CMS-PAS-B2G-17-003 | ||

Search for vector-like quark pair production $\mathrm{T\bar{T}}(\mathrm{Y\bar{Y}})\rightarrow\mathrm{bWbW}$ using kinematic reconstruction in lepton+jets final states at $\sqrt{s}= $ 13 TeV | ||

CMS Collaboration | ||

May 2017 | ||

| ||

Abstract:
A search is presented for the pair production of vector-like quarks, $\mathrm{T\bar{T}}$ or $\mathrm{Y\bar{Y}}$, with an electric charge of either 2/3$|\mathrm{e}|\mathrm{(T)}$ or -4/3$|\mathrm{e}|\mathrm{(Y)}$ in proton-proton collisions at $\sqrt{s} = $ 13 TeV at the LHC. The data were collected by the CMS experiment during the 2016 LHC run, and correspond to an integrated luminosity of 35.8 fb$^{-1}$. The $\mathrm{T(Y)}$ quarks are assumed to decay exclusively to a W boson and a b quark. The search is carried out using events with a single isolated electron or muon, large missing transverse energy and at least four jets with large transverse momenta. In the search a kinematic reconstruction of the final state is performed. Under the assumption of strong pair production of vector-like quarks and 100% branching fractions to bW, an observed (expected) lower limit of 1295 (1275) GeV at 95% CL is set on the T(Y) quark mass.
| ||

Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PLB 779 (2018) 82.The superseded preliminary plots can be found here. |

Figures & Tables | Summary | Additional Figures | References | CMS Publications |
---|

Figures | |

png pdf |
Figure 1:
Reconstructed mass spectra for e+jets (top) and $\mu $+jets (middle) channel and their sum (bottom). Errors are statistical only. |

png pdf |
Figure 1-a:
Reconstructed mass spectra for the e+jets channel. Errors are statistical only. |

png pdf |
Figure 1-b:
Reconstructed mass spectra for the $\mu $+jets channel. Errors are statistical only. |

png pdf |
Figure 1-c:
Reconstructed mass spectra for the sum of the e+jets and $\mu $+jets channels. Errors are statistical only. |

png pdf |
Figure 2:
Reconstructed mass spectra for the sum of the e+jets and $\mu $+jets channels in logarithmic scale for $M_{\mathrm {reco}}$ (top) and logarithmic vertical scale (bottom). Errors are statistical only. |

png pdf |
Figure 2-a:
Reconstructed mass spectra for the sum of the e+jets and $\mu $+jets channels in logarithmic scale for $M_{\mathrm {reco}}$. Errors are statistical only. |

png pdf |
Figure 2-b:
Reconstructed mass spectra for the sum of the e+jets and $\mu $+jets channels in logarithmic vertical scale. Errors are statistical only. |

png pdf |
Figure 3:
Reconstructed mass spectra for the sum of the selected e+jets and $\mu $+jets events for the "noWtag'' category of events (top), and for the "Wtag'' category of events (bottom). Errors are statistical only. |

png pdf |
Figure 3-a:
Reconstructed mass spectra for the sum of the selected e+jets and $\mu $+jets events for the "noWtag'' category of events. Errors are statistical only. |

png pdf |
Figure 3-b:
Reconstructed mass spectra for the sum of the selected e+jets and $\mu $+jets events for the "Wtag'' category of events. Errors are statistical only. |

png pdf |
Figure 4:
Exclusion limits obtained using W-tagged category of events only (top) and post-fit distribution of the reconstructed mass, $M_{\mathrm {reco}}$ (bottom). Shaded band on the histogram shows statistical and systematic uncertainties. |

png pdf |
Figure 4-a:
Exclusion limits obtained using W-tagged category of events only. Shaded band on the histogram shows statistical and systematic uncertainties. |

png pdf |
Figure 4-b:
Exclusion limits obtained using post-fit distribution of the reconstructed mass, $M_{\mathrm {reco}}$. Shaded band on the histogram shows statistical and systematic uncertainties. |

Tables | |

png pdf |
Table 1:
Background processes, number of data events observed and background events predicted for the integrated luminosity of data. The errors on the MC yields are statistical only. |

png pdf |
Table 2:
Selection efficiencies for $\mathrm {T \bar{T}}$ MC assuming $\mathcal {B}(\mathrm {T} \rightarrow \mathrm {bW}) = $ 100% and expected signal events after the final selection, for the integrated luminosity of data. The errors are statistical only. |

png pdf |
Table 3:
Variations of the yield of the selected MC events related to shape systematic uncertainties for a signal with a T quark mass of 1200 GeV and background (BG). |

