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

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


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


Organization

1 2.5

Morn

ing

Aft

ern

oo

n

Summary Talk

Summary Talk

Discussion

Discussion

QCD


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


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


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


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


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


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


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


QCD



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



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


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


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


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


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



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



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


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


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

QCD


LatticeData

Models

AcceleratorsDetectorsComputersLattice Algorithms

CONCLUSIONS

The Puzzles are old

At the threshold of significant progressin resolving the issues

Documents

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