\midheading{$W+b{\bar b}$ production ($m_b=0$), processes 21,26}
\label{subsec:wbbmassless}

This process is calculable at leading LO and next-to-leading order NLO. 
These processes are identical to {\tt 20} and {\tt 25} except for the fact
that the bottom quark mass is neglected. 
Processes {\tt nproc=20,25} with a massive $b$-quark should be used in preference.
However processes {\tt nproc=21,26} run
considerably faster than the corresponding processes with the mass
for the $b$ quark, ({\tt nproc=20,25}). 
In circumstances where both $b$ quarks are at large
transverse momentum, the inclusion of the mass for the $b$-quark is not mandatory
and a good estimate of the cross section may be obtained by using these processes.

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