Towards the ultimate differential SMEFT analysis

Abstract

We obtain SMEFT bounds using an approach that utilises the complete multi-dimensional differential information of a process. This approach is based on the fact that at a given EFT order, the full angular distribution in the most important electroweak processes can be expressed as a sum of a fixed number of basis functions. The coefficients of these basis functions — the so-called angular moments — and their energy dependance, thus form an ideal set of experimental observables that encapsulates the complete multi-dimensional differential information of the process. This approach is generic and the observables constructed allow to avoid blind directions in the SMEFT parameter space. While this method is applicable to many of the important electroweak processes, as a first example we study the pp → V(ℓℓ)h(bb) process (V ≡ Z/W±, ℓℓ ≡ ℓ+ℓ−/ℓ±ν), including QCD NLO effects, differentially. We show that using the full differential data in this way plays a crucial role in simultaneously and maximally constraining the different vertex structures of the Higgs coupling to gauge bosons. In particular, our method yields bounds on the $$ {hV}_{\mu \nu}{V}^{\mu \nu},{hV}_{\mu \nu}{\tilde{V}}^{\mu \nu} $$ hV μν V μν , hV μν V ˜ μν and $$ hVff\left( ff\equiv f\overline{f}/f\overline{f}^{\prime}\right) $$ hVff ff ≡ f f ¯ / f f ¯ ′ couplings, stronger than projected bounds reported in any other process. This matrix-element-based method can provide a transparent alternative to complement machine learning techniques that also aim to disentangle correlations in the SMEFT parameter space.

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

“…riety of studies of the SMEFT, for example, in electroweak processes [106][107][108][109][110][111], flavour physics [112][113][114][115][116][117][118][119][120], low-energy precision data [121][122][123], diboson measurements [124][125][126][127][128][129][130][131], at dimension 8 [87,88,[132][133][134][135][136] (where collider positivity constraints are particularly relevant [136][137][138][139][140]), and its connection with UV-complete models, both at tree-level [141][142][143][144][145][146][147] and one-loop [148][149][150]…”

A fully differential SMEFT analysis of the golden channel using the method of moments

“…This work can be seen as a continuation of ref. [51] where the method of moments was used to obtain the strongest reported projections for the measurement of the gauge-Higgs couplings in the Higgstrahlung processes, pp → W h/Zh. In this work we will finally combine the projections from the h → 4 channel with the results from ref.…”

“…In this work we will finally combine the projections from the h → 4 channel with the results from ref. [51] for the pp → W h/Zh process. As we will see, these processes probe complimentary directions in the EFT space so that their combination results in highly stringent bounds on the EFT deformations of the Higgs coupling to gauge bosons.…”

Precision from the diphoton Zh channel at FCC-hh

“…Hadron colliders have the advantage of probing a large range of energies, thus allowing us to test the high-energy tails of kinematic distributions, where new physics is more easily accessible. The exploitation of selected "clean" processes with small statistical and systematic uncertainty is key for this kind of precision studies, especially when they target the EW dynamics [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…One of the main limiting factors in carrying on the EW precision program at the LHC is the limited amount of events in many clean channels, which forces one to focus only on final states with high cross-section. Some of the best probes for new physics come from processes involving gauge bosons and/or the Higgs, most notably the di-boson production channels [2][3][4][5][6][7][8][9][10][11][15][16][17][18][19][20][21][22][23]. These processes are sensitive to many operators that describe the couplings of the SM gauge bosons and the high-energy dynamics of the Higgs.…”