We present analytic results for electroweak precision observables (EWPO) at next-to-leading order (NLO) in dimension-six SMEFT, with no assumptions on the flavour structure of SMEFT Wilson coefficients. The results are given in five different electroweak input schemes, thus offering a simple means, along with scale variations, of estimating theory uncertainties related to higher-order terms in the SMEFT expansion. Our results will be useful to assess the constraining power of existing and future lepton colliders for new physics scenarios.

Germany

Anke Biekötter

United Kingdom

Benjamin Pecjak

Analytic results for electroweak precision observables at NLO in SMEFT

Global analyses in the Standard Model Effective Field Theory (SMEFT) framework serve as a tool to probe potential directions of new physics. To break degeneracies between the Wilson coefficients of the SMEFT, it is essential to combine observables from various experiments. Since different observables entering global fits may be measured at different energy scales, it becomes increasingly important to account for this fact through the renormalisation group evolution (RGE) of the Wilson coefficients. In this work, we investigate the effects of the RGE on a global SMEFT fit under the assumption of a U(3) symmetry within the minimal flavour violation framework. We comment on the role of next-to-leading order SMEFT predictions for breaking potential degeneracies between Wilson coefficients arising as a result of RGE effects.

Riccardo Bartocci

Tobias Hurth

Renormalisation group evolution effects on global SMEFT analyses

We present an analysis of the sensitivity of current and future LHC searches for new spin-0 particles in top–anti-top-quark $$ \left(t\overline{t}\right) $$ final states, focusing on generic axion-like particles (ALPs) that are coupled to top quarks and gluons. As a first step, we derive new limits on the effective ALP Lagrangian in terms of the Wilson coefficients and $$ {c}_{\overset{\sim }{G}} $$ based on the results of the CMS search using 35 9 fb 1 of data, collected at $$ \sqrt{s} $$ = 13 TeV. We then investigate how the production of an ALP with generic couplings to gluons and top quarks can be distinguished from the production of a pseudoscalar which couples to gluons exclusively via a top-quark loop. To this end, we make use of the invariant $$ t\overline{t} $$ mass distribution and angular correlations that are sensitive to the $$ t\overline{t} $$ spin correlation. Using a mass of 400 GeV as an example, we find that already the data collected during Run 2 and Run 3 of the LHC provides an interesting sensitivity to the underlying nature of a possible new particle. We also analyze the prospects for data anticipated to be collected during the high-luminosity phase of the LHC. Finally, we compare the limits obtained from the $$ t\overline{t} $$ searches to existing experimental bounds from LHC searches for narrow di-photon resonances, from measurements of the production of four top quarks, and from global analyses of ALP–SMEFT interference effects.

Afiq Anuar

Spain

Thomas Biekötter

Alexander Grohsjean

Sven Heinemeyer

Laurids Jeppe

Christian Schwanenberger

Georg Weiglein

ALP-ine quests at the LHC: hunting axion-like particles via peaks and dips in

We investigate the interactions of a light scalar with the Higgs boson and second-generation fermions, which trigger new rare decays of the Higgs boson into 4 <italic>&#956;</italic>, <math altimg='si1.svg'><mn>2</mn><mi>&#956;</mi><mn>2</mn><mi>&#947;</mi></math>, 6 <italic>&#956;</italic> and <math altimg='si2.svg'><mn>4</mn><mi>&#956;</mi><mn>2</mn><mi>j</mi></math>. We recast current LHC searches to constrain these decays and develop new collider analyses for those channels which are only poorly tested by existing studies. With the currently collected data we can probe branching ratios as small as <math altimg='si3.svg'><mn>1.5</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>5</mn></mrow></msup></math>, <math altimg='si4.svg'><mn>8.7</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>5</mn></mrow></msup></math>, <math altimg='si5.svg'><mn>5.7</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>8</mn></mrow></msup></math> and <math altimg='si6.svg'><mn>1.6</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>7</mn></mrow></msup></math>, respectively. For the High-Luminosity LHC run, considered here to involve 3 ab <sup>&#8722;1</sup> of integrated luminosity, these numbers go down to <math altimg='si7.svg'><mn>1.3</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>5</mn></mrow></msup></math>, <math altimg='si8.svg'><mn>2.0</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>6</mn></mrow></msup></math>, <math altimg='si9.svg'><mn>3.0</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>9</mn></mrow></msup></math> and <math altimg='si10.svg'><mn>5.4</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>9</mn></mrow></msup></math>, respectively. We also comment on other channels that remain still unexplored.

Mikael Chala

Michael Spannowsky

New Higgs decays to axion-like particles

We present comprehensive global fits of the SMEFT under the minimal minimal flavour violation (MFV) hypothesis, i.e. assuming that only the flavour-symmetric and CP-invariant operators are relevant at the high scale. The considered operator set is determined by this flavour assumption rather than the used datasets. We establish global limits on these Wilson coefficients using leading order and next-to-leading order SMEFT predictions for electroweak precision observables, Higgs, top, flavour and dijet data as well as measurements from parity violation experiments and lepton scattering. Our investigations reveal an intriguing crosstalk among different observables, underscoring the importance of combining diverse observables from various energy scales in global SMEFT analyses.

