H Dibaryon Search Experiment E813 at BNL

We have searched for the H dibaryon (a six-quark uuddss state ) at Brookhaven National Laboratory's 2 GeV/c K^- beam line. This experiment was insensitive to the H decay modes and life time, and looked directly for H formation through Ξ^- capture on the deuteron via (Ξ^-,d)_atom arrow H+n. The key number of this experiment is the product of (Ξ^-,d)_atom formation efficiency and the neutron detection efficiency, in order to quantitatively estimate the upper limit on H formation branching ratio. We calibrated this combined efficiency through Σ^- capture on hydrogen. The details of the calibration will be discussed.