Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The spin of neutral pion

  1. Nov 4, 2012 #1
    In Perkins's Introduction to High Energy Physics, the author obtained the spin of neutral pions from the decay [tex]\pi^0 → 2\gamma[/tex] He argued that the z-component of the total photon spin in the above decay can have the value [itex]S_z=0[/itex] or [itex]2[/itex]. If [itex]s_\pi=1[/itex], then only [itex]S_z=0[/itex] is possible, and the two-photon amplitude must behave under rotation like [itex]P_1^m(\cos \theta)[/itex] with [itex]m=0[/itex].
    Why does the orbit angular momentum [itex]l=1[/itex] in his reasoning? Acually I do not understand why only [itex]S_z=0[/itex] is possible. Since if there is a [itex]l_z[/itex], then [itex]S_z[/itex] can be both 0 and 2.
     
  2. jcsd
  3. Nov 4, 2012 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    How do you get an lz with two photons flying back to back in z-direction? I can imagine how you get lx and ly.
     
  4. Nov 4, 2012 #3
    What about the total angular momentum [itex]l=1[/itex]? This is the real issue that bothers me.
     
  5. Nov 4, 2012 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    I think the idea is that you get the total spin as combination of the photon spin (##S_z=0##) and the angular momentum (in a different direction, therefore ##s_\pi \geq S_z##). But that is a bit speculative.
     
  6. Nov 5, 2012 #5
    photon's mass is zero.the spin component along z-axis can be only +1 or -1.Since it still behaves like boson(integral spin),you should use the same rotation rotation matrix for m=0.If s=1,for pion then of course,0 is the only possible value.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: The spin of neutral pion
  1. Neutral pions (Replies: 15)

  2. Spin of the pion (Replies: 2)

  3. Neutral pions (Replies: 2)

Loading...