Studying Higgs bosons by top pair production at photon colliders
  We study the effect of heavy neutral Higgs bosons on the top pair production process at photon linear colliders.The interference patterns betwenn the resonant Higgs production amplitudes and the continuum QED amplitudes are examined. The patterns are sensitive to the phase of the photon-photon-Higgs vertex which is a good probe of new charged particles. 
Eri Asakawa