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Kab/SC-PAC2001-6.19.01 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator.

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Presentation on theme: "Kab/SC-PAC2001-6.19.01 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator."— Presentation transcript:

1 kab/SC-PAC Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Hadron Structure at Light Quark Masses DWF Valence on a Asqtad light sea Nucleon Properties: Form Factors g A Momentum and Spin Fraction GPDs Pion Form Factor David Richards (Jefferson Laboratory) for LHPC

2 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 LHP Collaboration Dru Renner University of Arizona Richard Brower, James Osborn Boston University Rebecca Irwin, Michael Ramsey-Musolf CalTech Robert Edwards, David Richards JLab Bojan Bistrovic, Jonathan Bratt, Patrick Dreher, Oliver Jahn, John Negele, Kostas Orginos, Andrew Pochinsky, Dmitry Sigaev MIT Matthias Burkardt, Michael Engelhardt New Mexico State University George Fleming Yale Constantia Alexandrou, Antonios Tsapalis Cyprus, Wolfram Schroers DESY, Philippe de Forcrand EHT-Zurich, Philipp Hägler Vrije Universiteit Many transparencies

3 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Onward to light pion masses…. Flavor-non-singlet momentum fraction in nucleon. Light quark masses Detmold et al, PRL87, (2001) Achievable precision limited by lightest pion mass Exact chiral symmetry at Finite Spacing a Domain-wall fermions (DWF) in five dimensions Expt value

4 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 DWF Computations MILC Asqtad lattices – staggered sea quarks Conventional DWF valence quarks computed on HYP-smeared lattices: use non-perturbative HYP parameters. Lattices bisected in temporal direction – DWF propagators computed using Dirichlet boundary conditions on half lattice M 5 = 1.7 – L s = 16 Parameter matching – tune DWF pion to match Asqtad Goldstone pion mass m  a = 0.13 fm, two volumes at lightest pion mass PRD64,

5 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 DWF parameters Alternate configs on first and second halves of lattice m  L = 4.5 m  L = 6.3

6 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Pion mass matching.. DWF Pion matched to Goldstone Pion

7 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Setting L 5 Residual mass Finite L5 induces extra term in divergence of axial current 0L D PCAC from 5-D CVC Domain walls J a 5q

8 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Residual mass….

9 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Residual Mass….. Pion Nucleon

10 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Meson masses….. Pion Rho

11 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Baryon masses…. Nucleon Delta

12 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Spectrum summary…

13 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 DIS and GPD’s for Nucleons Measures light-cone correlation functions DIS gives diagonal matrix element DVCS gives off-diagonal matrix element

14 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Moments of Structure Functions and GPD’s Generates tower of twist-two operators Expand O(x) around light-cone Diagonal matrix element Off-diagonal matrix element NN JJ pq

15 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Moments….. GPDs and GFFs are related through Mellin Transformation: Generalized Form Factors familiar quantities

16 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Renormalization of Operators One-loop renormalization of operators in boosted perturbation theory: HYP Constants close to unity B. Bistrovic, PhD Thesis, MIT 2005

17 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Nucleon EM Form Factors - I At large Q 2, scaling predicted by Brodsky and Lepage: F 1 » Q -4 and F 2 » Q -6 Perturbative corrections Phys. Rev. Lett. 88, (2002) Brodsky; Belitsky, Ji, Yuan

18 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Nucleon EM Form Factors - II I = 1 form factors to remove disconnected contributions F 1 I = 1 = F 1p – F 1n Neutron form factors poorly known for Q 2 > 1 GeV 2 Form factors normalized F 2 (Q 2 ) !  as Q 2 ! 0 Preliminary

19 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Nucleon EM Form Factors - III F 2 I=1 /F 1 I=1 !  p -  n as Q 2 ! 0. Use PDG  ’s

20 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Nucleon Axial Charge - I Nucleon axial charge – benchmark computation Chiral behavior expected to be mild LHPC Preliminary Two volumes

21 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Axial Charge - II Hemmert, hep-lat/ Two free parameters: g NN A, and g  A. Remaining parameters from phenomenology f , g N  A, m  - m N, B 9 - g A B 20.

22 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Momentum Fraction - Preliminary Unsmeared links Smeared links Z = 1

23 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Polarized - Preliminary Smeared links Z = 1 Orginos, Blum, Ohta – hep-lat/

24 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Generalized form factors… Decrease slope : decreasing transverse size as x ! 1 Burkardt

25 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Transverse distribution A 30 : GeV A 20 :

26 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Pion Form Factor –I Laboratory for observing interplay between perturbative and non-perturbative aspects of QCD Asymptotic normalization determined Small Q 2, vector-meson dominance provides faithful description Free of disconnected contributions – straightforward lattice calculation Scale?

27 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Pion Form Factor –II Current and Projected Experimental Situation

28 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Pion Form Factor –III LHPC, Bonnet et al hep-lat/ Pion Form factor over Q 2 commensurate with experiment Pion GPDs and transition form factors

29 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility SciDAC – June 2005 Conclusions and Perspective Use of hybrid Asqtad/DWF calculation providing entry into pion-cloud regime for range of physical quantities – spectrum, nucleon and meson form factors and transition form factors, moments of PDF’s and GPD’s… Preliminary results – more complete analysis for Dublin Computations being extended both to smaller values of lattice spacing (a=0.9, 0.6 fm), and to lighter m  = 250 MeV – reveal effects of pion cloud. Disconnected diagrams, transition form factors…


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