Browsing by Author "Drach, V."

Now showing items 1-17 of 17

    • 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  

      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 ...
    • 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  

      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  

      Lattice calculation of parton distributions 

      Alexandrou, Constantia; Cichy, K.; Drach, V.; Garcia-Ramos, E.; Hadjiyiannakou, Kyriakos; Jansen, K.; Steffens, F.; Wiese, C. (2015)
      We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using N f = 2 + 1 + 1 twisted ...
    • Article  

      Light baryon masses with dynamical twisted mass fermions 

      Alexandrou, Constantia; Baron, R.; Blossier, B.; Brinet, M.; Carbonell, J.; Dimopoulos, Petros; Drach, V.; Farchioni, F.; Frezzotti, R.; Guichon, P.; Herdoiza, G.; Jansen, K.; Korzec, T.; Koutsou, Giannis; Liu, Z.; Michael, C.; Pène, O.; Shindler, A.; Urbach, C.; Wenger, U. (2008)
      We present results on the mass of the nucleon and the Δ using two dynamical degenerate twisted mass quarks and the tree-level Symanzik improved gauge action. The evaluation is performed at four quark masses corresponding ...
    • Conference Object  

      Looking at the gluon moment of the nucleon with dynamical twisted mass fermions 

      Alexandrou, Constantia; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kostrzewa, B.; Wiese, C. (Proceedings of Science (PoS), 2013)
      To understand the structure of hadrons it is important to know the PDF of their constituents, the quarks and gluons. In our work we aim to compute the first moment of the gluon PDF h(x)ig for the nucleon. We follow two ...
    • Article  

      Low-lying baryon spectrum with two dynamical twisted mass fermions 

      Alexandrou, Constantia; Baron, R.; Carbonell, J.; Drach, V.; Guichon, P.; Jansen, K.; Korzec, T.; Pène, O. (2009)
      The masses of the low-lying baryons are evaluated using two degenerate flavors of twisted mass sea quarks corresponding to pseudoscalar masses in the range of about 270-500 MeV. The strange valence quark mass is tuned to ...
    • Article  

      Nucleon form factors and moments of generalized parton distributions using Nf=2+1+1 twisted mass fermions 

      Alexandrou, Constantia; Constantinou, Martha; Dinter, S.; Drach, V.; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis (2013)
      We present results on the axial and the electromagnetic form factors of the nucleon, as well as on the first moments of the nucleon generalized parton distributions using maximally twisted mass fermions. We analyze two N ...
    • Conference Object  

      Nucleon generalized form factors with twisted mass fermions 

      Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis (Proceedings of Science (PoS), 2013)
      We present results on the nucleon form factors, momentum fraction and helicity moment for Nf = 2 and Nf = 2+1+1 twisted mass fermions for a number of lattice volumes and lattice spacings. First results for a new Nf = 2 ...
    • Article  

      Nucleon structure using lattice QCD 

      Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Leontiou, Theodoros; Vaquero, A. (2013)
      A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods ...
    • Article  

      Precision study of excited state effects in nucleon matrix elements 

      Dinter, S.; Alexandrou, Constantia; Constantinou, Martha G.; Drach, V.; Jansen, K.; Renner, D. B. (2011)
      We present a dedicated analysis of the influence of excited states on the calculation of nucleon matrix elements. This calculation is performed at a fixed value of the lattice spacing, volume and pion mass that are typical ...
    • Conference Object  

      The quark contents of the nucleon and their implication for dark matter search 

      Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Strelchenko, A.; Vaquero, A. (Proceedings of Science (PoS), 2013)
      We present results concerning the light and strange quark contents of the nucleon using Nf = 2+1+1 flavours of maximally twisted mass fermions. The corresponding σ- Terms are casting light on the origin of the nucleon mass ...
    • Article  

      A stochastic method for computing hadronic matrix elements 

      Alexandrou, Constantia; Constantinou, Martha; Dinter, S.; Drach, V.; Jansen, K.; Hadjiyiannakou, Kyriakos; Renner, D. B. (2014)
      We present a stochastic method for the calculation of baryon three-point functions that is more versatile than the typically used sequential method. We analyze the scaling of the error of the stochastically evaluated ...
    • Article  

      Strange and charm baryon masses with two flavors of dynamical twisted mass fermions 

      Alexandrou, Constantia; Carbonell, J.; Christaras, D.; Drach, V.; Gravina, M.; Papinutto, M. (2012)
      The masses of the low-lying strange and charm baryons are evaluated using two degenerate flavors of twisted mass sea quarks for pion masses in the range of about 260 to 450MeV. The strange and charm valence quark masses ...
    • Article  

      Strangeness of the nucleon from lattice QCD 

      Alexandrou, Constantia; Constantinou, Martha; Dinter, S.; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Vaquero, A. (2015)
      We present a nonperturbative calculation of the strangeness of the nucleon yN within the framework of lattice QCD. This observable is known to be an important cornerstone to interpret results from direct dark matter detection ...