Novel applications of Lattice QCD: Parton distribution functions, proton charge radius and neutron electric dipole moment

We briefly discuss the current status of lattice QCD simulations and review selective results on nucleon observables focusing on recent developments in the lattice QCD evaluation of the nucleon form factors and radii, parton distribution functions and their moments, and the neutron electric dipole moment. Nucleon charges and moments of parton distribution functions are presented using simulations generated at physical values of the quark masses, while exploratory studies are performed for the parton distribution functions and the neutron electric dipole moment at heavier than physical value of the pion mass.Comment: Plenary talk at XII Quark Confinement, 29 August - 3 September, 2016, Thessaloniki, Greece, 20 pages, 21 figure

Hadron structure from lattice QCD - outlook and future perspectives

We review results on hadron structure using lattice QCD simulations with pion masses close or at to the physical value. We pay particular attention to recent successes on the computation of the mass of the low-lying baryons and on the challenges involved in evaluating energies of excited states and resonance parameters, as well as, in studies of nucleon structure.Comment: Corrected figure 1 and added references. Conference proceedings, 10 pages and 8 figures. Plenary talk presented at the 20th Particle and Nuclear International Conference (PANIC 2014), 25-29 Hamburg, German

Nucleon structure from lattice QCD - recent achievements and perspectives

We present recent developments in lattice QCD simulations as applied in the study of hadron structure. We discuss the challenges and perspectives in the evaluation of benchmark quantities such as the nucleon axial charge and the isovector parton momentum fraction, as well as, in the computation of the nucleon $\sigma$-terms, which involve the calculation of disconnected quark loop contributions.Comment: Invited talk at the 13th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2013), Rome, Italy, 30 Sept- Oct. 4, 2013. 6 pages, 10 figure

The volume dependence of spectral weights and the pentaquark state

Before studying the pentaquark system we examine the spectral weights of the two lowest scattering states in the two-pion system in the isospin I=2 channel on lattices of size $16^3\times 32$, $24^3 \times 32$ and $32^3 \times 64$ at $\beta=6.0$ in the quenched theory. We find that the spectral weights scale with the volume for large time separations. Therefore very accurate data are necessary in order that the spectral weights determined on different volumes yield a ratio that is precise enough to distinguish a scattering state from a single particle state. The pentaquark system is studied on the same lattices and scaling of the spectral weights of the low lying state is investigated. The accuracy of the results obtained for the scaling of spectral weights do not allow us to exclude a pentaquark resonance.Comment: 6 pages, 7 Figures, presented at Lattice 2005 (Hadron sprectrum), uses PoS.cl

Nucleon to Δ\Delta and Δ\Delta form factors in Lattice QCD

We present recent lattice QCD results on the electroweak nucleon to $\Delta$ transition and $\Delta$ form factors using dynamical fermion gauge configurations with a lowest pion mass of about 300 MeV, with special emphasis in the determination of the sub-dominant quadrupole $N\gamma^*\rightarrow \Delta$ and $\Delta$ electromagnetic form factors.Comment: Invited talk presented at the 8th International Workshop on the Physics of Excited Nucleons May 17-20, 2011, Thomas Jefferson National Accelerator Facility Newport News, Virginia USA. 6 pages and 6 figure

Multigrid accelerated simulations for Twisted Mass fermions

Simulations at physical quark masses are affected by the critical slowing down of the solvers. Multigrid preconditioning has proved to deal effectively with this problem. Multigrid accelerated simulations at the physical value of the pion mass are being performed to generate $N_f = 2$ and $N_f = 2 + 1 + 1$ gauge ensembles using twisted mass fermions. The adaptive aggregation-based domain decomposition multigrid solver, referred to as DD-$\alpha$AMG method, is employed for these simulations. Our simulation strategy consists of an hybrid approach of different solvers, involving the Conjugate Gradient (CG), multi-mass-shift CG and DD-$\alpha$AMG solvers. We present an analysis of the multigrid performance during the simulations discussing the stability of the method. This significant speeds up the Hybrid Monte Carlo simulation by more than a factor $4$ at physical pion mass compared to the usage of the CG solver.Comment: 8 pages, 5 figures, proceedings for LATTICE 201