Hadron deformation from Lattice QCD

We address the issue of hadron deformation within the framework of lattice QCD. For hadrons with spin greater than 1/2 the deformation can be determined by evaluating the charge and matter distributions. Deviation of the nucleon shape from spherical symmetry is determined by evaluating the quadrupole strength in the transition $\gamma N \to \Delta(1232)$ both in the quenched and in the unquenched theory.Comment: 7 pages, Talk given at the second Workshop on Lattice Hadron Physics, Cairns, Australia, 22-30 July 2003. Corrected typo

The nucleon to Delta electromagnetic transition form factors in lattice QCD

The electromagnetic nucleon to Delta transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain wall valence quarks. The two subdominant quadrupole form factors are evaluated for the first time in full QCD to sufficient accuracy to exclude a zero value, which is taken as a signal for deformation in the nucleon-Delta system. For the Coulomb quadrupole form factor the unquenched results show deviations from the quenched results at low q^2 bringing dynamical lattice results closer to experiment, thereby confirming the importance of pion cloud contributions on this quantity.Comment: 15 pages, 8 Figure

Hadron wave functions and the issue of nucleon deformation

Using gauge invariant hadronic two- and three- density correlators we extract information on the spatial distributions of quarks in hadrons, and on hadron shape and multipole moments within quenched lattice QCD. Combined with the calculation of N to Delta transition amplitudes the issue of nucleon deformation can be addressed.Comment: 4 pages, 7 figures. Talk presented at the PANIC02 conference, Sept. 30 - Oct. 4, 2002, Osaka, Japan. Discussion of the N to Delta results modifie

The ground state of three quarks

We measure the static three-quark potential in SU(3) lattice gauge theory with improved accuracy, by using all available technical refinements, including Luscher-Weisz exponential variance reduction. Together with insight gained from 3-state Potts model simulations, our results allow us to sort out the merits of the Delta- and Y-ansaetze.Comment: 3 pages, 4 figures, talk presented at Lattice2002(topology

Hadron Deformation and Form Factors from Lattice QCD

We review the current status of lattice QCD studies of the nucleon system. In particular, we focus on the determination of the shape of the nucleon by probing its wave function as well as by evaluating the N to Delta transition form factors.Comment: 14 pages, 8 figures. Talk presented at the Workshop "The Shape of Hadrons", Athens, Greece, 27-30 April 200

Momentum dependence of the N to Delta transition form factors

We present a new method to determine the momentum dependence of the N to Delta transition form factors and demonstrate its effectiveness in the quenched theory at $\beta=6.0$ on a $32^3 \times 64$ lattice. We address a number of technical issues such as the optimal combination of matrix elements and the simultaneous overconstrained analysis of all lattice vector momenta contributing to a given momentum transfer squared, $Q^2$.Comment: Talk presented at Lattice 2004 (spectrum), Fermilab, 21-26 Jun. 2004. 3 pages, 3 figures. One typo in phenomenological Ansatz correcte

N to Delta electromagnetic and axial form factors in full QCD

Lattice results on the N to Delta electromagnetic, axial-vector and pseudoscalar form factors are evaluated using dynamical staggered sea quarks and domain wall valence quarks for pion masses in the range of 580-350 MeV, as well as, dynamical and quenched Wilson fermions for similar pion masses.Comment: 8 pages, 6 Figures. Invited talk given at the Workshop Exclusive Reactions at High Momentum Transfer, Jefferson Lab, Newport News, USA, May 21-24 200

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

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