Observable effects of general new scalar particles

106

The couplings of the electroweak effective theory contain information on the heavy-mass scales which are no-longer present in the low-energy Lagrangian. We build a general effective Lagrangian, implementing the electroweak chiral symmetry breaking SU(2) L ⊗ SU(2) R → SU(2) L+R , which couples the known particle fields to heavier states with bosonic quantum numbers J P = 0 ± and 1 ± . We consider colour-singlet heavy fields that are in singlet or triplet representations of the electroweak group. Integrating out these heavy scales, we analyze the pattern of low-energy couplings among the light fields which are generated by the massive states. We adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs, without making any assumption about its possible doublet structure. Special attention is given to the different possible descriptions of massive spin-1 fields and the differences arising from naive implementations of these formalisms, showing their full equivalence once a proper short-distance behaviour is required.

Section: Jhep04(2017)012mentioning

confidence: 54%

Fingerprints of heavy scales in electroweak effective Lagrangians

Pich

Rosell

Santos

et al. 2017

106

“…Assuming that the new scalar states are significantly heavier than m h , the effective theory of extended Higgs sectors provides a way to study these effects systematically, as has already been shown e.g. in [32]. In particular, it is plausible that the new scalar states from the extended Higgs sector are very hard to probe at LHC (they might be very heavy, or have no decay branching fractions to SM gauge bosons), but their effect might be possible to detect either in precision EW measurements or using differential information in LHC measurements.…”

Section: Higgs Eft From Extended Higgs Sectorsmentioning

confidence: 96%

Benchmarks for Higgs effective theory: extended Higgs sectors

Gorbahn

Sanz

2015

101

Precise measurements of SM particles properties at the LHC allows to look for heavy New Physics in the context of an Effective Field Theory (EFT). These searches, however, often rely on kinematic regions where the validity of the EFT may be compromised. In this paper we propose to address this issue by comparing with benchmark models. The connection between models and their manifestations as EFTs at low energies allows us to quantify the breakdown of the EFT, and describe ways to combine different sources of constraints beyond Higgs physics. To illustrate these techniques, in this paper we propose a set of benchmark models based on extensions of the Higgs sector, namely the inclusion of a singlet, a dilaton and generic 2HDMs. We obtain the matching between these models and the EFT involving the Higgs, electroweak bosons and fermions. We then describe current and future indirect and direct constraints, consider the effect of correlations among the coefficients within models, and discuss the validity of the EFT.

“…Indeed, the EFT formalism provides a robust theoretical framework where both physical calculations and the connection with UV scenarios can be performed in a well-defined manner. On the one hand, EFTs can be connected easily to a given UV-model when the heavy degrees of freedom are integrated out [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. On the other hand, the precision of the predictions computed with the effective Lagrangian can be systematically improved by including higher orders of both, the EFT expansion as well as perturbation theory.…”

Section: Jhep07(2018)048mentioning

confidence: 99%

Current and future constraints on Higgs couplings in the nonlinear Effective Theory

Blas

Eberhardt

Krause

2018

We perform a Bayesian statistical analysis of the constraints on the nonlinear Effective Theory given by the Higgs electroweak chiral Lagrangian. We obtain bounds on the effective coefficients entering in Higgs observables at the leading order, using all available Higgs-boson signal strengths from the LHC runs 1 and 2. Using a prior dependence study of the solutions, we discuss the results within the context of natural-sized Wilson coefficients. We further study the expected sensitivities to the different Wilson coefficients at various possible future colliders. Finally, we interpret our results in terms of some minimal composite Higgs models.