TOP-15-007 Fiducial t-channel single-top cross section at √8 CMS.TeV

Abstract

A measurement is presented of the t-channel single-top-quark production cross section in a fiducial volume in pp-collisions at a centre-of-mass energy of 8 CMS.TeV. The data were recorded in 2012 at the CMS experiment at the CERN LHC, and correspond to an integrated luminosity of 19.7 fb-1. Reconstructed signal events contain one identified muon or electron as well as two jets, one of which is associated with a b-hadron. The definition of the fiducial phase space follows closely these constraints. The total fiducial cross section σfid is measured using different generators at next-to-leading order plus parton-shower accuracy, and the differences between the results are discussed. Using as reference aMC@NLO in the four-flavor scheme, σfid is measured to be 3.38 0.25 (exp.) 0.20 (theo.) pb, in good agreement with theory predictions.

The analysis strategy follows closely the one described in a previous publication http://dx.doi.org/10.1007/JHEP06(2014)090.

Results

Measured fiducial cross section σfid for t-channel single top quark production (using the generator aMC@NLO in the four-flavour scheme (4FS) for the extraction of the result):

eqn1.png

Measured fiducial cross section σfid for t-channel single top quark production (using the POWHEG generator for the extraction of the result in the four-flavour scheme (4FS) or five-flavour scheme (5FS), respectively):

eqn2.png

The fiducial cross section is defined for the following phase space:

  • one "dressed" lepton (electron or muon) with transverse momentum pT>30 CMS.GeV and pseudo-rapidity |η| < 2.4.
  • exactly two jets (anti-kt with ΔR = 0.5, excluding all neutrinos) with transverse momentum pT>40 CMS.GeV and pseudo-rapidity |η| < 5.0.
  • One of the two jets is required to contain a b hadron (using "ghost-matching").
The procedures for "dressing" of the lepton and "ghost-matching" of the b hadron follow closely the conventions by the LHCtopWG.

The measured total cross section σobs as obtained by extrapolation of the measured fiducial cross sections to the full phase space, using the three different Monte Carlo generators aMC@NLO 4FS, POWHEG 4FS and POWHEG 5FS.

eqn3.png

Public Document

The CMS Physics Analysis Summary will be available soon on cds.

Figures

TotFidXSecs.png Figure 2: Fiducial cross sections measured with aMC@NLO 4FS, POWHEG 4FS and POWHEG 5FS compared to the predictions from the same generators. The inner error bars represent the experimental uncertainties. The outer error bars represent the uncertainty including the experimental uncertainty as well as the pdf and scale uncertainties. The uncertainties on the NLO-subtraction scheme are not included in the total uncertainties.

PDF - PNG
TotXSecs.png Figure 3: Total cross section measured with the same generators compared with theoretical predictions. Inner and outer error bars represent the experimental and total uncertainties of the measurements, respectively.

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FidXSecs.png Figure 4: Comparison of the measured fiducial cross section with the predictions from different Monte Carlo generators. The reported measurement refers to the result obtained with aMC@NLO in the four-flavour scheme. The yellow and green bands represent the experimental and the total uncertainties respectively. The error bars on the predictions reflect the uncertainties on scales and PDF.

PDF - PNG

Tables

table1.png Table 1: Event selection requirements at reconstruction and particle level. The phase space for the fiducial cross section measurement is defined by the requirements at particle level.

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table2.png Table 2: Predictions for the fiducial cross section and uncertainties due to acceptance in different scenarios. The scale variations for POWHEG 4FS have been taken from aMC@NLO.

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table3.png Table 3: Acceptance corrections to the fiducial volume εfid or to the full volume εfid Afid.

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Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf FidXSecs.pdf r2 r1 manage 13.8 K 2015-09-14 - 14:20 AlbertoOrsoMariaIorio  
PNGpng FidXSecs.png r2 r1 manage 10.2 K 2015-09-14 - 14:21 AlbertoOrsoMariaIorio  
PDFpdf TotFidXSecs.pdf r2 r1 manage 14.0 K 2015-09-14 - 21:31 AlbertoOrsoMariaIorio  
PNGpng TotFidXSecs.png r2 r1 manage 12.6 K 2015-09-14 - 21:29 AlbertoOrsoMariaIorio  
PDFpdf TotXSecs.pdf r3 r2 r1 manage 14.6 K 2015-09-15 - 12:08 AlbertoOrsoMariaIorio  
PNGpng TotXSecs.png r2 r1 manage 13.6 K 2015-09-14 - 21:17 AlbertoOrsoMariaIorio  
PNGpng eqn1.png r1 manage 54.7 K 2015-09-17 - 18:16 AndreasMeyer  
PNGpng eqn2.png r1 manage 104.2 K 2015-09-17 - 18:16 AndreasMeyer  
PNGpng eqn3.png r1 manage 139.8 K 2015-09-17 - 18:16 AndreasMeyer  
PDFpdf table1.pdf r2 r1 manage 43.4 K 2015-09-18 - 11:19 AlbertoOrsoMariaIorio  
PNGpng table1.png r2 r1 manage 82.9 K 2015-09-18 - 11:18 AlbertoOrsoMariaIorio  
PDFpdf table2.pdf r1 manage 139.8 K 2015-09-17 - 09:45 AndreasMeyer  
PNGpng table2.png r1 manage 288.9 K 2015-09-17 - 10:04 AndreasMeyer  
PDFpdf table3.pdf r1 manage 62.7 K 2015-09-17 - 10:04 AndreasMeyer  
PNGpng table3.png r1 manage 115.1 K 2015-09-17 - 10:04 AndreasMeyer  
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Topic revision: r19 - 2015-11-18 - AndreasMeyer
 
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