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DNP Long Range Plan January 2007 1 Nuclei at Short Distance Scale Ronald Ransome Rutgers, The State University of New Jersey Piscataway, NJ
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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
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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DNP Long Range Plan January 2007 12 Deuteron photo-disintegration
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DNP Long Range Plan January 2007 13 Deuteron Photo-disintegration Measurements can be extended to larger angles and momentum transfer with 12 GeV upgrade
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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)
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DNP Long Range Plan January 2007 15 Short Range Correlations Short range correlations give a picture at the highest densities.
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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)
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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
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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
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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
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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
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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
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