impact of lattice qcd on nuclear physicsweb.physics.ucsb.edu/~sugar/nuclear.pdf · impact of...
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Impact of Lattice QCDon Nuclear Physics
J. W. Negele
NSF October 10, 2003
GOAL: Understand the structureand interactions of hadrons andthe properties of hadronic matterfrom first principles
• Quantitative calculation of
experimental observables
• Insight into how QCD works
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Nuclear Physics Perspective
• Nuclear physics
Finite nuclei
Structure
EM Probes
Spectroscopy
Nuclear matter
Bulk properties
Pairing
Neutron stars
• Hadronic physics
Hadrons
Structure
EM Probes
Spectroscopy
Hadronic matter
Bulk properties
Color superconductivity
Neutron stars
Ambiguity in N-N interaction - scales
Fundamental QCD Lagrangian
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Three Areas of QCD PhysicsLattice calculations essential to understandingphysics in each case
• Heavy Quark Systems
Confirm standard model or elucidate physicsbeyond it
• QCD Thermodynamics
Properties of hadronic matter under extremeconditions
Foundation for RHIC physics → LHC
• Hadron Structure
Quark and gluon structure of hadrons
Spectroscopy
Hadron-hadron interactions
Crucial to understand physics from Bates,Jlab, SLAC, Fermilab and RHIC-spin
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Hadron Structure
• Form factors
GE , GM Jlab
Strangeness FF Sample, Happex
• Transition form factors
N → ∆ - deformation Bates, JLab
• Parton Distributions RHIC spin, Hermes …
Quark distributions <x>q
Spin distribution - spin crisis ∆Σ ~ <1>∆q
Transversity distribution <1>δq
• Generalized Parton Distributions Jlab
Total quark angular momentum J
Transverse structure of nucleon
Transverse size → 0 as x → 1
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Electromagnetic Form Factors
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Nucleon-Delta Transition Form Factor
• Calculate transition amplitudes
M1 dominates
C2 and E2 vanish if nucleon and deltaspherical
• Lattice calculations
hep-lat/030007018 Alexandrou, Tsapalis, J.N et. al.
M1/E2 expt
= -1.6 (.4)
Quenched
= -4.8 (1.1)
Full QCD
= -3.5 (1.2)
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Momentum Fraction <x>
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Momentum Fraction <x>
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Quark Angular Momentum
Connected diagram contributions
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Transverse Structure of Parton Distribution
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Spectroscopy
• N* Spectroscopy JLab
Number and structure of states
• Exotics JLab
Glueballs
Exotic mesons - gluonic excitations
Pentaquark
• Hadronic Interactions
Heavy-light meson and baryon interactions
• Light quark exchange
• Gluon contributions
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Exotic Mesons
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Roper Resonance
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Pentaquarks
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QCD Thermodynamics
• Phase diagram of QCD
• Zero baryon density (µ = 0)
Transition to Quark Gluon Plasma
E(T), P(T)
• Non-zero baryon density (µ ≠ 0)
Critical point - RHIC signatures
Equation of state - neutron stars
Superconducting phases
• Quark number susceptibility
Event by event fluctuations
• Quark-antiquark potential
J/Ψ production
• Current correlation functions - spectral function
Dilepton and photon emission
Transport coefficients
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Quark Susceptibility
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Screening of Heavy Quark Potential
Kaczmarek et al hep-lat/0309121
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Spectral Functions
J/Ψ survives up to 2.25 TC
Petreczky et al hep-lat/0309012
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Fundamental aspects of QCD
Insight into how QCD works
• Confinement
Mechanism, flux tubes
• Chiral symmetry breaking
Instantons, zero modes
• Low energy effective theory
Parameters of chiral perturbation theory
• Structure of wave functions
Variational wave functions
Density-density correlation functions
• Configurations that dominate path integral
Instantons
• Dependence on parameters of QCD
Nc , Nf , gauge group, mq
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Long Term Effort
• Quantities for which we already have theoreticaland computational tools
Need 10’s of Teraflops - Petaflops for precisioncalculations at level of few percent
• Challenges with the potential for opening stillmore vistas
Example: Finite chemical potential
Cluster algorithms
• Sustained effort at leading edge of technologycurve provides outstanding opportunity forfundamental advances in Nuclear Theory
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Computational Issues
• Fermion determinant - Full QCD
• Lattice spacing small
• Quark mass small
• Lattice volume large
• Disconnected diagrams