Fourth-generation fermions

MSEL = 7, 8, 37, 38
ISUB =

1	$\mathrm{f}_i \overline{\mathrm{f}}_i \to \gamma^* / \mathrm{Z}^0$
2	$\mathrm{f}_i \overline{\mathrm{f}}_j \to \mathrm{W}^+$
81	$\mathrm{q}_i \overline{\mathrm{q}}_i \to \mathrm{Q}_k \overline{\mathrm{Q}}_k$
82	$\mathrm{g}\mathrm{g}\to \mathrm{Q}_k \overline{\mathrm{Q}}_k$
83	$\mathrm{q}_i \mathrm{f}_j \to \mathrm{Q}_k \mathrm{f}_l$
84	$\mathrm{g}\gamma \to \mathrm{Q}_k \overline{\mathrm{Q}}_k$
85	$\gamma \gamma \to \mathrm{F}_k \overline{\mathrm{F}}_k$
141	$\mathrm{f}_i \overline{\mathrm{f}}_i \to \gamma/\mathrm{Z}^0/\mathrm{Z}'^0$
142	$\mathrm{f}_i \overline{\mathrm{f}}_j \to \mathrm{W}'^+$

The prospects of a fourth generation currently seem rather dim, but the appropriate flavour content is still found in the program. In fact, the fourth generation is included on an equal basis with the first three, provided MSTP(1)=4. Also processes other than the ones above can therefore be used, e.g. all other processes with gauge bosons, including non-standard ones such as the $\mathrm{Z}'^0$. We therefore do not repeat the descriptions found elsewhere, e.g. how to set only the desired flavour in processes 81-85. Note that it may be convenient to set CKIN(1) and other cuts such that the mass of produced gauge bosons is enough for the wanted particle production -- in principle the program will cope even without that, but possibly at the expense of very slow execution.