Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-PAS-TOP-16-010 | ||
| Measurement of the cross section ratio $ \sigma_{\rm t\bar{t}b\bar{b}} $ / $ \sigma_{\rm t\bar{t}jj} $ using dilepton final states in pp collisions at $\sqrt{s} =$ 13 TeV | ||
| CMS Collaboration | ||
| July 2016 | ||
| Abstract: The measurement of the cross section ratio $ \sigma_{\rm t\bar{t}b\bar{b}} $ / $ \sigma_{\rm t\bar{t}jj} $ is presented using a data sample corresponding to an integrated luminosity of 2.3 fb$^{-1}$ collected in pp collisions at $\sqrt{s} =$ 13 TeV with the CMS detector at the LHC. Events with two leptons (${\rm e}$ or $\mu$) and at least four reconstructed jets, including at least two identified as b quark jets, in the final state are selected. The measured ratio is 0.022 $\pm$ 0.003 (stat) $\pm$ 0.006 (syst) and cross section $ \sigma_{\rm t\bar{t}b\bar{b}} $ is 3.9 $\pm$ 0.6 (stat) $\pm$ 1.3 (syst) pb and $ \sigma_{\rm t\bar{t}jj} $ is 176 $\pm$ 5 (stat) $\pm$ 33 (syst) pb in the full phase space. The measurement is compatible with the expectation obtained from the POWHEG simulation interfaced with PYTHIA. | ||
|
Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PLB 776 (2018) 355. The superseded preliminary plots can be found here. |
||
| Figures | |
png pdf |
Figure 1-a:
Normalized distributions of the b jet discriminator for the third (a) and fourth (b) jets in an event, sorted in decreasing order of b-tagging discriminator value, after the full event selection. The histograms are obtained from MC simulation and are separated according to jet flavour. |
png pdf |
Figure 1-b:
Normalized distributions of the b jet discriminator for the third (a) and fourth (b) jets in an event, sorted in decreasing order of b-tagging discriminator value, after the full event selection. The histograms are obtained from MC simulation and are separated according to jet flavour. |
png pdf |
Figure 2-a:
Distributions of b jet discriminator for the third (a) and fourth (b) jets in events in decreasing order of b-tagging discriminator value, after the full event selection. Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panels. |
png pdf |
Figure 2-b:
Distributions of b jet discriminator for the third (a) and fourth (b) jets in events in decreasing order of b-tagging discriminator value, after the full event selection. Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panels. |
png pdf |
Figure 3-a:
Distribution of b jet multiplicity after the 4 jet requirement but without the b-tagging requirement for the ${\mathrm{ e }^+\mathrm{ e }^- }$ (a), ${\mathrm {e^\pm }\mu ^\mp }$ (b) and ${\mu^+ \mu^- }$ (c) final states and the sum of the three final states (d). Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panel. |
png pdf |
Figure 3-b:
Distribution of b jet multiplicity after the 4 jet requirement but without the b-tagging requirement for the ${\mathrm{ e }^+\mathrm{ e }^- }$ (a), ${\mathrm {e^\pm }\mu ^\mp }$ (b) and ${\mu^+ \mu^- }$ (c) final states and the sum of the three final states (d). Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panel. |
png pdf |
Figure 3-c:
Distribution of b jet multiplicity after the 4 jet requirement but without the b-tagging requirement for the ${\mathrm{ e }^+\mathrm{ e }^- }$ (a), ${\mathrm {e^\pm }\mu ^\mp }$ (b) and ${\mu^+ \mu^- }$ (c) final states and the sum of the three final states (d). Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panel. |
png pdf |
Figure 3-d:
