Now showing items 1-13 of 13

  • Baryon spectrum using Nf=2+1+1 ensembles of twisted mass fermions 

    Alexandrou, C; Drach, V; Hadjiyiannakou, K; Jansen, K; Kallidonis, C; Koutsou, G (2014-12-02)
    We present results on the masses of the low-lying baryons using ten ensembles of gauge configurations with $N_f =2+1+1$ dynamical twisted mass fermions, at three values of the lattice spacing, spanning a pion mass range ...
  • Disconnected quark loop contributions to nucleon observables in lattice QCD 

    Abdel-Rehim, A; Alexandrou, C; Constantinou, M; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A (2013-10-23)
    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 ...
  • Evaluation of disconnected contributions using GPUs 

    Alexandrou, C; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Strelchenko, A; Vaquero, A (2012-11-01)
    We calculate on GPUs the disconnected diagrams associated with the nucleon form factors and moments of generalized parton distributions using Nf=2+1+1 twisted mass fermions. We employ the truncated solver method (TSM) for ...
  • Evaluation of disconnected quark loops for hadron structure using GPUs 

    Alexandrou, C; Constantinou, M; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Strelchenko, A; Vaquero, A (2013-09-09)
    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 ...
  • First moment of the flavour octet nucleon parton distribution function using lattice QCD 

    Alexandrou, C; Constantinou, M; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A (2015-01-15)
    We perform a lattice computation of the flavour octet contribution to the average quark momentum in a nucleon, $\la x\ra^{(8)}_{\mu^2 = 4 \gev^2}$. In particular, we fully take the disconnected contributions into account ...
  • First results with twisted mass fermions towards the computation of parton distribution functions on the lattice 

    Alexandrou, C; Cichy, K; Drach, V; Garcia-Ramos, E; Hadjiyiannakou, K; Jansen, K; Steffens, F; Wiese, C (2014-11-04)
    We report on our exploratory study for the evaluation of the parton distribution functions from lattice QCD, based on a new method proposed in Ref.~arXiv:1305.1539. Using the example of the nucleon, we compare two different ...
  • Lattice calculation of parton distributions 

    Alexandrou, C; Cichy, K; Drach, V; Garcia-Ramos, E; Hadjiyiannakou, K; Jansen, K; Steffens, F; Wiese, C
  • Looking at the gluon moment of the nucleon with dynamical twisted mass fermions 

    Alexandrou, C; Drach, V; Hadjiyiannakou, K; Jansen, K; Kostrzewa, B; Wiese, C (2013-11-13)
    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 $\langle x \rangle_g$ for the nucleon. ...
  • The quark contents of the nucleon and their implication for dark matter search 

    Alexandrou, C; Constantinou, M; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Strelchenko, A; Vaquero, A (2013-11-24)
    We present results concerning the light and strange quark contents of the nucleon using $N_f=2+1+1$ flavours of maximally twisted mass fermions. The corresponding $\sigma$-terms are casting light on the origin of the ...
  • Results on the disconnected contributions for hadron structure 

    Alexandrou, C; Constantinou, M; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A (2014-10-31)
    We present results on the disconnected contributions to three point functions entering in studies of hadron structure. We use $N_F = 2+1+1$ twisted mass fermions and give a detailed description on the results of the nucleon ...
  • Sigma terms and strangeness content of the nucleon with $Nf=2+1+1$ twisted mass fermions 

    Alexandrou, C; Constantinou, M; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Strelchenko, A; Vaquero, A (2012-11-19)
    We investigate excited state contaminations in a direct computation of the nucleon $\sigma$-terms. This is an important source of systematic effects that needs to be controlled besides the light quark mass dependence and ...
  • A Stochastic Method for Computing Hadronic Matrix Elements 

    Alexandrou, C; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Renner, DB (2013-02-11)
    We present a stochastic method for the calculation of baryon three-point functions that is more versatile compared to the typically used sequential method. We analyze the scaling of the error of the stochastically evaluated ...
  • Strangeness of the nucleon from lattice QCD 

    Alexandrou, C; Constantinou, M; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A

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