Outline how interactions in particle physics are understood in terms of exchange particles.

Determine whether or not strangeness is conserved in this decay.

The total energy of the particle represented by the dotted line is 1.2 GeV more than what is allowed by energy conservation. Determine the time interval from the emission of the particle from the s quark to its conversion into the d \({\rm{\bar d}}\) pair.

The pion is unstable and decays through the weak interaction into a neutrino and an anti-muon.

Draw a Feynman diagram for the decay of the pion, labelling all particles in the diagram.

exchange particles are virtual particles/bosons;
that mediate/carry/transmit the weak/strong/em force between interacting particles / OWTTE;
Award first marking point for named bosons also, e.g. photons, W, Z, gluons.

strangeness in initial state is –1 and zero in the final;
hence it is not conserved;

Award [0] for unsupported second marking point.

\(\Delta t \approx \frac{h}{{4\pi \Delta E}} = \frac{{6.63 \times {{10}^{ - 34}}}}{{4\pi  \times 1.2 \times {{10}^9} \times 1.6 \times {{10}^{ - 19}}}}\);
\(\Delta t \approx 3 \times {10^{ - 25}}{\rm{s}}\);

diagram as above;
correctly labelled W⁺;

Allow time to run vertically. Allow particle symbols. Ignore missing or wrong arrow directions.