Medium dependence of the bag constant in the quark-meson coupling model |
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| Institution: | 1. Department of Physics and Mathematical Physics and Special Research Center for the Subatomic Structure of Matter, University of Adelaide, Australia 5005;2. Physics Division, Tohoku College of Pharmacy, Sendai 981, Japan;1. Institute for Nuclear Theory, University of Washington, Seattle WA 91195-1550, USA;2. Paul Scherrer Institut, 5232 Villigen PSI, Switzerland;3. Physik-Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland;4. Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland;5. INFN Laboratori Nazionali di Frascati, 00044 Frascati RM, Italy |
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| Abstract: | Possible variations of the quark-meson coupling (QMC) model are examined in which the bag constant decreases in the nuclear medium. The reduction is supposed to depend on either the mean scalar field or the effective mass of the nucleon. It is shown that the electric and magnetic radii of the bound nucleon are almost linearly correlated with the bag constant. Using the fact that the size of the bound nucleon inside a nucleus is strongly constrained by y-scaling data in quasi-elastic, electron-nucleus scattering, we set a limit for the reduction allowed in the bag constant for these two models. The present study implies that the bag constant can decrease up to 10–17% at average nuclear density, depending on the details of the model. |
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