SUBROUTINE QIGMUL(WGTFCT) - Generates gluon multiplicity $n_g$

• Checks, whether there is enough energy to generate even one gluon.

• If there is enough energy, then, by default, it uses GMULT to calculate expected average gluon multiplicity, $\langle n_g\rangle$.

• The gluon multiplicity $n_g$ is then generated according to a Poisson distribution with mean $\langle n_g\rangle$,
  

  $$P(n_g) = \frac{\langle n_g\rangle^{n_g}}{n_g!}\, {\rm e}^{-\langle n_g\rangle} .$$ (1)

  
  

• For default settings, an upper limit on $n_g$ is enforced and kinematical constraints are checked.

Table 1: Variables (re-)set in QIGMUL.

Name	Description
WGTFCT	0.0, if mass too high; 1.0 else
GMUL	Number of gluons in instanton-subprocess final state, $n_g$
QINGLU	Number of gluons participating in instanton-subprocess, $n_g+1$