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16 pages, 317 KiB

Open AccessArticle

Decoupling Limits in Effective Field Theories via Higher Dimensional Operators

by Andrea Quadri

Universe 2024, 10(2), 85; https://doi.org/10.3390/universe10020085 - 11 Feb 2024

Cited by 1 | Viewed by 1392

Abstract

The non-decoupling effects of heavy scalars and vector fields play an important role in the indirect search for Beyond the Standard Model (BSM) physics at the LHC. By exploiting some new differential equations for the 1-PI amplitudes, we show that such non-decoupling effects [...] Read more.

The non-decoupling effects of heavy scalars and vector fields play an important role in the indirect search for Beyond the Standard Model (BSM) physics at the LHC. By exploiting some new differential equations for the 1-PI amplitudes, we show that such non-decoupling effects are absent for quite a general class of effective field theories involving dimension six two-derivative and dimension eight four-derivative operators, once the resummation in certain BSM couplings is taken into account and some particular regimes of the relevant couplings are considered. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

17 pages, 485 KiB

Open AccessArticle

Theoretical Arguments and Experimental Signals for a Second Resonance of the Higgs Field

by Maurizio Consoli, Leonardo Cosmai and Fabrizio Fabbri

Universe 2023, 9(2), 99; https://doi.org/10.3390/universe9020099 - 15 Feb 2023

Cited by 2 | Viewed by 1277

Abstract

Theoretical arguments and lattice simulations suggest that, beside the known resonance of mass

m_{h} =

125 GeV, the Higgs field could exhibit a second mass scale [...] Read more.

Theoretical arguments and lattice simulations suggest that, beside the known resonance of mass

m_{h} =

125 GeV, the Higgs field could exhibit a second mass scale

{(M_{H})}^{theor} = 690 \pm 10 (stat) \pm 20 (sys) GeV

. In spite of its large mass, the heavier state would couple to longitudinal Ws with the same typical strength as the low-mass state at 125 GeV and thus represent a relatively narrow resonance mainly produced at LHC by gluon–gluon fusion. After summarizing these general aspects, we review a recent analysis of LHC data which support the idea of a new resonance in the predicted mass range. Since the correlation among these measurements is very small and since, with a definite theoretical prediction in some mass region, local excesses should not be downgraded by the look-elsewhere effect, we emphasize the present substantial statistical evidence which could become an important discovery by simply adding two, still missing, key analyses of the full RUN2 statistics. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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17 pages, 763 KiB

Open AccessArticle

Gauge Couplings Evolution from the Standard Model, through Pati–Salam Theory, into E₈ Unification of Families and Forces

by Alfredo Aranda, Francisco J. de Anda, António P. Morais and Roman Pasechnik

Universe 2023, 9(2), 90; https://doi.org/10.3390/universe9020090 - 8 Feb 2023

Cited by 3 | Viewed by 1193

Abstract

We explore the potential of ultimate unification of the Standard Model matter and gauge sectors into a single

E_{8}

superfield in ten dimensions via an intermediate Pati–Salam gauge theory. Through a consistent realisation of a [...] Read more.

We explore the potential of ultimate unification of the Standard Model matter and gauge sectors into a single

E_{8}

superfield in ten dimensions via an intermediate Pati–Salam gauge theory. Through a consistent realisation of a

T^{6} / (Z_{6} \times Z_{2} \times Z_{2})

orbifolding procedure and renormalisation group evolution of gauge couplings, we establish several novel benchmark scenarios for New Physics that are worth further phenomenological exploration. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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13 pages, 1688 KiB

Open AccessArticle

Dilaton Effective Field Theory

by Thomas Appelquist, James Ingoldby and Maurizio Piai

Universe 2023, 9(1), 10; https://doi.org/10.3390/universe9010010 - 23 Dec 2022

Cited by 25 | Viewed by 1439

Abstract

We review and extend recent studies of dilaton effective field theory (dEFT) that provide a framework for the description of the Higgs boson as a composite structure. We first describe the dEFT as applied to lattice data for a class of gauge theories [...] Read more.

We review and extend recent studies of dilaton effective field theory (dEFT) that provide a framework for the description of the Higgs boson as a composite structure. We first describe the dEFT as applied to lattice data for a class of gauge theories with near-conformal infrared behavior. This includes the dilaton associated with the spontaneous breaking of (approximate) scale invariance and a set of pseudo-Nambu–Goldstone bosons (pNGBs) associated with the spontaneous breaking of an (approximate) internal global symmetry. The theory contains two small symmetry-breaking parameters. We display the leading-order (LO) Lagrangian and review its fit to lattice data for the

S U (3)

gauge theory with

N_{f} = 8

Dirac fermions in the fundamental representation. We then develop power-counting rules to identify the corrections emerging at next-to-leading order (NLO) in the dEFT action. We list the NLO operators that appear and provide estimates for the coefficients. We comment on implications for composite Higgs model building. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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18 pages, 379 KiB

Open AccessArticle

Stueckelberg and Higgs Mechanisms: Frames and Scales

by Alexander D. Popov

Universe 2022, 8(7), 361; https://doi.org/10.3390/universe8070361 - 29 Jun 2022

Cited by 3 | Viewed by 1708

Abstract

We consider Yang–Mills theory with a compact gauge group G on Minkowski space

R^{3, 1}

and compare the introduction of masses of gauge bosons using the Stueckelberg and Higgs mechanisms. The Stueckelberg field

ϕ

is identified with a G-frame on [...] Read more.

