SUBROUTINE QICCON - Set up colour/flavour connections

In this routine the colour and flavour connections of the instanton subprocess are set up. The colour flow is constructed by connecting the colour lines of neighbouring partons within each of the strings constructed in the subroutines QIGLST and QIGPAR. The flavour flow is constructed by connecting the flavour lines of the quark at the beginning of a string with the flavour line of the anti-quark at the end of a string.

The routine starts with the following steps:

• The IHEP pointer of the ``hard process'' $eg$ is searched for. By default, it is IHEP=7.
• The IHEP pointer of the current quark $q^{\prime\prime}$, IHEP=10, set up in QIHGEN, is added to the array of IHEP pointers QIPLIS(JLP,ILP) at the position of the virtual quark $q^\prime$.
• The IHEP pointer of the incoming $g$, IHEP=6, set up in QIHGEN, is added to the array of IHEP pointers QIPLIS(JLP,ILP) at the position of the incoming $g$.

Continuing our example from the description of QIPSTO, where we had the following array of particle identities QIPTYP(JLP,ILP),

$$\begin{array}{cc\vert rrr} & & \multicolumn{3}{\vert c}{{\... ...& 3 & -2& 21& -1\\ & 4 & & {\bf -3} & \\ \end{array} \, ,$$ (1)

the array of IHEP pointers QIPLIS(JLP,ILP) has now, after applying the steps above, the form

$$\begin{array}{cc\vert rrr} & & \multicolumn{3}{\vert c}{{\... ... & 3 & 12& 15& 18\\ & 4 & &{\bf 10}& \\ \end{array} \, .$$ (2)

The corresponding HERWIG [1] mother/daughter pointers¹specifying the colour/flavour flow are then, according to the prescription above,

$$\begin{tabular}{\vert r\vert c\vert c\vert c\vert}\hline IHEP & D... ...out & 18 & 16\\ 18 & $\overline{d}$\ out & 16 & 17\\ \hline \end{tabular}\, .$$ (3)