Distribution of b jet multiplicity after the 4 jet requirement but without the b-tagging requirement for the ${\mathrm{ e }^+\mathrm{ e }^- }$ (a), ${\mathrm {e^\pm }\mu ^\mp }$ (b) and ${\mu^+ \mu^- }$ (c) final states and the sum of the three final states (d). Points are from data and stacked histograms from MC simulation. The ratio of the number of data events to the total number of MC events after the fit is shown in the lower panel. |
| Tables | |
png pdf |
Table 1:
The predicted number of events for each physics process and for each dilepton category, their total, and the observed total number of events. The results are shown after the final event selection. The $\mathrm{Z}/\gamma ^* \to \ell \ell $ uncertainty is from data, while all other uncertainties include only the statistical uncertainties in the MC samples. |
png pdf |
Table 2:
Summary of the systematic uncertainties from various sources contributing to $ {\sigma _{ {\mathrm{ t \bar{t} } \mathrm{ b \bar{b} } } }} $, $ {\sigma _{ {\mathrm{ t \bar{t} } \mathrm {jj}} }} $, and the ratio $ {\sigma _{ {\mathrm{ t \bar{t} } \mathrm{ b \bar{b} } } }} $/$ {\sigma _{ {\mathrm{ t \bar{t} } \mathrm {jj}} }} $ for a jet ${p_{\mathrm {T}}} $threshold of ${p_{\mathrm {T}}} > $ 20 GeV in the visible phase space. |
png pdf |
Table 3:
The measured cross sections ${\sigma _{ {\mathrm{ t \bar{t} } \mathrm{ b \bar{b} } } }} $ and ${\sigma _{ {\mathrm{ t \bar{t} } \mathrm {jj}} }} $ and their ratio are given for the visible phase space defined as exclusively two leptons with $ {p_{\mathrm {T}}} >$ 20 GeV and $ {| \eta | }< $ 2.4 plus 4 jets, including two b jets with $ {p_{\mathrm {T}}} >$ 20 GeV and $ {| \eta | }< $ 2.5, and the full phase space, corrected for acceptance and branching fractions. The uncertainties shown are statistical and systematic, respectively, for the measurements. |
| Summary |
| A measurement of the cross section ratio ${\sigma_{ {\mathrm{t }\mathrm{ \bar{t} }\mathrm{ b \bar{b} }}}} /{\sigma_{{\mathrm{t }\mathrm{ \bar{t} }{jj}} }}$ is presented using a data sample produced after collisions at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 2.3 fb$^{-1}$. The individual cross sections ${\sigma_{{\mathrm{t }\mathrm{ \bar{t} }{jj}} }}$ and ${\sigma_{{\mathrm{t }\mathrm{ \bar{t} }\mathrm{ b \bar{b} }}}}$ have also been determined. The cross section ratio was measured in a visible phase space region using the dilepton decay mode of $\mathrm{ t \bar{t} }$ events and corrected to the particle level, corresponding to the detector acceptance. The measured cross section ratios in the visible and full phase space are ${\sigma_{ {\mathrm{t }\mathrm{ \bar{t} }\mathrm{ b \bar{b} }}}} /{\sigma_{{\mathrm{t }\mathrm{ \bar{t} }{jj}} }} =$ 0.024 $\pm$ 0.003 (stat) $\pm$ 0.007 (syst) and ${\sigma_{ {\mathrm{t }\mathrm{ \bar{t} }\mathrm{ b \bar{b} }}}} /{\sigma_{{\mathrm{t }\mathrm{ \bar{t} }{jj}} }} =$ 0.022 $\pm$ 0.003 (stat) $\pm$ 0.006 (syst), respectively, requiring a minimum $p_{\mathrm{T}}$ for the particle-level jets of 20 GeV. The measurement is compatible with the expectation obtained from the POWHEG simulation (interfaced with PYTHIA) which is 0.014 $\pm$ 0.001 for the visible and 0.012 $\pm$ 0.001 for full phase space. The measured cross section ${\sigma_{{\mathrm{t }\mathrm{ \bar{t} }\mathrm{ b \bar{b} }}} }$ is 3.9 $\pm$ 0.6 (stat) $\pm$ 1.3 (syst) pb and ${\sigma_{{\mathrm{t }\mathrm{ \bar{t} }{jj}} }} $ is 176 $\pm$ 5 (stat) $\pm$ 33 (syst) pb. The result provides important information about the main background in the search for ${\mathrm{t }\mathrm{ \bar{t} }{H}} $ and as a figure of merit for testing the validity of NLO QCD calculations at $\sqrt{s}$ = 13 TeV. |
| References | ||||
| 1 | ATLAS Collaboration | Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC | PLB 716 (2012) 1 | 1207.7214 |
