Relatively light Top Partners are unmistakable signatures of reasonably Natural Composite Higgs models and as such they are worth searching for at the LHC. Their phenomenology is characterized by a certain amount of model-dependence, which makes the interpretation of Top Partner experimental searches not completely straightforward especially if one is willing to take also single production into account. We describe a model-independent strategy by which the interpretation is provided on the parameter space of a Simplified Model that captures the relevant features of all the explicit constructions. The Simplified Model limits are easy to interpret within explicit models, in a way that requires no recasting and no knowledge of the experimental details of the analyses. We illustrate the method by concrete examples, among which the searches for a charge 5/3 Partner in same-sign dileptons and the searches for a charge 2/3 singlet. In each case we perform a theory recasting of the available 8 TeV Run-1 results and an estimate of the 13 TeV Run-2 reach, also including the effect of single production for which dedicated experimental analyses are not yet available. A rough assessment of the reach of a hypothetical 100 TeV collider is also provided.
We assess how different ATLAS and CMS searches for supersymmetry in the $t\bar t + E_T^{\rm miss}$ final state at Run 1 of the LHC constrain scenarios with a fermionic top partner and a dark matter candidate. We find that the efficiencies of these searches in all-hadronic, 1-lepton and 2-lepton channels are quite similar for scalar and fermionic top partners. Therefore, in general, efficiency maps for stop-neutralino simplified models can also be applied to fermionic top-partner models, provided the narrow width approximation holds in the latter. Owing to the much higher production cross-secti…
Partial top quark compositeness is a crucial aspect of theories with strong electroweak symmetry breaking. Together with the heavy top partners that lift the top quark mass to its observed value, these theories predict correlated modifications of the top quark's electroweak couplings. Associated measurements therefore provide direct constraints on the ultraviolet structure of the underlying hypercolour dynamics. In this paper we employ a minimal version of top compositeness to discuss how measurements related to the top's electroweak gauge interactions can inform the potential composite nature…
Two of the most important parameters in supersymmetry are the masses of the stop and sbottom, the supersymmetric partners of the third generation quarks. A stop mass lighter than 1 TeV is favored theoretically, however, conventional searches based on the simplified models have not produced experimental evidence for a light stop. It is possible that the light stop evades our searches due to a compressed sparticle mass spectrum. Therefore, the searches are extended to cover a broader range of signal scenarios with different mass splittings between the stop, neutralino(s), and chargino(s). The se…
Searches for supersymmetric partner particles of the top and bottom quarks at the Large Hadron Collider are reviewed. The focus is on the status of searches for a relatively light partner of the top quark performed by the CMS and ATLAS Collaborations. No excess beyond Standard Model expectations is observed and exclusion limits are set on the masses of supersymmetric particles.
We propose a new search strategy for heavy top partners at the early stages of the LHC run-II, based on lepton-jet final states. Our results show that final states containing a boosted massive jet and a hard lepton, in addition to a top quark and possibly a forward jet, offer a new window to both detecting and measuring top partners of mass $\sim 2$ TeV. Our resulting signal significance is comparable or superior to the same sign di-lepton channels for top partner masses heavier than roughly 1 TeV. Unlike the di-lepton channel, the selection criteria we propose are sensitive both to $5/3$ and …
Improving sensitivity of vectorlike top partner searches with jet substructure
Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）；Indian Institute of Science Education and Research Kolkata（印度科学教育研究所加尔各答分校）；Indian Institute of Science Education and Research, Knowledge City, Sector 81, S. A. S. Nagar, Manauli PO 140306, Punjab, India（印度科学教育研究所旁遮普邦分校）；The Institute of Mathematical Sciences（数学科学研究所）
Colored fermionic partners of the top quark are well-known signatures of the Composite Higgs scenario and for this reason they have been and will be subject of an intensive experimental study at the LHC. Performing an assessment of the theoretical implications of this experimental effort is the goal of the present paper. We proceed by analyzing a set of simple benchmark models, characterized by simple two-dimensional parameter spaces where the results of the searches are conveniently visualized and their impact quantified. We only draw exclusion contours, in the hypothesis of no signal, but of…
A feasibility study of searches for top partners with charge 5e/3 at the upgraded Large Hadron Collider is performed. The discovery potential and exclusion limits are presented using integrated luminosities of 300 fb$^{-1}$ and 3000 fb$^{-1}$ at center-of-mass energies of 14 and 33 TeV.
