LHC EFT WG meeting

Monday 28 Apr 2025, 16:00 → 17:30 Europe/Zurich

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16:00 → 16:30 More variables or more bins? Impact on the EFT interpretation of Drell-Yan measurements

We generalize previous studies on constraining operators of the Standard Model Effective Field Theory using Drell-Yan (DY) measurements to include at the same time all relevant operators and uncertainties. It has been shown that fully differential measurements (triple differential for neutral and double differential for charged) are more sensitive to EFT effects. Nevertheless, due to the finite statistics, the fully differential measurements sacrifice some statistical power on the shape (less invariant mass or transverse momentum bins) in favour of more kinematic variables. We show that when the observables are particularly sensitive to the shape of the distributions, such as the invariant mass of the two leptons in neutral DY, the single differential measurement with more bins, may be as sensitive as the fully differential one, at least for specific EFT operators. This suggests to always supplement fully differential analyses with projections into the relevant distributions evaluated with finer bins.

Speaker: Samuele Grossi (Università degli studi di Genova & INFN sezione di Genova)

Slides_LHC_EFT_WG.pdf

16:30 → 17:00 On the EFT validity for Drell-Yan tails at the LHC

In this article, we examine the validity range of the Effective Field Theory (EFT) description of high-energy Drell-Yan processes at the LHC. To this purpose, we consider explicit mediators that contribute to these processes in the s- and t-channels, comparing their effects in Drell-Yan distributions with the ones obtained by matching onto the corresponding EFT. We determine the conditions for the EFT results to accurately describe these scenarios. In particular, we explore the impact of including dimension-eight (d=8) operators in the faster convergence of the EFT series, at the analytical and numerical level, considering contributions to the cross section up to the square of d=8 EFT operator insertions. Moreover, we discuss the possible implications of clipping LHC data and illustrate results for a specific New-Physics scenario motivated by low-energy flavor data.

Speaker: Matheus Martines de Azevedo da Silva (Universidade de São Paulo)

LHC-WG-Meeting-EFT_Validity_DY_v2.pdf

17:00 → 17:30 Drell-Yan production in universal theories beyond dimension-six SMEFT

We study Drell-Yan production in universal theories consistently including effects beyond dimension six in the SMEFT. Within universal SMEFT and with C and P conservation we find that eleven dimension-eight operators contribute in addition to the six contributing at dimension-six. We first work in an operator basis in which operators with higher derivatives of the bosonic fields have been rotated by equations of motion in favor of combinations of operators involving SM fermion currents. We derive the general form of the amplitudes consistently in the expansion to O(Λ−4) and identify eight combinations of the 17 Wilson coefficients which are physically distinguishable by studying the invariant mass distribution of the lepton pairs produced. We then introduce an extension of the parametrization of universal effects in terms of oblique parameters obtained by linearly expanding the self-energies of the electroweak gauge-bosons to O(q6). It contains eleven oblique parameters of which only eight are generated within SMEFT at dimension-eight: Sˆ, Tˆ, W, Y, Uˆ, X, plus two additional which we label W′ and Y′ and show how they match at linear order with the eight identified combinations of operator coefficients. We then perform a combined analysis of a variety of LHC data on the neutral- and charged-current Drell-Yan processes with the aim of constraining the eight combinations. We compare and combine the LHC bounds with those from electroweak precision W and Z pole observables which can only provide constraints in four directions of the eight-parameter space. We present the results in terms of limits on the eight effective Wilson coefficients as well as on the eight oblique parameters. In each case, we study the dependence of the derived constraints on the order of the expansion considered.

Speaker: Jay Desai (Stony Brook University)

Drell-Yan production in universal theories beyond dimension-six SMEFT.pdf

Drell-Yan production in universal theories beyond dimension-six SMEFT.pptx

Drell-Yan production in universal theories beyond dimension-six SMEFT.pptx