Simulation study on luminosity feedback for horizontal beam stabilization at SuperKEKB

The SuperKEKB e(+) e(-) collider uses highly focused ultra-low emittance bunches colliding every 4 ns to reach a very high luminosity of 8x10(35) cm(-2)s(-1). It is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between the colliding beams in the presence of ground motion disturbances. For the horizontal motion, a luminosity monitoring system, based on measuring the rate of the Bhabha process at vanishing scattering angle, is developed as input signal to the feedback system. The relative precision needed for this monitor is studied in detail, for the different successive stages of luminosity operation, based on a full simulation of this system, including the detector, DAQ, lock-in amplifier, and feedback control.