A series of measurements were carried out to investigate the dynamic beam-beam effects at KEKB. The beam-beam kick and the coherent beam-beam tune shift were measured by comparing the beam parameters between a colliding bunch and a noncolliding one. We found that collisions occur with a horizontal orbit offset to obtain the maximum luminosity, and that this reproducible offset appears to be attributed to an electron cloud effect, which might play an important role in the beam-beam interaction. The horizontal beam size estimated from the beam-beam kick slightly decreased as the beam-beam parameter increased. The horizontal emittance estimated from the beam-beam tune shift was higher than an unperturbed emittance, and agreed with the calculated emittance using a higher-mode tune. The ratio of the square-root betatron function between two locations in the ring was measured as a function of the beam-beam parameter. These experimental results would provide useful information on dynamic beam-beam effects.
