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2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Linda M. Carpenter ◽  
Taylor Murphy ◽  
Matthew J. Smylie

Abstract 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.


2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Zhan Sun ◽  
Hong Fei Zhang

Abstract In this paper, we present a comprehensive study of ϒ inclusive production in Z boson decay, including the first complete next-to-leading-order calculations of the color-octet (CO) contributions. With the inclusion of the newly-calculated remarkable QCD corrections, the CO processes exhibit crucially phenomenological influence on the existing predictions built on the color-singlet mechanism. We also include the exhaustive evaluations of the feed-down contributions, which remained ignored in the literature, and find them to be considerable. Summing up all the contributions, the ℬZ → ϒ(nS) + X still notably undershoot the data released by the L3 Collaboration.


2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
An-Ping Chen ◽  
Xiao-Bo Jin ◽  
Yan-Qing Ma ◽  
Ce Meng

Abstract We study the fragmentation function of the gluon to color-octet 3S1 heavy quark-antiquark pair using the soft gluon factorization (SGF) approach, which expresses the fragmentation function in a form of perturbative short-distance hard part convoluted with one-dimensional color-octet 3S1 soft gluon distribution (SGD). The short distance hard part is calculated to the next-to-leading order in αs and all orders in velocity expansion. By deriving and solving the renormalization group equation of the SGD, threshold logarithms are resummed to all orders in perturbation theory. The comparison with gluon fragmentation function calculated in NRQCD factorization approach indicates that the SGF formula resums a series of velocity corrections in NRQCD which are important for phenomenological study.


2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Linda M. Carpenter ◽  
Taylor Murphy

Abstract In this work we study the collider phenomenology of color-octet scalars (sgluons) in supersymmetric models with Dirac gaugino masses that feature an explicitly broken R symmetry (R-broken models). We construct such models by augmenting minimal R-symmetric models with a fairly general set of supersymmetric and softly supersymmetry-breaking operators that explicitly break R symmetry. We then compute the rates of all significant two-body decays and highlight new features that appear as a result of R symmetry breaking, including enhancements to extant decay rates, novel tree- and loop-level decays, and improved cross sections of single sgluon production. We demonstrate in some detail how the familiar results from minimal R-symmetric models can be obtained by restoring R symmetry. In parallel to this discussion, we explore constraints on these models from the Large Hadron Collider. We find that, in general, R symmetry breaking quantitatively affects existing limits on color-octet scalars, perhaps closing loopholes for light CP-odd (pseudoscalar) sgluons while opening one for a light CP-even (scalar) particle. Qualitatively, however, we find that — much as for minimal R-symmetric models, despite stark differences in phenomenology — scenarios with broken R symmetry and two sgluons below the TeV scale can be accommodated by existing searches.


2021 ◽  
Vol 103 (7) ◽  
Author(s):  
Daniël Boer ◽  
Cristian Pisano ◽  
Pieter Taels
Keyword(s):  

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Nabarun Chakrabarty ◽  
Indrani Chakraborty ◽  
Dilip Kumar Ghosh

AbstractColor-octet scalars arise in various Grand Unification scenarios and also in other models of new physics. They are also postulated for minimal flavour violation. Purely phenomenological imprints of such scalars are therefore worth looking at. Motivated by this, we perform a complete one-loop calculation of the $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) decay in a two Higgs doublet model augmented by a color-octet $$SU(2)_L$$ S U ( 2 ) L scalar doublet. The computation is conveniently segregated into colorless and colored components. The color-octet part of the amplitude, being scaled by the color-factor, provides an overall enhancement to the form factors. Crucial constraints from perturbative unitarity, positivity of the scalar potential, oblique parameters, Higgs signal strengths and direct search of a charged Higgs and color-octet scalars are folded-in into the analysis. Sensitivity of the loop-induced $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) vertex to other model parameters is elucidated. Finally, the prospect of observing a loop-induced $$H^+ \rightarrow W^+ Z (\gamma )$$ H + → W + Z ( γ ) interaction at the future hadronic collisions is also discussed.


2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Linda M. Carpenter ◽  
Taylor Murphy ◽  
Matthew J. Smylie

Abstract In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous R symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.


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