The charm quark and the charm antiquark in a 
(eta-c) meson annihilate into a
pion (
) and two kaons.
Frames 2 and 3 show the annihilation into virtual gluons. In frame 4, a strange quark and a strange antiquark emerge from the gluon cloud.
The intermediate stages of this process occur in less than almost a billionth of a billionth of a billionth of a second, and are not observable.
