Performance of the calorimeter triggers

The purpose of this note is to review the performances of the three triggers using the calorimeters, namely the hadron trigger, the electron trigger and the photon triggers. The previously available numbers were obtained at the time of the Technical Proposal (( ] using the 30 method. In June 1999, the collaboration has decided to implement the calorimeter triggers as proposed by the Bologna and Orsay groups, as described in several LHCb notes (2], (3], (4] and (5). For various physics channels the various trigger performances are measured versus the PT cut, and this cut is adjusted to obtain the wanted rejection on Minimum Bias events so that the LO rate stays at the required level of no more than I MHz. For the hadron trigger, we study B;, -- DS K and B~° -> 7C7i ,for the electron trigger we study B° -4 e + X and B " --)J / TK s .