I'm studying the semileptonic decay of the kaon and I'm currently reading about the Ademollo-Gatto theorem. The question is probably silly. However, here it is.(adsbygoogle = window.adsbygoogle || []).push({});

The proof starts by just considering that [itex][V_-,V_+]=V_3[/itex], where V is the V-spin. Now, we consider the matrix element [itex]\langle K^0|V_3|K^0\rangle=1[/itex].

I understand that the [itex]|K^0\rangle[/itex] state is an eigenstate of V_{3}(is the same thing that happens for the usual isospin), but why exactly 1? Consider for example the third component of isospin. As K^{0}has I_{3}=1/2 I'd expect that matrix element to be 1/2. Why is 1?

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Doubt on Ademollo-Gatto theorem proof

**Physics Forums | Science Articles, Homework Help, Discussion**