MA, WH (reprint author), CCAST, WORLD LAB, CTR THEORET PHYS, POB 8730, BEIJING 100080, PEOPLES R CHINA.
In this paper we search quark degrees of freedom in nuclei by studying electromagnetic processes and double-charge-exchange reaction at the resonance region. We propose a hybrid quark hadron (HQH) model to describe nuclear structure. The model solves many long-standing puzzles in nuclear physics. Our principal finding in this paper is that multiquark cluster effect plays an important role in nuclear phenomena at higher monumentum transfers.