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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 ccc̄c̄ tetraquark are also outlined.
We present results on the mass of the nucleon and the ∆ using two dynamical degenerate twisted mass quarks. The evaluation is performed at four quark masses corresponding to a pion mass in the range of 690-300 MeV on lattices of size 2.1 fm and 2.7 fm. We check for cutoff effects by evaluating these baryon masses on lattices of spatial size 2.1 fm with… (More)
We evaluate the static qqqq ¯ q potential in the quenched theory at β = 5.8 and β = 6.0 on a lattice of size 16 3 × 32. The mass and density-density correlator for the Θ + is investigated in the quenched theory at β = 6.0 on lattices of size 16 3 × 32, 24 3 × 32 and 32 3 × 64.
PLQCD is a stand–alone software library developed under PRACE for lattice QCD. It provides an implementation of the Dirac operator for Wilson type fermions and few efficient linear solvers. The library is optimized for multi-core machines using a hybrid parallelization with OpenMP+MPI. The main objectives of the library is to provide a scalable… (More)
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 evaluate the disconnected quark loops to sufficient accuracy to determine the strange and charm nucleon σ terms in addition to the light quark… (More)
We determine the quark mass ratio m(c)/m(s) on the lattice, using Wilson-type fermions. Configurations with N(f)=2 dynamical clover-improved fermions by the QCDSF Collaboration are used, which were made available through the ILDG. In the valence sector we use a sophisticated, mass-independently O(a)-improved Wilson-type action with small cutoff effects even… (More)
We discuss the techniques to extract the electromagnetic ∆ form factors in Lattice QCD. We evaluate these form factors using dynamical fermions with smallest pion mass of about 350 MeV. We pay particular attention to the extraction of the electric quadrupole form factor that signals a deformation of the ∆. The magnetic moment of the ∆ is extrapolated using… (More)
We present a study of gauge invariant density-density correlators. Density-density correlators probe hadron wave functions and thus can be used to study hadron deformation. Their zero momentum projection requires the computation of all-to-all propagators, which are evaluated with the standard stochastic technique, the dilution method and the stochastic… (More)
We present the first calculation on the Δ axial vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axial charge, N to Δ axial transition coupling constant and Δ axial charge.