Theories which provide a dynamical explanation for the large top-quark mass often include TeV-scale vector-like top-quark and bottom-quark partner states which can be potentially discovered at the LHC. These states are currently probed through model-independent searches for pair-production via gluon fusion, as well as through model-dependent complementary electroweak single production. In this paper we study the potential to extend those searches for the partners of the third-generation Standard Model quarks on the basis of their expected chromomagnetic interactions. We discuss how current sea…
In composite Higgs models, the generation of quark masses requires the standard model-like quarks to be partially or fully composite states which are accompanied by composite quark partners. The composite quark partners decay into a standard model-like quark and an electroweak gauge boson or Higgs boson, which can be searched for at the LHC. In this article, we study the phenomenological implications of composite quarks in the minimal composite Higgs model based on the coset $SO(5)/SO(4)$. We focus on light quark partners which are embedded in the $SO(4)$ singlet representation. In this case, …
Searches for new fermionic states heavier than the top quark are being pursued by the CMS & ATLAS collaborations, pushing the mass bounds towards the TeV scale. Although a chiral fourth generation of quarks is now excluded by the LHC results, models going beyond the Standard Model predict the existence of heavy vector-like top partners as potential smoking gun signatures. Relying on a model-independent parametrisation, we present the first results of a dedicated software called XQCAT (eXtra Quark Combined Analysis Tool), which recasts publicly available experimental data from direct and Supers…
In our recent paper, we have investigated the potential for the LHC to discover vector-like quark partner states singly produced via their chromomagnetic moment interactions. These production mechanisms extend traditional searches which rely on pair-production of top-quark partner states or on the single production of these states through electroweak interactions, in the sense of providing greatly increased reach in parameter space regions where traditional searches are insensitive. In this study we determine the potential of both the 14 TeV high-luminosity LHC (HL-LHC) and a 100 TeV proton-pr…
Fermionic third generation top partners are generic in composite Higgs models. They are likely to decay into third generation quarks and electroweak bosons. We propose a novel cut-and-count-style analysis in which we cross correlate the model-dependent single and model-independent pair production processes for the top partners $X_{5/3}$ and $B$. In the class of composite Higgs models we study, $X_{5/3}$ is very special as it is the lightest exotic fermion. A constraint on the mass of $X_{5/3}$ directly extends to constrains on all top partner masses. By combining jet substructure methods with …
We consider how best to search for top partners in generic composite Higgs models. We begin by classifying the possible group representations carried by top partners in models with and without a custodial $SU(2)\times SU(2) \rtimes \mathbb{Z}_2$ symmetry protecting the rate for $Z \rightarrow b\overline{b}$ decays. We identify a number of minimal models whose top partners only have electric charges of $\frac{1}{3}, \frac{2}{3},$ or $\frac{4}{3}$ and thus decay to top or bottom quarks via a single Higgs or electroweak gauge boson. We develop an inclusive search for these based on a top veto, wh…
We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Also the naturalness pressure coming from the top partners is stronger than that induced by the gauge partners. This observation implies that the search strategy for vector resonances at the LHC needs to be modified. In…
We review the model-independent description of the couplings of the top quark to the Higgs and gauge bosons in theories beyond the Standard Model. Then we examine these couplings in the case of arbitrary heavy vector-like quarks mixing with the third family. We also discuss the couplings of these top partners, and comment on implications for LHC searches.
