CMS-PAS-FTR-22-002

CMS-PAS-FTR-22-002
Search for a vector-like quark T decaying to bW, tZ, tH in the single lepton final state at the HL-LHC
CMS Collaboration
2 December 2022

Abstract: A simulation-based projection study is presented for a search for a vector-like top quark partner T in proton-proton (pp) collisions at $ {\sqrt{\text{s}}} = $ 14 TeV. The search considers the operational conditions of the High-Luminosity LHC (HL-LHC). The production $ {\text{pp} \rightarrow \text{T}\bar{\text{T}}} $ is followed by the decays $ {\text{T} \rightarrow \text{bW}} $, $ {\text{T} \rightarrow \text{tH}} $, and $ {\text{T} \rightarrow \text{tZ}} $ with equal branching fractions of 1/3. Events with one electron or muon, missing transverse momentum and jets are considered. For an integrated luminosity of 3000 fb$ ^{-1} $, the search projects to exclude a T mass below 1750 GeV at the 95% confidence level assuming equal branching fractions for $ {\text{T}\rightarrow \text{bW}/\text{tH}/\text{tZ}} $. Conversely, a T quark with mass up to 1440 GeV can be discovered at the HL-LHC with a significance of five standard deviations.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Leading-order Feynman diagrams showing $ \mathrm{T}\overline{\mathrm{T}} $ production along with the subsequent decays $ \mathrm{T}\rightarrow \mathrm{b}\mathrm{W} $ (left), $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{Z} $ (middle) and $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{H} $ (right).
png pdf	Figure 1-a: Leading-order Feynman diagrams showing $ \mathrm{T}\overline{\mathrm{T}} $ production along with the subsequent decay $ \mathrm{T}\rightarrow \mathrm{b}\mathrm{W} $.
png pdf	Figure 1-b: Leading-order Feynman diagrams showing $ \mathrm{T}\overline{\mathrm{T}} $ production along with the subsequent decay $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{Z} $.
png pdf	Figure 1-c: Leading-order Feynman diagrams showing $ \mathrm{T}\overline{\mathrm{T}} $ production along with the subsequent decay $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{H} $.
png pdf	Figure 2: Number of AK4 jets (left) and b-tagged AK4 jets (right) for signal and background processes. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 2-a: Number of AK4 jets for signal and background processes. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 2-b: Number of b-tagged AK4 jets for signal and background processes. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 3: Multiplicity for the W-tagged (top), single b-tagged H (bottom left) and doubly b-tagged H AK8 jets (bottom right). The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 3-a: Multiplicity for the W-tagged AK8 jets. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 3-b: Multiplicity for the single b-tagged H AK8 jets. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 3-c: Multiplicity for the doubly b-tagged H AK8 jets. The signal distributions are scaled by factors of 20, 2000 and 200'000, depending on the T mass.
png pdf	Figure 4: Distributions in $ S_{\text{T}} $ for signal and background processes. The signal distributions are scaled by factors of 20, 2000 and 200\,000, depending on the T mass.
png pdf	Figure 5: Expected upper limits at 95% CL on the $ \mathrm{T}\overline{\mathrm{T}} $ production cross section. The inner (green) and the outer (yellow) bands indicate the regions containing 68 and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 6: Projected exclusion limits at 95% CL on the T mass (left) and the expected discovery significances (right), as a function of integrated luminosity at the HL-LHC, assuming equal branching fractions for $ {\mathrm{T}\rightarrow \mathrm{b}\mathrm{W}} $, $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{H}} $, and $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{Z}} $ decays.
png pdf	Figure 6-a: Projected exclusion limits at 95% CL on the T mass, as a function of integrated luminosity at the HL-LHC, assuming equal branching fractions for $ {\mathrm{T}\rightarrow \mathrm{b}\mathrm{W}} $, $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{H}} $, and $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{Z}} $ decays.
png pdf	Figure 6-b: Expected discovery significances, as a function of integrated luminosity at the HL-LHC, assuming equal branching fractions for $ {\mathrm{T}\rightarrow \mathrm{b}\mathrm{W}} $, $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{H}} $, and $ {\mathrm{T}\rightarrow \mathrm{t}\mathrm{Z}} $ decays.
png pdf	Figure 7: Discovery potential of a fermionic top partner T as a function of T mass versus integrated luminosity. The blue dashed and red solid lines represent discoveries at expected significances of three and five standard deviations, respectively.

Tables
png pdf	Table 1: Definition of eight exclusive SRs on the basis of number of H-tagged, W-tagged, and b-tagged jets in the event.
png pdf	Table 2: Summary of the systematic uncertainties used in this analysis and their effect on signal cross-section.

Summary

This study presented the expected sensitivity of the CMS experiment to a $ \mathrm{T}\overline{\mathrm{T}} $ production in single lepton final states, considering the subsequent decays $ \mathrm{T}\rightarrow \mathrm{b}\mathrm{W} $, $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{H} $, and $ \mathrm{T}\rightarrow \mathrm{t}\mathrm{Z} $, with a dataset of 3000 fb$ ^{-1} $ of 14 TeV proton proton collisions, expected to be collected at the LHC. The signal and background samples have been simulated with DELPHES 3 considering the CMS Phase-2 detector geometry. At 95% CL, the study projects to exclude a T mass up to 1750 GeV, which is significantly higher than the existing Run 2 results. With 3000 fb$ ^{-1} $, this study shows the prospect for a T discovery up to masses of 1440 GeV.

