\midheading{$W+b$ production, processes 12,17}
\label{subsec:wb}

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

The effect of the bottom quark mass is included throughout the calculation.  
For this case the CKM matrix elements $V_{cb}$ and $V_{ub}$,
(if they are equal to zero in the input data file, {\tt mdata.f})
are set equal to $0.041$ and $0.00347$ respectively. 
Otherwise the non-zero values specified in {\tt mdata.f} are used. 
The calculation of this process may
be performed at LO and NLO.

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