Download PowerPoint file - University of Regina

Key Scientific Issues in Hadron Physics
November 6-9, 2000 Duck, NC (Curtis A. Meyer)
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 Issues in Hadron Physics
QCD
Participants at the Workshop
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
Key Issues in Hadron Physics
QCD
1
2.5
Morning
Summary
Talk
Discussion
Afternoon
Organization
Summary
Talk
Discussion
Key Issues in Hadron Physics
QCD
Strong interaction physics poses a wealth of fundamental
questions with profound significance for our understanding
of Nature and the structure of the matter of which we and our
universe are composed. Answering these questions lies at the
heart of contemporary nuclear science and will deeply impact
particle physics, astrophysics, and cosmology.
Key Issues in Hadron Physics
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 universe
cosmology.
Key Issues in Hadron Physics
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?
Key Issues in Hadron Physics
QCD
Science Highlighted in New Department of Energy Strategic
Plan
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,"
Key Issues in Hadron Physics
QCD
The QCD Lagrangian : LQCD
m d mu
L
, ms m Z
The parameters: QCD s , ,
m d  mu
What are the degrees of freedom?
What are the mechanisms responsible
for confinement?
for chiral symmetry breaking?
for the UA(1) symmetry breaking?
Reality
Experiment
Models
Physical Insights
Numerical Precision
LGT
Key Issues in Hadron Physics
QCD
Quark and Gluon Structure of Hadronic Matter from Hard
Scattering
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
quarks carry 30%, L?, polarized glue DG strange quark -10%
PN 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?
Key Issues in Hadron Physics
QCD
Quark and Gluon Structure of Hadronic Matter from Hard
Map
out the quark and gluon structure of the nucleon
Scattering
{
e'
e
x
Deep inelastic scattering
Q2
qv x
p
q v x
q
q
e
g*
s x 
s x 0
G x,Q 2
2
G x,Q
s0.1
Drell-Yan
Directly sensitive to antiquark distributions
l+
u
 d0
l-
e'
Deep exclusive scattering
g,p,h,...
p
valence quarks, sea quarks, gluons, virtual mesons,
tranversity, skewed parton distributions
p'
Key Issues in Hadron Physics
H x, , t
E x, , t
 x , , t
H
E x ,, t
u
d ?
Connected to GM(t), GE(t)
}
Connected to Lq
QCD
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
Key Issues in Hadron Physics
QCD
Quark and Gluon Structure of Hadronic Matter from Hard Scattering
Understand how a quark becomes a hadron
Hadronization, Exlcusive Processes
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.
qq
How are 
pairs formed from the vacuum? 3P0 model?
dq(x) transversity is related to the T-odd frag.fcn.
H 1 z
Semi-inclusive DIS can tag quark flavour.
Fragmentation is what happened in the Big Bang
Key Issues in Hadron Physics
QCD
Quark and Gluon Structure of Matter from
Spectroscopy
Quark Model of Hadrons
Rest frame structure of hadrons - "dressed quarks"
q

q
What are the fundamental degrees of freedom?
Where is the glue?
What role does glue play?
What can be excited?
Key Issues in Hadron Physics
QCD
Quark and Gluon Structure of Matter from Spectroscopy
Lattice Calculations
Quenched Glueball Spectrum
N* up to spin 5/2
Exotic Spectrum
Models
Quark Models .. work too well
Instantons
Fluxtubes
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 Baryons
K-beams could provide new important information
Key Issues in Hadron Physics
Data
Scalar Meson Sector
f0(1370) f0(1500) f0(1710)
Mesons with Exotic
Quantum Numbers
1-+ at 1.4 and 1.6
Decays of mesons.
Missing states
photocouplings
Q2 Dependence
Decays
Parity Doubling UA(1)?
Y* States X*States
High Quality
High Statistics
Significantly change our
understanding.
QCD
Quark and Gluon Structure of Matter from
Spectroscopy
c
c b
b Hybrids
Heavy-light systems
B D Hybrids
Gift of Nature?
Final State Interactions
CP Studies:
B  
Decays
D, DS Decays
Windows of opportunity in gg physics and y Decays
Key Issues in Hadron Physics
QCD
Models - Physical Intuition
Understand Hadronic data in terms of the appropriate degrees of freedom
Q2 << 1
Structure
Q2 ~ 1
Substructure
Q2 >> 1
Partonic Regime
Key Issues in Hadron Physics
}
Connect to the QCD
Vacuum
QCD
Models - Physical
Intuition
Structure:
Substructure
Key Issues in Hadron Physics
Constituent Quarks
potential models vs flux tubes vs bags.
Properties derivable on the lattice
Easiest comparison to experiment
low energy hadron-hadron interactions
Decays - why does 3P0 work
Degrees of freedom in terms of fundamental QCD fields
connect 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
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
Key Issues in Hadron Physics
QCD
Hadron Structure: Complementary Perspectives
Snapshots in quark and glue
Quark Model Picture
Deep inelastic scattering
Hadron Spectroscopy
Charge Radius
Magnetic Moment
What are the relevant
degrees of freedom?
Relationship?
Caculable on the Lattice
Pictures with dressed quarks
Key Issues in Hadron Physics
quarks and glue in the infinite
momentum frame
Structure functions measure
quarks and gluons releated
directly to the QCD Lagrangian
Low moments calculable
QCD
QCD in the wider world
QCD is the essential ingredient of the standard
model that is not yet under quantitative control
Astrophysics
p ms s 
s p
neutralino "dark matter"
High Energy Physics
B  

KK
mnm p
Extreme Conditions
Measures b+g
Mixing vs fundamental parameters
The grand challenge
QCD in the early universe
QGP
Low x vs High energy n scattering
High densities
Condensed Matter Physics
Key Issues in Hadron Physics
neutron stars/supernovaes
Insights and techniques
QCD
CONCLUSIONS
Accelerators
Detectors
Computers
Lattice Algorithms
Data
Lattice
The Puzzles are old
Models
Key Issues in Hadron Physics
At the threshold of
significant progress
in resolving the issues
QCD