We consider Yang–Mills theory with a compact gauge group G on Minkowski space

R^{3, 1}

and compare the introduction of masses of gauge bosons using the Stueckelberg and Higgs mechanisms. The Stueckelberg field

ϕ

is identified with a G-frame on the gauge vector bundle E and the kinetic term for

ϕ

leads to the mass of the gauge bosons. The Stueckelberg mechanism is extended to the Higgs mechanism by adding to the game a scalar field describing rescaling of metric on fibres of E. Thus, we associate Higgs fields as well as running coupling parameters with conformal geometry on fibres of gauge bundles. In particular, a running coupling tending to zero or to infinity is equivalent to an unbounded expansion of G-fibres or its contraction to a point. We also discuss scale connection, space-time dependent Higgs vacua and compactly supported gauge and quark fields as an attribute of confinement. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

24 pages, 1224 KiB

Open AccessArticle

General Deflections in Deflected AMSB

by Fei Wang and Ying-Kai Zhang

Universe 2022, 8(5), 251; https://doi.org/10.3390/universe8050251 - 19 Apr 2022

Cited by 1 | Viewed by 1600

Abstract

The (extra)ordinary gauge mediation extension of deflected AMSB scenarios can be interesting because it can accommodate together the deflection in the Kahler potential and the superpotential. We derive the analytical expressions for soft SUSY breaking parameters in such EOGM extension of deflected AMSB [...] Read more.

The (extra)ordinary gauge mediation extension of deflected AMSB scenarios can be interesting because it can accommodate together the deflection in the Kahler potential and the superpotential. We derive the analytical expressions for soft SUSY breaking parameters in such EOGM extension of deflected AMSB scenarios with the presence of both types of deflections. The Landau pole and proton decay constraints are also discussed. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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Review

Jump to: Research

21 pages, 2683 KiB

Open AccessReview

A Concise Review on Some Higgs-Related New Physics Models in Light of Current Experiments

by Lei Wang, Jin Min Yang, Yang Zhang, Pengxuan Zhu and Rui Zhu

Universe 2023, 9(4), 178; https://doi.org/10.3390/universe9040178 - 4 Apr 2023

Cited by 9 | Viewed by 2114

Abstract

The Higgs boson may serve as a portal to new physics beyond the standard model (BSM), which is implied by the theoretical naturalness or experimental anomalies. This review aims to briefly survey some typical Higgs-related BSM models. First, for the theories to solve [...] Read more.

The Higgs boson may serve as a portal to new physics beyond the standard model (BSM), which is implied by the theoretical naturalness or experimental anomalies. This review aims to briefly survey some typical Higgs-related BSM models. First, for the theories to solve the hierarchy problem, the two exemplary theories, the low energy supersymmetry (focusing on the minimal supersymmetric model) and the little Higgs theory, are discussed. For the phenomenological models without addressing the hierarchy problem, we choose the two-Higgs-doublet models (2HDMs) to emphatically elucidate their phenomenological power in explaining current measurements of muon

g - 2

, the W-boson mass and the dark matter (DM) data. For the singlet extensions, which are motivated by the cosmic phase transition and the DM issue, we illustrate the singlet-extended standard model (xSM) and the singlet-extended 2HDM (2HDM+S), emphasizing the vacuum stability. In the decade since the discovery of the Higgs boson, these theories have remained the typical candidates of new physics, which will be intensively studied in future theoretical and experimental research. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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17 pages, 6151 KiB

Open AccessReview

A Short Overview on Low Mass Scalars at Future Lepton Colliders

by Tania Robens

Universe 2022, 8(5), 286; https://doi.org/10.3390/universe8050286 - 20 May 2022

Cited by 14 | Viewed by 1791

Abstract

In this manuscript, I give a short summary on scenarios with new physics scalars that could be investigated at future

e^{+} e^{-}

colliders. I concentrate on cases where at least one of the additional scalars has a mass below 125 GeV, [...] Read more.

In this manuscript, I give a short summary on scenarios with new physics scalars that could be investigated at future

e^{+} e^{-}

colliders. I concentrate on cases where at least one of the additional scalars has a mass below 125 GeV, and discuss both models where this could be realized, as well as studies which focus on such scenarios. This work is based on several overview talks I recently gave at the CEPC workshop, FCC week and ECFA future collider workshop, as well as a Snowmass White Paper. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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14 pages, 587 KiB

Open AccessReview

Methodologies to Measure the

CP

Structure of the Higgs Yukawa Coupling to Tau Leptons

by Andrea Cardini

Universe 2022, 8(5), 256; https://doi.org/10.3390/universe8050256 - 21 Apr 2022

Viewed by 1966

Abstract

One of the central goals of the Large Hadron Collider has been the search, and later the study, of the Higgs boson. Its coupling structure under charge conjugation and parity (

CP

) symmetries has been extensively investigated as a probe for new [...] Read more.

One of the central goals of the Large Hadron Collider has been the search, and later the study, of the Higgs boson. Its coupling structure under charge conjugation and parity (

CP

) symmetries has been extensively investigated as a probe for new physics. This paper presents a review of the methods collected in the literature to access the

CP

structure of the Yukawa coupling of the Higgs boson to tau leptons at proton colliders. A new notation is introduced to classify already existing methods, highlighting their common features and favoring the investigation of new, more performing alternatives. Full article

(This article belongs to the Special Issue Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson)

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