As mentioned in detail in the proposal, the study of semileptonic decays of charmed baryons is intimately connected to the question of event purification. CLEO II has observed about 700 decays. With the start-up of CLEO III in 1999 the total statistics available from CLEO will probably go up by about a factor 10 by the year 2001 leading to about 7000 decays. COMPASS will observe a similar number in one run of 65 days. For , the currently existing sample from CLEO II contains about 40-50 events which may thus go up to about 400. It is currently difficult to predict the production rate for in proton beams but estimates lead to a total sample of about 600-1000 reconstructed events. The advantage of COMPASS is an acceptance almost independent of the momentum transfer q involved while CLEO has almost no acceptance for small values of q , where predictions of form factor ratios leading to decay asymmetries are safest. It should be noted that identification of s.l. decays is difficult and will be subject to very different systematic errors in CLEO and COMPASS.
Another competitor in this field is E781. Aiming at a total charm yield about a factor 10 down of COMPASS they might have an advantage for charmed hyperons due to the use of a hyperon beam. No identification is foreseen in E781 but a TRD in conjunction with an electromagnetic calorimeter should give very good electron identification. This information, however, will not be used in the trigger and the use of electrons might be less favourable than the use of of owing to bremsstrahlung losses. No rate estimates were given in the E781 proposal.