scholarly journals Pulling the Higgs and top needles from the jet stack with feature extended supervised tagging

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
J. A. Aguilar-Saavedra
Keyword(s):  
Higgs Boson ◽  
Top Quark ◽  
Top Quarks ◽  
High Energy ◽  
New Physics ◽  
Higgs Bosons ◽  
Jet Substructure ◽  
Final State ◽  
Charged Leptons ◽  
Energy Frontier

AbstractJet tagging has become an essential tool for new physics searches at the high-energy frontier. For jets that contain energetic charged leptons we introduce Feature Extended Supervised Tagging (FEST) which, in addition to jet substructure, considers the features of the charged lepton within the jet. With this method we build dedicated taggers to discriminate among boosted $$H \rightarrow \ell \nu q {\bar{q}}$$ H → ℓ ν q q ¯ , $$t \rightarrow \ell \nu b$$ t → ℓ ν b , and QCD jets (with $$\ell $$ ℓ an electron or muon). The taggers have an impressive performance, allowing for overall light jet rejection factors of $$10^4-10^5$$ 10 4 - 10 5 , for top quark/Higgs boson efficiencies of 0.5. The taggers are also excellent in the discrimination of Higgs bosons from top quarks and vice versa, for example rejecting top quarks by factors of 100–300 for Higgs boson efficiencies of 0.5. We demonstrate the potential of these taggers to improve the sensitivity to new physics by using as example a search for a new $$Z'$$ Z ′ boson decaying into ZH, in the fully-hadronic final state.

scholarly journals Analysis of Top Quark Pair Production Signal from Neutral 2HDM Higgs Bosons at LHC

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Majid Hashemi ◽  
Mahbobeh Jafarpour
Keyword(s):  
Higgs Boson ◽  
Pair Production ◽  
Top Quark ◽  
Top Quarks ◽  
Higgs Doublet ◽  
Higgs Bosons ◽  
Type I ◽  
Final State ◽  
Doublet Model ◽  
Two Higgs Doublet Model

In this paper, the top quark pair production events are analyzed as a source of neutral Higgs bosons of the two Higgs doublet model type I at LHC. The production mechanism is pp→H/A→tt¯ assuming a fully hadronic final state through t→Wb→jjb. In order to distinguish the signal from the main background which is the standard model tt¯, we benefit from the fact that the top quarks in signal events acquire large Lorentz boost due to the heavy neutral Higgs boson. This feature leads to three collinear jets (a fat jet) which is a discriminating tool for identification of the top quarks from the Higgs boson resonances. Events with two identified top jets are selected and the invariant mass of the top pair is calculated for both signal and background. It is shown that the low tan β region has still some parts which can be covered by this analysis and has not yet been excluded by flavor physics data.

scholarly journals Recent CMS results in top and Higgs physics

2017 ◽  
Vol 32 (29) ◽  
pp. 1730026
Author(s):  
Rebeca Gonzalez Suarez
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Large Scale ◽  
Top Quarks ◽  
Large Mass ◽  
New Physics ◽  
Higgs Bosons ◽  
Physics Program ◽  
The Standard Model

After the Higgs boson discovery in 2012, the investigation of its properties and compatibility with the Standard Model predictions is central to the physics program of the LHC experiments. Likewise, the study of the top quark is still relevant at the LHC, more than two decades after its discovery at the Tevatron. Top quarks and Higgs bosons are produced at the LHC on a large scale and share a deep connection based on the large mass of the top quark. Both particles provide an excellent laboratory in which to search for new physics: the measurement of their properties tests the foundations of the Standard Model; and they feature prominently in a variety of exotic signals. The coupling of the Higgs boson to the top quark, a fundamental Standard Model parameter, can only be measured directly in processes where the two particles are produced together. The production of a Higgs boson together with one or two top quarks is also sensitive to several exciting new physics effects. A brief overview of the current experimental status of top quark and Higgs boson physics is presented using results from the CMS Collaboration.

scholarly journals tt̄H Coupling Measurement with the ATLAS Detector at the LHC

2018 ◽  
Vol 182 ◽  
pp. 02052
Author(s):  
Asma Hadef
Keyword(s):  
Higgs Boson ◽  
Cross Sections ◽  
Top Quark ◽  
High Energy Physics ◽  
Center Of Mass ◽  
High Energy ◽  
New Physics ◽  
Decay Modes ◽  
Center Of Mass Energy ◽  
Higgs Decay

The Higgs boson was discovered on the 4th of July 2012 with a mass around 125 GeV by ATLAS and CMS experiments at LHC. Determining the Higgs properties (production and decay modes, couplings,...) is an important part of the high-energy physics programme in this decade. A search for the Higgs boson production in association with a top quark pair (tt̄H) at ATLAS [1] is summarized in this paper at an unexplored center-of-mass energy of 13 TeV, which could allow a first direct measurement of the top quark Yukawa coupling and could reveal new physics. The tt̄H analysis in ATLAS is divided into 3 channels according to the Higgs decay modes: H → Hadrons, H → Leptons and H → Photons. The best-fit value of the ratio of observed and Standard Model cross sections of tt̄H production process, using 2015-2016 data and combining all tt̄H final states, is 1:8±0:7, corresponds to 2:8σ (1:8σ) observed (expected) significance.

