These are selected among the events with no detected muon or electron
daughter. It is required that the hadron is negative and that its measured
momentum is between 2.5 and 30 GeV/c.
These limits are justified by the improvement of the signal to noise ratio.
The white kink background is important at low momentum (and small kink angles).
For this reason a slightly harder cut on the transverse momentum of
the decay is required here ( 
300 MeV/c).
The final sensitivity is again higher by a factor 3 over that expected in
CHORUS [20], as seen in Tab. 6.
The charm and prompt contribution to background are shown in Tab. 7.
Table 7: Charm and prompt 
background in the hadron decay channel.
However, in this case, the main source are the white kinks
and the 
coherent production.
The background from white kinks depends on the number
of negative charged tracks at the primary vertex ( 
)
in the sample of events
selected for scanning, on the scanning length 
and on the cross-section.
A mean free path of 
= 370 m for 
300 MeV/c,
as measured by a dedicated experiment with 4 GeV/c pions [55],
has been used in this calculation. It is also assumed that the
measured exponential 
fall-off is independent of the pion kinematics.
These assumptions can be checked by the new measurements at lower momentum
expected to be available soon.
Within the envisaged experiment itself, results
can be obtained by relaxing selection criteria.
Thus the white kink contribution is given by:
The coherent production has not been modelled.
It was estimated within the CHORUS
experiment
and its effect turns out to be similar to the one of the white kink
( 
= 1.18).
.