The CLEO III upgrade

Abstract CLEO has pioneered the collection of large numbers of B mesons, in order to explore rare decays and thus test the Standard Model. In its third phase, CESR and CLEO plan to increase the total integrated luminosities by a factor 5–10, collecting ≃15 fb −1 per year. This will enable us to probe currently unobserved rare processes, and also perform measurements of 2-body B decays to overconstrain the parameters which describe CP violation. The CLEO III detector will be optimized to achieve this goal.