Different from other multiple top-quark productions, triple top-quark production requires the presence of both flavor violating neutral interaction and flavor conserving neutral interaction. We describe the interaction of triple top-quarks and up-quark in terms of two dimension-6 operators; one can be induced by a new heavy vector resonance, the other by a scalar resonance. Combining same-sign top-quark pair production and four top-quark production, we explore the potential of the 13 TeV LHC on searching for the triple top-quark production.
In this brief review we study the discovery potential of heavy Higgs induced single-top, same-sign top and triple-top quark productions at the Large Hadron Collider (LHC). The context is general two Higgs doublet model where such processes can be induced by additional Yukawa couplings and sub-Tev Higgs bosons. We show that these processes can be discovered at the ongoing or future high luminosity LHC run. Discovery of these multi-top productions may shed light on the mechanism behind baryogenesis or cosmic inflation.
Multi-top quark production is a staple program at the LHC. Single-top and $t\bar t$ productions are studied extensively, while current efforts are zooming in on four-top search, where the Standard Model (SM) cross section is at ${\cal O}(10)$ fb. In contrast, only at the fb level in SM, triple-top production has not been targeted for study so far. But such a small cross section makes it a unique probe for New Physics. Without the usual discrete $Z_2$ symmetry, the general two Higgs doublet model (g2HDM) can naturally raise the triple-top production to pb level. We illustrate how certain signal…
The alignment phenomenon, that the 125 GeV $h^0$ boson so resembles the Standard Model Higgs boson, can be understood in a two Higgs doublet model without discrete symmetry. New Yukawa couplings $ρ_{tt}$ and $ρ_{tc}$ offer new avenues to discover the extra scalar $H^0$ and pseudoscalar $A^0$. We propose to search for $cg \to tH^0$, $tA^0$ followed by $H^0$, $A^0 \to t\bar t$, $t\bar c$, where same-sign dileptons could be the harbinger, with triple-top, in the signature of three leptons plus three $b$-jets, as confirmation. Discovery could touch upon the origin of baryon asymmetry of the Univer…
Our main aim in this paper is to present detailed studies to probe the top quark flavor changing neutral current (FCNC) interactions at $tqg$, $tqγ$, $tqH$ and $tqZ (σ^{μν}, γ_μ)$ vertices in the triple-top signal $p p \to t \bar t t \, (\bar t t \bar t)$ at the high energy proposal of Large Hadron Collider (HE-LHC) and future circular hadron-hadron collider (FCC-hh). To this end, we investigate the production of three top quarks which arises from the FCNC couplings taken into account the fast simulation at $\sqrt{s} = 27$ TeV of HE-LHC and 100 TeV of FCC-hh considering the integrated luminosi…
Effective field theory techniques provide us important tools to probe for physics beyond the Standard Model in a relatively model-independent way. In this work, we revisit the CP-even dimension-6 purely gluonic operator to investigate the possible constraints on it by studying its effect on top-pair production at the LHC, in particular the high $p_T$ and $m_{t\bar{t}}$ tails of the distribution. Cut-based analysis reveals that the scale of New Physics when this operator alone contributes to the production process is greater than 3.4 TeV at 95% C.L., which is a much stronger bound compared to t…
The triple top quark production processes have been investigated and calculated in the scope of the Standard Model. The cross sections for different channels are provided for the proton-proton collision energies of $\sqrt{s}=$ 14 and 100 TeV. The importance of the electroweak contribution has been demonstrated. For the main channels the interference between the gluon and the weak bosons mediated contributions is negative and significant, therefore the complete set of diagrams has to be taken into account. Estimated total rates are about 1.9 fb for $\sqrt{s}=14$ TeV and 530 fb for $\sqrt{s}=100…
In this paper, we study the triple top quark production at the future high-energy proton-proton colliders to probe the four-fermion interactions involving three top quarks. We employ the Standard Model Effective Field Theory (SMEFT) to find the upper limits at $95\%$ CL on the Wilson coefficients of these kinds of four-fermion operators. We consider a detailed analysis with a unique signal signature of two same-sign leptons. A full simulation chain includes all the relevant backgrounds, realistic detector simulations and a cut-based technique are taken into account. This study is presented for…
