Speaker
Description
The generation of single top production in the Wt channel at NLO
gives rise to doubleresonant diagrams that overlap with tt, and
similarly for associated production with a Z or Higgs boson. Several
methods exist to remove this overlap, thus avoiding double counting
and separating between the two processes.
In Diagram Removal I, the amplitudes of doubleresonant diagrams are
set to zero, which also removes the interference of Wt with tt. If a
measurement is performed in a region where this interference is not
negligible, it would be of interest it into account. Another method,
Diagram Subtraction, preserves the interference. However, it relies
upon momentum reshuffling, which introduces uncertainties to the
prediction. An alternative method, Diagram Removal II, does not
involve reshuffling and preserves the interference by subtracting
the amplitude squared of the doubleresonant diagrams from the total.
The predictions of Diagram Removal II from aMC@NLO are compared with
other predictions for Wt and WtZ production in the context of
analyses at the ATLAS experiment. Implications of using Diagram
Removal II are discussed, both for measurements of single top
processes and when Wt or WtZ are treated as a background.
Differential distributions are shown, investigating in what regions
the predictions differ the most.
Summary
Modelling Wt and WtZ production at NLO for ATLAS analyses
