CMS-PAS-B2G-16-019

CMS-PAS-B2G-16-019
Search for heavy vector-like quarks decaying to same-sign dileptons
CMS Collaboration
March 2017

Abstract: A search for the production of heavy partners of the top quark with charge 5/3 decaying to same-sign dileptons is presented. The data sample was collected at a center of mass energy of $\sqrt{s} = $ 13 TeV by the CMS experiment at the Large Hadron Collider in 2016 and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The same-sign dilepton final state has three main sources of background: background from prompt standard model processes, background from events where the charge of one of the leptons is misidentified, and background from non-prompt or fake leptons. No significant excess is seen above the expected background and lower limits are placed on the $\mathrm{X}_{5/3}$ mass of 1.16 (1.10) TeV for right (left) handed chirality particle while the expected limits are 1.20 (1.15) TeV for a right (left) handed $\mathrm{X}_{5/3}$.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagrams for the production of pairs of $\mathrm{X}_{5/3} $particles via QCD processes.
png pdf	Figure 1-a: Feynman diagram for the production of pairs of $\mathrm{X}_{5/3} $particles via QCD processes.
png pdf	Figure 1-b: Feynman diagram for the production of pairs of $\mathrm{X}_{5/3} $particles via QCD processes.
png pdf	Figure 2: The $H^{\text {lep}}_{\text {T}}$ distributions after the same-sign dilepton selection, Z/quarkonia lepton invariant mass vetoes, and requiring at least two AK4 jets in the event. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and the uncertainty, including both statistical and systematic, on the background.
png pdf	Figure 2-a: The $H^{\text {lep}}_{\text {T}}$ all-channel distribution after the same-sign dilepton selection, Z/quarkonia lepton invariant mass vetoes, and requiring at least two AK4 jets in the event.
png pdf	Figure 2-b: The $H^{\text {lep}}_{\text {T}}$ ee distribution after the same-sign dilepton selection, Z/quarkonia lepton invariant mass vetoes, and requiring at least two AK4 jets in the event.
png pdf	Figure 2-c: The $H^{\text {lep}}_{\text {T}}$ e$\mu$ distribution after the same-sign dilepton selection, Z/quarkonia lepton invariant mass vetoes, and requiring at least two AK4 jets in the event.
png pdf	Figure 2-d: The $H^{\text {lep}}_{\text {T}}$ $\mu\mu$ distribution after the same-sign dilepton selection, Z/quarkonia lepton invariant mass vetoes, and requiring at least two AK4 jets in the event.
png pdf	Figure 3: 95% CL observed and expected limits for a left-handed (left) and right-handed (right) $\mathrm{X}_{5/3} $ for all channels combined. The theoretical uncertainty on the signal cross section is shown as a red band around the central prediction.
png pdf	Figure 3-a: 95% CL observed and expected limits for a left-handed $\mathrm{X}_{5/3} $ for all channels combined. The theoretical uncertainty on the signal cross section is shown as a red band around the central prediction.
png pdf	Figure 3-b: 95% CL observed and expected limits for a right-handed $\mathrm{X}_{5/3} $ for all channels combined. The theoretical uncertainty on the signal cross section is shown as a red band around the central prediction.

Tables
png pdf	Table 1: $\mathrm{X}_{5/3} $signal samples and their cross sections. Samples for both LH and RH chiralities were generated for the different mass points.
png pdf	Table 2: Details of systematic uncertainties applied for lepton triggering, identification ("ID''), isolation ("ISO''), and luminosity.
png pdf	Table 3: Systematic uncertainties associated with the background processes which we take from simulation. "JES'' refers to the uncertainty from the jet energy scale while "Theory'' refers to uncertainties from the cross section normalization and choice of PDF.
png pdf	Table 4: Summary of yields from prompt same-sign dilepton Monte Carlo (PSS MC), same-sign non-prompt (NonPrompt), and opposite-sign prompt (ChargeMisID) backgrounds after the full analysis selection. Also shown are the number of expected events for a right handed 1000 GeV $\mathrm{X}_{5/3} $. The errors include both statistical and all systematic uncertainties.

Summary

In summary, we have performed a search for an exotic top partner with charge 5/3 decaying to same-sign dileptons using 35.9 fb$^{-1}$ of data collected by the CMS experiment at $\sqrt{s} = $ 13 TeV. No significant excess above the expected values is seen and observed (expected) limits are placed on the $\mathrm{X}_{5/3}$ mass of 1.16 (1.20) TeV for a right handed $\mathrm{X}_{5/3}$ and 1.10 (1.15) TeV for a left handed $\mathrm{X}_{5/3}$.

