Wednesday 20 September 2017

particle physics - Change of flavour, Weak interaction



I couldn't find a straight and clear answer to this question on the internet: Why is the weak interaction (charged), the only interaction which can change the flavours of the quarks?



Answer



Lets look at the weak isospin doublet of for the first generation of quraks \begin{equation} \begin{pmatrix} u\\d' \end{pmatrix}_{L} \end{equation} Where $d'$ is represents the quantum mixing of $d$ and $s$ quark. From gauge theory, we know that, the role of gauge bosons is to transform a particle to another one, which living in the same mutiplet. So, if a $u$ quark turns into $d$ quark, that can be possible if a positively charge gauge boson can mediate such a transition.


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