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Related papers: First results with non-perturbative fermion improv…

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We present preliminary results on the electromagnetic form factors and axial charge of the nucleon from ensembles generated by the CLS effort with $N_\mathrm{f}=2+1$ flavours of non-perturbatively $\mathrm{O}(a)$-improved Wilson fermions…

High Energy Physics - Lattice · Physics 2015-11-25 Dalibor Djukanovic , Tim Harris , Georg von Hippel , Parikshit Junnarkar , Harvey B. Meyer , Hartmut Wittig

Very light particles with CP-violating couplings to ordinary matter, such as axions or axion-like particles, can mediate long-range forces between polarized and unpolarized fermions. We describe a new experimental search for such forces…

High Energy Physics - Experiment · Physics 2018-04-25 Junyi Lee , Attaallah Almasi , Michael Romalis

We present our first set of results for charm physics, using the mixed-action setup introduced in a companion paper. Maximally twisted Wilson valence fermions are used on a sea of non-perturbatively $O(a)$-improved Wilson fermions, made up…

First results from lattice QCD revealing the chiral nonanalytic behavior of nucleon and Delta baryon magnetic moments are presented. Numerical simulations in the light quark mass regime employing the nonperturbatively O(a)-improved…

Nuclear Theory · Physics 2010-02-17 D. B. Leinweber , A. W. Thomas , A. G. Williams , R. D. Young , J. M. Zanotti , J. B. Zhang

We extend the epsilon-expansion of continuum chiral perturbation theory to nonzero lattice spacing in the framework of Wilson Chiral Perturbation Theory. We distinguish various regimes by defining the relative power counting of the quark…

High Energy Physics - Lattice · Physics 2010-11-05 Oliver Bar , Silvia Necco , Stefan Schaefer

Using Schroedinger functional techniques, we determine the coefficient of the clover term necessary for non-perturbative O(a) improvement of hypercubic smeared Wilson fermions on a quenched plaquette action background. Unlike for unsmeared…

High Energy Physics - Lattice · Physics 2008-11-26 Roland Hoffmann , Anna Hasenfratz , Stefan Schaefer

We present details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on 32^3x56 - 64^3x112 lattices at…

We present results on the nucleon axial vector form factors $G_A(q^2)$ and $G_p(q^2)$ in the quenched theory and using two degenerate flavors of dynamical Wilson fermions for momentum transfer squared from about 0.1 to about 2 GeV^2 and for…

High Energy Physics - Lattice · Physics 2008-11-26 C. Alexandrou , G. Koutsou , Th. Leontiou , J. W. Negele , A. Tsapalis

We present preliminary results for heavy to light transitions of pseudoscalar mesons, induced by the vector and tensor operators. This lattice study is performed in quenched approximation, by using the nonperturbatively improved Wilson…

High Energy Physics - Lattice · Physics 2015-06-25 A. Abada , D. Becirevic , Ph. Boucaud , J. P. Leroy , V. Lubicz , G. Martinelli , F. Mescia

We have constructed a new fermion action which is an approximation to the (chirally symmetric) Fixed-Point action, containing the full Clifford algebra with couplings inside a hypercube and paths built from renormalization group inspired…

High Energy Physics - Lattice · Physics 2015-06-25 P. Hasenfratz , S. Hauswirth , K. Holland , T. Jorg , F. Niedermayer

We make a comparison between our quenched-hadron-spectroscopy results for the non-perturbatively-improved Wilson action and the corresponding unimproved case, at beta=6.2 on the same set of gauge configurations. Within our statistics, we…

High Energy Physics - Lattice · Physics 2009-10-31 A. Cucchieri , T. Mendes , R. Petronzio

We calculate the effects of including dynamical fermion loops in the lattice QCD estimates of meson decay constants, by extrapolating the results from negative flavour numbers after a suitable matching of the pion and rho mass. For…

High Energy Physics - Lattice · Physics 2009-10-28 G. M. de Divitiis , R. Frezzotti , M. Guagnelli , M. Masetti , R. Petronzio

The $O(a)$ improved Wilson quark action on the anisotropic lattice is investigated. We carry out numerical simulations in the quenched approximation at three values of lattice spacing ($a_{\sigma}^{-1}=1$--2 GeV) with the anisotropy…

High Energy Physics - Lattice · Physics 2009-11-07 Hideo Matsufuru , Tetsuya Onogi , Takashi Umeda

We report on our computation of the leading hadronic contribution to the anomalous magnetic moment of the muon using two dynamical flavours of non-perturbatively O(a) improved Wilson fermions. The strange quark is introduced in the quenched…

High Energy Physics - Lattice · Physics 2015-06-03 Michele Della Morte , Benjamin Jäger , Andreas Jüttner , Hartmut Wittig

We compare overlap fermions, which are chirally invariant, and Wilson twisted mass fermions in the approach to the chiral limit. Our quenched simulations reveal that with both formulations of lattice fermions pion masses of O(250 MeV) can…

We present updated results on the nucleon electromagnetic form factors and axial coupling calculated using CLS ensembles with $N_\mathrm{f}=2+1$ dynamical flavours of Wilson fermions. The measurements are performed on large, fine lattices…

High Energy Physics - Lattice · Physics 2017-03-01 Dalibor Djukanovic , Tim Harris , Georg von Hippel , Parikshit Junnarkar , Harvey B. Meyer , Hartmut Wittig

Masses of positive and negative parity excited nucleons and hyperons are calculated in quenched lattice QCD using an O(a^2) improved gluon action and a fat-link clover fermion action in which only the irrelevant operators are constructed…

High Energy Physics - Lattice · Physics 2010-03-04 W. Melnitchouk , J. N. Hedditch , D. B. Leinweber , A. G. Williams , J. M. Zanotti , J. B. Zhang

Without chiral extrapolation, we achieved a realistic nucleon to (\rho)-meson mass ratio of (m_N/m_\rho = 1.23 \pm 0.04 ({\rm statistical}) \pm 0.02 ({\rm systematic})) in our quenched lattice QCD numerical calculation with staggered…

High Energy Physics - Lattice · Physics 2009-10-31 Seyong Kim , Shigemi Ohta

We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the CLS ensembles with $N_f=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved vector…

High Energy Physics - Lattice · Physics 2019-12-10 Dalibor Djukanovic , Konstantin Ottnad , Jonas Wilhelm , Hartmut Wittig

Results for nucleon matrix elements (arising from moments of structure functions) and form factors from a mixture of runs using Wilson, clover and overlap fermions (both quenched and unquenched) are presented and compared in an effort to…

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