T. Tauchi and K. Yokoya
National Laboratory for High Energy Physics, KEK
1-1 Oho, Tsukuba-shi, Ibaraki, 305, Japan
December 21, 1996
We describe a new method to measure a nanometer beam size during collisions at future linear colliders by using pairs. A huge number of pairs are deflected in a strong Coulomb potential made by an oncoming beam. Since the potential is a function of the beam size(), the pairs are expected to carry this information, especially in their angular distributions. We investigated this process in detail by a simulation use of ABEL under realistic experimental conditions as well as by analytic studies. Besides the beam size, a vertical displacement between two beams and rotations in the transverse beam profile can be precisely measured. Because of the high statistics of pairs, the results from these measurements can be used for feedback during real-time operation of linear colliders.