Browsing by Author "Tsapalis, Antonios"

Now showing items 1-20 of 29

    • 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  

      Calculation of the N to Δ electromagnetic transition matrix element 

      Alexandrou, Constantia; de Forcrand, Ph; Lippert, Th; Neff, H.; Negele, J. W.; Schilling, K.; Schroers, W.; Tsapalis, Antonios (2003)
      We present results on the ratio of electric quadrupole to magnetic dipole amplitudes, REM = GE2/GM1, for the transition γN → Δ from lattice QCD. We consider both the quenched and the 2-flavor theory.
    • 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  

      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  

      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  

      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  

      Free energy and plaquette expectation value for gluons on the lattice, in three dimensions 

      Panagopoulos, Haralambos G.; Skouroupathis, A.; Tsapalis, Antonios (2006)
      We calculate the perturbative value of the free energy in lattice QCD in three dimensions, up to three loops. Our calculation is performed using the Wilson formulation for gluons in SU(N) gauge theories. The free energy ...
    • 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 ...
    • Article  

      Hadron wave functions and the issue of nucleon deformation 

      Alexandrou, Constantia; de Forcrand, Ph; Tsapalis, Antonios (2003)
      Using gauge invariant hadronic two- and three- density correlators we extract information on the spatial distributions of quarks in hadrons, and on hadron shape and multipole moments within quenched lattice QCD. Combined ...
    • Article  

      Higher loop results for the plaquette, using the clover and overlap actions 

      Athenodorou, A.; Panagopoulos, Haralambos G.; Tsapalis, Antonios (2005)
      We calculate the perturbative value of the free energy in QCD on the lattice. This quantity is directly related to the average plaquette. Our calculation is done to 3 loops using the clover action for fermions
    • Article  

      The lattice free energy of QCD with clover fermions, up to three-loops 

      Athenodorou, A.; Panagopoulos, Haralambos G.; Tsapalis, Antonios (2008)
      We calculate the perturbative value of the free energy in Lattice QCD, up to three loops. Our calculation is performed using Wilson gluons and the Sheikholeslami-Wohlert (clover) improved action for fermions. The free ...
    • Article  

      Lattice study of pentaquark states 

      Alexandrou, Constantia; Tsapalis, Antonios (2006)
      We present a study of the pentaquark system in quenched lattice QCD using diquark-diquark and kaon-nucleon local and smeared interpolating fields. We examine the volume dependence of the spectral weights of local correlators ...
    • Article  

      Matter and pseudoscalar densities in lattice QCD 

      Alexandrou, Constantia; De Forcrand, Ph; Tsapalis, Antonios (2003)
      The matter and the pseudoscalar densities inside a hadron are calculated via gauge-invariant equal-time correlation functions. A comparison is made between the charge and the matter density distributions for the pion, the ...
    • Article  

      The matter density distribution for mesons and baryons 

      Alexandrou, Constantia; de Forcrand, Ph; Tsapalis, Antonios (2004)
      The matter density distribution inside a hadron is evaluated using gauge-invariant correlation functions within the quenched and the unquenched theory. Comparison with the charge density distribution suggests that hadron ...
    • Article  

      Momentum dependence of the N to Δ transition form factors 

      Alexandrou, Constantia; de Forcrand, Ph; Neff, H.; Negele, J. W.; Schroers, W.; Tsapalis, Antonios (2005)
      We present a new method to determine the momentum dependence of the N to Δ transition form factors and demonstrate its effectiveness in the quenched theory at β = 6.0 on a 323 × 64 lattice. We address a number of technical ...
    • Article  

      N to Δ electromagnetic transition form factors from lattice QCD 

      Alexandrou, Constantia; De Forcrand, Ph; Lippert, Th; Neff, H.; Negele, J. W.; Schilling, K.; Schroers, W.; Tsapalis, Antonios (2004)
      The magnetic dipole, the electric quadrupole, and the Coulomb quadrupole amplitudes for the transition γN→Δ are evaluated both in quenched lattice QCD at β=6.0 and using two dynamical Wilson fermions simulated at β=5.6. ...
    • Article  

      N-to-Δ axial transition form factors from lattice QCD 

      Alexandrou, Constantia; Leontiou, Theodoros; Negele, J. W.; Tsapalis, Antonios (2007)
      We evaluate the N to Δ axial transition form factors in lattice QCD with no dynamical sea quarks, with two degenerate flavors of dynamical Wilson quarks, and using domain wall valence fermions with three flavors of staggered ...
    • Article  

      N-to-Δ electromagnetic-transition form factors from lattice QCD 

      Alexandrou, Constantia; De Forcrand, P.; Neff, H.; Negele, J. W.; Schroers, W.; Tsapalis, Antonios (2005)
      The magnetic dipole (M1), the electric quadrupole (E2), and the Coulomb quadrupole (C2) amplitudes for γN → Δ are calculated in quenched lattice QCD. Using a new method, which combines an optimal choice of interpolating ...
    • Article  

      Nucleon electromagnetic form factors from lattice QCD 

      Alexandrou, Constantia; Koutsou, Giannis; Negele, J. W.; Tsapalis, Antonios (2006)
      We evaluate the isovector nucleon electromagnetic form factors in quenched and unquenched QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at β=6.0 enabling us to reach ...
    • Article  

      Nucleon to delta electromagnetic transition form factors in lattice QCD 

      Alexandrou, Constantia; Koutsou, Giannis; Neff, H.; Negele, J. W.; Schroers, W.; Tsapalis, Antonios (2008)
      The electromagnetic nucleon to Δ transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain-wall valence quarks. The two subdominant ...