The question is from "Advanced Physics" by Adams and Allday. It is from section 9 "The Physics of Particles", "Practice Exam Questions". It is question 11, part c. The level of this study is between school and University.
Figure 9.5 represents a simple particle interaction. State the nature of the interaction and describe what happens to the particles involved. State three properties of the exchange particle.
[Figure 9.5 is in the attachment]
The Attempt at a Solution
The particles in the interaction are leptons (electrons) so it must be a weak force interaction.
It looks like nothing happens to the particles involved!!! The same particles are present before and after the interaction (possibly at different energies).
It is not clear which way the exchange particle moves and there is no transfer of charge.
Because there is no transfer of charge and the weak force is acting, I guess the only unidentified particle must be the uncharged weak force exchange particle, the Z0.
I further guess that the directionless nature of the reaction means the exchange particle must be one that is its own anti-particle; again the Z0.
I don't like guessing -- it means lack of understanding
Illumination gratefully received.
As for the three properties, I don't think we are required to recall actual figures so how about: massive (hence very unstable), uncharged, own anti-partcle?