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 50 cm in the bubble chamber.

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

Here two charged particles leave the collision (one positive and one negative). In addition, a neutral particle is formed in the collision. This travels forward slightly to the right of the beam direction and it decays into two oppositely charged particles.

The most likely interpretation in the absence of measurements is:

K-p ® p+ p- K0 or L

p p-

p+p -