Fermionic top partners are a feature of many models of physics beyond the Standard Model. We propose a search strategy for single production of top partners focussing specifically on the dominant decay to $Wb$. The enormous background can be reduced by requiring a forward jet and exploiting jet substructure to suppress top-pair production. This simple strategy is shown to produce a sensitive search for single top-partner production, in the context of composite Higgs models, that has competitive mass reach with existing experimental searches for top-partner-pair production at the 8TeV LHC.
Vector-like quarks are introduced in various new physics models beyond the standard model (SM) at the TeV scale. We especially consider the case that the quark is singlet (triplet) under the SU(2)$_L$ (SU(3)$_c$) gauge group and couples only to the third generation quarks of the SM. The vector-like quark of this kind is often called a top partner. The top partoner $t_p$ decays into $bW, tZ$ and $th$. In the ATLAS and CMS collaborations, the top partner has been searched in the final states of $bW$ and $tZ$, while the search based on the decay mode $t_p\to th$ has not been started yet. However,…
We propose a model-independent and general framework to study the LHC phenomenology of top partners, i.e. Vector-Like quarks including particles with different electro-magnetic charge. We consider Vector-Like quarks embedded in general representations of the weak SU(2)L, coupling to all Standard Model quarks via Yukawa mixing focusing on the case of a single multiplet. We show that, with very minimal and quite general assumptions, top partners may be studied in terms of few parameters in an effective Lagrangian description with a clear and simple connection with experimental observables. We al…
We investigate indirect constraints on the top partner within the minimal fermionic top partner model. By performing a global fit of the latest Higgs data, $B_s \to μ^+μ^-$ measurements and the electroweak precision observables we find that the top partner with the mass up to 830 GeV is excluded at $2σ$ level. Our bound on the top partner mass is much stronger than the bounds obtained from the direct searches at the LHC. Under the current constraints the fine-tuning measure is less than 9% and the branching ratio of $T \to tZ$ is bounded between 14% and 25%. We also find that precise measureme…
Many standard model extensions, including composite Goldstone Higgs models, predict vector-like fermionic top-partners at the TeV scale. The intensive search programmes by ATLAS and CMS focus on decays into a 3$^{\rm rd}$ generation quark and an electroweak boson ($W,Z,h$). However, underlying models of partial compositeness contain additional states that give rise to exotic top partner decays. We consider a well-motivated scenario in which a charge-$2/3$ top-partner decays into a pseudo-scalar, $T\rightarrow t\ a$, with $a\rightarrow gg \mbox{ or } b\bar{b}$ dominating below the $t\bar{t}$ th…
Single production of vector-like top partners is becoming a major focus of new searches, as the increasing mass limits on vector-like quarks obtained by the ATLAS and CMS collaborations are such that single production is becoming competitive with respect to pair production. Typically searches focus on decays containing leptons in the final state in order to have less background from the Standard Model processes. However the current centre of mass energies available in the latest LHC runs limit the searches to low masses. Fully hadronic final states may be an alternative option for discovery, a…
In a previous work, a classically scale invariant extension of the standard model was proposed, as a potential candidate for resolving the hierarchy problem, by minimally introducing a complex gauge singlet scalar, and generating radiative electroweak symmetry breaking by means of the Coleman- Weinberg Mechanism. Postulating the singlet sector to respect the CP-symmetry, the existence of a stable pseudoscalar dark matter candidate with a mass in the TeV range was demonstrated. More- over, the model predicted the presence of another physical CP-even Higgs boson (with suppressed tree-level coupl…
Fermionic top-partners arise in models such as Composite Higgs and Little Higgs. They modify Higgs properties, in particular how the Higgs couples to top quarks. Alas, there is a low-energy cancellation acting in the coupling of the Higgs boson to gluons and photons. As a result of this cancellation, no information about the spectrum and couplings of the top-partners can be obtained in gluon fusion to Higgs, just the overall new physics scale. In this paper we show that this is not the case when hard radiation is taken into account. Indeed, differential distributions in Higgs plus jets are sen…
