• Article  

      The 4D SU(3) gauge theory with an imaginary θ term 

      Panagopoulos, Haralambos G.; Vicari, E. (2011)
      We study the scaling behavior of the 4D SU(3) lattice gauge theory in the presence of a θ term, by Monte Carlo simulations computing the topological properties at imaginary θ. The numerical results provide a good evidence ...
    • 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 ...
    • 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 ...
    • Conference Object  

      Computation of correlation matrices for tetraquark candidates with Jp = 0+ and flavor structure q1q2q3q3 

      Berlin, J.; Abdel-Rehim, 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 quark-Antiquark pair, but by a four-quark structure, is being actively investigated both theoretical and ...
    • 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 pion-nucleon state, extracting the pND 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 ...
    • 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  

      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 ...
    • Conference Object  

      Hadron deformation and form factors from lattice QCD 

      Alexandrou, Constantia (2007)
      We review the current status of lattice QCD studies of the nucleon system. In particular, we focus on the determination of the shape of the nucleon by probing its wave function as well as by evaluating the N to Δ transition ...
    • Conference Object  

      Hadron physics and lattice QCD 

      Alexandrou, Constantia (2013)
      A review of recent lattice QCD hadron structure calculations is presented. Important hadronic properties such as the axial charge and spin content of the nucleon, as well as, the mass and axial charge of hyperons and charmed ...
    • Article  

      Hadron properties from lattice QCD 

      Alexandrou, Constantia (2014)
      We discuss the status of current dyanmical lattice QCD simulations in connection to the emerging results on the low-lying baryon spectrum, excited states of the nucleon and the investigation of the structure of scalar ...
    • Article  

      Hadron structure from lattice QCD 

      Alexandrou, Constantia; Jansen, K. (2015)
      We review results for hadron masses and hadron structure using maximally twisted mass fermions for our non-perturbative studies of lattice QCD. We demonstrate that hadron masses can be computed reliably in this setup and ...
    • Article  

      Hadron structure in lattice QCD 

      Alexandrou, Constantia (2012)
      Recent progress in hadron structure calculations within lattice QCD is reviewed. Results on key observables such as the axial charge, the quark momentum fraction and the spin content of the nucleon are discussed with focus ...
    • Article  

      Higher representations on the lattice: Perturbative studies 

      Del Debbio, L.; Frandsen, M. T.; Panagopoulos, Haralambos G.; Sannino, F. (2008)
      We present analytical results to guide numerical simulations with Wilson fermions in higher representations of the colour group. The ratio of Λ parameters, the additive renormalization of the fermion mass, and the ...
    • Conference Object  

      Importance of closed quark loops for lattice QCD studies of tetraquarks 

      Berlin, J.; Abdel-Rehim, A.; Alexandrou, Constantia; Brida, M. D.; Finkenrath, J.; Gravina, M.; Leontiou, Theodoros; Wagner, M. (Proceedings of Science (PoS), 2016)
      To investigate the light scalar tetraquark candidate a0(980) (quantum numbers JP =0+), a correlation matrix including a variety of two- and four-quark interpolating operators has to be computed. We discuss efficient ...
    • Article  

      Investigating efficient methods for computing four-quark correlation functions 

      Abdel-Rehim, A.; Alexandrou, Constantia; Berlin, J.; Dalla Brida, M.; Finkenrath, J.; Wagner, M. (2017)
      We discuss and compare the efficiency of various methods, combinations of point-to-all propagators, stochastic timeslice-to-all propagators, the one-end trick and sequential propagators, to compute two-point correlation ...
    • Article  

      Investigation of light and heavy tetraquark candidates using lattice QCD 

      Wagner, M.; Abdel-Rehim, A.; Alexandrou, Constantia; Brida, M. D.; Gravina, M.; Koutsou, Giannis; Scorzato, L.; Urbach, C. (2014)
      We review the status of an ongoing long-term lattice investigation of the spectrum and structure of tetraquark candidates. We focus on the light scalar meson a0(980). First steps regarding the study of a possibly existing ...
    • Article  

      Large Wilson loops with overlap and clover fermions: Two-loop evaluation of the b-quark mass shift and the quark-antiquark potential 

      Athenodorou, A.; Panagopoulos, Haralambos G. (2008)
      We compute, to two loops in perturbation theory, the fermionic contribution to rectangular R × T Wilson loops, for different values of R and T. We use the overlap fermionic action. We also employ the clover action, for ...
    • Conference Object  

      A lattice calculation of parton distributions 

      Alexandrou, Constantia; Cichy, K.; Hadjiyiannakou, Kyriakos; Jansen, K.; Steffens, F.; Wiese, C. (Proceedings of Science (PoS), 2016)
      We present results for the x dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. ...