Implementation of upper limit calculation for a Poisson variable by Bayesian approach

The calculation of Bayesian confidence upper limit for a Poisson variable including both signal and background with and without systematic uncertainties has been formulated.A Fortran 77 routine,BPULE, has been developed to implement the calculation.The routine can account for systematic uncertainties in the background expectation and signal efficiency.The systematic uncertainties may be separately parameterized by a Gaussian,Log-Gaussian or flat probability density function (pdf).Some technical details of BPULE have been discussed.