Re: How does the rho meson decay to a pair of pions?

Date: Tue Feb 6 05:27:33 2007
Posted By: Samuel Silverstein, Lecturer in physics
Area of science: Physics
ID: 1169683738.Ph

Message:

The rho decay to two pions is mediated by the strong nuclear force, so the Feynman diagrams are pretty simple; for example here is one for rho0->pi+pi-:


              (u   d*) pi+
 Rho0         /   /
             /   /
  u --------/   /
               /
             g/\
  u*--------\/  \
             \   \
              \   \
             (u*  d) pi-
 
(g = gluon)

Even though pions are spinless, the two pions in the final state both have mass, and it is a two-body system, which means that they will have (if you think in the classical sense) some angular moment of inertia. So angular momentum is conserved here by the final system having a total angular momentum of 1.

It's not as satisfying as other examples of systems where the spins all add up (but no angular momentum in the system), but there it is.

Hope this helps!

--Sam

Current Queue | Current Queue for Physics | Physics archives

Try the links in the MadSci Library for more information on Physics.