Phenomenological studies of top-pair production at NLO
Phenomenological studies of top-pair production at NLO Phenomenological studies of top-pair production at NLO
Introduction 8-10 partons in the final state @ LO, well separated to avoid divergences Standard Model and beyond tools @ tree level (just few examples) ALPGEN, AMEGIC++/SHERPA, CARLOMAT, COMIX/SHERPA, COMPHEP, HELAC-PHEGAS, MADGRAPH/MADEVENT, O'MEGA/WHIZARD, ... General purpose Monte Carlo programs (parton shower, hadronization, multiple interactions, hadrons decays, etc.) HERWIG, HERWIG++, PYTHIA 6.4, PYTHIA 8.1, SHERPA, ... High sensitivity to unphysical input scales Higher order calculations are needed to improve accuracy of prediction 4
Motivation for NLO Stabilizing the scale in the QCD input parameters: Strong coupling constant and PDFs More reliable theoretical error related to the scale dependence Normalization and shape of distributions first known at NLO Many scale processes: V+ jets, ttH, tt + jets, bb + jets, njets ... How do we know which scale to choose ? Improved description of jets Jets: LO NLO Parton Hadron Shower Level 5
- Page 1 and 2: Phenomenological studies of top-pai
- Page 3: HELAC-NLO Group G. Bevilacqua (RWTH
- Page 7 and 8: Structure of NLO Calculations σ N
- Page 9 and 10: One-loop amplitude and rational par
- Page 11 and 12: Top Pair Production Complete off-s
- Page 13 and 14: Top Pair Production TeVatron Diffe
- Page 15 and 16: TeVatron Top Pair Production A t FB
- Page 17 and 18: Top Pair + 2 Jets Partonic subproc
- Page 19 and 20: TeVatron Top Pair + 2 Jets Correct
- Page 21 and 22: Top Pair + 2 Jets A t FB,LO = −0.
- Page 23 and 24: LHC Top Pair + 2 Jets m tt 20% 30%
- Page 25: Summary & Outlook Already calculat
Motiv<strong>at</strong>ion for <strong>NLO</strong><br />
Stabilizing the scale in the QCD input parameters:<br />
Strong coupling constant and PDFs<br />
More reliable theoretical error rel<strong>at</strong>ed to the scale dependence<br />
Normaliz<strong>at</strong>ion and shape <strong>of</strong> distributions first known <strong>at</strong> <strong>NLO</strong><br />
Many scale processes: V+ jets, ttH, tt + jets, bb + jets, njets ...<br />
How do we know which scale to choose ?<br />
Improved description <strong>of</strong> jets<br />
Jets: LO <strong>NLO</strong> Parton Hadron<br />
Shower<br />
Level<br />
5
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