One of the most challenging tasks for future high-luminosity electron-positron colliders is to extract Higgs triple coupling. It was proposed that this can be carried out via the precisely measuring the cross section of ZH associated production up to $0.4\%$. In this paper, we example the possible heavy pollution from Higgs-top anomalous coupling. Our numerical results show that the pollution is small for $\sqrt{s}_{e^+e^-}= 240 GeV$. However for the higher energy collider, pollution is sizable, which should be taken into account. We further explored the possibility to measure CP-violated Higg…
The observation of double and triple scalar boson production at hadron colliders could provide key information on the Higgs self couplings and the potential. As for single Higgs production the largest rates for multiple Higgs production come from gluon-gluon fusion processes mediated by a top-quark loop. However, at variance with single Higgs production, top-quark mass and width effects from the loops cannot be neglected. Computations including the exact top-quark mass dependence are only available at the leading order, and currently predictions at higher orders are obtained by means of approx…
In the absence of a concrete discovery of new physics at the LHC, global analyses of the standard model effective field theory (SMEFT) are important to find and describe the impact of new physics beyond the energy reach of the LHC. Among the SMEFT operators that can be constrained via various measurements, the dimension six triple gluon operator involves neither the Higgs boson nor the top quark, yet its variation can have measurable effects on top and Higgs production. Without independent constraints on its impact, the sensitivity of measurements in the top and Higgs sectors to new physics is…
We study the impact of triple-leptoquark interactions on matter stability for two specific proton decay topologies that arise at the tree- and one-loop level if and when they coexist. We demonstrate that the one-loop level topology is much more relevant than the tree-level one when it comes to the proton decay signatures despite the usual loop-suppression factor. We subsequently present detailed analysis of the triple-leptoquark interaction effects on the proton stability within one representative scenario to support our claim, where the scenario in question simultaneously features a tree-leve…
Within the framework of the type-II Two Higgs Doublet Model (2HDM-II) we study the production of three top quarks at the Large Hadron Collider (LHC). In the Standard Model the production cross section of three tops is low ($\approx 3$fb), while it is expected to be significant in the 2HDM-II for reasonable choices of the parameters. We study the production of a charged Higgs in association with a top quark, followed by the decays $H^{\pm} \to W^{\pm}A$ and $A \to t\bar{t}$. We undertake a full detector simulation of the signal, and use simple conservative cuts, focusing on the final states tha…
In this work we analyse the triple Higgs boson production cross section at hadron colliders via gluon fusion, and present for the first time the full set of QCD NNLO corrections in the heavy top limit. In order to account for finite top mass effects we perform two different reweighting procedures, and study the dependence of the result on the choice of the approximation. Combining the most accurate predictions available to date, we present the following result for the total NNLO cross section for triple Higgs boson production at a 100 TeV collider: $σ_\text{NNLO}=5.56^{+5\%}_{-6\%} \pm 20\%$ f…
Multi-parton distributions in a proton, the nonperturbative quantities needed to make predictions for multiple scattering rates, are poorly constrained from theory and data and must be modelled. All Monte Carlo event generators that simulate multiple parton interactions (e.g. Pythia) contain such a model of multi-parton PDFs. One important theoretical constraint for the case of double parton distributions is provided by the so-called number and momentum sum rules. In this paper we investigate to what extent the double parton distribution functions used in the Pythia event generator obey these …
On the Experimental Effects of the Off-shell Structure in Anomalous Neutral Triple Gauge Vertices
我们讨论了在寻找异常中性三重规范耦合$\mathrm{e^+ e^-}$碰撞壳和壳外处理之间的差异。我们发现，通常的外壳框架代表了一个最佳的起点，涵盖了所有的情况下，预计一个合理的实验灵敏度。我们表明，离壳效应导致在实验水平上的偏差可以忽略不计，只要$\mathrm{e^+ e^-}\to\mathrm{f}\bar{\mathrm{f}}γ$和$\mathrm{e^+ e^-}\to\mathr performed in regions where $ \mathrm{Z}^* \to \mathrm{f} \bar{\mathrm{f}}，\mathrm{f^\prime} \math生产是占主导地位的。出于一致性的原因，我们提倡使用对外壳上定义的自然扩展，它考虑了正确的外壳外依赖。与文献中最近提出的相反，我们发现在一般情况下，中性三规范耦合之间没有$SU(2)_L\times U(1)_Y$约束。