scholarly journals The present and future of four top operators

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Giovanni Banelli ◽  
Ennio Salvioni ◽  
Javi Serra ◽  
Tobias Theil ◽  
Andreas Weiler
Keyword(s):  
Top Quark ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
Proton Proton ◽  
Strongly Coupled ◽  
Composite Higgs ◽  
Electron Positron ◽  
Energy Frontier ◽  
The Impact

Abstract We study the phenomenology of a strongly-interacting top quark at future hadron and lepton colliders, showing that the characteristic four-top contact operators give rise to the most significant effects. We demonstrate the extraordinary potential of a 100 TeV proton-proton collider to directly test such non-standard interactions in four-top production, a process that we thoroughly analyze in the same-sign dilepton and trilepton channels, and explore in the fully hadronic channel. Furthermore, high-energy electron-positron colliders, such as CLIC or the ILC, are shown to exhibit an indirect yet remarkable sensitivity to four-top operators, since these constitute, via renormalization group evolution, the leading new-physics deformations in top-quark pair production. We investigate the impact of our results on the parameter space of composite Higgs models with a strongly-coupled (right-handed) top quark, finding that four-top probes provide the best sensitivity on the compositeness scale at the future energy frontier. In addition, we investigate mild yet persisting LHC excesses in multilepton plus jets final states, showing that they can be consistently described in the effective field theory of such a new-physics scenario.

scholarly journals Lepton flavor violating decay of 125 GeV Higgs boson to μτ channel and excess in tt̄H

2016 ◽  
Vol 31 (30) ◽  
pp. 1650174 ◽  
Author(s):  
Biplob Bhattacherjee ◽  
Sabyasachi Chakraborty ◽  
Swagata Mukherjee
Keyword(s):  
Higgs Boson ◽  
Top Quark ◽  
Center Of Mass ◽  
New Physics ◽  
Final State ◽  
Center Of Mass Energy ◽  
Lepton Flavor ◽  
Higgs Decay ◽  
Energy Formula ◽  
8 Tev

A recent search for the lepton flavor violating (LFV) decays of the Higgs boson, performed by CMS collaboration, reports an interesting deviation from the Standard Model (SM). The search conducted in the channel [Formula: see text] and [Formula: see text] shows an excess of 2.4[Formula: see text] signal events with 19.6 fb[Formula: see text] data at a center-of-mass energy [Formula: see text] = 8 TeV. On the other hand, a search performed by CMS collaboration for the SM Higgs boson produced in association with a top quark pair [Formula: see text] also showed an excess in the same-sign dimuon final state. In this work, we try to find out if these two seemingly uncorrelated excesses are related or not. Our analysis reveals that a LFV Higgs decay [Formula: see text] can partially explain the excess in the same-sign dimuon final state in the [Formula: see text] search, infact brings down the excess well within 2[Formula: see text] error of the SM expectation. Probing such non-standard Higgs boson decay is of interest and might contain hints of new physics at the electroweak scale.

scholarly journals Improving heavy dijet resonance searches using jet substructure at the LHC

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Aruna Kumar Nayak ◽  
Santosh Kumar Rai ◽  
Tousik Samui
Keyword(s):  
Light Quark ◽  
Hadron Collider ◽  
High Energy ◽  
New Physics ◽  
Higgs Bosons ◽  
Final States ◽  
Jet Substructure ◽  
Charged Higgs Bosons ◽  
Quark Jets ◽  
Positive Step

AbstractThe search for new physics at high energy accelerators has been at the crossroads with very little hint of signals suggesting otherwise. The challenges at a hadronic machine such as the LHC is compounded by the fact that final states are swamped with jets which one needs to understand and unravel. A positive step in this direction would be to separate the jets in terms of their gluonic and quark identities, much in a similar spirit of distinguishing heavy quark jets from light quark jets that has helped in improving searches for both neutral and charged Higgs bosons at the LHC. In this work, we utilise this information using the jet substructure techniques to comment on possible improvements in sensitivity as well as discrimination of new resonances in the all hadronic mode that would be crucial in pinning down new physics signals at HL-LHC, HE-LHC and any future 100 TeV hadron collider.

scholarly journals Leading Weak Corrections to the Production of Heavy Top Quarks at Hadron Colliders

1997 ◽  
Vol 12 (07) ◽  
pp. 1341-1372 ◽  
Author(s):  
Chung Kao ◽  
G. A. Ladinsky ◽  
C.-P. Yuan
Keyword(s):  
Higgs Boson ◽  
Parity Violation ◽  
Top Quark ◽  
Top Quarks ◽  
New Physics ◽  
Threshold Region ◽  
Hadron Colliders ◽  
Top Quark Mass ◽  
Quark Pairs ◽  
The Standard Model

