.; Wenger, U. (2016)
      We present results on the nucleon scalar, axial, and tensor charges as well as on the momentum fraction and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key ...
    • Article  

      Evaluation of disconnected quark loops for hadron structure using GPUs 

      Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Strelchenko, A.; Vaquero, A. (2014)
      A number of stochastic methods developed for the calculation of fermion loops are investigated and compared, in particular with respect to their efficiency when implemented on Graphics Processing Units (GPUs). We assess ...
    • Article  

      Evaluation of fermion loops applied to the calculation of the η ′ mass and the nucleon scalar and electromagnetic form factors 

      Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Koutsou, Giannis; O Cais, A.; Strelchenko, A. (2012)
      The exact evaluation of the disconnected diagram contributions to the flavor-singlet pseudo-scalar meson mass, the nucleon σ-term and the nucleon electromagnetic form factors is carried out utilizing GPGPU technology with ...
    • Article  

      Evidence for diquarks in lattice QCD 

      Alexandrou, Constantia; De Forcrand, Ph; Lucini, B. (2006)
      Diquarks may play an important role in hadron spectroscopy, baryon decays, and color superconductivity. We investigate the existence of diquark correlations in lattice QCD by considering systematically all the lowest energy ...
    • Article  

      First moment of the flavour octet nucleon parton distribution function using lattice QCD 

      Alexandrou, Constantia; Constantinou, Martha; Dinter, S.; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Vaquero, A. (2015)
      Abstract: We perform a lattice computation of the flavour octet contribution to the average quark momentum in the nucleon, (Formula presented.). In particular, we fully take the disconnected contributions into account in ...
    • Article  

      First physics results at the physical pion mass from Nf=2 Wilson twisted mass fermions at maximal twist 

      Petschlies, Marcus; Abdel-Rehim, A.; Alexandrou, Constantia; Burger, F.; Constantinou, Martha; Dimopoulos, Petros; Frezzotti, R.; Hadjiyiannakou, Kyriakos; Helmes, C.; Jansen, K.; Jost, C.; Kallidonis, Christos; Knippschild, B.; Kostrzewa, B.; Koutsou, Giannis; Liu, L.; Mangin-Brinet, M.; Ottnad, K.; Pientka, G.; Rossi, G. C.; Urbach, C.; Wenger, U.; Werner, M. (2017)
      We present physics results from simulations of QCD using Nf=2 dynamical Wilson twisted mass fermions at the physical value of the pion mass. These simulations are enabled by the addition of the clover term to the twisted ...
    • Article  

      First principles calculations of nucleon and pion form factors: Understanding the building blocks of nuclear matter from lattice QCD 

      Alexandrou, Constantia; Bistrovic, B.; Edwards, R. G.; De Forcrand, P.; Fleming, G.; Hägler, P.; Negele, J. W.; Orginos, K.; Pochinsky, A.; Renner, D. B.; Richards, D. G.; Schroers, W.; Tsapalis, Antonios (2005)
      Lattice QCD is an essential complement to the current and anticipated DOE-supported experimental program in hadronic physics. In this paper we address several key questions central to our understanding of the building ...
    • Article  

      Fourier path integrals, partial averaging, and the polaron problem 

      Alexandrou, Constantia; Fleischer, W.; Rosenfelder, R. (1990)
      We evaluate the Fourier path integral for an optical polaron by the method of partial averaging. Higher Fourier coefficients are taken into account by averaging with Feynmans trial action, whereas the first N coefficients ...
    • Article  

      Full QCD with the Lüscher local bosonic action 

      Alexandrou, Constantia; Borrelli, A.; de Forcrand, Ph; Galli, A.; Jegerlehner, F. (1995)
      We investigate Lüscher's method of including dynamical Wilson fermions in a lattice simulation of QCD with two quark flavours. We measure the accuracy of the approximation by comparing it with Hybrid Monte Carlo results ...
    • Article  

      Gauge-invariant two- and three- density correlators 

      Alexandrou, Constantia; de Forcrand, Ph; Tsapalis, Antonios (2003)
      Gauge-invariant spatial correlations between two and three quarks inside a hadron are measured within quenched and unquenched QCD. These correlators provide information on the shape and multipole moments of the pion, the ...