| 2 | CMS Collaboration | Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC | PLB 716 (2012) 30 | CMS-HIG-12-028 1207.7235 |
| 3 | CMS Collaboration | Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s} $ = 7 and 8 TeV | JHEP 06 (2013) 081 | CMS-HIG-12-036 1303.4571 |
| 4 | CMS Collaboration | Measurement of the properties of a Higgs boson in the four-lepton final state | Phy. Rev. D 89 (2014) 092007 | CMS-HIG-13-002 1312.5353 |
| 5 | CMS Collaboration | Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states | JHEP 01 (2014) 096 | CMS-HIG-13-023 1312.1129 |
| 6 | CMS Collaboration | Evidence for the 125 GeV Higgs boson decaying to a pair of $ \tau $ leptons | JHEP 05 (2014) 104 | CMS-HIG-13-004 1401.5041 |
| 7 | CMS Collaboration | Search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to bottom quarks | PRD 89 (2014) 012003 | CMS-HIG-13-012 1310.3687 |
| 8 | ATLAS Collaboration | Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC | PLB 726 (2013) 88 | 1307.1427 |
| 9 | ATLAS Collaboration | Evidence for the spin-0 nature of the Higgs boson using ATLAS data | PLB 726 (2013) 120 | 1307.1432 |
| 10 | ATLAS, CMS Collaboration | Measurement of the Higgs boson production and decay rates and contraints on its couplings from a combined ATLAS and CMS analysis of the LHC $ pp $ collision data at $ \sqrt{s} $ = 7 and 8 TeV | 1606.02266 | |
| 11 | CMS Collaboration | Search for $ t\bar{t}H $ production in the H $ \to $ $ b\bar{b} $ decay channel with $ \sqrt{s} $ = 13 TeV pp collisions at the CMS experiment | PAS HIG-16-004 (2016) | |
| 12 | M. Worek and G. Bevilacqua | On the ratio of $ $\mathrm{ t \bar{t} b \bar{b} }$ $ and $ $\mathrm{ t \bar{t} jj }$ $ cross sections at the CERN Large Hadron Collider | JHEP 07 (2014) 135 | 1403.2046 |
| 13 | A. Bredenstein, A. Denner, S. Dittmaier, and S. Pozzorini | Next-To-Leading Order QCD Corrections to $ pp \to $\mathrm{ t \bar{t} b \bar{b} }$+X $ at the LHC | PRL 103 (2009) 012002 | 0905.0110 |
| 14 | A. Bredenstein, A. Denner, S. Dittmaier, and S. Pozzorini | NLO QCD corrections to $ $\mathrm{ t \bar{t} b \bar{b} }$ $ production at the LHC: 1. quark-antiquark annihilation | JHEP 08 (2008) 108 | 0807.1248 |
| 15 | CMS Collaboration | First Measurement of the Cross Section Ratio $ $ \sigma(\mathrm{ t \bar{t} b \bar{b} })$/$ \sigma(\mathrm{ t \bar{t} jj })$ $ in pp Collisions at $ \sqrt{s} $ = 7 TeV | PAS TOP-12-024 (2012) | |
| 16 | CMS Collaboration | Measurement of the cross section ratio $ $ \sigma(\mathrm{ t \bar{t} b \bar{b} })$/$ \sigma(\mathrm{ t \bar{t} jj })$ $ in pp collisions at $ \sqrt{s} $ = 8 TeV | PLB 746 (2015) 132 | |
| 17 | CMS Collaboration | Measurement of the $ \mathrm{ t \bar{t} } $ cross section and the ratio $ $ \sigma(\mathrm{ t \bar{t} b \bar{b} })$/$ \sigma(\mathrm{ t \bar{t} jj })$ $ in the lepton+jets final state at 8 TeV | PAS TOP-13-016 (2015) | |
| 18 | CMS Collaboration | Measurement of $ \mathrm{ t \bar{t} } $ production with additional jet activity, including b quark jets, in the dilepton decay channel using pp collisions at $ \sqrt{s} $ = 8 TeV | CMS-TOP-12-041 1510.03072 |
|
| 19 | ATLAS Collaboration | Measurements of fiducial cross-sections for $ \mathrm{ t \bar{t} } $ production with one of two additional b-jets in pp collisions at $ \sqrt{s} $ = 8 TeV using the ATLAS detector | EPJC 76 (2016) 11 | |
| 20 | CMS Collaboration | CMS Luminosity Measurement for the 2015 Data Taking Period | PAS LUM-15-001 (2016) | |
| 21 | P. Nason | A new method for combining NLO QCD with shower Monte Carlo algorithms | JHEP 11 (2004) 040 | hep-ph/0409146 |
