The Higgs di-photon decay in the standard model effective field theory

Starting from the Standard Model (SM) of elementary particle physics, we assume that new physics effects can be encoded in higher-dimensional operators added in the SM Lagrangian. The resulting theory, the SM Effective Field Theory (SMEFT), is then used for high-accuracy phenomenological studies. Through this paper, the di-photon decay of the Higgs boson is used as a sample of a concrete calculation in the SMEFT framework.

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Long-lived heavy neutral leptons at the LHC: four-fermion single-NR operators

Journal of High Energy Physics ◽

10.1007/jhep01(2022)044 ◽

2022 ◽

Vol 2022 (1) ◽

Author(s):

Rebeca Beltrán ◽

Giovanna Cottin ◽

Juan Carlos Helo ◽

Martin Hirsch ◽

Arsenii Titov ◽

...

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

New Physics ◽

Effective Field ◽

High Luminosity ◽

The Past ◽

The Standard Model ◽

Model Independent

Abstract Interest in searches for heavy neutral leptons (HNLs) at the LHC has increased considerably in the past few years. In the minimal scenario, HNLs are produced and decay via their mixing with active neutrinos in the Standard Model (SM) spectrum. However, many SM extensions with HNLs have been discussed in the literature, which sometimes change expectations for LHC sensitivities drastically. In the NRSMEFT, one extends the SM effective field theory with operators including SM singlet fermions, which allows to study HNL phenomenology in a “model independent” way. In this paper, we study the sensitivity of ATLAS to HNLs in the NRSMEFT for four-fermion operators with a single HNL. These operators might dominate both production and decay of HNLs, and we find that new physics scales in excess of 20 TeV could be probed at the high-luminosity LHC.

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Probing the nonunitarity of the leptonic mixing matrix at the CEPC

International Journal of Modern Physics A ◽

10.1142/s0217751x16440061 ◽

2016 ◽

Vol 31 (33) ◽

pp. 1644006 ◽

Cited By ~ 11

Author(s):

Stefan Antusch ◽

Oliver Fischer

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

New Physics ◽

Effective Field ◽

Neutrino Masses ◽

Performance Parameters ◽

The Standard Model ◽

Mixing Matrix ◽

Theory Framework

The nonunitarity of the leptonic mixing matrix is a generic signal of new physics aiming at the generation of the observed neutrino masses. We discuss the Minimal Unitarity Violation (MUV) scheme, an effective field theory framework which represents the class of extensions of the Standard Model (SM) by heavy neutral leptons, and discuss the present bounds on the nonunitarity parameters as well as estimates for the sensitivity of the CEPC, based on the performance parameters from the preCDR.

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A FB in the SMEFT: precision Z physics at the LHC

Journal of High Energy Physics ◽

10.1007/jhep08(2021)021 ◽

2021 ◽

Vol 2021 (8) ◽

Author(s):

Víctor Bresó-Pla ◽

Adam Falkowski ◽

Martín González-Alonso

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

New Physics ◽

Effective Field ◽

Precision Measurements ◽

Vertex Corrections ◽

The Standard Model ◽

Electroweak Precision

Abstract We study the forward-backward asymmetry AFB in pp → ℓ+ℓ− at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks, which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current AFB data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties.

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Beyond the Standard Model physics at CLIC

International Journal of Modern Physics A ◽

10.1142/s0217751x20410158 ◽

2020 ◽

Vol 35 (15n16) ◽

pp. 2041015 ◽

Cited By ~ 1

Author(s):

Roberto Franceschini

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

New Physics ◽

Effective Field ◽

Direct Search ◽

Beyond The Standard Model ◽

The Standard Model ◽

Open Issues

A summary of the recent results from CERN Yellow Report on the CLIC potential for new physics is presented. Greater emphasis is put on the direct search for new physics scenarios motivated by the open issues of the Standard Model as well as on interpretations of Standard Model measurements as probes of new physics in the context of effective field theory extensions of the Standard Model.

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Comments on gauge anomalies at dimension-six in the Standard Model Effective Field Theory

Journal of High Energy Physics ◽

10.1007/jhep05(2021)153 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

Quentin Bonnefoy ◽

Luca Di Luzio ◽

Christophe Grojean ◽

Ayan Paul ◽

Alejo N. Rossia

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

Effective Field ◽

Goldstone Bosons ◽

Fermion Masses ◽

Higher Dimensional ◽

The Standard Model ◽

Gauge Anomalies ◽

Working Out

Abstract We study whether higher-dimensional operators in effective field theories, in particular in the Standard Model Effective Field Theory (SMEFT), can source gauge anomalies via the modification of the interactions involved in triangle diagrams. We find no evidence of such gauge anomalies at the level of dimension-6 operators that can therefore be chosen independently to each others without spoiling the consistency of SMEFT, at variance with recent claims. The underlying reason is that gauge-invariant combinations of Goldstone bosons and massive gauge fields are allowed to couple to matter currents which are not conserved. We show this in a toy model by computing the relevant triangle diagrams, as well as by working out Wess-Zumino terms in the bosonic EFT below all fermion masses. The same approach applies directly to the Standard Model both at the renormalisable level, providing a convenient and unusual way to check that the SM is anomaly free, as well as at the non-renormalisable level in SMEFT.

