QCD Key Issues in Hadron Physics QCD fundamentals. The quark structure of matter seen using PQCD and...
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Transcript of QCD Key Issues in Hadron Physics QCD fundamentals. The quark structure of matter seen using PQCD and...
QCD
Key Issues in Hadron Physics
QCD fundamentals.
The quark structure of matter seen using PQCD and elastic form factors
The quark structure of matter as seen using spectroscopy.
The quark structure of matter as seen using chiral dynamics
Models of the quark structure of matter
Key Scientific Issues in Hadron PhysicsNovember 6-9, 2000 Duck, NC (Curtis A. Meyer)
QCD
Key Issues in Hadron Physics
P. Barnes, T. Barnes, J.Bjorken, S. Capstick, L.Cardman, C. Carlson. S.Chandrasekharan, J.Peng, F.Close, T.Cohen, K.Dejager, J.Domingo, S.Dytman, A.Dzierba, R.Edwards, R.Ent, G.Garvey, R.Holt, D.Isenhower, N.Isgur,R.Jaffe, S.Jeschonnek, X.Ji, E.Kinney, F.Lee, M.Leitch, N.Makins, A.Manohar, J.McCelland, L.McLerran, W.Melnitchouk, M.Mestayer, C.Meyer, C. Michael, R.Milner, C.Morningstar, J.Moss, B.Nefkens, A.Radyushkin, D.Richards, E.Shuryak, M.Strikman,
E.Swanson, A.Szczepaniac, H.Thacker, B.Tippens, F.Wilczek
Participants at the Workshop
QCD
Key Issues in Hadron Physics
Organization
1 2.5
Morn
ing
Aft
ern
oo
n
Summary Talk
Summary Talk
Discussion
Discussion
QCD
Key Issues in Hadron Physics
Strong interaction physics poses a wealth of fundamentalquestions with profound significance for our understanding of Nature and the structure of the matter of which we and ouruniverse are composed. Answering these questions lies at the heart of contemporary nuclear science and will deeply impactparticle physics, astrophysics, and cosmology.
QCD
Key Issues in Hadron Physics
The main goals of hadronic physics are to determine the effective degrees of freedom which describe hadronic phenomena at all scales, to establish the connection of these degrees of freedom to the parameters of Quantum Chromodynamics, and to employ the subsequent understanding to describe a wide array of phenomena ranging from nuclear physics to early universecosmology.
QCD
Key Issues in Hadron Physics
Establish the place of QCD in the Standard Model.
Understand the origin and dynamics of confinement and chiral symmetry breaking
Understand the structure of the QCD vacuum and its topological characteristics
How do quarks and gluons evolve into hadrons?
Establish the link between the parton picture in the infinite momentum frame with the structure of hadrons in the rest frame.
Construct quantitatively reliable models of QCD
Establish rigorous connections with nuclear physics, electroweak physics, astrophysics and condensed matter physics.
What is the role of quarks and gluons in nuclei and extreme matter?
QCD
Key Issues in Hadron Physics
2.) "Develop a quantitative understanding of how quarks and gluons provide the binding and spin of the nucleon based on quantum chromodynamics, further clarifying the theory of strong interaction as a component of the Standard Model,"
Science Highlighted in New Department of Energy Strategic Plan
QCD
Key Issues in Hadron Physics
The QCD Lagrangian : LQCD
The parameters: L
What are the degrees of freedom?What are the mechanisms responsible for confinement? for chiral symmetry breaking? for the UA(1) symmetry breaking?
ModelsExperiment
LGT
Reality
Physical Insights
Numerical Precision
mdm
u
mdm
u
QCD
s, , ,m
smZ
QCD
Key Issues in Hadron Physics
What is the structure of hadrons in terms of their quark and gluon constituents?
How do quarks and gluons evolve into hadrons via the dynamics of confinement?
What is the role of quarks and gluons in the structure of nuclei?How can nuceli be used to study matter under extreme conditions?
SN
PN
quarks carry 30%, L?, polarized glue DG strange quark -10%
gluons? strange quarks about 0%
At large x, expect all the spin on struck quark
1st generation lattice of spin and form factors have good agreement.Can compute the lowest order moments
Do other hadrons (mesons, hyperons) have the same structure?
