Browsing by Author "Koutsou, Giannis"

Now showing items 1-20 of 50

    • Article  

      Axial nucleon and nucleon to Δ form factors and the Goldberger-Treiman relations from lattice QCD 

      Alexandrou, Constantia; Koutsou, Giannis; Leontiou, Theodoros; Negele, J. W.; Tsapalis, Antonios (2007)
      We evaluate the nucleon axial form factor, GA(q2), and induced pseudoscalar form factor, Gp(q2), as well as the pion-nucleon form factor, GπNN(q2), in lattice QCD. We also evaluate the corresponding nucleon to Δ transition ...
    • Article  

      Baryon spectrum with Nf=2+1+1 twisted mass fermions 

      Alexandrou, Constantia; Drach, V.; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis (2014)
      The masses of the low-lying baryons are evaluated using a total of ten ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using two degenerate flavors of light quarks, and a ...
    • Conference Object  

      Computation of disconnected contributions to nucleon observables 

      Alexandrou, Constantia; Drach, V.; Jansen, K.; Koutsou, Giannis; Avilés-Casco, A. V. (Proceedings of Science (PoS), 2013)
      We compare several methods for computing disconnected fermion loops contributing to nucleon three-point functions. The comparison is carried out using one ensemble of Nf =2+1+1 twisted mass fermions with pion mass of 373 ...
    • Article  

      Determination of the Δ(1232) axial and pseudoscalar form factors from lattice QCD 

      Alexandrou, Constantia; Gregory, E. B.; Korzec, T.; Koutsou, Giannis; Negele, J. W.; Sato, T.; Tsapalis, Antonios (2013)
      We present a lattice QCD calculation of the Δ(1232) matrix elements of the axial-vector and pseudoscalar currents. The decomposition of these matrix elements into the appropriate Lorentz invariant form factors is carried ...
    • 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 ...
    • 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  

      Exploiting Very-Wide Vector Processing for Scientific Applications 

      Diavastos, Andreas; Stylianou, Georgios; Koutsou, Giannis (2015)
    • Conference Object  

      Exploiting Very-Wide Vectors on Intel Xeon Phi with Lattice-QCD Kernels 

      Diavastos, Andreas; Stylianou, Georgios; Koutsou, Giannis (2016)
    • 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 ...
    • Doctoral Thesis  Open Access

      Hadron form factors and hadron deformation from lattice QCD 

      Koutsou, Giannis (Πανεπιστήμιο Κύπρου, Σχολή Θετικών και Εφαρμοσμένων Επιστημών/ University of Cyprus, Faculty of Pure and Applied Sciences, 2008-09)
      Σε αυτή την εργασία μελετάμε παράγοντες μορφής (Form Factors) αδρονίων και την παραμόρφωση αδρονίων. Οι παράγοντες μορφές των αδρονίων περιέχουν πληροφορίες για την σύσταση τους, το μέγεθος τους και το σχήμα τους. Ο ...
    • Conference Object  

      Implementation of the twisted mass fermion operator in the QUDA library 

      Strelchenko, A.; Alexandrou, Constantia; Koutsou, Giannis; Avilés-Casco, A. V. (Proceedings of Science (PoS), 2013)
      We discuss an extension of the QUDA library for the Wilson twisted mass operator. A performance analysis is presented for both degenerate and non-degenerate flavor doublets. The degenerate twisted mass fermion operator ...