Can New Physics Hide inside the Proton?

201

167

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.

Section: Jhep04(2021)279mentioning

confidence: 99%

Top, Higgs, diboson and electroweak fit to the Standard Model effective field theory

Ellis

Madigan

Mimasu

et al. 2021

201

167

“…Here, Λ corresponds to the energy scale in which the EFT expansion becomes invalid, and Γ µ represents the general Lorentz structure for the interaction. Since any theory with a single non-zero coupling a q i l j is theoretically consistent [82], any cross-sections computed with it must be positive definite, including the ones that lead to our positivity observables. Then one can take the Λ → ∞ limit, in which case the cross section will be vanishingly small, yet still remain positive, as we demand in our fit via the positivity constraint.…”

Section: Jhep09(2020)183mentioning

confidence: 99%

nNNPDF2.0: quark flavor separation in nuclei from LHC data

Khalek

Ethier

Rojo

et al. 2020

Self Cite

We present a model-independent determination of the nuclear parton distribution functions (nPDFs) using machine learning methods and Monte Carlo techniques based on the NNPDF framework. The neutral-current deep-inelastic nuclear structure functions used in our previous analysis, nNNPDF1.0, are complemented by inclusive and charm-tagged cross-sections from charged-current scattering. Furthermore, we include all available measurements of W and Z leptonic rapidity distributions in proton-lead collisions from ATLAS and CMS at $$ \sqrt{s} $$ s = 5.02 TeV and 8.16 TeV. The resulting nPDF determination, nNNPDF2.0, achieves a good description of all datasets. In addition to quantifying the nuclear modifications affecting individual quarks and antiquarks, we examine the implications for strangeness, assess the role that the momentum and valence sum rules play in nPDF extractions, and present predictions for representative phenomenological applications. Our results, made available via the LHAPDF library, highlight the potential of high-energy collider measurements to probe nuclear dynamics in a robust manner.

“…A proper approach would be to perform a combined SMEFT and PDF fit. First steps in this direction show discriminating power between EFT and PDF effects in the context of deep inelastic scattering [88].…”

Section: Jhep11(2020)080mentioning

confidence: 99%

Charm physics confronts high-pT lepton tails

Fuentes-Martín

Greljo

Camalich

et al. 2020

We present a systematic survey of possible short-distance new-physics effects in (semi)leptonic charged- and neutral-current charmed meson decays. Using the Standard Model Effective Field Theory (SMEFT) to analyze the most relevant experimental data at low and high energies, we demonstrate a striking complementarity between charm decays and high invariant mass lepton tails at the LHC. Interestingly enough, high-pT Drell-Yan data offer competitive constraints on most new physics scenarios. Furthermore, the full set of correlated constraints from K, π and τ decays imposed by SU(2)L gauge invariance is considered. The bounds from D(s) decays, high-pT lepton tails and SU(2)L relations chart the space of the SMEFT affecting semi(leptonic) charm flavor transitions.