Browsing by Author "Alexandrou, Constantia"
Now showing items 120 of 155

Article
Adaptive aggregationbased domain decomposition multigrid for twisted mass fermions
Alexandrou, Constantia; Bacchio, S.; Finkenrath, J.; Frommer, A.; Kahl, K.; Rottmann, M. (2016)The adaptive aggregationbase domain decomposition multigrid method [A. Frommer, SIAM J. Sci. Comput. 36, A1581 (2014)] is extended for two degenerate flavors of twisted mass fermions. By finetuning the parameters we ...

Article
Axial charges of hyperons and charmed baryons using Nf=2+1+1 twisted mass fermions
Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Kallidonis, Christos (2016)The axial couplings of the low lying baryons are evaluated using a total of five ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using the Iwasaki gauge action and two ...

Article
Axial nucleon and nucleon to Δ form factors and the GoldbergerTreiman 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 pionnucleon form factor, GπNN(q2), in lattice QCD. We also evaluate the corresponding nucleon to Δ transition ...

Article
Axial nucleon form factors from lattice QCD
Alexandrou, Constantia; Brinet, M.; Carbonell, J.; Constantinou, Martha; Harraud, P. A.; Guichon, P.; Jansen, K.; Korzec, T.; Papinutto, M. (2011)We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1fm and ...

Article
Bmeson properties from lattice QCD
Alexandrou, Constantia; Jegerlehner, F.; Güsken, S.; Schilling, K.; Sommer, R. (1991)A high statistics computation of the decay constant f{hook}B is presented to study scaling and finite size effects. Smooth wave functions for the Bmeson allow to suppress excited state contributions effectively. We observe ...

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 lowlying 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 ...

Article
Baryon structure from Lattice QCD
Alexandrou, Constantia (2009)We present recent lattice results on the baryon spectrum, nucleon electromagnetic and axial form factors, nucleon to Δ transition form factors as well as the Δ electromagnetic form factors. The masses of the low lying ...

Article
Beautiful baryons from lattice QCD
Alexandrou, Constantia; Borrelli, A.; Güsken, S.; Jegerlehner, F.; Schilling, K.; Siegert, G.; Sommer, R. (1994)We perform a lattice study of heavy baryons, containing one (Λb) or two bquarks Ξb. Using the quenched approximation we obtain for the mass of Λb, MΛb = 5.728 ± 0.144 ± 0.018 GeV. The mass splitting between the λb and the ...

Article
Bounds on B from lattice QCD
Alexandrou, Constantia; Güsken, S.; Jegerlehner, F.; Schiling, K.; Sommer, R. (1992)We present a study of finitea effects in the leptonic decay constant P of heavy pseudoscalar mesons. Exploiting results on three lattices  with inverse lattice spacing a1 = 3.35, 2.3 and 1.53 GeV  to extrapolate P ...

Conference Object
Calculation of the decay width of decuplet baryons
Petschlies, Marcus; Alexandrou, Constantia; Negele, J. W.; Pochinsky, A. V.; Syritsyn, S. S. (Proceedings of Science (PoS), 2015)We calculate the coupling constant and decay width of the decuplet to octet baryon transitions in lattice QCD using the transfer matrix method. The transition amplitude is related to the coupling constant and via the Fermi's ...

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 2flavor theory.

Article
Colloquium: The shape of hadrons
Alexandrou, Constantia; Papanicolas, Costas N.; Vanderhaeghen, M. (2012)This Colloquium addresses the issue of the shape of hadrons and, in particular, that of the proton. The concept of shape in the microcosm is critically examined. Special attention is devoted to properly define the meaning ...

Article
Comparison of meanfield and exact Monte Carlo solutions of a onedimensional nuclear model
Alexandrou, Constantia; Myczkowski, J.; Negele, J. W. (1989)The ground states of nuclear matter and finite nuclei are calculated for a onedimensional model having a twobody potential with strong shortrange repulsion and longrange attraction. Meanfield theory with a phenomenological ...

Article
A complete nonperturbative renormalization prescription for quasiPDFs
Alexandrou, Constantia; Cichy, K.; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Panagopoulos, Haralambos G.; Steffens, F. (2017)In this work we present, for the first time, the nonperturbative renormalization for the unpolarized, helicity and transversity quasiPDFs, in an RI′ scheme. The proposed prescription addresses simultaneously all aspects ...

Conference Object
Computation of correlation matrices for tetraquark candidates with Jp = 0+ and flavor structure q1q2q3q3
Berlin, J.; AbdelRehim, A.; Alexandrou, Constantia; Dalla Brida, M.; Gravina, M.; Wagner, M. (Proceedings of Science (PoS), 2015)The conjecture that several recently observed mesons have a structure, which is not dominated by an ordinary quarkAntiquark pair, but by a fourquark structure, is being actively investigated both theoretical and ...

Conference Object
Computation of disconnected contributions to nucleon observables
Alexandrou, Constantia; Drach, V.; Jansen, K.; Koutsou, Giannis; AvilésCasco, A. V. (Proceedings of Science (PoS), 2013)We compare several methods for computing disconnected fermion loops contributing to nucleon threepoint functions. The comparison is carried out using one ensemble of Nf =2+1+1 twisted mass fermions with pion mass of 373 ...

Conference Object
DDalphaAMG for twisted mass fermions
Bacchio, S.; Alexandrou, Constantia; Finkenrath, J.; Frommer, A.; Kahl, K.; Rottmann, M. (Proceedings of Science (PoS), 2016)We present the Adaptive Aggregationbased Domain Decomposition Multigrid method extended to the twisted mass fermion discretization action. We show comparisons of results as a function of tuning the parameters that enter ...

Article
Deconfinement phase transition in oneflavor QCD
Alexandrou, Constantia; Boriçi, A.; Feo, A.; De Forcrand, P.; Galli, A.; Jegerlehner, F.; Takaishi, T. (1999)We present a study of the deconfinement phase transition of oneflavor QCD using the multiboson algorithm. The mass of the Wilson fermions relevant for this study is moderately large and the nonHermitian multiboson method ...

Conference Object
Determination of the Δ resonance width from lattice QCD
Petschlies, Marcus; Alexandrou, Constantia; Negele, J. W. (Proceedings of Science (PoS), 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 pionnucleon state, extracting the pND coupling constant and Δ ...

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 axialvector and pseudoscalar currents. The decomposition of these matrix elements into the appropriate Lorentz invariant form factors is carried ...