Transcript Parton to Hadron Transition in Nuclear Physics Carl Carlson1, Haiyan Gao2, R.J.

Parton to Hadron Transition in
Nuclear Physics
Carl Carlson1, Haiyan Gao2, R.J. Holt3
1. College of William and Mary
2. Duke University & MIT
3. Argonne National Lab
Jefferson Lab 12 GeV PAC Meeting
Jan 18, 2003
Parton-Hadron Transition in
Nuclear Physics
• Introduction
• Simplest systems: pion, nucleon, deuteron
– Deuteron Photodisintegration
– Charged pion form factor
– Photopion production from nucleon
• Photopion production from nuclei
• Summary
Possible signatures for the
transition
• Constituent quark counting rule
– Dimensional analysis
– pQCD analysis
– Support by experiments
• Hadron helicity conservation
– Possible quark angular momentum
– New experiments suggest quark angular momentum
• What else?
– QCD oscillation
– Nuclear filtering effect
– Color transparency effect , …….
Constituent quark counting
predicts for proton-proton
elastic scattering
d
1
 10
dt s
  d  p n
Simplest nuclear reaction
d 1
 11
dt s
Data seem to show scaling at
70 and 90 degree, onset of
scaling at higher energies is
suggested at 36 and 52 degree
With MAD, deuteron
Photodisintegration
cross-section can be
extended to 7 GeV
at forward angles
(less than one month)
Hadron Helicity Conservation???
Orbital angular momentum
Recent data on proton
form factor ratio from
polarization transfer
measurements
 d  p  n
 p  p  
e d e d
o
Polarization measurements in deuteron photodisintegration
Charged Pion Elastic Form
Factor
• Simplest valence quark structure
• pQCD is expected to manifest at low
momentum transfer
• Reputable pQCD and non-pQCD
calculations exist
• The asymptotic pion form factor
12 f  CF s (Q )
f  (Q ) 
Q2
2
2
2
 /  Ratio for the


  N    N Reaction
Quark model: Huang and Kroll, Euro. Phys. J. C17 (2000)
d (n   p)
ued  seu 2
(
)

d (p   n)
ueu  sed


Oscillatory Scaling (QCD oscillation)
Proton-proton elastic scattering
d
s
dt
10
Origin of the oscillation?
• Interference between short-distance and
long-distance amplitudes
• New resonance states associated with
crossing a new quark flavor threshold
• Intriguing momentum transfer dependence
in nuclear transparency T from A(p,2p)
suggests nuclear filtering effect?
(suppression of long-distance amplitude in nuclear medium)

Generalized counting rule
Ji, Ma, Yuan (hep-ph/0301141) derived the
following generalized counting rule
involving parton orbital angular momentum:
1
  s
 (n H  lzH 1)
H
When lzH  0 and minimal n, reduces to the counting
Rule of Brodsky-Farrar, and MatveevMuradian-Tavkhelidze
Why photopion production from
nucleon?
• Pion has the simplest valence quark structure
• Photopion production cross-section decreases
relatively slower with the increase of energy
d 1
 7
dt s
Advantageous for the study of QCD oscillation
and the test of the generalized counting rule
prediction by Ji, Ma and Yuan

JLab 12 GeV Projection
HRS (100 hrs)
HMS+SHMS (600 hrs)
JLab 12 GeV Projection
HRS+calorimeter (360 hrs)
 p   p
o
Photopion production from
nuclear targets
Transition in the nuclear medium
– Color transparency effect
• Pion simple valence quark structure, more likely for
point-like configuration
• Light nuclei more amenable to theoretical
calculations
– Nuclear filtering effect
• Relatively large photopion production cross-section
allows detailed study of the nuclear transparency
Jain, Kundu, Ralston
Phys. Rev. D 65 (2002) 094027
HMS +SHMS (600 hrs)
  n  p


HMS +SHMS (600 hrs)
More theoretical
calculations of CT
is needed
Preliminary E94-104
results are very
Interesting
Exact wave function
configurations can
be used for 4He
Summary
• 12 GeV upgrade would provide an
outstanding opportunity for the study of the
transition region in nuclear physics
• The planned new detection systems are
crucial for this study
• Studies with the simplest nuclear systems
are essential in understanding this transition
region
Acknowledgement
D. Dutta, R. Gilman, G. Huber, D. Mack, E.
Schulte, K. Wijesooriya, L.Y. Zhu
J. Arrington, C. Keppel, P. Stoler,
R. Schiavilla, L. Weinstein