This article describes an efficient procedure for computing approximate
confidence levels for searches for new particles where the expected signal and
background levels are small enough to require the use of Poisson statistics.
The results of many independent searches for the same particle may be combined
easily, regardless of the discriminating variables which may be measured for
the candidate events. The effects of systematic uncertainty in the signal and
background models are incorporated in the confidence levels. The procedure
described allows efficient computation of expected confidence levels.Comment: 17 pages, 2 figures, LaTeX, program available at
http://home.cern.ch/~thomasj/searchlimits/ecl.html one replacement to fix a
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