Updated Global SMEFT Fit to Higgs, Diboson and Electroweak Data

Abstract: 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 $h \to \gamma\gamma$ and $h \to ZZ$ 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 across 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.

• The paper conducts a comprehensive SMEFT fit integrating precision electroweak, Higgs, and diboson data to assess potential BSM effects.
• It employs linear approximations across 20 dimension-6 operators, enhancing correlations and constraints using LHC Run 2 data.
• The study guides future searches by benchmarking SMEFT analyses and setting model-independent bounds on new physics scenarios.

Updated Global SMEFT Fit to Higgs, Diboson, and Electroweak Data

The presented paper details a comprehensive analysis performed within the framework of the Standard Model Effective Field Theory (SMEFT). The researchers evaluate precision electroweak data, as well as Higgs and diboson data from the Large Hadron Collider (LHC) Runs 1 and 2, seeking potential hints of physics beyond the Standard Model (BSM). This global SMEFT fit considers 20 dimension-6 operators and provides constraints on them across both the Warsaw and SILH operator bases.

Summary of Results

The study underscores the challenges of detecting BSM physics amidst high-precision Standard Model (SM) predictions. It is thorough, incorporating various data sets:

• Precision Electroweak Observables: These include Z-pole and W mass measurements from LEP and the Tevatron.
• Higgs Production and Decay: Data from the ATLAS and CMS experiments during LHC Runs 1 and 2 are analyzed.
• Diboson Productions: The analysis uses both the LHC and LEP measurements of W+W- production processes.

In the fitting process, the researchers employ linear approximations to predict SMEFT corrections to the SM, allowing for comprehensive correlations and interactions assessment. The paper highlights improvements in constraints brought by LHC Run 2 data, showcasing its crucial role in advancing potential sensitivities to new physics.

Implications for Physics Beyond the Standard Model

The paper explores the theoretical and practical implications of the global fit results:

• New Physics Models: The researchers assess a variety of single- and multi-parameter extensions to the SM, including vector-like fermions and scalar bosons. These models are explored for any potential compatibility with the results of the global fit. However, this analysis reveals no significant deviations from the SM predictions.
• MSSM Stop Constraints: Constraints are placed on supersymmetric scenarios, particularly focusing on stop squarks in the Minimal Supersymmetric Standard Model (MSSM). Here, the SMEFT provides insights that are model-independent, albeit the constraints primarily emerge at loop levels.

Conclusion and Future Directions

The constraints provided by this comprehensive study are crucial for guiding future searches for BSM physics. Given the importance of precision in measurements, ongoing and upcoming LHC runs are expected to further tighten these constraints. The researchers emphasize the importance of kinematic information from experimental collaborations to maximize the potential of SMEFT analyses.

Additionally, Table~\ref{tab:impact} in the paper is illustrative of which data sets are most influential for different operators, and its insights will likely shape experimental priorities. As experimental techniques evolve, the integrated approach demonstrated in this work will serve as a benchmark for future SMEFT analyses.

Overall, the global SMEFT fit marks an essential step in the ongoing search for new physics, emphasizing the power of comprehensive data analysis in corroborating or challenging the extent of the Standard Model.