scholarly journals Unitarity violation and the geometry of Higgs EFTs

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Timothy Cohen ◽  
Nathaniel Craig ◽  
Xiaochuan Lu ◽  
Dave Sutherland
Keyword(s):  
Standard Model ◽  
Higgs Field ◽  
Higgs Sector ◽  
High Energy ◽  
Effective Field ◽  
Energy Limit ◽  
Geometric Invariants ◽  
Energy Behavior ◽  
The Standard Model ◽  
Derivatives Of

Abstract We derive the scale of unitarity violation from the geometry of Effective Field Theory (EFT) extensions of the Standard Model Higgs sector. The high-energy behavior of amplitudes with more than four scalar legs depends on derivatives of geometric invariants with respect to the physical Higgs field h, such that higher-point amplitudes begin to reconstruct the scalar manifold away from our vacuum. In theories whose low-energy limit can be described by the Higgs EFT (HEFT) but not the Standard Model EFT (SMEFT), non-analyticities in the vicinity of our vacuum limit the radius of convergence of geometric invariants, leading to unitarity violation at energies below 4πv. Our results unify approaches to the HEFT/SMEFT dichotomy based on unitarity, analyticity, and geometry, and more broadly illustrate the sense in which observables probe the geometry of an EFT. Along the way, we provide novel basis-independent results for Goldstone/Higgs boson scattering amplitudes expressed in terms of geometric covariant quantities.

scholarly journals Precision SMEFT bounds from the VBF Higgs at high transverse momentum

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Jack Y. Araz ◽  
Shankha Banerjee ◽  
Rick S. Gupta ◽  
Michael Spannowsky
Keyword(s):  
Standard Model ◽  
Vector Boson ◽  
High Energy ◽  
Effective Field ◽  
Higgs Bosons ◽  
Quadratic Growth ◽  
Final States ◽  
High Transverse Momentum ◽  
The Standard Model ◽  
Independent Operator

Abstract We study the production of Higgs bosons at high transverse momenta via vector-boson fusion (VBF) in the Standard Model Effective Field Theory (SMEFT). We find that contributions from four independent operator combinations dominate in this limit. These are the same ‘high energy primaries’ that control high energy diboson processes, including Higgs-strahlung. We perform detailed collider simulations for the diphoton decay mode of the Higgs boson as well as the three final states arising from the ditau channel. Using the quadratic growth of the SMEFT contributions relative to the Standard Model (SM) contribution, we project very stringent bounds on these operators that far surpass the corresponding bounds from the LEP experiment.

scholarly journals Loops and trees in generic EFTs

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Nathaniel Craig ◽  
Minyuan Jiang ◽  
Ying-Ying Li ◽  
Dave Sutherland
Keyword(s):  
Standard Model ◽  
High Energy ◽  
Tree Level ◽  
Energy Limit ◽  
High Energy Limit ◽  
Functional Methods ◽  
Weakly Coupled ◽  
The Standard Model ◽  
Helicity Amplitudes ◽  
The Impact

Abstract We consider aspects of tree and one-loop behavior in a generic 4d EFT of massless scalars, fermions, and vectors, with a particular eye to the high-energy limit of the Standard Model EFT at operator dimensions 6 and 8. First, we classify the possible Lorentz structures of operators and the subset of these that can arise at tree-level in a weakly coupled UV completion, extending the tree/loop classification through dimension 8 using functional methods. Second, we investigate how operators contribute to tree and one-loop helicity amplitudes, exploring the impact of non-renormalization theorems through dimension 8. We further observe that many dimension 6 contributions to helicity amplitudes, including rational parts, vanish exactly at one-loop level. This suggests the impact of helicity selection rules extends beyond one loop in non-supersymmetric EFTs.

scholarly journals General non-leptonic ∆F = 1 WET at the NLO in QCD

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Jason Aebischer ◽  
Christoph Bobeth ◽  
Andrzej J. Buras ◽  
Jacky Kumar ◽  
Mikołaj Misiak
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Effective Field Theory ◽  
High Energy ◽  
Effective Field ◽  
Effective Theory ◽  
Leading Order ◽  
The Standard Model ◽  
Complete Set ◽  
The One

Abstract We reconsider the complete set of four-quark operators in the Weak Effective Theory (WET) for non-leptonic ∆F = 1 decays that govern s → d and b → d, s transitions in the Standard Model (SM) and beyond, at the Next-to-Leading Order (NLO) in QCD. We discuss cases with different numbers Nf of active flavours, intermediate threshold corrections, as well as the issue of transformations between operator bases beyond leading order to facilitate the matching to high-energy completions or the Standard Model Effective Field Theory (SMEFT) at the electroweak scale. As a first step towards a SMEFT NLO analysis of K → ππ and non-leptonic B-meson decays, we calculate the relevant WET Wilson coefficients including two-loop contributions to their renormalization group running, and express them in terms of the Wilson coefficients in a particular operator basis for which the one-loop matching to SMEFT is already known.