| 22 | S. Frixione, P. Nason, and C. Oleari | Matching NLO QCD computations with parton shower simulations: the POWHEG method | JHEP 11 (2007) 070 | 0709.2092 |
| 23 | S. Alioli, P. Nason, C. Oleari, and E. Re | A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX | JHEP 06 (2010) 043 | 1002.2581 |
| 24 | T. Sj\"ostrand, S. Mrenna, and P. Skands | PYTHIA 6.4 physics and manual | JHEP 05 (2006) 026 | hep-ph/0603175 |
| 25 | T. Sj\"ostrand, S. Mrenna, and P. Skands | A Brief Introduction to PYTHIA 8.1 | CPC 178 (2008) 852 | 0710.3820 |
| 26 | NNPDF Collaboration | Parton distributions for the LHC Run II | JHEP 04 (2015) 040 | 1410.8849 |
| 27 | J. Alwall et al. | MadGraph 5: going beyond | JHEP 06 (2011) 128 | 1106.0522 |
| 28 | J. Alwall et al. | The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations | JHEP 07 (2014) 079 | 1405.0301 |
| 29 | M. Czakon and A. Mitov | Top++: A Program for the Calculation of the Top-Pair Cross-Section at Hadron Colliders | CPC 185 (2014) 2930 | 1112.5675 |
| 30 | Y. Li and F. Petriello | Combining QCD and electroweak corrections to dilepton production in FEWZ | PRD 86 (2012) 094034 | 1208.5967 |
| 31 | N. Kidonakis | NNLL threshold resummation for top-pair and single-top production | Phys. Part. Nucl. 45 (2014) 714 | 1210.7813 |
| 32 | GEANT4 Collaboration | GEANT4---a simulation toolkit | NIMA 506 (2003) 250 | |
| 33 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ k_t $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 34 | M. Cacciari, G. P. Salam, and G. Soyez | The catchment area of jets | JHEP 04 (2008) 005 | 0802.1188 |
| 35 | CMS Collaboration | Particle-Flow Event Reconstruction in CMS and Performance for Jets, Taus, and $ E_{\mathrm{T}}^{\text{miss}} $ | CDS | |
| 36 | CMS Collaboration | Commissioning of the Particle-Flow Event Reconstruction with the first LHC collisions recorded in the CMS detector | CDS | |
| 37 | CMS Collaboration | Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s} = 7 $$ TeV $ | JINST 7 (2012) P10002 | |
| 38 | CMS Collaboration | Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at $ \sqrt{s} $ = 8 TeV | JINST 10 (2015) P08010 | |
| 39 | CMS Collaboration | Electron and Photon performance using data collected by CMS at $ \sqrt{s} $ = 13 TeV and 25 ns | CDS | |
| 40 | CMS Collaboration | Identification of b-quark jets with the CMS experiment | JINST 8 (2013) P04013 | |
| 41 | CMS Collaboration | Measurement of differential $ \mathrm{ t \bar{t} } $ production cross sections in lepton + jets final states at 13 TeV | PAS TOP-16-008 (2016) | |
| 42 | Particle Data Group, K. A. Olive et al. | Review of Particle Physics | CPC 38 (2014) 090001 | |
| 43 | CMS Collaboration | CMS Luminosity Based on Pixel Cluster Counting - Summer 2013 Update | CMS-PAS-LUM-13-001 | CMS-PAS-LUM-13-001 |
| 44 | CMS Collaboration | Search for the associated production of the Higgs boson with a top-quark pair | JHEP 09 (2014) 087, . [Erratum: \DOI10.1007/JHEP10(2014)106] | |
| 45 | CMS Collaboration | Determination of jet energy calibration and transverse momentum resolution in CMS | JINST 6 (2011) P11002 | |
| 46 | G. Antchev et al. | First measurement of the total proton-proton cross section at the LHC energy of $ \sqrt{s} $ =7 TeV | Europhys. Lett. 96 (2011) 21002 | 1110.1395 |
| 47 | M. Botje et al. | The PDF4LHC Working Group Interim Recommendations | 1101.0538 | |
| 48 | CMS Collaboration | Measurements of the differential cross section for top quark pair production in pp collisions at $ \sqrt{s} $ = 8 TeV | EPJC 75 (2015) 542 | |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|