Putting standard model EFT fits to work

The calculation of next-to-leading order (NLO) perturbative corrections at fixed operator dimension in Standard Model Effective Field Theory (SMEFT) has been a topic of much recent interest. In this paper we obtain the NLO corrections from dimension-6 operators to the Higgs boson decays $$ h\to f\overline{f} $$ h → f f ¯ , where the fermions f ∈ {μ, τ, c}. This extends previous results for $$ h\to b\overline{b} $$ h → b b ¯ to all phenomenologically relevant Higgs boson decays into fermions, and provides the basis for future precision analyses of these decays within effective field theory. We point out the benefits of studying ratios of decay rates into different fermions in SMEFT, the most surprising of which is enhanced sensitivity to anomalous hγγ and hgg couplings induced by flavor-universal SMEFT operators, especially in scenarios where flavor-dependent Wilson coefficients are constrained by Minimal Flavor Violation.

“…However, this coefficient is quite constrained by LHC data, again using the 95% C.L. limits from the recent global fit [67] we find contributions to R c/b that are below the 1% level.…”

Section: Jhep11(2020)079mentioning

confidence: 62%

“…illustrate the sensitivity of R τ /µ to these coefficients, we have varied them to the extreme edges of the 95% C.L. limits from a recent global fit marginalized over a set of 19 SMEFT Wilson coefficients in [67], and found that deviations in R τ /µ from the SM value on the order of a few percent are not ruled out.…”

Section: Jhep11(2020)079mentioning

confidence: 99%

Higgs decay to fermion pairs at NLO in SMEFT

Cullen

Pecjak

2020

“…These include, in particular, the very precise measurements at the Z pole performed at the Large Electron-Positron (LEP) collider and the Stanford Linear Collider (SLC). In corroboration with the Higgs-boson discovery and the experimental information collected at LHC and Tevatron, they provide strong constraints on theories beyond the SM (BSM) that lead to important deformations of the standard EW sector [1][2][3][4][5][6][7][8][9][10]. Intriguingly, the interplay between the TeV region under scrutiny at the LHC and the NP probes represented by EW precision tests may be of fundamental importance for the study of the B-physics anomalies [11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 70%

“…that characterize the mixing pattern of SM fields and vector-like partners. 10 Symmetry breaking of U(1) X is triggered by S 2 = −µ 2 S /(2λ S ) ≡ η 2 = 0, that implies the following fermionic mixing patterns:…”

Section: Z With Vector-like Partnersmentioning

confidence: 99%

B anomalies under the lens of electroweak precision

Alasfar

Azatov

Blas

et al. 2020

The measurements carried out at LEP and SLC projected us into the precision era of electroweak physics. This has also been relevant in the theoretical interpretation of LHCb and Belle measurements of rare B semileptonic decays, paving the road for new physics with the inference of lepton universality violation in $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ ratios. The simplest explanation of these flavour anomalies — sizeable one-loop contributions respecting Minimal Flavour Violation — is currently disfavoured by electroweak precision data. In this work, we discuss how to completely relieve the present tension between electroweak constraints and one-loop minimal flavour violating solutions to $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ . We determine the correlations in the Standard Model Effective Field Theory that highlight the existence of such a possibility. Then, we consider minimal extensions of the Standard Model where our effective-field-theory picture can be realized. We discuss how these solutions to b → sℓℓ anomalies, respecting electroweak precision and without any new source of flavour violation, may point to the existence of a Z′ boson at around the TeV scale, within the discovery potential of LHC, or to leptoquark scenarios.

“…This approach however may not be directly applicable to the sum rules of dimension-6 operators. A more general question, sometimes named as the Inverse Problem [72,73], can be phrased as follows: given the measured values of the operator coefficients around the electroweak scale, to what extent can we possibly determine the nature of the new physics beyond the SM? New developments on the amplitude tools might be able to help us further tackle this problem in the future.…”

Section: Jhep03(2021)149mentioning

confidence: 99%

Sum rules in the standard model effective field theory from helicity amplitudes

Wang

2021

The dispersion relation of an elastic 4-point amplitude in the forward direction leads to a sum rule that connects the low energy amplitude to the high energy observables. We perform a classification of these sum rules based on massless helicity amplitudes. With this classification, we are able to systematically write down the sum rules for the dimension-6 operators of the Standard Model Effective Field Theory (SMEFT), some of which are absent in previous literatures. These sum rules offer distinct insights on the relations between the operator coefficients in the EFT and the properties of the full theory that generates them. Their applicability goes beyond tree level, and in some cases can be used as a practical method of computing the one loop contributions to low energy observables. They also provide an interesting perspective for understanding the custodial symmetries of the SM Higgs and fermion sectors.