Summary |

The results of a search for vector-like quarks $\mathrm{T}$ or $\mathrm{Y}$ that are pair produced in pp interactions at $\sqrt{s}= $ 13 TeV and decay exclusively to bW have been presented. Events were selected in which one of the W bosons decays to leptons and the other to a quark-antiquark pair. The selection required a muon or electron, significant missing transverse energy, and at least four jets. A kinematic fit assuming $\mathrm{T\bar{T}}$ or $\mathrm{Y\bar{Y}}$ production was performed and for every event a candidate $\mathrm{T}/\mathrm{Y}$-quark mass $M_{\text{reco}}$ was reconstructed. No significant deviations from the standard model expectations have been found in the $M_{\text{reco}}$ distribution. Upper limits have been set on the production cross section of such $\mathrm{T}/\mathrm{Y}$ quarks as a function of their mass. By comparing with the predicted cross section for vector like quark pair production, the strong pair production of $\mathrm{T}/\mathrm{Y}$ quarks is excluded at 95%CL for masses below 1295 GeV (1275 GeV expected). This is the most restrictive result for T(Y) VLQ pair production at the time of this publication. The search is equally sensitive to any kind of quarks decaying to the same channel. The results can be interpreted as upper limits on the production cross section times the branching fraction of decay to bW. |

Additional Figures | |

png pdf |
Additional Figure 1:
Distributions of $\mathrm {T\bar{T}}$ mass for the $e$+jets (top) and $\mu $+jets (middle) channel and their sum (bottom). Errors are statistical only. |

png pdf |
Additional Figure 1-a:
Distributions of $\mathrm {T\bar{T}}$ mass for the $e$+jets channal. Errors are statistical only. |

png pdf |
Additional Figure 1-b:
Distributions of $\mathrm {T\bar{T}}$ mass for the $\mu $+jets channel. Errors are statistical only. |

png pdf |
Additional Figure 1-c:
Distributions of $\mathrm {T\bar{T}}$ mass for the sum of the $e$+jets and $\mu $+jets channels. Errors are statistical only. |

png |
Additional Figure 2-a:
Display of the data event with highest reconstructed mass of 2775 GeV for the hypothesis $\mathrm {T\bar{T}}\rightarrow \mathrm {bWbW} \rightarrow \mathrm {e}\nu 4 \text{jets} $ |

png |
Additional Figure 2-b:
Display of the data event with highest reconstructed mass of 2775 GeV for the hypothesis $\mathrm {T\bar{T}}\rightarrow \mathrm {bWbW} \rightarrow \mathrm {e}\nu 4 \text{jets} $ |

png |
Additional Figure 2-c:
Display of the data event with highest reconstructed mass of 2775 GeV for the hypothesis $\mathrm {T\bar{T}}\rightarrow \mathrm {bWbW} \rightarrow \mathrm {e}\nu 4 \text{jets} $ |

If we assume the the existence of a heavy resonance, decaying to a pair of VLQs (like, for example $\mathrm{ Z' \rightarrow T\bar{T} }$), we can consider the mass spectrum M($\mathrm{T\bar{T}}$) as another signal distribution, which permits to search for heavy resonances. This distribution is shown in Additional Fig.1 for selected events. We do not observe any significant excess of data over the expected background. |

References | ||||

1 |
L. Randall and R. Sundrum | A large mass hierarchy from a small extra dimension | PRL 83 (1999) 3370--3373 | hep-ph/9905221 |

2 |
D. Choudhury, T. Tait, and C. Wagner | Beautiful Mirrors and Precision Electroweak Data | PRD 65 (2002) 053002 | hep-ph/0109097 |

3 |
N. Arkani-Hamed, A. Cohen, E. Katz, and A. Nelson | The Littlest Higgs | JHEP 0207 (2002) 034 | hep-ph/0206021v2 |

4 |
M. Schmaltz | Physics beyond the standard model (Theory): Introducing the Little Higgs | NPPS 117 (2003) 40 | hep-ph/0210415 |

5 |
T. Han, H. E. Logan, B. McElrath, and L.-T. Wang | Loop induced decays of the little Higgs: H$ \rightarrow \mathrm{gg},\,\gamma\gamma $ | Physics Letters B 563 (2003) 191--202 | |

6 |
M. Schmaltz and D. Tucker-Smith | Little Higgs Review | Ann. Rev. Nucl. Part. Sci 55 (2005) 229 | hep-ph/0502182v1 |

7 |
L.-T. W. H-C. Cheng, I. Low | Top Partners in Little Higgs Theories with T-parity | PRD 74 (2006) | |

8 |
D. Marzocca, M. Serone, and J. Shu | General Composite Higgs Models | JHEP 08 (2012) 013 | 1205.0770v3 |

9 |
H.-C. Cheng, B. Dobrescu, and C. Hill | Electroweak Symmetry Breaking and Extra Dimensions | Nucl. Phys. B 589 (2000) 249 | hep-ph/9912343v3 |

10 |
J. Kang, P. Langacker, and B. Nelson | Theory and Phenomenology of Exotic Isosinglet Quarks and Squarks | PRD 77 (2008) 035003 | 0708.2701v2 |

11 |
D. Guadagnoli, R. Mohapatra, and I. Sung | Gauged Flavor Group with Left-Right Symmetry | JHEP 1104 (2011) 093 | 1103.4170v3 |

