| A formalism based on a chiral quark model ($\\chi$QM) approach
complemented with a one-gluon exchange model, to take into account
the breakdown of the $SU(6)\\otimes O(3)$ symmetry, is presented. The
configuration mixing of wave functions for nucleon and resonances
are derived.
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With few adjustable parameters, differential cross-section and
polarized beam asymmetry for the $\\gamma~p~\\to~\\eta~p$ process are
calculated and successfully compared with the data in the
centre-of-mass energy range from threshold up to 2 GeV. The known
resonances $S_{11}(1535)$, $S_{11}(1650)$, $P_{13}(1720)$,
$D_{13}(1520)$, and $F_{15}(1680)$, as well as two new $S_{11}$ and
$D_{15}$ resonances are found to be dominant in the reaction
mechanism. Besides, connections among the scattering amplitudes of
the $\\chi$QM approach and the helicity amplitudes, as well as decay
widths of resonances are established. Possible contributions from
the so-called \"missing resonances\" are investigated and found to be
negligible. |
