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34 lines
1.7 KiB
34 lines
1.7 KiB
\midheading{$Z+Q$ production, processes 261--267}
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\label{subsec:ZQ}
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These processes represent the production of a $Z$
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boson that decays into a pair of electrons,
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in association with a heavy quark, $Q$.
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For more details on this calculation, please see Ref.~\cite{Campbell:2003dd}.
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For processes {\tt 261}, {\tt 262}, {\tt 266} and {\tt 267} the initial
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state at lowest order is the heavy quark and a gluon and
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the calculation may be performed at NLO.
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As for $H+b$ production, the matrix elements are divided into two
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sub-processes at NLO. Thus the user must sum over these after performing
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more runs than usual. At lowest order one can proceed as normal, using
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{\tt nproc=261} (for $Z+b$) or {\tt nproc=262} (for $Z+c$).
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For a NLO calculation, the sequence of runs is as follows:
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\begin{itemize}
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\item Run {\tt nproc=261} (or {\tt 262}) with {\tt part=virt} and
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{\tt part=real} (or, both at the same time using {\tt part=tota});
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\item Run {\tt nproc=266} (or {\tt 267}) with {\tt part=real}.
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\end{itemize}
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The sum of these yields the cross-section with one identified heavy quark in
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the final state when {\tt inclusive} is set to {\tt .false.} . To calculate the
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rate for at least one heavy quark, {\tt inclusive} should be {\tt .true.}.
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For processes {\tt 263} and
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{\tt 264}, the calculation uses the matrix elements for the production
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of a $Z$ and a heavy quark pair and demands that one of the heavy quarks
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is not observed. It may either lie outside the range of $p_T$ and $\eta$
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required for a jet, or both quarks may be contained in the same jet.
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Due to the extra complexity (the calculation must retain the full
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dependence on the heavy quark mass), this can only be computed at LO.
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When {\tt removebr} is true, the $Z$ boson does not decay.
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