We investigate mono-top signatures arising from phenomenological models of fermionic top-partners, which are degenerate in mass and decay into a bosonic dark matter candidate, either spin-0 or spin-1. Such a model provides a mono-top signature as a smoking-gun, while conventional searches with $t\bar t$ + missing transverse momentum are limited. Two such scenarios: i) a phenomenological 3rd generation extra dimensional model with excited top and electroweak sectors, and ii) a model where only a top-partner and a dark matter particle are added to the SM, are studied in the degenerate mass regim…
Top partners from a new strong sector can be discovered soon, at the 8 TeV LHC, by analyzing their single production, which exhibits a large enhancement in the cross section compared to the analogous productions of bottom partners and exotic quarks. We analyze the subsequent decay of the top partners into a 125 GeV Higgs. This channel proves to be very promising for both the discovery of top partners and a test of the Higgs sector. For a reference value $λ_{\tilde{T}}=3$ of the Higgs coupling to the top partner, we could have a discovery (observation) at the 8 TeV LHC, with 30 fb$^{-1}$, for t…
The top partner as a hallmark of the Littlest Higgs model with $T$-parity (LHT model) has been extensively searched for during the Large Hadron Collider (LHC) Run-1. With the increasing mass limits on the top partner, the single production of the top partner will be dominant over the pair production. Under the constraints from the Higgs data, the electroweak precision observables and $R_b$, we find that the mass of $T$-even top partner ($T_+$) has to be heavier than 730 GeV. Then, we investigate the observability of the single $T$-even top partner production through the process $pp \to T_+ j$ …
We investigate the potential to search for the vector-like top partner in fully hadronic final states at the LHC. An algorithm is developed that kinematically reconstructs the vector-like top. We show that for moderate masses and a large branching fraction into the top quark and Higgs boson, the reconstruction works with good quality.
LHC searches for fermionic top partners $T$ focus on three decay topologies: $T\to bW$, $T\to tZ$, and $T\to th$. However, top partners may carry new conserved quantum numbers that forbid these decays. The simplest possibility is a conserved parity, under which the top partner is odd and all SM states are even. In this case, decays of top partners may involve new particle-odd scalars, leading to signal topologies more commonly associated with supersymmetry, either with or without R-parity conservation. We study a simplified model in which this possibility is realized, and estimate the bounds o…
The search for Top and Bottom Partners is a major focus of analyses at both the ATLAS and CMS experiments. When singly produced, these vector-like partners of the Standard Model third generation quarks retain a sizeable cross-section that makes them attractive search candidates in their respective topologies. While most efforts have concentrated on the resonant mode for single production of these hypothetical particles, the most dominant mode at narrow widths, recent studies have revealed a wide and rich phenomenology involving the non-resonant diagrams. In this letter we categorically investi…
Direct searches for superpartners and precision measurements of the properties of the $\sim 126$ GeV Higgs boson lead to important inter-dependent constraints on the underlying parameter space of the MSSM. The 19/20-parameter p(henomenological)MSSM offers a flexible framework for the study of a wide variety of both Higgs and SUSY phenomena at the LHC and elsewhere. Within this scenario we address the following questions: `What will potentially null searches for SUSY at the LHC tell us about the possible properties of the Higgs boson?' and, conversely, `What do precision measurements of the pro…
Many standard model extensions that address the hierarchy problem contain Dirac-fermion partners of the top quark, which are typically expected around the TeV scale. Searches for these vector-like quarks mostly focus on their decay into electroweak gauge bosons and Higgs plus a standard model quark. In this article, backed by models of composite Higgs, we propose a set of simplified scenarios, with effective Lagrangians and benchmarks, that include more exotic decay channels, which modify the search strategies and affect the bounds. Analysing several classes of underlying models, we show that …
