R4b

1. Weak interactions produce left-handed massive particles. How does their helicity evolve with time?
2. Estimate the ratio of the cross sections [math]\displaystyle{ p\bar p\to H^0 }[/math] and [math]\displaystyle{ p\bar p\to W }[/math], for [math]\displaystyle{ \sqrt{s}\approx 500 }[/math] GeV.
3. Positively charged pions decay mostly into [math]\displaystyle{ \mu^+\nu_\mu }[/math] and not into [math]\displaystyle{ e^+ \nu_e }[/math]. Why?
4. Show that [math]\displaystyle{ \tilde\psi=i\sigma_2\psi^* }[/math] transforms as a right-handed spinor if [math]\displaystyle{ \psi }[/math] is left-handed.