1. DNP Long Range Plan January 2007 1 Nuclei at Short Distance Scale Ronald Ransome Rutgers, The State University of New Jersey Piscataway, NJ

2. DNP Long Range Plan January 2007 2 Some unanswered questions  How is the nucleon affected by the nuclear medium? t Change in quark distributions t Change in nucleon size and shape  How do we get from quarks and gluons to nucleons and mesons? t At what distance scale does this occur? t What are the signatures?  What is the short-range behavior of the nuclear force? t Nature of the force in cold, dense nuclear matter

3. DNP Long Range Plan January 2007 3 Experimental approaches  In medium form factors using polarization transfer  Elastic form factors of light nuclei  Deuteron photo-disintegration  Inclusive cross section measurements

4. DNP Long Range Plan January 2007 4 In medium form factors  Question – can the effects of the nuclear environment on the nucleon structure be “summarized” in a change to the form factor?  Of interest for many years, but difficult to approach experimentally and theoretically  Measurements on 4 He show standard calculations are inadequate, QMC model of form factor modification seems to improve calculations

5. DNP Long Range Plan January 2007 5 In medium form factors E03-104 ran in Oct. 2006, will check both increase at Q 2 =1.6 and make improved induced polarization measurement.

6. DNP Long Range Plan January 2007 6 Axial form factor K. Tsushima, et al., PRC 70, 038501, (2004) QMC model also predicts substantional modification of the axial form factor with a 10% change at low Q 2

7. DNP Long Range Plan January 2007 7 Axial form factor  QMC model also predicts a 5% difference between carbon and lead  First measurements of this will be done by the MINER A experiment at FNAL

8. DNP Long Range Plan January 2007 8 Future needs  The only nucleus explored in detail have been 2 H, and 4 He t Would like to have high statistics measurements on 3 H, 3 He, and some heavier nuclei, such as 12 C or 16 O t Requires continued running at lower energies  High intensity neutrino beams offer many new opportunities

9. DNP Long Range Plan January 2007 9 Deuteron form factors  As the smallest nucleus, the deuteron is a key to understanding short range behavior  Elastic form factors at high Q 2 are sensitive to models of the short range correlations  Good statistics at high Q 2 requires the 12 GeV upgrade

10. DNP Long Range Plan January 2007 10 Deuteron form factors For elastic ed, d  M (A+B tan 2 (  Calculation of B has most model dependence Projected data for 12 GeV beam

11. DNP Long Range Plan January 2007 11 Deuteron Photo-disintegration  Both polarization and cross section measurements have given indications of the transition from the nucleon- meson regime to the quark-gluon regime

12. DNP Long Range Plan January 2007 12 Deuteron photo-disintegration

13. DNP Long Range Plan January 2007 13 Deuteron Photo-disintegration Measurements can be extended to larger angles and momentum transfer with 12 GeV upgrade

14. DNP Long Range Plan January 2007 14 3 He  pp)n  Photo-disintegration of 3 He through pp pair can be compared photo-disintegration of pn pair in deuteron  Measurements made at CLAS (PRC 70, 064003, 2004), will continue with JLab experiment 03-005, which will make measurements in the coming year (Congress willing)

15. DNP Long Range Plan January 2007 15 Short Range Correlations  Short range correlations give a picture at the highest densities.

16. DNP Long Range Plan January 2007 16 Short Range Correlations 1N state 2N SRC 3N SRC 2 H96 ± 0.7 4.0 ± 0.7 --- 3 He92 ± 1.6 8.0 ± 1.60.18 ± 0.06 4 He86 ± 3.315.4 ± 3.30.42 ± 0.14 12 C80 ± 4.119.3 ± 4.10.55 ± 0.18 56 Fe76 ± 4.723.0 ± 4.70.79 ± 0.25 Measured Composition ( %) K. Egiyan, et al, (CLAS), PRC 68:014313,2003; PRL 96, 082501,2006. A(e,e’)X, A = 3 He, 4 He, 12 C, 56 Fe M. Strikman “Jefferson Lab may have directly observed short-range nucleon correlations, with densities similar to those at the heart of a neutron star.” (CERN Courier 11/2005)

17. DNP Long Range Plan January 2007 17 Future work  Search for short range correlations needs higher beam energies to explore higher x regime  JLab proposal 12-06-105 will explore up to x=3

18. DNP Long Range Plan January 2007 18 Summary of existing progress  Good progress in determining the nature of the transition from nucleon-meson regime to quark-meson regime  Polarization has been a key tool, but experimentally difficult to pursue to much higher Q 2  Good progress in determining short-range correlations

19. DNP Long Range Plan January 2007 19 Future  In medium form factor measurements need to be done on more nuclei with good statistics t Needs beam time at < 5 GeV on many nuclei t Neutrino beams would add significant new information  Photo-disintegration of deuteron, 3 He needs higher beam energies to continue studies  Form factors of deuteron need 12 GeV to explore high Q 2 region  Light nuclei form factors, esp. 3 H, still could be greatly improved

20. DNP Long Range Plan January 2007 20 Conclusions  Still work to be done with lower energy beams  JLab upgrade will allow more efficient exploration of the short range nature of the nuclear force  Neutrino beams will provide a useful new tool

21. DNP Long Range Plan January 2007 21 Thanks  Thanks to Rolf Ent, Ron Gilman, Makis Petratros, Steffen Strauch, Elaine Schulte, and Wally Melnitchouk for help with this talk