Motivated by UV explanations of the $B$-physics anomalies, we study a dark sector containing a Majorana dark matter candidate and a coloured coannihilation partner, connected to the Standard Model predominantly via a $U_1$ vector leptoquark. A TeV scale $U_1$ leptoquark, which couples mostly to third generation fermions, is the only successful single-mediator description of the $B$-physics anomalies. After calculating the dark matter relic surface, we focus on the most promising experimental avenue: LHC searches for the coloured coannihilation partner. We find that the coloured partner hadroni…
In scenarios that stabilize the electroweak scale, the top quark is typically accompanied by partner particles. In this work, we demonstrate how extended stabilizing symmetries can yield scalar or fermionic top partners that transform as ordinary color triplets but carry exotic electric charges. We refer to these scenarios as "hypertwisted" since they involve modifications to hypercharge in the top sector. As proofs of principle, we construct two hypertwisted scenarios: a supersymmetric construction with spin-0 top partners, and a composite Higgs construction with spin-1/2 top partners. In bot…
Theories of physics beyond the Standard Model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs to the top quark. With extensions of the Standard Model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the Standard Model particles. …
We perform a detailed study of top-quark partner production in the ttbar plus large missing energy final-state at the LHC, presenting results for both scalar and fermionic top-quark partners in the semi-leptonic and dileptonic decay modes of the top quarks. We compare the results of several simulation tools: leading-order matrix elements, next-to-leading order matrix elements, leading-order plus parton shower simulations, and merged samples that contain the signal process with an additional hard jet radiated. We find that predictions from leading-order plus parton shower simulations can signif…
We discuss the properties and LHC phenomenology of a potentially discoverable heavy scalar boson ($s$) that arises in the context of the renormalizable coloron model; the model also contains a light scalar, $h$, identifiable with the 125 GeV state discovered by the LHC. These two scalar mass eigenstates are admixtures of a weak doublet gauge eigenstate and a weak singlet gauge eigenstate. A previous study set exclusion limits on the heavy $s$ scalar, using the stability of the scalar potential, unitarity, electroweak precision tests, LHC searches for the 125 GeV Higgs; it also briefly discusse…
Light top partners are the prime sign of naturalness in composite Higgs models. We explore here the possibility of non-standard top partner phenomenology. We show that even in the simplest extension of the minimal composite Higgs model, featuring an extra singlet pseudo Nambu-Goldstone boson, the branching ratios of the top partners into standard channels can be significantly altered, with no substantial change in the generated Higgs potential. Together with the variety of possible final states from the decay of the pseudo-scalar singlet, this motivates more extensive analyses in the search fo…
Top-partners -- vector-like quarks which mix predominantly with the top quark -- are simple extensions of the standard model present in many theories of new physics such as little Higgs models, topcolor models, and extra dimensions. Through renormalizable mixing with the top quark, these top-partners inherit couplings to the Higgs boson. Higgs bosons produced from the decay of top-partners are often highly boosted and ideal candidates for analyses based on jet substructure. Using substructure methods, we show that light Higgs bosons decaying to b b-bar can be discovered at the 14 TeV LHC with …
We consider a particular composite Higgs model which contains SU(3) color octet top partners besides the usually considered triplet representations. Moreover, color singlet top partners are present as well which can in principle serve as dark matter candidates. We investigate the LHC phenomenology of these unusual top partners. Some of these states could be confused with gluinos predicted in supersymmetric models at first glance.
