Evidence for $$t\bar{t}t\bar{t}$$ production in the multilepton final state in proton–proton collisions at $$\sqrt{s}=13$$ $$\text {TeV}$$ with the ATLAS detector

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.

Section: Operators Expectations and Current Constraintssupporting

confidence: 68%

Section: Jhep02(2021)043mentioning

confidence: 89%

Section: Jhep02(2021)043 4 Future Proton-proton Collidersmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

The present and future of four top operators

Banelli

Salvioni

Serra

et al. 2021

“…Previous similar studies have concentrated on narrower (r < 0.2) resonances [17,18], or tried to fit the large forward-backward (FB) asymmetry at the Tevatron using decay channels involving top-quark partners [19][20][21], or considered the case of KK resonances in the electroweak (model dependent) sector, which then allows lepton channels as possible final states [22,23]. We will also apply our theoretical results to the study of other final state channels, in particular to ttW , ttZ, ttH, and tttt, whose experimental detection is currently work in progress [24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

On broad Kaluza-Klein gluons

Escribano

Mendizabal

Quirós

et al. 2021

In theories with a warped extra dimension, composite fermions, as e.g. the right-handed top quark, can be very strongly coupled to Kaluza-Klein (KK) fields. In particular, the KK gluons in the presence of such composite fields become very broad resonances, thus remarkably modifying their experimental signatures. We have computed the pole mass and the pole width of the KK gluon, triggered by its interaction with quarks, as well as the prediction for proton-proton cross-sections using the full propagator and compared it with that obtained from the usual Breit-Wigner approximation. We compare both approaches, along with the existing experimental data from ATLAS and CMS, for the $$ t\overline{t} $$ t t ¯ , $$ t\overline{t}W $$ t t ¯ W , $$ t\overline{t}Z $$ t t ¯ Z , $$ t\overline{t}H $$ t t ¯ H , and $$ tt\overline{tt} $$ tt tt ¯ channels. We have found differences between the two approaches of up to about 100%, highlighting that the effect of broad resonances can be dramatic on present, and mainly future, experimental searches. The channel $$ tt\overline{tt} $$ tt tt ¯ is particularly promising because the size of the cross-section signal is of the same order of magnitude as the Standard Model prediction, and future experimental analyses in this channel, especially for broad resonances, can shed light on the nature of possible physics beyond the Standard Model.

$$ t\overline{t}t\overline{t} $$ signatures through the lens of color-octet scalars

Carpenter

Murphy

Smylie

2022

We reinterpret two recent LHC searches for events containing four top quarks $$ \left(t\overline{t}t\overline{t}\right) $$ t t ¯ t t ¯ in the context of supersymmetric models with Dirac gauginos and color-octet scalars (sgluons). We explore whether sgluon contributions to the four-top production cross section $$ \sigma \left( pp\to t\overline{t}t\overline{t}\right) $$ σ pp → t t ¯ t t ¯ can accommodate an excess of four-top events recently reported by the ATLAS collaboration. We also study constraints on these models from an ATLAS search for new phenomena with high jet multiplicity and significant missing transverse energy $$ \left({E}_{\mathrm{T}}^{\mathrm{miss}}\right) $$ E T miss sensitive to signals with four top quarks. We find that these two analyses provide complementary constraints, with the jets + $$ {E}_{\mathrm{T}}^{\mathrm{miss}} $$ E T miss search exceeding the four-top cross section measurement in sensitivity for sgluons heavier than about 800 GeV. We ultimately find that either a scalar or a pseudoscalar sgluon can currently fit the ATLAS excess in a range of reasonable benchmark scenarios, though a pseudoscalar in minimal Dirac gaugino models is ruled out. We finally offer sensitivity projections for these analyses at the HL-LHC, mapping the 5σ discovery potential in sgluon parameter space and computing exclusion limits at 95% CL in scenarios where no excess is found.