Comments:

Picture from CERN 2-metre hydrogen bubble chamber exposed to a beam of negative kaons (K-) with energy 4.2 GeV.

This piece corresponds to about 60 cm in the bubble chamber.

Knock-on spiralling electrons show that negative particles curve to the right.

One beam particle interacts producing four outgoing tracks. One of the positive tracks kinks; this shows that the positive particle has decayed at this point into another positive particle and a neutral particle that leaves no trace in the bubble chamber.

Without measurements it is very difficult to make positive identifications for the tracks.

Exercises:

1) Find the point where a charged particle decays.
2) What charge does it have?
3) What is the charge of the particle coming from the kink?
4) Was there another particle produced from the kink?
5) Draw an arrow to specify approximately which way it went.