12 |
F. del Aguila, L. Ametller, G. Kane, and J. Vidal | Vector like fermion and standard Higgs production at hadron colliders | Nucl. Phys. B 334 (1990) 1 | |

13 |
J. A. Aguilar-Saavedra, R. Benbrik, S. Heinemeyer, and M. P\'erez-Victoria | Handbook of vector-like quarks: mixing and single production | PRD 88 (2013) 094010 | 1306.0572 |

14 |
CMS Collaboration |
Search for vector-like charge 2/3 T quarks in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | PRD 93 (2016) 012003 | CMS-B2G-13-0051509.04177 |

15 |
ATLAS Collaboration |
Search for production of vector-like quark pairs and of four top quarks in the lepton-plus-jets final state in pp collisions at $ \sqrt{s} = $ 8 TeV with the ATLAS detector | JHEP 08 (2015) 105 | arXiv:1505.04306 |

16 |
A. J. Larkoski, S. Marzani, G. Soyez, and J. Thaler | Soft Drop | JHEP 1405 (2014) 146 | 1402.2657 |

17 |
CMS Collaboration |
The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |

18 |
J. Baglio | Next-To-Leading Order QCD Corrections to Associated Production of a SM Higgs Boson with a Pair of Weak Bosons in the POWHEG-BOX | 1512.05787 | |

19 |
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 |

20 |
T. Sjostrand, S. Mrenna, and P. Z. Skands | A Brief Introduction to PYTHIA 8.1 | CPC 178 (2008) 852--867 | 0710.3820 |

21 |
P. F. M. Czakon and A. Mitov | Total Top-Quark Pair-Production Cross Section at Hadron Colliders Through $ O({\alpha_S}^4) $ | PRL 110 (2013) 252004 | 1303.6254 |

22 |
GEANT4 Collaboration | GEANT4 -- a simulation toolkit | NIMA 506 (2003) 250 | |

23 |
CMS Collaboration |
Particle-Flow Event Reconstruction in CMS and Performance for Jets, Taus, and MET | ||

24 |
CMS Collaboration |
Commissioning of the Particle-Flow Reconstruction in Minimum-Bias and Jet Events from pp Collisions at 7 TeV | ||

25 |
CMS Collaboration |
Particle-flow commissioning with muons and electrons from J/Psi and W events at 7 TeV | ||

26 |
CMS Collaboration |
Reconstruction of Electrons with the Gaussian-Sum Filter in the CMS Tracker at the LHC | CDS | |

27 |
M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ k_t $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |

28 |
M. Cacciari, G. P. Salam, and G. Soyez | Fastjet User Manual | EPJC 72 (2012) 1896 | 1111.6097 |

29 |
M. Cacciari and G. P. Salam | Dispelling the $ N^{3} $ myth for the $ k_t $ jet-finder | PLB 641 (2006) 57 | hep-ph/0512210 |

30 |
CMS Collaboration |
Determination of jet energy calibration and transverse momentum resolution in CMS | JINST 6 (2011) P11002 | CMS-JME-10-0111107.4277 |

31 |
M. Cacciari, G. P. Salam, and G. Soyez | The catchment area of jets | JHEP 04 (2008) 005 | 0802.1188 |

32 |
M. Cacciari and G. P. Salam | Pileup subtraction using jet areas | PLB 659 (2008) 119 | 0707.1378 |

33 |
V. Lefebure, S. Banerjee, and I. Gonzalez | CMS Simulation Software Using Geant4 | CMS-NOTE-1999-072 | |

34 |
CMS Collaboration |
Identification of b quark jets at the CMS Experiment in the LHC Run 2 | CMS-PAS-BTV-15-001 | CMS-PAS-BTV-15-001 |

35 |
H. Sumowidagdo | |||

36 |
S. S. Snyder | Measurement of the top quark mass at D0. PhD thesis | Technical Report FERMILAB-THESIS-1995-27, State University of New York, Stony Brook | |

37 |
Particle Data Group, K. A. Olive et al. | Review of particle physics | CPC 38 (2014) 090001 | |

38 |
CMS Collaboration |
Measurement of the top quark pair production cross section using eμ events in proton-proton collisions at $ \sqrt{s} = $ 13 TeV with the CMS detector. | CDS | |

39 |
CMS Collaboration |
CMS luminosity measurements for the 2016 data-taking period | CDS | |

40 |
CMS Collaboration |
Measurement of inclusive W and Z boson production cross sections in pp collisions at $ \sqrt{s} = $ 13 TeV . | CDS | |

41 |
CMS Collaboration |
Measurement of the inclusive cross section of single top quark production in the t channel at $ \sqrt{s} = $ 13 TeV. | CDS | |

42 |
J. S. Conway | Incorporating Nuisance Parameters in Likelihoods for Multisource Spectra | 1103.0354 | |

43 |
J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |

44 |
C. Collaboration | Measurement of the differential cross section for top quark pair production in pp collisions at $ \sqrt{s} = $ 8 TeV | EPJC 75 (2015) 542 | 1505.04480 |

45 |
J. Ott |

Compact Muon Solenoid LHC, CERN |