The FINUDA trigger selects 
decays in charged kaons, against decays to
, Bhabha scattering, cosmic rays. Bhabha events are naturally
reduced by the geometrical acceptance covered by the TOFINO scintillator array
. The trigger requirements exploit the
back-to-back topology of
the 
pairs, their large 
and the coincidence with the prompt negative pion emitted from the hypernuclear formation as detected by the TOFONE:
.
The prompt coincidence with TOFONE
is dictated by the need of rejecting 
from 
decay.
Table 2 shows typical triggering efficiencies for hypernuclear
events and residual background contaminations.
Table 2: Efficiency, rejection and
rates for production of hypernuclear states and background processes