Quark and Gluon Structure of Hadronic Matter from Hard Scattering
QCD
Key Issues in Hadron Physics
Deep inelastic scatteringe e'
px Q2
e e'
p p'
g,p,h,...Deep exclusive scattering
H x, , t E x, , t
H x , , t E x , , t }Connected to Lq
Connected to GM(t), GE(t)
Drell-Yanq
q
l+
l -
g*Directly sensitive to antiquark distributions
Map out the quark and gluon structure of the nucleonvalence quarks, sea quarks, gluons, virtual mesons,tranversity, skewed parton distributions{
ud 0
qvx
qvx
G x,Q2
G x,Q2
u d ?
s x s x 0
s0.1
Quark and Gluon Structure of Hadronic Matter from Hard Scattering
QCD
Key Issues in Hadron Physics
Quark and Gluon Structure of Hadronic Matter from Hard Scattering
Understand the role of quarks and gluons in nuclei:Nuclear Binding, Quarks and gluons in nuclear medium
We know that structure functions change in the nucleus
Can we see x>1 effects?Are the nuclear enhancements of valence quarks, sea quarks or gluons?Would these give us information on which exchanges are important for binding at various scales
QCD
Key Issues in Hadron Physics
Quark and Gluon Structure of Hadronic Matter from Hard Scattering
Hadronization, Exlcusive Processes
Understand how a quark becomes a hadron
Still a very open question, done via Lund but no spin effects are included in fragmentation. How is spin transferred to the hadronic daughter particle.
How are pairs formed from the vacuum? 3P0 model?
dq(x) transversity is related to the T-odd frag.fcn.
q q
H1
z
Semi-inclusive DIS can tag quark flavour.
Fragmentation is what happened in the Big Bang
QCD
Key Issues in Hadron Physics
Quark and Gluon Structure of Matter from Spectroscopy
q
q
Where is the glue?
What can be excited?
Quark Model of Hadrons
Rest frame structure of hadrons - "dressed quarks"
What are the fundamental degrees of freedom?
What role does glue play?
QCD
Key Issues in Hadron Physics
Quark and Gluon Structure of Matter from Spectroscopy
Lattice Calculations Data
Scalar Meson Sector f0(1370) f0(1500) f0(1710)Mesons with Exotic Quantum Numbers 1-+ at 1.4 and 1.6Decays of mesons.
High QualityHigh StatisticsSignificantly change our understanding.
Quenched Glueball Spectrum
N* up to spin 5/2
Exotic Spectrum
Missing statesphotocouplingsQ2 DependenceDecays Parity Doubling UA(1)?Y* States X*States
Models
Quark Models .. work too wellInstantonsFluxtubes
We are on the verge of seeing gluonic excitations Mapping out the spectrum will tell us how glue is manifested in the real world Opportunity exists with photon beams
Much new information will be emerging on BaryonsK-beams could provide new important information
QCD
Key Issues in Hadron Physics
Quark and Gluon Structure of Matter from Spectroscopy c c b b Hybrids Heavy-light systems
B D Hybrids
Gift of Nature?
CP Studies:B D, DS Decays
Final State Interactions
Decays
Windows of opportunity in gg physics and y Decays
QCD
Key Issues in Hadron Physics
Models - Physical Intuition
Understand Hadronic data in terms of the appropriate degrees of freedom
Q2 << 1
Q2 ~ 1
Q2 >> 1
Structure
Substructure
Partonic Regime
}Connect to the QCD Vacuum
QCD
Key Issues in Hadron Physics
Models - Physical Intuition
Structure:
Substructure
Constituent Quarkspotential models vs flux tubes vs bags.Properties derivable on the latticeEasiest comparison to experimentlow energy hadron-hadron interactionsDecays - why does 3P0 work
Degrees of freedom in terms of fundamental QCD fieldsconnect to the constituent quarks. Constituent Quarks -- evolve from Dyn.Chiral Sym Break. Topological configurations: Instantons -- break UA(1) Sym monopoles, center vortices ...Flux tubes -- confinement.
QCD
Key Issues in Hadron Physics
Models - Physical Intuition
Partonic Regime: What is the connection to Q2=1
How are inclusive observables (structure functions) related to exclusive observables (form factors)?
What are the primordial structure functions as input to QCD evolution?
Explanation for observed sea quark isospin and spin structure
Bloom Gilman Duality
QCD
Key Issues in Hadron Physics
Hadron Structure: Complementary PerspectivesSnapshots in quark and glue
Pictures with dressed quarks
Deep inelastic scattering
quarks and glue in the infinitemomentum frame
Quark Model Picture
Charge RadiusMagnetic Moment
Structure functions measurequarks and gluons releated directly to the QCD Lagrangian
What are the relevant degrees of freedom?
Caculable on the Lattice Low moments calculable
Relationship?Hadron Spectroscopy
QCD
Key Issues in Hadron Physics
QCD in the wider world QCD is the essential ingredient of the standard model that is not yet under quantitative control
BHigh Energy Physics
Astrophysics
p msss p neutralino "dark matter"
Measures +b g
mnm
p The grand challenge
K K Mixing vs fundamental parameters
Extreme Conditions QCD in the early universe
Low x vs High energy n scattering
High densitiesneutron stars/supernovaes
Condensed Matter Physics Insights and techniques
QGP