Bubble chamber picture of decay of sigma+ to a neutron and a pi+
This 
was produced in a high energy neutrino interaction (hence no visible beam track
particles). The neutron 
goes
on to strike a proton 
which
leaves a very small dark track; the 
decays
to a 
and
an positron 
in
a characteristic manner (click here).
For more details of this (rather complicated but) rich event, click here.
For another example of click
on the picture below.
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