Plot the mass distribution of neutral kaon 
which decays to two charged pions:
![\[K_s \longrightarrow \pi^+ \pi^-\]](https://belle2.ijs.si/public/wp-content/ql-cache/quicklatex.com-51a4bcf4eb2d8e946ea0f2aa557a57a3_l3.png "Rendered by QuickLaTeX.com")
You will find a peak at 0.498 
, which is exactly the mass of the neutral kaon
Plot the mass distribution of neutral kaon which decays to two charged pions:
You will find a peak at 0.498 , which is exactly the mass of the neutral kaon