We investigate CP-violating effects induced by light top partners in composite Higgs theories. We find that sizable contributions to the dipole moments of the light SM quarks and leptons are generically generated at the two-loop level through Barr-Zee-type diagrams. The present constraints on the electron and neutron electric dipole moments translate into bounds on top partner masses of order few TeV and are competitive with the reach of LHC direct searches. Interestingly, we find that CP-violation effects are sensitive to the same operators that control top partner single production. Near-fut…
Composite Higgs models with a fermionic UV completion can contain additional colored states beside the usual top-partners. We focus here on a model which contains in addition SU(3) color octet top partners as well as color singlet ones. The latter can in principle serve as a dark matter candidate. We consider a particular composite Higgs model which contains SU(3) color octet top partners besides the usually considered triplet representations. Moreover, color singlet top partners are present as well which can in principle serve as dark matter candidates. We investigate the LHC phenomenology of…
In the Littlest Higgs model with T-parity (LHT), top-partners (T_-) are produced in pairs at the Large Hadron Collider (LHC). Each top-partner decays into a top quark (t) and the lightest T-odd gauge partner A_H. We demonstrate reconstruction of the ttbar system decaying hadronically, and measurement of the top-partner mass from the m_{T2} distribution. A top quark from a T_{-} decay is polarized, and we discuss the effect of this polarization on the decay distributions. Because the events consist of highly collinear jets which occasionally overlap each other, we compare distributions using di…
In this paper we study the discovery potential of the LHC run II for heavy vector-like top quarks in the decay channel to a top and a $Z$ boson. Despite the usually smaller branching ratio compared to charged-current decays, this channel is rather clean and allows for a complete mass reconstruction of the heavy top. The latter is achieved in the leptonic decay channel of the $Z$ boson and in the fully hadronic top channel using boosted jet and jet substructure techniques. To be as model-independent as possible, a simplified model approach with only two free parameters has been applied. The res…
We demonstrate that the inclusion of a realistic lepton sector can relax significantly the upper bound on top partner masses in minimal composite Higgs models, induced by the lightness of the Higgs boson. To that extend, we present a comprehensive survey of the impact of different realizations of the fermion sectors on the Higgs potential, with a special emphasis on the role of the leptons. The non-negligible compositeness of the $τ_R$ in a general class of models that address the flavor structure of the lepton sector and the smallness of the corresponding FCNCs, can have a significant effect …
We investigate the kinetic heating of neutron stars due to dark matter scattering in minimal models with scalar lepton partners mediating interactions which can account for the anomalous magnetic moment of the muon. In particular, such models in which the dark matter is a thermally produced Majorana fermion can be extremely difficult to detect at conventional searches. We demonstrate that future infrared observations of an old neutron star population could definitively probe the entire parameter space of this scenario.
The left-right twin Higgs model (LRTHM) predicts the existence of the top partner $T$. In this work, we make a systematic investigation for the single and pair production of this top partner $T$ through the processes: $e^{+}e^{-}\to t\ov{T} + T\bar{t}$ and $ T\ov{T}$, the neutral scalar (the SM-like Higgs boson $h$ or neutral pseudoscalar boson $ϕ^{0}$) associate productions $e^{+}e^{-}\to t\ov{T}h +T\bar{t}h$, $T\ov{T}h$, $t\ov{T}ϕ^{0}+T\bar{t}ϕ^{0}$ and $ T\ov{T}ϕ^{0}$. From the numerical evaluations for the production cross sections and relevant phenomenological analysis we find that (a) th…
The possibility of a vectorlike top partner decaying to a new colourless weak-singlet scalar or pseudoscalar has attracted some attention in the literature. We investigate the production of a weak-singlet charge-$2/3$ $T$ quark that can decay to a spinless boson ($Φ$) and a top quark at the LHC. Earlier, in 2203.13753, we have shown that in a large part of the parameter space, the $T\to tΦ$ and the loop-induced $Φ\to gg$ decays become the dominant decay modes for these particles. Here, we investigate the discovery prospects of the $T$ quark in this region through the above decays. In particula…
