The Ĥ-parameter: an oblique Higgs view

Englert, Christoph; Giudice, Gian F.; Greljo, Admir; McCullough, Matthew

doi:10.1007/jhep09(2019)041

Cited by 47 publications

(45 citation statements)

References 50 publications

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“…Samples and cross sections used for constraining the modified Higgs boson propagator are generated using MadGraph5_amc@nlo at LO, matching the prescription of Ref. [11]. Cross sections used for SM tt tt enhanced by scalar and vector off-shell diagrams are obtained at LO from Ref.…”

Section: Background and Signal Simulationmentioning

confidence: 99%

“…Additionally, less massive particles can enhance σ (pp → tt tt) via off-shell contributions [9]. In the model-independent framework of SM effective field theory, four-fermion couplings [10], as well as a modifier to the Higgs boson propagator [11], can be constrained through a measurement of σ (pp → tt tt). Conversely, models with new particles with masses on the order of 1 TeV, such as gluino pair production in the framework of supersymmetry [12][13][14][15][16][17][18][19][20][21], are more effectively probed through studies of tt tt production in boosted events or by requiring very large imbalances in momentum.…”

Section: Introductionmentioning

confidence: 99%

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Search for production of four top quarks in final states with same-sign or multiple leptons in proton–proton collisions at $$\sqrt{s}=13$$ $$\,\text {TeV}$$

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2020

Eur. Phys. J. C

103

116

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The standard model (SM) production of four top quarks (tt tt) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 fb −1 at a center-of-mass energy of 13 TeV. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the tt tt signal are respectively 2.6 and 2.7 standard deviations, and the tt tt cross section is measured to be 12.6 +5.8 −5.2 fb. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, y t , yielding a limit of |y t /y SM t | < 1.7 at 95% confidence level, where y SM t is the SM value of y t. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework,Ĥ < 0.12. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 GeV and 350-550 GeV for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

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Section: Background and Signal Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Search for production of four top quarks in final states with same-sign or multiple leptons in proton–proton collisions at $$\sqrt{s}=13$$ $$\,\text {TeV}$$

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2020

Eur. Phys. J. C

103

116

View full text Add to dashboard Cite

show abstract

“…A priori, one could also consider dimension-six operators, which are formally dominant, scaling as 1/M 2 (for recent progress in this direction, see Ref. [70]). Indeed, generically two insertions of a dimension-six operator would compete with dimension-eight terms.…”

Section: Introductionmentioning

confidence: 99%

Consistency of the standard model effective field theory

Remmen¹,

Rodd²

2019

J. High Energ. Phys.

125

117

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We derive bounds on couplings in the standard model effective field theory (SMEFT) as a consequence of causality and the analytic structure of scattering amplitudes. In the SMEFT, there are 64 independent operators at mass dimension eight that are quartic in bosons (either Higgs or gauge fields) and that contain four derivatives and/or field strengths, including both CP-conserving and CP-violating operators. Using analytic dispersion relation arguments for two-to-two bosonic scattering amplitudes, we derive 27 independent bounds on the sign or magnitude of the couplings. We show that these bounds also follow as a consequence of causality of signal propagation in nonvacuum SM backgrounds. These bounds come in two qualitative forms: i) positivity of (various linear combinations of) couplings of CP-even operators and ii) upper bounds on the magnitude of CP-odd operators in terms of (products of) CP-even couplings. We exhibit various classes of example completions, which all satisfy our EFT bounds. These bounds have consequences for current and future particle physics experiments, as part of the observable parameter space is inconsistent with causality and analyticity. To demonstrate the impact of our bounds, we consider applications both to SMEFT constraints derived at colliders and to limits on the neutron electric dipole moment, highlighting the connection between such searches suggested by infrared consistency.

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“…See also Ref [42]. for a derivation that does not rely on ignoring the IR part of the integral, and Ref [43]. for a discussion in the context of the 2-point functions.…”

mentioning

confidence: 99%

Massive higher spins: effective theory and consistency

Bellazzini

Riva

Serra

et al. 2019

J. High Energ. Phys.

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We construct the effective field theory for a single massive higher-spin particle in flat spacetime. Positivity bounds of the S-matrix force the cutoff of the theory to be well below the naive strong-coupling scale, forbid any potential and make therefore higher-derivative operators important even at low energy. As interesting application, we discuss in detail the massive spin-3 theory and show that an extended Galileon-like symmetry of the longitudinal modes, even with spin, emerges at high energy.1 arXiv:1903.08664v2 [hep-th]

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The Ĥ-parameter: an oblique Higgs view

Cited by 47 publications

References 50 publications

Search for production of four top quarks in final states with same-sign or multiple leptons in proton–proton collisions at $$\sqrt{s}=13$$ $$\,\text {TeV}$$

Search for production of four top quarks in final states with same-sign or multiple leptons in proton–proton collisions at $$\sqrt{s}=13$$ $$\,\text {TeV}$$

Consistency of the standard model effective field theory

Massive higher spins: effective theory and consistency

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