\midheading{$Z+c{\bar c}$ production ($m_c=0$), process 56}
\label{subsec:zccmassless}

Process {\tt 56} is the equivalent of {\tt 51}, with the bottom quarks
replaced by charm. Although the charm mass is neglected, the calculation
contains diagrams with two gluons in the initial state and a
$Z$ coupling to the heavy quark line -- hence the dependence upon the quark
flavour.

When {\tt removebr} is true in process {\tt 56}, the $Z$ boson does not decay.