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Parton to Hadron Transition in Nuclear Physics

Parton to Hadron Transition in Nuclear Physics. Carl Carlson 1 , Haiyan Gao 2 , R.J. Holt 3 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.

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Parton to Hadron Transition in Nuclear Physics

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  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

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

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

  12. 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)

  13. Generalized counting rule Ji, Ma, Yuan (hep-ph/0301141) 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

  14. 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

  15. JLab 12 GeV Projection HRS (100 hrs)

  16. HMS+SHMS (600 hrs)

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

  18. 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

  19. Jain, Kundu, Ralston Phys. Rev. D 65 (2002) 094027 HMS +SHMS (600 hrs)

  20. 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)

  21. 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

  22. 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

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