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.
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