\midheading{$W+c$ production, processes 13,18}
\label{subsec:wc}

These processes represent the production of a $W$ boson which
subsequently decays leptonically, in association with a charm
quark. 
This is produced at leading order by an initial state which
contains a strange anti-quark (or Cabibbo suppressed $d$ anti-quark) and a
gluon, e.g
$ \bar{d}(-p_1)+g(p_2) \to W^+(\to \nu(p_3)+e^+(p_4))+\bar{c}(p_5)$
and
$ \bar{u}(-p_1)+g(p_2) \to W^+(\to \nu(p_3)+e^+(p_4))+\bar{c}(p_5)$
or the charge conjugate process for $W^{-}$.
This process is somewhat analogous to single top production.

The effect of the charm quark mass is included throughout the
calculation.  The calculation of this process may
be performed both at LO and NLO.

When {\tt removebr} is true, the $W$ boson does not decay.