Understanding the Wu Experiment: ParityV and Gamma-Ray Anisotropy Explained

[ChrisVer]

Hi, a fast question while I was reading the results of the Wu experiment:
http://iktp.tu-dresden.de/uploads/media/Experimental_test_of_parity_in_beta_decay_-_Wu.pdf
It says that "the observed gamma-ray anisotropy was used as a measure of polarization and effectively temperature"
However, I don't understand why there should be any gamma-ray anisotropy for the EM transition of Nickel-60* to its ground state. Any explanation for that?

 

[Vanadium 50]

If you go back one paragraph, you will see the first time this is mentioned, there is a a little number 2. This indicates a reference, and if you are unclear about this, you should look at that reference. (Ambler et al., who is one of the authors of this paper)

In that paper, it is explained that there are two gamma rays in Co-60, and a) they have a characteristic angular distribution between them, and b) this distribution also depends on the spin axis of the Co-60 nucleus. If you want to calculate this, it's what you get from a 5+ nucleus transitioning to a 0+ nucleus by emission of two photons.

 

[ChrisVer]

I don't have access at the moment in the references.