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Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
Validation of the matched MadEvent Single-Top
Sample with ZTOP NLO Calculations
CDF-Note 7701
Jan Lueck
IEKP Karlsruhe, Germany
Higgs Workshop
Ohio, 7/26/2005
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 01/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
MadEvent: MC Event generator by F. Maltoni, T. Stelzer
Matching by Catalin Ciobanu
if pT (b) < 10 GeV
(PYTHIA showering)
ZTOP:
if pT (b) > 10 GeV
Software by Z. Sullivan calculating NLO-distributions (pT , η) of top quark,
pT-leading jets and pT-2nd-leading jets. It does not decay the top quark.
It distinguishes between jets with or without b-quark content.
Comparison with: - no top-decay
- distributions of pT, η normalized to ZTOP total cross section
- cuts on all but top quark distributions: pT > 15 GeV and |η |< 2.8
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 02/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
Top quark
- Distributions have equal area
- Used for normalization of all other distributions
- Reasonable good agreement
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 03/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
b jet when pT-leading jet
- pT-leading jets represented by MadEvent quarks at parton level (here 2nd-b quark)
- Underestimated by MadEvent by a factor of about 0.8
- Good agreement with spectrum
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 04/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
light jet when pT-leading jet
- In 71.7 % of all events, the light quark jet is the leading jet
- Very good agreement
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 05/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
b jet when pT-2nd-leading jet
- Slightly underestimated by MadEvent by a factor of about 0.93
- Very good agreement in the shapes
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 06/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
parton level 2nd-leading light quark ≠ 2nd-leading light jet
- NLO matrix elements not included in the matched MadEvent sample:
IS gluon splitting
IS + FS gluon radiation
- contribution especially to soft pT-2nd-leading light jets
- FS gluon radiation modeled by PYTHIA => not visible at parton level
=> jet-clustering of stable particles (kT cluster algorithm)
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 07/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
Light jet when pT-2nd-leading jet
- should appear in 17.2 % of all events, rate is too high by factor of 1.18
- light jet, if per jet less than 30 % of the energy of the clustered particles are
from decay of b-hadrons.
- poor agreement for η distributions, far too central
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 08/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
Systematic Error Estimation on MC model
Concept:
Jan Lueck
- Use deviations of all validated distributions
- Obtain correlation matrix from MadEvent sample
- Calculate upper and lower deviation for each event passing acceptance
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 09/10
Validation of the matched MadEvent Single-Top Sample with ZTOP NLO Calculations
Conclusion
Matched sample successfully describes kinematics
For all but light pT-2nd-leading jet we have good agreement.
Differences were to be expected
Next goal:
- Estimation of systematic error due to MC generator
Jan Lueck
Institut für Experimentelle Kernphysik
Universität Karlsruhe (TH)
page 10/10