We present a new way to interpret Top Standard Model measurements going beyond the SMEFT framework. Instead of the usual paradigm in Top EFT, where the main effects come from tails in momenta distributions, we propose an interpretation in terms of new physics which only shows up at loop-level. The effects of these new states, which can be lighter than required within the SMEFT, appear as distinctive structures at high momenta, but may be suppressed at the tails of distributions. As an illustration of this phenomena, we present the explicit case of a UV model with a   <math> <mi>Z</mi> </math>  $$ \mathcal{Z} $$  2 symmetry, including a Dark Matter candidate and a top-partner. This simple UV model reproduces the main features of this class of signatures, particularly a momentum-dependent form factor with more structure than the SMEFT. As the new states can be lighter than in SMEFT, we explore the interplay between the reinterpretation of direct searches for colored states and Dark Matter, and Top measurements, made by ATLAS and CMS in the differential   <math> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ t\overline{t} $$  final state. We also compare our method with what one would expect using the SMEFT reinterpretation, finding that using the full loop information provides a better discriminating power.

Brazil

André Lessa

Spain

Verónica Sanz

Going beyond Top EFT

In this paper we explore the possibility of observable gravitational waves as a manifestation of the QCD axion dynamics. In particular, we focus on dynamical axion models which solve the strong CP problem, and include the confinement of a QCD-like gauge group at the TeV scale. We study the resulting chiral symmetry breaking phase transition for models with N  F  = 3 and N  F  = 4 light flavors using the linear sigma model. This model describes the scalar meson spectrum and its interactions, with the diagonal field φ as the order parameter. We find that the amplitude of the gravitational wave spectrum depends on the mass of the dynamical axion η′ via the ratio   <math> <msub> <mi>m</mi> <msup> <mi>η</mi> <mo>′</mo> </msup> </msub> <mo>/</mo> <msub> <mi>m</mi> <mi>φ</mi> </msub> </math>  $$ {m}_{\eta^{\prime }}/{m}_{\varphi } $$ . The resulting spectra may be observed at future mid-range gravitational wave experiments such as AION/MAGIS, DECIGO, and BBO. Moreover, the TeV states can be searched for at colliders and their quantum numbers characterized, providing a unique connection between axion physics, gravitational waves and collider searches.

Canada

Djuna Croon

Rachel Houtz

United Kingdom

Dynamical axions and gravitational waves

In this paper we study the use of machine learning techniques to exploit kinematic information in <math><mi>V</mi><mi>H</mi></math>, the production of a Higgs in association with a massive vector boson. We parametrize the effect of new physics in terms of the standard model effective field theory (SMEFT) framework. We find that the use of a shallow neural network allows us to dramatically increase the sensitivity to deviations in <math><mi>V</mi><mi>H</mi></math> respect to previous estimates. We also discuss the relation between the usual measures of performance in machine learning, such as area under the curve or accuracy, with the more adept measure of Asimov significance. This relation is particularly relevant when parametrizing systematic uncertainties. Our results show the potential of incorporating machine learning techniques to the SMEFT studies using the current datasets.

China

Felipe F. Freitas

Charanjit K. Khosa

Exploring the standard model EFT in <math><mi>V</mi><mi>H</mi></math> production with machine learning

Using the production of a Higgs boson in association with a W boson as a test case, we assess the impact of dimension-8 operators within the context of the Standard Model Effective Field Theory. Dimension-8-SM-interference and dimension-6-squared terms appear at the same order in an expansion in 1/Λ, hence dimension-8 effects can be treated as a systematic uncertainty on the new physics inferred from analyses using dimension-6 operators alone. To study the phenomenological consequences of dimension-8 operators, one must first determine the complete set of operators that can contribute to a given process. We accomplish this through a combination of Hilbert series methods, which yield the number of invariants and their field content, and a step-by-step recipe to convert the Hilbert series output into a phenomenologically useful format. The recipe we provide is general and applies to any other process within the dimension ≤ 8 Standard Model Effective Theory. We quantify the effects of dimension-8 by turning on one dimension-6 operator at a time and setting all dimension-8 operator coefficients to the same magnitude. Under this procedure and given the current accuracy on σ(pp → h W +), we find the effect of dimension-8 operators on the inferred new physics scale to be small,   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (few %), with some variation depending on the relative signs of the dimension-8 coefficients and on which dimension-6 operator is considered. The impact of the dimension-8 terms grows as σ(pp → hW +) is measured more accurately or (more significantly) in high-mass kinematic regions. We provide a FeynRules implementation of our operator set to be used for further more detailed analyses.

