1. 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

2. 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

3. 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 , …….

4. Constituent quark counting
predicts for proton-proton
elastic scattering

5. Simplest nuclear reaction
Data seem to show scaling at
70 and 90 degree, onset of
scaling at higher energies is
suggested at 36 and 52 degree

6. With MAD, deuteron
Photodisintegration
cross-section can be
extended to 7 GeV
at forward angles
(less than one month)

7. Hadron Helicity Conservation???
Orbital angular momentum
Recent data on proton
form factor ratio from
polarization transfer
measurements

8. Polarization measurements in deuteron photodisintegration

9. 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

11. Ratio for the Reaction
Quark model: Huang and Kroll, Euro. Phys. J. C17 (2000)

13. Oscillatory Scaling (QCD oscillation)
Proton-proton elastic scattering

14. 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)

15. Generalized counting rule
Ji, Ma, Yuan (hep-ph/ ) derived the following generalized counting rule involving parton orbital angular momentum:
When and minimal n, reduces to the counting
Rule of Brodsky-Farrar, and Matveev-
Muradian-Tavkhelidze

16. Why photopion production from nucleon?
Pion has the simplest valence quark structure
Photopion production cross-section decreases relatively slower with the increase of energy
Advantageous for the study of QCD oscillation
and the test of the generalized counting rule prediction by Ji, Ma and Yuan

17. JLab 12 GeV Projection
HRS (100 hrs)

18. HMS+SHMS (600 hrs)

19. JLab 12 GeV Projection
HRS+calorimeter (360 hrs)

21. 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

22. Jain, Kundu, Ralston
Phys. Rev. D 65 (2002)
HMS +SHMS (600 hrs)

23. More theoretical
calculations of CT
is needed
Preliminary E94-104
results are very
Interesting
Exact wave function
configurations can
be used for 4He
HMS +SHMS (600 hrs)

24. 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

25. 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