We calculate the leading weak corrections at [Formula: see text] to the QCD production of heavy top quark pairs via [Formula: see text] at hadron colliders and compare them with the complete one-loop weak corrections. We find that these corrections dominate the threshold region for a heavy top quark if the Higgs boson is light. For a heavy Higgs boson, these corrections are generally small. The chromo-anapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM). The parity violation effect in [Formula: see text] from the SM weak corrections is found to be very small, so any observation of large parity violation in this process would indicate new physics. The polarization of the [Formula: see text] pairs is also discussed, including the effect that this has on proposed techniques for measuring the top quark mass.

scholarly journals Topping-up multilepton plus b-jets anomalies at the LHC with a Z′ boson

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Ezequiel Alvarez ◽  
Aurelio Juste ◽  
Manuel Szewc ◽  
Tamara Vazquez Schroeder
Keyword(s):  
Parameter Space ◽  
Top Quark ◽  
Global Analysis ◽  
Charge Asymmetry ◽  
Top Quarks ◽  
New Physics ◽  
Initial State ◽  
Final State ◽  
The Standard Model ◽  
Physics Model

Abstract During the last years ATLAS and CMS have reported a number of slight to mild discrepancies in signatures of multileptons plus b-jets in analyses such as $$ t\overline{t}H $$ t t ¯ H , $$ t\overline{t}{W}^{\pm } $$ t t ¯ W ± , $$ t\overline{t}Z $$ t t ¯ Z and $$ t\overline{t}t\overline{t} $$ t t ¯ t t ¯ . Among them, a recent ATLAS result on $$ t\overline{t}H $$ t t ¯ H production has also reported an excess in the charge asymmetry in the same-sign dilepton channel with two or more b-tagged jets. Motivated by these tantalizing discrepancies, we study a phenomenological New Physics model consisting of a Z′ boson that couples to up-type quarks via right-handed currents: $$ {t}_R{\gamma}^{\mu }{\overline{t}}_R $$ t R γ μ t ¯ R , $$ {t}_R{\gamma}^{\mu }{\overline{c}}_R $$ t R γ μ c ¯ R , and $$ {t}_R{\gamma}^{\mu }{\overline{u}}_R $$ t R γ μ u ¯ R . The latter vertex allows to translate the charge asymmetry at the LHC initial state protons to a final state with top quarks which, decaying to a positive lepton and a b-jet, provides a crucial contribution to some of the observed discrepancies. Through an analysis at a detector level, we select the region in parameter space of our model that best reproduces the data in the aforementioned $$ t\overline{t}H $$ t t ¯ H study, and in a recent ATLAS $$ t\overline{t}t\overline{t} $$ t t ¯ t t ¯ search. We find that our model provides a better fit to the experimental data than the Standard Model for a New Physics scale of approximately ∼500 GeV, and with a hierarchical coupling of the Z′ boson that favours the top quark and the presence of FCNC currents. In order to estimate the LHC sensitivity to this signal, we design a broadband search featuring many kinematic regions with different signal-to-background ratio, and perform a global analysis. We also define signal-enhanced regions and study observables that could further distinguish signal from background. We find that the region in parameter space of our model that best fits the analysed data could be probed with a significance exceeding 3 standard deviations with just the full Run-2 dataset.

scholarly journals Indirect $$ \mathcal{CP} $$ probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Henning Bahl ◽  
Philip Bechtle ◽  
Sven Heinemeyer ◽  
Judith Katzy ◽  
Tobias Klingl ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Decay Channel ◽  
New Physics ◽  
Current Data ◽  
Quark Interaction ◽  
The Standard Model ◽  
Vector Bosons ◽  
Selection Of

Abstract The $$ \mathcal{CP} $$ CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the $$ \mathcal{CP} $$ CP -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant $$ \mathcal{CP} $$ CP -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the $$ \mathcal{CP} $$ CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the $$ t\overline{t}H $$ t t ¯ H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

scholarly journals Highly boosted Higgs bosons and unitarity in vector-boson fusion at future hadron colliders

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Wolfgang Kilian ◽  
Sichun Sun ◽  
Qi-Shu Yan ◽  
Xiaoran Zhao ◽  
Zhijie Zhao
Keyword(s):  
Pair Production ◽  
Vector Boson ◽  
New Physics ◽  
Higgs Bosons ◽  
Vector Boson Fusion ◽  
Final State ◽  
Proton Proton ◽  
Effective Lagrangian ◽  
Discovery Potential ◽  
New Interactions

Abstract We study the observability of new interactions which modify Higgs-pair production via vector-boson fusion processes at the LHC and at future proton-proton colliders. In an effective-Lagrangian approach, we explore in particular the effect of the operator $$ {h}^2{W}_{\mu \nu}^a{W}^{a,\mu \nu} $$ h 2 W μν a W a , μν , which describes the interaction of the Higgs boson with transverse vector-boson polarization modes. By tagging highly boosted Higgs bosons in the final state, we determine projected bounds for the coefficient of this operator at the LHC and at a future 27 TeV or 100 TeV collider. Taking into account unitarity constraints, we estimate the new-physics discovery potential of Higgs pair production in this channel.

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