scholarly journals NONPERTURBATIVE EFFECTIVE MODEL FOR THE HIGGS SECTOR OF THE STANDARD MODEL

2010 ◽  
Vol 25 (32) ◽  
pp. 5865-5884 ◽  
Author(s):  
FABIO SIRINGO ◽  
LUCA MAROTTA
Keyword(s):  
Standard Model ◽  
Strong Coupling ◽  
Effective Potential ◽  
Higgs Sector ◽  
Effective Model ◽  
Scalar Theory ◽  
The Standard Model ◽  
Gaussian Effective Potential ◽  
Derivatives Of ◽  
Good Agreement

A nonperturbative effective model is derived for the Higgs sector of the Standard Model which is described by a simple scalar theory. The renormalized couplings are determined by the derivatives of the Gaussian effective potential that are known to be the sum of infinite bubble graphs contributing to the vertex functions. A good agreement has been found with strong coupling lattice simulations when a comparison can be made.

scholarly journals Sum rules in the standard model effective field theory from helicity amplitudes

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Jiayin Gu ◽  
Lian-Tao Wang
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Effective Field Theory ◽  
Sum Rules ◽  
High Energy ◽  
Effective Field ◽  
Low Energy ◽  
Tree Level ◽  
The Standard Model ◽  
Helicity Amplitudes

Abstract The dispersion relation of an elastic 4-point amplitude in the forward direction leads to a sum rule that connects the low energy amplitude to the high energy observables. We perform a classification of these sum rules based on massless helicity amplitudes. With this classification, we are able to systematically write down the sum rules for the dimension-6 operators of the Standard Model Effective Field Theory (SMEFT), some of which are absent in previous literatures. These sum rules offer distinct insights on the relations between the operator coefficients in the EFT and the properties of the full theory that generates them. Their applicability goes beyond tree level, and in some cases can be used as a practical method of computing the one loop contributions to low energy observables. They also provide an interesting perspective for understanding the custodial symmetries of the SM Higgs and fermion sectors.

scholarly journals Testing anomalous $$H-W$$ couplings and Higgs self-couplings via double and triple Higgs production at $$e^+e^-$$ colliders

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
M. Gonzalez-Lopez ◽  
M. J. Herrero ◽  
P. Martinez-Suarez
Keyword(s):  
Standard Model ◽  
Higgs Field ◽  
Effective Field ◽  
Higgs Production ◽  
Beyond The Standard Model ◽  
Effective Lagrangian ◽  
The Standard Model ◽  
Non Linear ◽  
First Time ◽  
Chiral Lagrangian

AbstractIn the present work we study the implications at the future $$e^+e^-$$ e + e - colliders of the modified interaction vertices WWH, WWHH, HHH and HHHH within the context of the non-linear effective field theory given by the Electroweak Chiral Lagrangian. These vertices are given by four parameters, a, b, $$\kappa _3$$ κ 3 and $$\kappa _4$$ κ 4 , respectively, that are independent and without any constraint from symmetry considerations in this non-linear effective Lagrangian context, given the fact the Higgs field is a singlet. This is in contrast to the Standard Model, where the vertices are related by $$V_{WWH}^\mathrm{SM}=v V_{WWHH}^\mathrm{SM}$$ V WWH SM = v V WWHH SM and $$V_{HHH}^\mathrm{SM}=v V_{HHHH}^\mathrm{SM}$$ V HHH SM = v V HHHH SM , with $$v=246$$ v = 246 GeV. We investigate the implications of the absence of these relations in the Electroweak Chiral Lagrangian case. We explore the sensitivity to these Higgs anomalous couplings in the two main channels at these colliders: double and triple Higgs production (plus neutrinos). Concretely, we study the access to a and b in $$e^+e^- \rightarrow HH \nu {\bar{\nu }}$$ e + e - → H H ν ν ¯ and the access to $$\kappa _3$$ κ 3 and $$\kappa _4$$ κ 4 in $$e^+e^- \rightarrow HHH \nu {\bar{\nu }}$$ e + e - → H H H ν ν ¯ . Our study of the beyond the Standard Model couplings via triple Higgs boson production at $$e^+e^-$$ e + e - colliders is novel and shows for the first time the possible accessibility to the quartic Higgs self-coupling.

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