Medium Modification of the Proton Form Factor

Abstract

I argue that the double ratio of proton-recoil polarization-transfer coefficients, P'_x and P'_z, of the quasielastic 4He(e,e'p)3H reaction with respect to the elastic 1H(e,e'p) reaction is sensitive to possible medium modifications of the proton form factor in 4He. Recent measurements at both Mainz and Jefferson Lab of this double ratio at four-momentum transfers squared between between 0.4 GeV2 and 2.6 GeV2 are discussed. I show that the data challenge state-of-the-art conventional meson-nucleon calculations, as these are unable to describe the results. The data hint at the need to include medium modifications of the proton form factor, as predicted by a quark-meson-coupling model, in the calculations. A recently approved follow-up experiment at a Q2 of 0.8 GeV2 and 1.3 GeV2 with unprecedented precision will provide one of the most stringent tests of the applicability of various calculations.

presented at ``Fourth International Conference on Perspectives in Hadronic Physics'', ICTP, Trieste, 12 -- 16 May 2003

References in corpus (1)

• Polarization Transfer in the ^4He(\vec e,e'\vec p)^3H Reaction up to Q^2 = 2.6 (GeV/c)^2

Cited by in corpus (9)

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• Octet baryon electromagnetic form factor double ratios $(G_E^{\ast }/G_M^{\ast })/(G_E/G_M)$ in a nuclear medium
• Nuclear Quasi-Elastic Electron Scattering Limits Nucleon Off-Mass Shell Properties
• Effect of bound nucleon internal structure change on nuclear structure functions
• In-medium mass shift of two-flavored heavy mesons, $B_c$, $B_c^{\ast }$, $B_s$, $B_s^{\ast }$, $D_s$ and $D_s^{\ast }$
• Electroweak form factors of baryons in dense nuclear matter
• Heavy-heavy and heavy-light mesons in cold nuclear matter