Top, Higgs, Diboson and Electroweak Fit to the Standard Model Effective Field Theory

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.

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

“…Parametrising low-energy observables in terms of these WCs and analysing them in global fits allows us to constrain potential NP in a (rather) modelindependent way. Global analyses in the SMEFT framework have been performed for the EWPO [82], Higgs [46,47,81,[83][84][85][86][87], di-boson [63,66,[88][89][90], the top sector [91][92][93][94][95][96][97], and for combinations of these sectors [47,54,75,[98][99][100][101][102][103]. In this work, we consider constraints from EWPO, single and di-Higgs data, as well as distributions from the di-boson production channels.…”

Global Searches for New Physics with Top Quarks

“…At the LHC, associated tZ, tW , th production are very sensitive processes [12], as well as tails of kinematic distributions that probe new physics at the highest available energies [13,14]. Combined fits to LHC data in the top, Higgs, and electroweak sectors [15], as well as combinations of Higgs and electroweak observables with flavor observables [6] are promising steps towards a truly global SMEFT analysis that will allow us to resolve more and more of what might be hiding in the UV.…”

A new generation of simultaneous fits to LHC data using deep learning

“…However, for an indirect detection of new physics, it is pivotal to have a robust framework that is able to globally interpret all subtle deviations from the SM predictions that might arise. While huge progress has been made in determining key ingredients of theoretical predictions from the data [1], such as the Parton Distribution Functions (PDFs) of the proton [2][3][4][5], the strong coupling constant [6], and the coefficients of a suitable parametrisation of the effects of heavy new states via the addition of higher dimensional operators to the SM Lagrangian, such as the SMEFT [7,8], it is not yet evident how to combine all these partial fits into a global interpretation of the LHC data.…”