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38 lines
2.1 KiB
38 lines
2.1 KiB
\midheading{$t\bar{t}$ production with one hadronic decay, processes 146--151}
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This process is calculable at leading LO and next-to-leading order NLO.
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These processes describe the hadronic production of a pair of top
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quarks, with one quark decaying hadronically and one quark decaying
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semi-leptonically. For processes {\tt 146--148}, the top quark decays
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semi-leptonically whereas the anti-top quark decays hadronically. For
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processes {\tt 149--151}, the top quark decays hadronically whereas the
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anti-top quark decays semi-leptonically. The base processes for
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physics are process {\tt 146} and {\tt 149} which include
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radiative corrections in both production and decay. Switching {\tt zerowidth} from
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{\tt .true.} to {\tt .false.} only affects the $W$ bosons from the top
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quark decay, because our method of including spin correlations
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requires the top quark to be on shell.
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When one wishes to calculate observables related to the decay of the top
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quark, {\tt removebr} should be false in processes {\tt 146} and {\tt 149}.
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The LO calculation proceeds as normal. At NLO, there are two options:
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\begin{itemize}
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\item {\tt part=virt, real} or {\tt tota} : final state radiation is included
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in the production stage only
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\item {\tt part = todk} : radiation is included in the decay of the top
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quark also and the final result corresponds to the sum of real and virtual
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diagrams.
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Note that these runs automatically perform an extra integration, so
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will take a little longer.
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\end{itemize}
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Processes {\tt 147} and {\tt 150} include only the radiative
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corrections in the decay of the top quark without including
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the radiative corrections in the hadronic decay of the $W$-boson.
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Because of the method that we have used to include the radiation in the decays,
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the inclusion of the corrections in this stage of the decay does not change the
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total cross section.
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Process {\tt 148} ({\tt 151}) includes only the radiative corrections
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in the hadronic decay of the $W$-boson coming from the anti-top (top).
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The inclusion of the corrections in this stage of the decay increases the
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partial width by the normal $\alpha_s/\pi$ factor.
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