Portraying double Higgs at the Large Hadron Collider II

Huang, Li; Kang, Subeom; Kim, Jeong Han; Kong, Kyoungchul; Pi, Jun Seung

doi:10.1007/jhep08(2022)114

“…The above minimization procedure of − → p ν aims to find approximate three momentum of the neutrino which originates from the leptonic top quark decay without the missing transverse momentum constraint (see refs. [95][96][97] for similar reconstruction method using χ 2 ), and recent review [98] on general methods for kinematic reconstruction).…”

Section: Jhep05(2024)176mentioning

confidence: 99%

Probing the CP structure of the top quark Yukawa at the future muon collider

Cassidy,

Dong,

Kong

et al. 2024

J. High Energ. Phys.

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We study the top-Higgs coupling with a CP violating phase ξ at a future multi-TeV muon collider. We focus on processes that are directly sensitive to the top quark Yukawa coupling: $$ t\overline{t}h $$ t t ¯ h , tbhμν, and $$ t\overline{t} h\nu \overline{\nu} $$ t t ¯ hν ν ¯ with $$ h\to b\overline{b} $$ h → b b ¯ and semileptonic top decays. At different energies, different processes dominate the cross section, providing complementary information. At and above an energy of $$ \mathcal{O}(10) $$ O 10 TeV, vector boson fusion processes dominate. As we show, in the Standard Model there is destructive interference in the vector boson fusion processes $$ t\overline{t} h\nu \overline{\nu} $$ t t ¯ hν ν ¯ and tbhμν between the top quark Yukawa and Higgs-gauge boson couplings. A CP-violating phase changes this interference, and the cross section measurement is very sensitive to the size of the CP-violating angle. Although we find that the cross sections are measured to $$ \mathcal{O}\left(50\%\right) $$ O 50 % statistical uncertainty at 1σ, a 10 and 30 TeV muon collider can bound the CP-violating angle |ξ| ≲ 9.0° and |ξ| ≲ 5.4°, respectively. However, cross section measurements are insensitive to the sign of the CP-violating angle. To determine that the coupling is truly CP violating, observables sensitive to CP-violation must be measured. We find in the $$ t\overline{t}h $$ t t ¯ h process the azimuthal angle between the $$ t+\overline{t} $$ t + t ¯ plane and the initial state muon+Higgs plane shows good discrimination for ξ = ±0.1π. For the tbhμν and $$ t\overline{t} h\nu \overline{\nu} $$ t t ¯ hν ν ¯ processes, the operator proportional to $$ \left({\overrightarrow{p}}_{\mu}\times {\overrightarrow{p}}_h\right) $$ p → μ × p → h · $$ {\overrightarrow{p}}_t $$ p → t is sensitive to the sign of CP phase ξ. From these observables, we construct asymmetry parameters that show good distinction between different values and signs of the CP violating angle.

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“…This method becomes more powerful, especially when one can define two or more independent χ 2 values. Topness was introduced to reduce the t t background in the search for supersymmetric top quarks (Graesser and Shelton, 2013) and later further finetuned in the search for double Higgs production Huang et al, 2022). Topness basically aims to check the consistency of a given event with t t production.…”

Section: A Dimensionless Variablesmentioning

confidence: 99%

Kinematic variables and feature engineering for particle phenomenology

Franceschini,

Kim,

Kong

et al. 2023

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Kinematic variables play an important role in collider phenomenology, as they expedite discoveries of new particles by separating signal events from unwanted background events and allow for measurements of particle properties such as masses, couplings, and spins. For the past ten years, an enormous number of kinematic variables have been designed and proposed, primarily for the experiments at the CERN Large Hadron Collider, allowing for a drastic reduction of highdimensional experimental data to lower-dimensional observables, from which one can readily extract underlying features of phase space and develop better-optimized data-analysis strategies. Recent developments in the area of phase-space kinematics are reviewd, and new kinematic variables with important phenomenological implications and physics applications are summarized. Recently proposed analysis methods and techniques specifically designed to leverage new kinematic variables are also reviewed. As machine learning is currently percolating through many fields of particle physics, including collider phenomenology, the interconnection and mutual complementarity of kinematic variables and machine-learning techniques are discussed. Finally, the manner in which utilization of kinematic variables originally developed for colliders can be extended to other highenergy physics experiments, including neutrino experiments, is discussed.

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“…Boosted decision trees (BDTs) are used both by the ATLAS and CMS collaboration to tag bottom quarks [8]. An increased sensitivity to the trilinear Higgs self-coupling can be achieved by employing neural networks or BDTs [28][29][30][31][32]. The present analysis aims to go a step further.…”

Section: Jhep11(2022)045mentioning

confidence: 99%

Machine learning the trilinear and light-quark Yukawa couplings from Higgs pair kinematic shapes

Alasfar

¹

,

Gröber

²

,

Grojean

³

et al. 2022

J. High Energ. Phys.

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Revealing the Higgs pair production process is the next big challenge in high energy physics. In this work, we explore the use of interpretable machine learning and cooperative game theory for extraction of the trilinear Higgs self-coupling in Higgs pair production. In particular, we show how a topological decomposition of the gluon-gluon fusion Higgs pair production process can be used to simplify the machine learning analysis flow. Furthermore, we extend the analysis to include $$ q\overline{q} $$ q q ¯ → hh production, which is strongly suppressed in the Standard Model, to extract the trilinear Higgs coupling and to bound large deviations of the light-quark Yukawa couplings from the Standard Model values. The constraints on the rescaling of the trilinear Higgs self-coupling, κλ, and the rescaling of light-quark Yukawa couplings, κu and κd, at HL-LHC (FCC-hh) from single parameter fits are:$$ {\displaystyle \begin{array}{c}{\kappa}_{\lambda }=\left[0.53,1.7\right]\ \left(\left[0.97,1.03\right]\right)\\ {}{\kappa}_u=\left[-470,430\right]\ \left(\left[-58,55\right]\right)\\ {}{\kappa}_d=\left[-360,360\right]\ \left(\left[-26,28\right]\right)\end{array}} $$ κ λ = 0.53 1.7 0.97 1.03 κ u = − 470 430 − 58 55 κ d = − 360 360 − 26 28 We show that the simultaneous modification of the Yukawa couplings can dilute the constraints on the trilinear coupling significantly. We perform similar analyses for FCC-hh. We discuss some motivated flavourful new physics scenarios where such an analysis prevails.

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Portraying double Higgs at the Large Hadron Collider II

Cited by 9 publications

References 112 publications

Probing the CP structure of the top quark Yukawa at the future muon collider

Probing the CP structure of the top quark Yukawa at the future muon collider

Kinematic variables and feature engineering for particle phenomenology

Machine learning the trilinear and light-quark Yukawa couplings from Higgs pair kinematic shapes

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