A global analysis of the SMEFT under the minimal MFV assumption

We implement electroweak renormalisation schemes involving the effective weak mixing angle to NLO in Standard Model Effective Field Theory (SMEFT). After developing the necessary theoretical machinery, we analyse a select set of electroweak precision observables in such input schemes. An attractive feature is that large corrections from top-quark loops appearing in other schemes are absorbed into the definition of the effective weak mixing angle. On the other hand, the renormalisation condition which achieves this involves a large number of flavour-specific SMEFT couplings between the Z boson and charged leptons, motivating simple flavour assumptions such as minimal flavour violation for practical applications. The results of this paper provide a valuable new component for estimating systematic uncertainties in SMEFT fits by performing analyses in multiple input schemes.

Tommy Smith

Using the effective weak mixing angle as an input parameter in SMEFT

In the presence of axions or axion-like particles (ALPs) that couple to the Standard Model via dimension-five interactions, dimension-six SMEFT interactions are generated via renormalization-group evolution. As many of these SMEFT contributions are experimentally tightly constrained, this “ALP-SMEFT interference” can be used to derive indirect bounds on the ALP couplings to the Standard Model particles. We present a global analysis of the Wilson coefficients of the ALP effective Lagrangian based on Higgs, top, and low-energy data. The obtained bounds are model independent and are competitive or even stronger than direct bounds in the GeV to TeV ALP-mass range.

Javier Fuentes-Martín

Anne Galda

United States

Matthias Neubert

A global analysis of axion-like particle interactions using SMEFT fits

The choice of an electroweak (EW) input scheme is an important component of perturbative calculations in Standard Model Effective Field Theory (SMEFT). In this paper we perform a systematic study of three different EW input schemes in SMEFT, in particular those using the parameter sets {M  W , M  Z , G  F }, {M  W , M  Z , α}, or {α, M  Z , G  F }. We discuss general features and calculate decay rates of Z and W bosons to leptons and Higgs decays to bottom quarks in these three schemes up to next-to-leading order (NLO) in dimension-six SMEFT. We explore the sensitivity to Wilson coefficients and perturbative convergence in the different schemes, and show that while the latter point is more involved than in the Standard Model, the dominant scheme-dependent NLO corrections are universal and can be taken into account by a simple set of substitutions on the leading-order results. Residual NLO corrections are then of similar size between the different input schemes, and performing calculations in multiple schemes can give a useful handle on theory uncertainties in SMEFT predictions and fits to data.

Darren Scott

Electroweak input schemes and universal corrections in SMEFT

In this paper, we work with 16 different single scalar particle extensions of the Standard Model. We present the sets of dimension-six effective operators and the associated Wilson coefficients as functions of model parameters after integrating out the heavy scalars up to one loop, including the heavy-light mixing, for each such scenario. Using the correspondence between the effective operators and the observables at the electroweak scale, and employing Bayesian statistics, we compute the allowed ranges of new physics parameters that are further translated and depicted in two-dimensional Wilson coefficient space in light of the latest CMS and ATLAS data up to 137 and <math><mrow><mn>139</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>, respectively. We also adjudge the status of those new physics extensions that offer similar sets of relevant effective operators. In addition, we provide a model-independent fit of 23 Standard Model effective field theory Wilson coefficients using electroweak precision observables, single- and di-Higgs data, as well as kinematic distributions of diboson production.

India

 Anisha

Supratim Das Bakshi

CERN

Shankha Banerjee

Joydeep Chakrabortty

Sunando Kumar Patra

Effective limits on single scalar extensions in the light of recent LHC data

The determination of |V  ub | in inclusive semileptonic B → X  u  ℓν decays will be among the pivotal tasks of Belle II. In this paper we study the potential and limitations of machine-learning approaches that attempt to reduce theory uncertainties by extending the experimentally accessible fiducial region of the B → X  u  ℓν signal into regions where the B → X  c  ℓν background is dominant. We find that a deep neural network trained on low-level single particle features offers modest improvement in separating signal from background, compared to BDT set-ups using physicist-engineered high-level features. We further illustrate that while the signal acceptance of such a deep neural network deteriorates in kinematic regions where the signal is small, such as at high hadronic invariant mass, neural networks which exclude kinematic features are flatter in kinematics but less inclusive in the sampling of exclusive hadronic final states at fixed kinematics. The trade-off between these two set-ups is somewhat Monte Carlo dependent, and we study this issue using the multipurpose event generator Sherpa in addition to the widely used B-physics tool EvtGen.

Ka Kwok

Potential and limitations of machine-learning approaches to inclusive |V  ub  | determinations