Lattice QCD and GlueX

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Lattice QCD and GlueX

David Richards
GlueX Collaboration Meeting
Nov 10th, 2005
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Outline.

• 12 GeV Science Review
• Advances and future plans for lattice QCD
  exploiting theory, software and hardware
• LHP Collaboration and Spectroscopy
• First entrée into Hybrids radiative transitions
  in charmonium
• PWA and EBAC

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12 GeV Science Review

• What is the mechanism of confinement?
• The major theoretical effort with this program is
  the development of the PWA software. The exotic
  mesons can couple to the multi-meson continuum
  even though they have unusual quantum numbers.
  This will complicate the PWA. The present PWA
  assumes an isobar model for meson processes.
  Theoretical effort is needed to develop more
  advanced methods that are not limited by the
  isobar assumptions. Development of lattice QCD
  calculations that can estimate the mass spectrum
  and partial widths of the exotic states needs to
  be vigorously pursued.

My italics!
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Advances in Lattice QCD
Inclusion of Pion Cloud
Actions with exact chiral symmetry
Precise computations at Physical Pion Mass
Advances in high-performance computing
DOEs SciDAC Initiative
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Advances in Lattice QCD - II

• Achievable precision limited by lightest pion
  mass

Flavor-non-singlet momentum fraction in nucleon.
Detmold et al, PRL87, 172001 (2001)
Light quark masses
Expt value

• Exact chiral symmetry at Finite Spacing a
• Domain-wall fermions (DWF) in five dimensions

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JLab Lattice QCD Clusters - I

• JLab SciDAC Clusters
• 2002 128 singles, 0.1 TFlops
• 2003 256 singles, 0.37 TFlops
• 2004 384 singles, 0.65 TFlops

First teraflops LQCD machine to achieve 1 per
MFlops!
Sustained performance on lattice QCD code
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JLab Lattice QCD Clusters II

• New HEP NP LQCD Facilities money
• 2006
• 2 Tflop machine at FNAL
• 0.4 Tflop machine at JLAB
• 2007
• 3 Tflop machine at JLAB
• 2008, 2009 further machines planned

• White Paper to DOE, Feb 05, following
  recommendation of 2004 S and T Review - Program
  of lattice studies with milestones linked to 12
  GeV.

New 3-5 Proposal as part of SciDAC II in
preparation. Call for proposals expected 12/05
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Nucleon Axial-Vector Charge
Benchmark ab initio Calculation
LHPC hep-lat/0510062
Beane and Savage
Two volumes
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LHPC Collaboration - Spectroscopy

• Collaboration, established in 1998, dedicated to
  exploiting lattice QCD for hadronic physics
• Members in around 20 institutions
• Important component dedicated to understanding
  spectrum of QCD, and their transitions
• Initial focus on tools for extracting baryon
  resonance spectrum will be applied to Hybrid
  Mesons

• S. Basak, R. Edwards, G. Fleming, U. Heller, C.
  Morningstar, DGR, I. Sato, S. Wallace
  hep-lat/0506029, Phys.Rev. D72 (2005) 074501
• Adam Lichtl, Lattice 05
• Jimmy Juge, Jo Dudek, Nilmani Mathur
• Developing collaborations with TCD.

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Hybrid Resonance Spectrum - I

• Spectrum of hybrids composed of heavy quarks has
  been important lattice focus
• Adiabatic Potentials
• Spectrum of charmonium

• 1 GeV Excitation Energy associated with excited
  string
• 1- lightest hybrid

MILC Collaboration
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Hybrid Resonance Spectrum - II
Compilation of data for mass of 1- from MILC
Collaboration
Scale set by string tension
Naïve extrap. of NF 0 data

• Does picture of hybrids obtained in charmonium
  sector persist to light-quark sector?
• Need to extract energy levels including
  two-particle energies using techniques LHPC is
  developing.

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Radiative transitions in charmonium using lattice
QCD

• Jo Dudek
• with Robert Edwards, David Richards

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Photo-couplings and Transition FF H ! ? M

• Photo-couplings between hybrid and conventional
  mesons need to be calculated!
• GlueX proposal to produce hybrid mesons using
  real photons supported by flux-tube model
  calculations
• No suppression of conventional-hybrid
  photo-couplings for hybrids near 2 GeV

Close and Dudek, PRL91, 142001 (2003) PRD 69
034010 (2004)
Investigate and attempt to verify prediction
using lattice QCD
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Radiative transitions on the lattice
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Charmonium?

• many exptally measured transitions

• relatively successful quark-potential-model
  phenomenology

Eichten, Lane Quigg PRL.89162002,2002

• no ?al extrapn required, quenching effects
  smaller(?), smaller volume

• heavy fermions non-trivial on a lattice

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Determined on lattice
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Extrapolation to Q2 0 using quark model
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(No Transcript)
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Summary

• ambitious combination of lattice methods
• heavy quarks
• domain wall fermions
• anisotropic action
• three-point functions

• reasonable (but limited) charmonium spectrum
  given the faulty quark mass

• extracted form-factors for charmonium (heavy
  versions of )

• Extension to charmonium hybrids
• Continuation to light-quark sector

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Meson Partial Wave Analysis

• Analysis will begin with a standard isobar PWA
  but this cannot account for all physics

a well-known example beyond the isobar approx. is
the Deck effect e.g.
observed in recent E852 analysis to distort
simple resonance production would have same
line shape in S D waves
Developing a toolbox of analysis techniques to be
applied to GlueX data aim to avoid
interpretation ambiguities of previous exotic
meson studies - Dudek with GlueX at IU EBAC at
JLab
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Summary

• Rigorous lattice effort at JLAB as part of
  national effort to develop hardware and software
  for lattice QCD
• Central goal of LHPC is to apply these resources
  to understanding of Hybrid Spectrum and Decays
• Exciting first look at radiative transitions in
  charmonium motivated by GlueX project