Köln 2004 – wissenschaftliches Programm
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PV: Plenarvorträge
PV II
PV II: Plenarvortrag
Montag, 8. März 2004, 13:45–14:15, P
Do nucleons that are bound in nuclei change their structure? — •Steffen Strauch — The George Washington University, Washington DC
Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. Recent measurements at both Mainz [1] and Jefferson Lab [2] of the proton recoil polarization in the 4He(e→,e′p→ )3H reaction up to Q2 = 2.6 (GeV/c)2 will be presented. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation, indicating that the treatment of final-state interactions is under control. A recently approved follow-up experiment at values of Q2 of 0.8 (GeV/c)2 and 1.3 (GeV/c)2 with unprecedented precision will provide a stringent test of the applicability of these calculations.
[1] S. Dieterich et al., Phys. Lett. B 500, 47 (2001)
[2] S. Strauch et al., Phys. Rev. Lett. 91, 052301 (2003)