2. Estimate the ratio of the cross sections $p\bar p\to H^0$ and $p\bar p\to W$, for $\sqrt{s}\approx 500$ GeV.
3. Positively charged pions decay mostly into $\mu^+\nu_\mu$ and not into $e^+ \nu_e$. Why?
4. Show that $\tilde\psi=i\sigma_2\psi^*$ transforms as a right-handed spinor if $\psi$ is left-handed.