Tübingen 2003 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 11: Poster-Sitzung: Elektromagnetische und hadronische Proben
HK 11.25: Poster
Dienstag, 18. März 2003, 13:30–15:30, Foyer
Gluon-exchange currents and q q fluctuations in a quark model and nucleon electromagnetic form factors — •M.M. Kaskulov and P. Grabmayr — Physikalisches Institut, Universität Tübingen
The effect of one-gluon-exchange (OGE) pair-currents and q q fluctuations of constituent quarks on the nucleon electromagnetic form factors are investigated within the CQM and the 3P0 quark-pair creation model. We found that in the soft momentum transfer region, Q2<1 GeV2, q q components (mesonic cloud) are essential for the good reproduction of the nucleon form factors. At higher momentum transfer gluonic corrections to the CQM are important, and the recent experimental data for the ratio µp GEp/GMp are well reproduced by the SU(6) × O(3) wave function of the nonrelativistic quark model. Our results for the F2p/F1p indicate that the ratio falls as Q F2p/F1p ∼ 1/Q at asymptotic values of Q2. This allows to make a smooth transition to the scaling behaviour as expected from perturbative QCD. With the assumption that the OGE currents are the driving mechanism for the violation of the scaling law we give a prediction for ratio µn GEn/GMn of the neutron.
The generalization of the model and its application to higher baryonic resonances will be also discussed.