In the framework of the littlest Higgs Model with T-parity, we discuss the top partner production at future $e^{+}e^{-}$ collider. We calculate the cross sections of the top partner production processes and associated production processes of Higgs and top partner under current constraints. Then, we investigate the observability of the T-odd top partner pair production through the process $e^{+}e^{-}\rightarrow T_{-}\bar{T}_{-}\rightarrow t\bar{t}A_{H}A_{H}$ in the $t\bar{t}$ di-lepton channel for two T-odd top partner mass $m_{T_{-}}$=603(708) GeV at $\sqrt{s}$=1.5 TeV. We analyze the signal s…
The presence of weak-scale colored top partners is among the simplest solutions to the Higgs hierarchy problem and allows for a natural electroweak scale. We examine the constraints on generic colored top partners coming solely from their effect on the production and decay rates of the observed Higgs with a mass of 125 GeV. We use the latest Higgs precision data from the Tevatron and the LHC as of EPS 2017 to derive the current limits on spin-0, spin-1/2, and spin-1 colored top partners. We also investigate the expected sensitivity from the Run 3 and Run 4 of the LHC, as well from possible fut…
In the littlest Higgs model with T-parity(LHT), we study the single production of vector-like top partner with the subsequent decay $T_{+}\to Wb$ in the leptonic channel at the $ep$ colliders. Focus on the LHeC ($ \sqrt{s} $ = 1.98 TeV) and FCC-eh ($ \sqrt{s} $ = 5.29 TeV), we investigate the observability of the single top partner production with the unpolarized and polarized electron beams, respectively. As a result, the statistical significance can be enhanced by the polarized electron beams. Under the current constraints, the search for $T_{+}$ in the $Wb$ channel at the LHeC cannot provid…
In composite Higgs models light fermionic top partners often play an important role in obtaining a 126 GeV Higgs mass. The presence of these top partners implies that coloured vector mesons, or massive gluon partners, most likely exist. Since the coupling between the top partners and gluon partners can be large there are then sizeable two-loop contributions to the composite Higgs mass. We compute the radiative correction to the Higgs mass from a gluon partner in the minimal composite Higgs model and show that the Higgs mass is in fact reduced. This allows the top partner masses to be increased…
The single vector-like top partner hadroproduction in association with top quark in the five and the six-flavour schemes at the LHC is investigated. The inclusive cross section and the differential distributions are evaluated for many benchmark scenarios at leading and next-to-leading orders, both for fixed-order and fixed-order matched to parton shower. The associated Higgs production with a top quark pair, where the final state arises from the decay of the vector-like top partner into a Higgs boson and a top quark, is examined.
The top/bottom seesaw model, which extends the top seesaw in order to accomodate a 125 GeV Higgs boson, predicts vector-like top/bottom partners and these partners can be bounded to form several neutral and charged singlet composite scalars by some new strong dynamics. In this letter, we use such a singlet scalar to interpret the 750 GeV diphoton reseanance. This singlet scalar is dominantly produced through the gluon fusion process induced by the partners and its diphoton decay is induced by both the partners and the charged singlet scalars. We show that this scenario can readily account for …
Vector-like top partner plays a central role in many new physics models which attempt to address the hierarchy problem. The top partner is conventionally assumed to decay to a quark and a SM boson. However, it is also possible that the top partner decays to a non-SM scalar and a top quark. Such an exotic decay channel can be the main decay channel of top partner, and thus provides new windows to search for top partner at the LHC. In this paper, with classical machine learning method Boosted Decision Tree (BDT), we perform a model independent study of the discovery potential of this new signatu…
The Standard Model (SM) describes particle physics with great precision. However, it does not account for the generation of neutrino masses, whose nature we do not understand. Both a Dirac and a Majorana mass term could intervene, leading to the existence of heavy partners of the SM neutrinos, presumably more massive and nearly sterile. For suitable choices of parameters, heavy neutrinos can also provide dark matter candidates, and generate the observed baryon asymmetry of the universe. Heavy neutrinos can be searched for at beam dump facilities such as the proposed SHiP experiment if their ma…
