Abstract
To measure the top quark pair production cross section in the \(\ell \)+jets channel, the key feature is to distinguish between top quark pair production and the dominant background processes, \(W\)+jets production and QCD multijet production. This can be achieved by imposing harsh cuts on the event selection leading to a signal enriched sample with small backgrounds. In such a case, a simple counting experiment can be used to extract the cross section and is typically done for measurements with low statistics. However, once the statistics of the available data set grows, the limiting factor will be the systematic uncertainty.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
Or of the leading three jets, in case of \(n_{jet} = 3\)
- 2.
Or only third jet, if \(n_\mathrm{{jets}} = 3\)
- 3.
With the top quark pair production normalization associated to \({\beta }_0\)
- 4.
In principle, Berends scaling and the problem of modeling the ratio of events in different jet bins applies for \(Z\)+jets production in the same way as for \(W\)+jets production, but the contribution from this process is rather small.
- 5.
Technically, this means that if the \(+1\sigma \) shifted JES uncertainty is applied to one jet in the event it is also applied to every other jet in the event, regardless of their separation in \(\eta \) and \(p_T\).
- 6.
Such as different detector material or the amount of dead material as a function of the pseudorapidity.
- 7.
This effectively leads to an overestimation of this source of systematic uncertainty, but also accounts for differences in the 2010 data set used to derive the uncertainty and the 2011 data set as analysed.
- 8.
Four for the \(b\)-tag calibration, four for the mistag calibration.
- 9.
In general, a better strategy would be to use the exact same pseudo-data set with both fitter setups and quote the average difference between the two as systematic shift. However, this is not possible in the current implementation of the profile likelihood fit used in this work, and the described method yields equivalent results for large numbers of PEs, reducing the statistical component of the procedure.
- 10.
Where the systematics term only includes the sources of systematic uncertainties that are actually included as nuisance parameters.
References
A. Hoecker, P. Speckmayer, J. Stelzer, J. Therhaag, E. von Toerne, and H. Voss. TMVA: Toolkit for Multivariate Data Analysis. PoS, ACAT:040, 2007.
R. Brun and F. Rademakers, ROOT—An Object Oriented Data Analysis Framework. Proceedings AIHENP’96 Workshop, Lausanne, 1996, Nucl. Inst. Meth. in Phys. Res. A 389, 81–86 (1997). See also http://root.cern.ch/
F. James, M. Roos, Minuit: A System for Function Minimization and Analysis of the Parameter Errors and Correlations. Comput. Phys. Commun. 10, 343–367 (1975)
W. Johnson, Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events at the Tevatron. Phd Thesis, University of California, Davis, 2010.
N. Reid and D. A. S. Fraser, Likelihood Inference in the Presence of Nuisance Parameters. Proc. Statistical Problems in Particle Physics, Astrophysics, and Cosmology (PHYSTAT 2003), SLAC, Stanford, California, September 8–11, 2003, p. 265.
Botje, M. and others. The PDF4LHC Working Group Interim Recommendations. arXiv: hep-ph 1101.0538, 2011.
F.A. Berends, W.T. Giele, H. Kuijf, R. Kleiss, W.J. Stirling, Multijet Production in W, Z Events at \(p\bar{p}\) Colliders. Nucl. Phys. B 537, 1 (1991)
S.D. Ellis, R. Kleiss, W.J. Stirling, W’s. Z’s and Jets. Phys. Lett. B 154, 435 (1985)
The ATLAS Collaboration. Jet Energy Measurement with the ATLAS Detector in Proton-Proton Collisions at \(\sqrt{s} = 7\) TeV. arXiv: hep-ex 1112.6426, 2011.
The ATLAS Collaboration. ATLAS Calorimeter Responses to Single Isolated Hadrons and Estimation of the Calorimeter Jet Scale Uncertainty. ATLAS-CONF-2010-052, 2010.
The ATLAS Collaboration. ATLAS Calorimeter Responses to Single Isolated Hadrons and Estimation of the Calorimeter Jet Scale Uncertainty. ATLAS-CONF-2011-028, 2011.
The ATLAS Collaboration. Close-by Jet Effects on Jet Energy Scale Calibration in \(pp\) Collisions at \(\sqrt{s} = 7\) TeV with the ATLAS Detector. ATLAS-CONF-2011-062, 2011.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2014 Springer International Publishing Switzerland
About this chapter
Cite this chapter
Henrichs, A.C. (2014). General Analysis Strategy. In: Top Quark Pair Production. Springer Theses. Springer, Cham. https://doi.org/10.1007/978-3-319-01487-6_5
Download citation
DOI: https://doi.org/10.1007/978-3-319-01487-6_5
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-01486-9
Online ISBN: 978-3-319-01487-6
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)