Chris Hays

United States

Adam Martin

Jack Setford

On the impact of dimension-eight SMEFT operators on Higgs measurements

One way to hunt for top squarks is to look for deviations from the Standard Model in loop level processes involving Higgses. This method is indirect, but complementary to direct searches as it does not rely on specific top squark decays. Studying inclusive Higgs production pp → h alone is insufficient, since there are parameter regions where the effects of the two top squarks approximately cancel. This degeneracy can be broken by looking at the rate for highly boosted Higgses recoiling against a jet, pp → h + jet. In this paper we perform a detailed study of the complementarity of the inclusive and highly boosted processes at the LHC, both in existing Run 1 and Run 2 data, and looking forward to high luminosity. To break the degeneracy, our calculation must maintain the full mass dependence in the loop functions and therefore cannot be recast in an effective field theory framework. We quantify the dependence of both topologies in the top squark parameter space, and outline which levels of experimental and theoretical understanding would be needed for boosted Higgses to be competitive with inclusive Higgs production.

Andrea Banfi

Andrew Bond

Digging for top squarks from Higgs data: from signal strengths to differential distributions

In anticipation of upcoming gravitational wave experiments, we provide a comprehensive overview of the spectra predicted by phase transitions triggered by states from a large variety of dark sector models. Such spectra are functions of the quantum numbers and (self-) couplings of the scalar that triggers the dark phase transition. We classify dark sectors that give rise to a first order phase transition and perform a numerical scan over the thermal parameter space. We then characterize scenarios in which a measurement of a new source of gravitational waves could allow us to discriminate between models with differing particle content.

Graham White

Model discrimination in gravitational wave spectra from dark phase transitions

The ATLAS and CMS collaborations have recently released significant new data on Higgs and diboson production in LHC Run 2. Measurements of Higgs properties have improved in many channels, while kinematic information for h → γγ and h → ZZ can now be more accurately incorporated in fits using the STXS method, and W + W − diboson production at high p  T  gives new sensitivity to deviations from the Standard Model. We have performed an updated global fit to precision electroweak data, W + W − measurements at LEP, and Higgs and diboson data from Runs 1 and 2 of the LHC in the framework of the Standard Model Effective Field Theory (SMEFT), allowing all coefficients to vary the combined dataset, and present the results in both the Warsaw and SILH operator bases. We exhibit the improvement in the constraints on operator coefficients provided by the LHC Run 2 data, and discuss the correlations between them. We also explore the constraints our fit results impose on several models of physics beyond the Standard Model, including models that contribute to the operator coefficients at the tree level and stops in the MSSM that contribute via loops.

CERN

Estonia

John Ellis

Christopher Murphy

Tevong You

Updated global SMEFT fit to Higgs, diboson and electroweak data

Displaced vertices are relatively unusual signatures for dark matter searches at the LHC. We revisit the model of pseudo-Dirac dark matter (pDDM), which can accommodate the correct relic density, evade direct detection constraints, and generically provide observable collider signatures in the form of displaced vertices. We use this model as a benchmark to illustrate the general techniques involved in the analysis, the complementarity between monojet and displaced vertex searches, and provide a comprehensive study of the current bounds and prospective reach.

Italy

Alessandro Davoli

Andrea Simone

Thomas Jacques

Displaced vertices from pseudo-Dirac dark matter

We study the phenomenological consequences of several CP-violating structures that could arise in the Standard Model effective field theory framework. Focusing on operators involving electroweak gauge and/or Higgs bosons, we derive constraints originating from Run I LHC data. We then study the capabilities of the present and future LHC runs at higher energies to further probe associated CP-violating phenomena and we demonstrate how differential information can play a key role. We consider both traditional four-lepton probes of CP-violation in the Higgs sector and novel new physics handles based on varied angular and non-angular observables.

Felipe Ferreira

France

Benjamin Fuks

Dipan Sengupta

Probing $$\textit{CP}$$ <math><mi>CP</mi></math> -violating Higgs and gauge-boson couplings in the Standard Model effective field theory

We analyze a simple extension of the standard model (SM) with a dark sector composed of a scalar and a fermion, both singlets under the SM gauge group but charged under a dark sector symmetry group. Sterile neutrinos, which are singlets under both groups, mediate the interactions between the dark sector and the SM particles, and generate masses for the active neutrinos via the seesaw mechanism. We explore the parameter space region where the observed Dark Matter relic abundance is determined by the annihilation into sterile neutrinos, both for fermion and scalar Dark Matter particles. The scalar Dark Matter case provides an interesting alternative to the usual Higgs portal scenario. We also study the constraints from direct Dark Matter searches and the prospects for indirect detection via sterile neutrino decays to leptons, which may be able to rule out Dark Matter masses below and around 100 GeV.

Miguel Escudero

Nuria Rius

Sterile neutrino portal to Dark Matter II: exact dark symmetry