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.