The helicity structure of πN→πN* amplitude and symmetric quark model

The measurement of helicity structure is proposed, since it will give information on N structure. At first, the spin density matrix of N in Gottfried-Jackson frame is presented. It is necessary to measure the polarization of N or the dependence of N →Nπ angular distribution on the polarization of a target. The quark model prediction on matrix elements is presented, by assuming that N and N have SU(6) x O(3) structure, the N yiedls N transition is expressed by the sum of single quark transition, and the energy of the relative motion of quark can be neglected in comparison with that in the motion of center of gravity. The transition amplitude is expressed by the product of πQ scattering amplitude and N→N overlapping integral. The prediction is that the density matrix rhosub(mm)sup((0)) = 0 for /m/ or /m'/>S, where S is the total spin of 3 quarks. When S is 1/2, the only remaining parameter of rhosup((0)) is rhosub(1,-1) which is determined from the SU(6) structure of N only, and shows no L dependence. The forms of rho in case of S = 3/2 are presented in this paper. (Kato, T.)