Abstract
Modern global analyses of the structure of the proton include collider measurements which probe energies well above the electroweak scale. While these provide powerful constraints on the parton distribution functions (PDFs), they are also sensitive to beyond the standard model (BSM) dynamics if these affect the fitted distributions. Here we present a first simultaneous determination of the PDFs and BSM effects from deep-inelastic structure function data by means of the NNPDF framework. We consider representative four-fermion operators from the SM effective field theory (SMEFT), quantify to which extent their effects modify the fitted PDFs, and assess how the resulting bounds on the SMEFT degrees of freedom are modified. Our results demonstrate how BSM effects that might otherwise be reabsorbed into the PDFs can be systematically disentangled.
Highlights
Searches for physics beyond the standard model (BSM) at high-energy colliders can be divided into two main categories: direct searches, aiming to detect the production of new heavy particles, and indirect searches, whose goal is to identify subtle deviations in the interactions and properties of the SM particles
Our results demonstrate how BSM effects that might otherwise be reabsorbed into the parton distribution functions (PDFs) can be systematically disentangled
In the case of LHC data, high-energy processes such as Drell-Yan, diboson, and top-quark production at large invariant masses [23,24,25,26,27,28,29] play a key role since energy-growing effects often enhance the sensitivity to the SM effective field theory (SMEFT) contributions
Summary
Searches for physics beyond the standard model (BSM) at high-energy colliders can be divided into two main categories: direct searches, aiming to detect the production of new heavy particles, and indirect searches, whose goal is to identify subtle deviations in the interactions and properties of the SM particles The latter would arise from virtual quantum effects involving BSM dynamics at energies well beyond the collider center-of-mass energy. Both strategies are actively pursued at the LHC by exploiting its unique energy reach [1] and its thriving program of precision measurements [2,3,4] In this context, the SM effective field theory (SMEFT) [5,6,7,8,9,10,11,12,13] represents a powerful model-independent approach to identify, interpret, and correlate potential BSM effects from precision measurements under the assumption that the new physics scale, Λ, is well above the energies probed by the experimental data. BSM effects can be parametrized at low energies in terms of dimension-six operators Oi, constructed from SM fields satisfying its symmetries: LSMEFT
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