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	L. Susskind	Dynamics of spontaneous symmetry breaking in the Weinberg-Salam theory	PRD 20 (1979) 2619
5	M. Perelstein, M. E. Peskin, and A. Pierce	Top quarks and electroweak symmetry breaking in little Higgs models	PRD 69 (2004) 075002	hep-ph/0310039
6	O. Matsedonskyi, G. Panico, and A. Wulzer	Light top partners for a light composite Higgs	JHEP 01 (2013) 164	1204.6333
7	M. Schmaltz and D. Tucker-Smith	Little Higgs review	Ann. Rev. Nucl. Part. Sci. 55 (2005) 229	hep-ph/0502182
8	R. Contino, L. Da Rold, and A. Pomarol	Light custodians in natural composite Higgs models	PRD 75 (2007) 055014	hep-ph/0612048
9	R. Contino, T. Kramer, M. Son, and R. Sundrum	Warped/composite phenomenology simplified	JHEP 05 (2007) 074	hep-ph/0612180
10	D. B. Kaplan	Flavor at SSC energies: A new mechanism for dynamically generated fermion masses	NPB 365 (1991) 259
11	M. J. Dugan, H. Georgi, and D. B. Kaplan	Anatomy of a composite Higgs model	NPB 254 (1985) 299
12	F. del Aguila, L. Ametller, G. L. Kane, and J. Vidal	Vector like fermion and standard Higgs production at hadron colliders	NPB 334 (1990) 1
13	A. De Simone, O. Matsedonskyi, R. Rattazzi, and A. Wulzer	A first top partner hunter's guide	JHEP 04 (2013) 004	1211.5663
14	CMS Collaboration	Search for vector-like T and B quark pairs in final states with leptons at $ \sqrt{s} = $ 13 TeV	JHEP 08 (2018) 177	1805.04758
15	CMS Collaboration	Technical proposal for the Phase-II upgrade of the CMS detector	\ CERN-LHCC-2015-010, LHCC-P-008, CMS-TDR-15-02, CERN, Geneva, 2015 link
16	CMS Collaboration	The Phase-2 upgrade of the CMS barrel calorimeters	\ CERN-LHCC-2017-011, CMS-TDR-015, CERN, Geneva, 2017 CDS
17	CMS Collaboration	The Phase-2 upgrade of the CMS muon detectors	\ CERN-LHCC-2017-012, CMS-TDR-016, CERN, Geneva, 2017 CDS
18	CMS Collaboration	The Phase-2 upgrade of the CMS endcap calorimeter	\ CERN-LHCC-2017-023, CMS-TDR-019, CERN, Geneva, 2017 link
19	CMS Collaboration	A MIP timing detector for the CMS Phase-2 upgrade	CERN-LHCC-2019-003, CMS-TDR-020 CDS
20	CMS Collaboration	The Phase-2 upgrade of the CMS Level-1 trigger	CERN-LHCC-2020-004, CMS-TDR-021 CDS
21	CMS Collaboration	The Phase-2 upgrade of the CMS data acquisition and high level trigger	CERN-LHCC-2021-007, CMS-TDR-022 CDS
22	CMS Collaboration	Expected performance of the physics objects with the upgraded CMS detector at the HL-LHC	CMS-NOTE-2018-006, CERN-CMS-NOTE-2018-006 CDS
23	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
24	T. Sjöstrand, S. Mrenna, and P. Z. Skands	A brief introduction to PYTHIA 8.1	Comput. Phys. Commun. 178 (2008) 852	0710.3820
25	M. Czakon, P. Fiedler, and A. Mitov	Total top-quark pair-production cross section at hadron colliders through $ \mathcal{O}(\alpha^4_s) $	PRL 110 (2013) 252004	1303.6254
26	DELPHES 3 Collaboration	DELPHES 3, a modular framework for fast simulation of a generic collider experiment	JHEP 02 (2014) 057	1307.6346
27	CMS Collaboration	Particle-flow event reconstruction in CMS and performance for jets, taus, and met	\ , CERN, Geneva, 2009 CMS-PAS-PFT-09-001
28	M. Cacciari, G. P. Salam, and G. Soyez	The anti-$ k_{\mathrm{T}} $ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
29	D. Bertolini, P. Harris, M. Low, and N. Tran	Pileup per particle identification	JHEP 10 (2014) 059	1407.6013
30	A. J. Larkoski, S. Marzani, G. Soyez, and J. Thaler	Soft drop	JHEP 05 (2014) 146	1402.2657
31	J. Thaler and K. Van Tilburg	Identifying boosted objects with $ N $-subjettiness	JHEP 03 (2011) 015	1011.2268
32	E. X. Cid Vidal et al.	Beyond the Standard Model physics at the HL-LHC and HE-LHC	CERN Yellow Reports, 2019 Monographs 7 (2019) 585
33	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727