  We study the resonance spectroscopy of the proton-rich nucleus 7B in the
4He+p+p+p cluster model. Many-body resonances are treated on the correct
boundary condition as the Gamow states using the complex scaling method. We
predict five resonances of 7B and evaluate the spectroscopic factors of the
6Be-p components. The importance of the 6Be(2+)-p component is shown in several
states of 7B, which is a common feature of 7He, a mirror nucleus of 7B. For
only the ground state of 7B, the mixing of 6Be(2+) state is larger than that of
6He(2+) in 7He, which indicates the breaking of the mirror symmetry. This is
caused by the small energy difference between 7B and the excited 6Be(2+) state,
whose origin is the Coulomb repulsion.