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Top, Higgs, diboson and electroweak fit to the Standard Model effective field theory

Journal of High Energy Physics ◽

10.1007/jhep04(2021)279 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

John Ellis ◽

Maeve Madigan ◽

Ken Mimasu ◽

Veronica Sanz ◽

Tevong You

Keyword(s):

Field Theory ◽

Standard Model ◽

Effective Field Theory ◽

Particle Physics ◽

Global Analysis ◽

Ultra Violet ◽

Effective Field ◽

Decay Rates ◽

The Standard Model ◽

Low Mass

Abstract The search for effective field theory deformations of the Standard Model (SM) is a major goal of particle physics that can benefit from a global approach in the framework of the Standard Model Effective Field Theory (SMEFT). For the first time, we include LHC data on top production and differential distributions together with Higgs production and decay rates and Simplified Template Cross-Section (STXS) measurements in a global fit, as well as precision electroweak and diboson measurements from LEP and the LHC, in a global analysis with SMEFT operators of dimension 6 included linearly. We present the constraints on the coefficients of these operators, both individually and when marginalised, in flavour-universal and top-specific scenarios, studying the interplay of these datasets and the correlations they induce in the SMEFT. We then explore the constraints that our linear SMEFT analysis imposes on specific ultra-violet completions of the Standard Model, including those with single additional fields and low-mass stop squarks. We also present a model-independent search for deformations of the SM that contribute to between two and five SMEFT operator coefficients. In no case do we find any significant evidence for physics beyond the SM. Our underlying Fitmaker public code provides a framework for future generalisations of our analysis, including a quadratic treatment of dimension-6 operators.

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A new perspective on the electroweak phase transition in the Standard Model Effective Field Theory

Journal of High Energy Physics ◽

10.1007/jhep10(2021)127 ◽

2021 ◽

Vol 2021 (10) ◽

Author(s):

José Eliel Camargo-Molina ◽

Rikard Enberg ◽

Johan Löfgren

Keyword(s):

Field Theory ◽

Phase Transition ◽

Standard Model ◽

Effective Field Theory ◽

New Physics ◽

Effective Field ◽

Quartic Coupling ◽

Electroweak Phase Transition ◽

First Order ◽

The Standard Model

Abstract A first-order Electroweak Phase Transition (EWPT) could explain the observed baryon-antibaryon asymmetry and its dynamics could yield a detectable gravitational wave signature, while the underlying physics would be within the reach of colliders. The Standard Model, however, predicts a crossover transition. We therefore study the EWPT in the Standard Model Effective Field Theory (SMEFT) including dimension-six operators. A first-order EWPT has previously been shown to be possible in the SMEFT. Phenomenology studies have focused on scenarios with a tree-level barrier between minima, which requires a negative Higgs quartic coupling and a new physics scale low enough to raise questions about the validity of the EFT approach. In this work we stress that a first-order EWPT is also possible when the barrier between minima is generated radiatively, the quartic coupling is positive, the scale of new physics is higher, and there is good agreement with experimental bounds. Our calculation is done in a consistent, gauge-invariant way, and we carefully analyze the scaling of parameters necessary to generate a barrier in the potential. We perform a global fit in the relevant parameter space and explicitly find the points with a first-order transition that agree with experimental data. We also briefly discuss the prospects for probing the allowed parameter space using di-Higgs production in colliders.

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Renormalization Group evolution from on-shell SMEFT

Journal of High Energy Physics ◽

10.1007/jhep01(2021)101 ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Minyuan Jiang ◽

Teng Ma ◽

Jing Shu

Keyword(s):

Field Theory ◽

Renormalization Group ◽

Standard Model ◽

Effective Field Theory ◽

Effective Field ◽

High Dimensional ◽

Anomalous Dimensions ◽

The Standard Model ◽

Group Evolution

Abstract We describe the on-shell method to derive the Renormalization Group (RG) evolution of Wilson coefficients of high dimensional operators at one loop, which is a necessary part in the on-shell construction of the Standard Model Effective Field Theory (SMEFT), and exceptionally efficient based on the amplitude basis in hand. The UV divergence is obtained by firstly calculating the coefficients of scalar bubble integrals by unitary cuts, then subtracting the IR divergence in the massless bubbles, which can be easily read from the collinear factors we obtained for the Standard Model fields. Examples of deriving the anomalous dimensions at dimension six are presented in a pedagogical manner. We also give the results of contributions from the dimension-8 H4D4 operators to the running of V+V−H2 operators, as well as the running of B+B−H2D2n from H4D2n+4 for general n.

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