TOP-12-020 - Measurement of the W boson helicity in events with a single reconstructed top quark in pp collisions at sqrt(s) = 8 TeV

arXiv:1410.1154 - CERN-PH-EP-2014-242 - JHEP 01 (2015) 053
Inspire - HepData - RIVET

PDF from arXiv

Abstract

A measurement of the W boson helicity is presented, where the W boson originates from the decay of a top quark produced in pp collisions. The event selection, optimized for reconstructing a single top quark in the final state, requires exactly one isolated lepton (muon or electron) and exactly two jets, one of which is likely to originate from the hadronization of a bottom quark. The analysis is performed using data recorded at a center-of-mass energy of 8 TeV with the CMS detector at the CERN LHC in 2012. The data sample corresponds to an integrated luminosity of 19.7 fb-1. The measured helicity fractions are FL = 0.298 0.028 (stat) 0.032 (syst), F0 = 0.720 0.039 (stat) 0.037(syst), and FR = -0.018 0.019 (stat) 0.011 (syst). These results are used to set limits on the real part of the tWb anomalous couplings, gL and gR.

Results

The W boson helicity fractions are measured in the single top quark event topology, where the W boson from the top quark decays into a charged lepton (muon or electron) and a neutrino. The selected data complement the data from the standard CMS tt event selection and have different systematic uncertainties. The results from the analysis of 19.7 fb-1 of pp collision data at sqrt(s) = 8 TeV are in agreement, within their uncertainties, with the standard model NNLO predictions. The measurements have similar precision to those based on tt events. The combined results are used to set exclusion limits on the tWb anomalous couplings.

Figures

Figure 1 (top-left): The reconstructed top quark mass distribution for data and simulation in the muon decay channel. The normalization for simulated samples are corrected according to the single top quark cross section measurement in which the shape for QCD multijet events is obtained from data.

PDF - PNG - EPS
Figure 1 (top-right): The reconstructed top quark mass distribution for data and simulation in the electron decay channel. The normalization for simulated samples are corrected according to the single top quark cross section measurement in which the shape for QCD multijet events is obtained from data.

PDF - PNG - EPS
Figure 1 (bottom-left): The reconstructed cos(θl*) distribution for data and simulation in the muon decay channel. The normalization for simulated samples are corrected according to the single top quark cross section measurement in which the shape for QCD multijet events is obtained from data.

PDF - PNG - EPS
Figure 1 (bottom-right): The reconstructed cos(θl*) distribution for data and simulation in the electron decay channel. The normalization for simulated samples are corrected according to the single top quark cross section measurement in which the shape for QCD multijet events is obtained from data.

PDF - PNG - EPS
Figure 2: Combined results from the muon+jets and electron+jets events for the left-handed and longitudinal W boson helicity fractions, shown as 68% contours for statistical, systematic, and total uncertainties, compared with the SM predictions.

PDF - PNG - EPS
Figure 3: The right-handed helicity fraction of the W boson from the top quark decay. The results from this analysis (top three entries) are compared with the SM prediction and with the previous measurements, which are based on tt events.

PDF - PNG - EPS
Figure 4: Exclusion limits on the real part of gL and gR anomalous couplings, with VL = 1 and VR = 0, using the combined W boson helicity measurement in the single top quark event topology. Dashed blue lines show gL = 0 and gR = 0 as predicted by the SM at tree level.

PDF - PNG - EPS

Tables

Table Caption
Table 1: Event yields for data and simulation after the full event selection. Events with complex pz,nu solutions are discarded. This rejects 40% of the single top quark events and about 50% of events from the other processes. The expected number of simulated events is normalized to the integrated luminosity of 19.7 fb-1. Corrections from different sources are considered in simulation yields. The uncertainties are statistical only.

PDF - PNG
Table 2: Summary of the systematic uncertainties.

PDF - PNG

-- AndreasMeyer - 2015-02-05

Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formateps cms-top12020-fig01-bottom-left.eps r2 r1 manage 23.0 K 2015-02-06 - 15:58 AbidehJafari  
PDFpdf cms-top12020-fig01-bottom-left.pdf r1 manage 137.9 K 2015-02-06 - 12:01 AbidehJafari  
PNGpng cms-top12020-fig01-bottom-left.png r1 manage 21.7 K 2015-02-06 - 15:58 AbidehJafari  
Unknown file formateps cms-top12020-fig01-bottom-right.eps r1 manage 22.7 K 2015-02-06 - 15:58 AbidehJafari  
PDFpdf cms-top12020-fig01-bottom-right.pdf r1 manage 104.1 K 2015-02-06 - 12:01 AbidehJafari  
PNGpng cms-top12020-fig01-bottom-right.png r1 manage 21.9 K 2015-02-06 - 15:58 AbidehJafari  
Unknown file formateps cms-top12020-fig01-top-left.eps r1 manage 24.9 K 2015-02-06 - 15:21 AbidehJafari  
PDFpdf cms-top12020-fig01-top-left.pdf r1 manage 71.0 K 2015-02-06 - 12:01 AbidehJafari  
PNGpng cms-top12020-fig01-top-left.png r1 manage 24.7 K 2015-02-06 - 15:21 AbidehJafari  
Unknown file formateps cms-top12020-fig01-top-right.eps r1 manage 24.8 K 2015-02-06 - 15:21 AbidehJafari  
PDFpdf cms-top12020-fig01-top-right.pdf r1 manage 70.4 K 2015-02-06 - 12:01 AbidehJafari  
PNGpng cms-top12020-fig01-top-right.png r1 manage 24.8 K 2015-02-06 - 15:21 AbidehJafari  
Unknown file formateps cms-top12020-fig02.eps r1 manage 10.4 K 2015-02-06 - 15:21 AbidehJafari  
PDFpdf cms-top12020-fig02.pdf r1 manage 15.8 K 2015-02-06 - 12:06 AbidehJafari  
PNGpng cms-top12020-fig02.png r1 manage 16.5 K 2015-02-06 - 15:21 AbidehJafari  
Unknown file formateps cms-top12020-fig03.eps r1 manage 10.6 K 2015-02-06 - 16:21 AbidehJafari  
PDFpdf cms-top12020-fig03.pdf r1 manage 14.6 K 2015-02-06 - 12:06 AbidehJafari  
PNGpng cms-top12020-fig03.png r1 manage 19.7 K 2015-02-06 - 16:20 AbidehJafari  
Unknown file formateps cms-top12020-fig04.eps r1 manage 86.2 K 2015-02-06 - 16:36 AbidehJafari  
PDFpdf cms-top12020-fig04.pdf r1 manage 66.1 K 2015-02-06 - 12:06 AbidehJafari  
PNGpng cms-top12020-fig04.png r1 manage 15.2 K 2015-02-06 - 16:36 AbidehJafari  
PDFpdf cms-top12020-table01.pdf r1 manage 34.7 K 2015-02-06 - 16:55 AbidehJafari  
PNGpng cms-top12020-table01.png r1 manage 71.3 K 2015-02-06 - 16:55 AbidehJafari  
PDFpdf cms-top12020-table02.pdf r1 manage 28.5 K 2015-02-06 - 16:55 AbidehJafari  
PNGpng cms-top12020-table02.png r1 manage 54.4 K 2015-02-06 - 16:55 AbidehJafari  
Edit | Attach | Watch | Print version | History: r6 < r5 < r4 < r3 < r2 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r6 - 2015-03-17 - AndreasMeyer
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    CMSPublic All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback