Investigations of hadron structure on the lattice

Zanotti, J. M.

doi:10.22323/1.066.0007

Cited by 29 publications

(34 citation statements)

References 47 publications

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“…More attention has focused on the nucleon, with the first computations in (Martinelli and Sachrajda, 1989) and a brief contemporary overview in (Zanotti, 2008), but it remains true that disconnected diagrams are neglected in almost all extant studies. It follows that only results for isovector quantities are directly comparable with those determined empirically; i.e.,…”

Section: Lattice Qcdmentioning

confidence: 99%

“…The mixed-action results appear to differ from the others by a normalisation factor, which is perhaps understandable given that (Hägler et al, 2008) does not use the fully nonperturbative renormalization procedure employed in the other studies. [ Figure adapted from (Zanotti, 2008). ] namely, domain wall valence-quarks but 2 + 1 flavors of staggered sea-quarks, with lightquark masses corresponding to m π = 350 MeV.…”

Section: Lattice Qcdmentioning

confidence: 99%

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Nucleon and pion distribution functions in the valence region

2010

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We provide an experimental and theoretical perspective on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain; namely, Bjorken-x > ∼ 0.4. This domain is key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. We focus on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the Standard Model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, we explain that an upgraded Jefferson Lab facility is well-suited to provide new data on the nucleon, while a future electron ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, J-PARC and GSI, to push into the large-x domain for both mesons and nucleons. We argue furthermore that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum field theory; and a fuller exploitation of those methods. * Electronic address: holt@anl.gov † Electronic address: cdroberts@anl.gov

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Section: Lattice Qcdmentioning

confidence: 99%

Section: Lattice Qcdmentioning

confidence: 99%

Nucleon and pion distribution functions in the valence region

2010

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“…In the past years, many lattice QCD studies have been made for these isovector form factors in the above-mentioned contexts [17,18]. Many earlier works [1,19,20,21,22] were performed either in the quenched approximation, neglecting dynamical sea-quark effects or were either limited to two dynamical flavors of Wilson fermion quarks that explicitly violate chiral symmetry [23,24,25], limited to non-unitary combination of valence and sea quarks [26,27,28,29], or just two dynamical flavors of domain-wall fermions (DWFs) [2].…”

Section: Introductionmentioning

confidence: 99%

Nucleon form factors with2+1flavor dynamical domain-wall fermions

et al. 2009

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We report our numerical lattice QCD calculations of the isovector nucleon form factors for the vector and axialvector currents: the vector, induced tensor, axialvector, and induced pseudoscalar form factors. The calculation is carried out with the gauge configurations generated with N f = 2+1 dynamical domain wall fermions and Iwasaki gauge actions at β = 2.13, corresponding to a cutoff a −1 = 1.73 GeV, and a spatial volume of (2.7 fm) 3 . The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while the strange quark mass is about 12 % heavier than the physical one. We calculate the form factors in the range of momentum transfers, 0.2 < q 2 < 0.75 GeV 2 . The vector and induced tensor form factors are well described by the conventional dipole forms and result in significant underestimation of the Dirac and Pauli meansquared radii and the anomalous magnetic moment compared to the respective experimental values.We show that the axialvector form factor is significantly affected by the finite spatial volume of the lattice. In particular in the axial charge, g A /g V , the finite volume effect scales with a single dimensionless quantity, m π L, the product of the calculated pion mass and the spatial lattice extent.Our results indicate that for this quantity, m π L > 6 is required to ensure that finite volume effects are below 1%.

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“…In fact, there are many lattice QCD studies of the nucleon structure [2]. However, most of these calculations are limited to the so-called "connected insertion (CI)", and there have been few calculations considering "disconnected insertion (DI)" [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

Strangeness in the nucleon from lattice QCD

Doi¹,

Deka²,

Dong³

et al. 2009

Proceedings of the XXVI International Symposium on Lattice Field Theory — PoS(LATTICE 2008)

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χQCD collaborationWe study the strangeness contribution to nucleon matrix elements using N f = 2 + 1 dynamical clover fermion configurations generated by the CP-PACS/JLQCD collaboration. In order to evaluate the disconnected insertion (DI), we use the Z(4) stochastic method, along with unbiased subtraction from the hopping parameter expansion which reduces the off-diagonal noises in the stochastic method. Furthermore, we find that using many nucleon sources for each configuration is effective in improving the signal. Our results for the quark contribution to the first moment x q in the DI, and the strangeness magnetic moment show that the statistical errors are under control with these techniques. We also study the gluonic contribution to the nucleon using the overlap operator to construct the gauge field tensor, F µν . The application to the calculation of first moment, x G , gives a good signal in quenched lattice QCD.

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Investigations of hadron structure on the lattice

Cited by 29 publications

References 47 publications

Nucleon and pion distribution functions in the valence region

Nucleon and pion distribution functions in the valence region

Nucleon form factors with2+1flavor dynamical domain-wall fermions

Strangeness in the nucleon from lattice QCD

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