References
1	A. De Simone, O. Matsedonskyi, R. Rattazzi, and A. Wulzer	A First Top Partner Hunter's Guide	JHEP 04 (2013) 004	1211.5663
2	J. Mrazek and A. Wulzer	A Strong Sector at the LHC: Top Partners in Same-Sign Dileptons	PRD 81 (2010) 075006	0909.3977
3	G. Dissertori, E. Furlan, F. Moortgat, and P. Nef	Discovery potential of top-partners in a realistic composite Higgs model with early LHC data	JHEP 09 (2010) 019	1005.4414
4	R. Contino and G. Servant	Discovering the top partners at the LHC using same-sign dilepton final states	JHEP 06 (2008) 026	0801.1679
5	A. Azatov and J. Galloway	Light Custodians and Higgs Physics in Composite Models	PRD 85 (2012) 055013	1110.5646
6	CMS Collaboration	Search for top quark partners with charge 5/3 at $ \sqrt{s}= $ 13 TeV	CMS-PAS-B2G-15-006	CMS-PAS-B2G-15-006
7	ATLAS Collaboration Collaboration	Search for new physics using events with $ b $-jets and a pair of same charge leptons in 3.2 fb$ ^{-1} $ of $ pp $ collisions at $ \sqrt{s}= $ 13 TeV with the ATLAS detector	Technical Report ATLAS-CONF-2016-032, CERN, Geneva, Jun
8	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
9	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
10	P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietkerk	Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations	JHEP 03 (2013) 015	1212.3460
11	M. Czakon and A. Mitov	Top++: A Program for the Calculation of the Top-Pair Cross-Section at Hadron Colliders	CPC 185 (2014) 2930
12	M. Czakon, P. Fiedler, and A. Mitov	Total Top-Quark Pair-Production Cross Section at Hadron Colliders Through $ \mathcal{O}({ {\alpha}}_{S}^{4}) $	PRL 110 (2013) 252004
13	M. Czakon and A. Mitov	NNLO corrections to top pair production at hadron colliders: the quark-gluon reaction	JHEP 01 (2013) 080
14	M. Czakon and A. Mitov	NNLO corrections to top-pair production at hadron colliders: the all-fermionic scattering channels	JHEP 12 (2012) 054
15	P. Barnreuther, M. Czakon, and A. Mitov	Percent Level Precision Physics at the Tevatron: First Genuine NNLO QCD Corrections to $ q \bar{q} \to t \bar{t} + X $	PRL 109 (2012) 132001
16	M. Cacciari et al.	Top-pair production at hadron colliders with next-to-next-to-leading logarithmic soft-gluon resummation	PLB 710 (2012) 612
17	J. Alwall et al.	Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions	EPJC 53 (2008) 473	0706.2569
18	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
19	S. Frixione, P. Nason, and C. Oleari	Matching NLO QCD computations with Parton Shower simulations: the POWHEG method	JHEP 11 (2007) 070	0709.2092
20	T. Sjostrand, S. Mrenna, and P. Z. Skands	A Brief Introduction to PYTHIA 8.1	CPC 178 (2008) 852	0710.3820
21	T. Sjostrand et al.	An Introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
22	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040
23	P. Skands, S. Carrazza, and J. Rojo	Tuning PYTHIA 8.1: the Monash 2013 Tune	EPJC 74 (2014) 3024	1404.5630
24	CMS Collaboration Collaboration	Investigations of the impact of the parton shower tuning in Pythia 8 in the modelling of $ \mathrm{t\overline{t}} $ at $ \sqrt{s}= $ 8 and 13 TeV	Technical Report CMS-PAS-TOP-16-021, CERN, Geneva
25	GEANT4 Collaboration	GEANT4: A Simulation toolkit	NIMA 506 (2003) 250
26	CMS Collaboration	Particle-flow event reconstruction in CMS and performance for jets, taus, and $ E_{\mathrm{T}}^{\text{miss}} $	CDS
27	CMS Collaboration	Commissioning of the particle-flow event with the first LHC collisions recorded in the CMS detector	CDS
28	CMS Collaboration	Performance of Electron Reconstruction and Selection with the CMS Detector in Proton-Proton Collisions at $ \sqrt{s}= $ 8 TeV	JINST 10 (2015) P06005	CMS-EGM-13-001 1502.02701
29	CMS Collaboration Collaboration	CMS Tracking Performance Results from Early LHC Operation	EPJC 70 (Jul, 2010) 1165. 29 p
30	W. Adam, R. Fruhwirth, A. Strandlie, and T. Todorov	Reconstruction of electrons with the Gaussian sum filter in the CMS tracker at LHC	J. Phys G 31 (2005) N9	physics/0306087
31	CMS Collaboration	Measurement of the Inclusive $ W $ and $ Z $ Production Cross Sections in $ pp $ Collisions at $ \sqrt{s}= $ 7 TeV	JHEP 10 (2011) 132	CMS-EWK-10-005 1107.4789
32	M. Cacciari, G. P. Salam, and G. Soyez	The anti-$ k_t $ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
33	CMS Collaboration	Determination of jet energy calibration and transverse momentum resolution in CMS	JINST 6 (2011) P11002	CMS-JME-10-011 1107.4277
34	CMS Collaboration	Search for new physics with same-sign isolated dilepton events with jets and missing transverse energy at the LHC	JHEP 06 (2011) 077	CMS-SUS-10-004 1104.3168
35	T. Muller, J. Ott, and J. Wagner-Kuhr	theta - a framework for template-based modeling and inference	2010