Now showing items 1-14 of 14

  • Computation of disconnected contributions to nucleon observables 

    Alexandrou, C; Drach, V; Jansen, K; Koutsou, G; Vaquero, A (2014-01-27)
    We compare several methods for computing disconnected fermion loops contributing to nucleon three-point functions. The comparison is carried out using one ensemble of $N_f=2+1+1$ twisted mass fermions with pion mass of ...
  • Disconnected hadronic vacuum polarization contribution to the muon g-2 with HISQ 

    Yamamoto, S; DeTar, C; El-Khadra, AX; McNeile, C; Water, RSVD; Vaquero, A (2018-11-14)
    We describe a computation of the contribution to the anomalous magnetic moment of the muon from the disconnected part of the hadronic vacuum polarization. We use the highly-improved staggered quark (HISQ) formulation for ...
  • 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 ...
  • Hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment from four-flavor lattice QCD 

    Davies, CTH; DeTar, C; El-Khadra, AX; Gamiz, E; Gottlieb, S; Hatton, D; Kronfeld, AS; Laiho, J; Lepage, GP; Liu, Y; Mackenzie, PB; McNeile, C; Neil, ET; Primer, T; Simone, JN; Toussaint, D; Water, RSVD; Vaquero, A (American Physical Society, 2020-02-18)
    We calculate the contribution to the muon anomalous magnetic moment hadronic vacuum polarization from the connected diagrams of up and down quarks, omitting electromagnetism. We employ QCD gauge-field configurations with ...
  • Nucleon Structure using lattice QCD 

    Alexandrou, C; Constantinou, M; Drach, V; Hatziyiannakou, K; Jansen, K; Kallidonis, C; Koutsou, G; Leontiou, T; Vaquero, A (2013-03-27)
    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 ...
  • Numerical experiments using deflation with the HISQ action 

    Davies, C; DeTar, C; McNeile, C; Vaquero, A (2017-10-19)
    We report on numerical experiments using deflation to compute quark propagators for the highly improved staggered quark (HISQ) action. The method is tested on HISQ gauge configurations, generated by the MILC collaboration, ...
  • 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 ...
  • Strangeness of the nucleon from lattice QCD 

    Alexandrou, C; Constantinou, M; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A
  • Strong-isospin-breaking correction to the muon anomalous magnetic moment from lattice QCD at the physical point 

    Chakraborty, B; Davies, CTH; DeTar, C; El-Khadra, AX; Gámiz, E; Gottlieb, S; Hatton, D; Koponen, J; Kronfeld, AS; Laiho, J; Lepage, GP; Liu, Y; Mackenzie, PB; McNeile, C; Neil, ET; Simone, JN; Sugar, R; Toussaint, D; Water, RSVD; Vaquero, A
    All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to-date have been performed with degenerate up- and down-quark masses. Here we calculate directly the ...

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