A routine for onium decay

In PYONIA we have implemented the decays of heavy onia resonances into three gluons or two gluons plus a photon, which are the dominant non-background-like decays of $\Upsilon$.

Purpose:

to simulate the process $\mathrm{e}^+\mathrm{e}^-\to \gamma^* \to 1^{--}$ onium resonance $\to (\mathrm{g}\mathrm{g}\mathrm{g}$ or $\mathrm{g}\mathrm{g}\gamma) \to$ shower $\to$ hadrons.

KFL :

the flavour of the quark giving rise to the resonance.

= 0 :

generate $\mathrm{g}\mathrm{g}\mathrm{g}$ events alone.

= 1 - 8 :

generate $\mathrm{g}\mathrm{g}\mathrm{g}$ and $\mathrm{g}\mathrm{g}\gamma$ events in mixture determined by the squared charge of flavour KFL, see eq. (). Normally KFL= 5.

ECM :

total c.m. energy of system.