2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Timothy Cohen ◽  
Nathaniel Craig ◽  
Xiaochuan Lu ◽  
Dave Sutherland

Abstract There are two canonical approaches to treating the Standard Model as an Effective Field Theory (EFT): Standard Model EFT (SMEFT), expressed in the electroweak symmetric phase utilizing the Higgs doublet, and Higgs EFT (HEFT), expressed in the broken phase utilizing the physical Higgs boson and an independent set of Goldstone bosons. HEFT encompasses SMEFT, so understanding whether SMEFT is sufficient motivates identifying UV theories that require HEFT as their low energy limit. This distinction is complicated by field redefinitions that obscure the naive differences between the two EFTs. By reformulating the question in a geometric language, we derive concrete criteria that can be used to distinguish SMEFT from HEFT independent of the chosen field basis. We highlight two cases where perturbative new physics must be matched onto HEFT: (i) the new particles derive all of their mass from electroweak symmetry breaking, and (ii) there are additional sources of electroweak symmetry breaking. Additionally, HEFT has a broader practical application: it can provide a more convergent parametrization when new physics lies near the weak scale. The ubiquity of models requiring HEFT suggests that SMEFT is not enough.


2015 ◽  
Vol 92 (4) ◽  
Author(s):  
Yoshimasa Hidaka ◽  
Toshifumi Noumi ◽  
Gary Shiu

2005 ◽  
Vol 20 (02n03) ◽  
pp. 358-364 ◽  
Author(s):  
JULIA SCHWEIZER

We describe the spectra and decays of π+π-and π±K∓atoms within a non-relativistic effective field theory. The evaluations of the energy shifts and widths are performed at next-to-leading order in isospin symmetry breaking. The prediction for the lifetime of the π±K∓atom in its ground-state yields τ10=(3.7±0.4)·10-15s .


1990 ◽  
Vol 05 (23) ◽  
pp. 1901-1908
Author(s):  
DAIJIRO SUEMATSU

We re-examine the possibility of large hierarchical symmetry breaking in the effective field theory of Calabi-Yau compactified superstring. We introduce the general superpotential containing the allowed moduli couplings. In certain manifolds one-loop radiative correction gives the non-trivial minimum and that solution suggests the possibility of large hierarchical symmetry breaking. To realize such a large hierarchy, it seems to require that 27(h2,1 + h1,1) > 48π2 and H1 ( End T) chiral superfields should have certain types of couplings to moduli fields.


2016 ◽  
Vol 31 (19) ◽  
pp. 1630026
Author(s):  
Thomas Flacke

Composite Higgs models have the potential to provide a solution to the hierarchy problem and a dynamical explanation for the generation of the Higgs potential. They can be tested at the LHC as the new sector which underlies electroweak symmetry breaking must become strong in the TeV regime, which implies additional bound states beyond the Higgs. In this paper, we first discuss prospects and search strategies for top partners (and other quark partners) in the strongly coupled sector, which we study in an effective field theory setup. In the second part of the proceedings, we go beyond the effective field theory approach. We discuss potential UV embeddings for composite Higgs models which contain a Higgs as well as top partners. We show that in all of these models, additional pseudo-Nambu–Goldstone bosons beyond the Higgs are present. In particular, all of the models contain a pseudoscalar which couples to the Standard Model gauge fields through Wess–Zumino–Witten terms, providing a prime candidate for a di-boson (including a di-photon) resonance. The models also contain colored pNGBs which can be searched for at the LHC.


2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Andreas Crivellin ◽  
Martin Hoferichter

Abstract With the long-standing tension between experiment and Standard-Model (SM) prediction in the anomalous magnetic moment of the muon aμ recently reaffirmed by the Fermilab experiment, the crucial question becomes which other observables could be sensitive to the underlying physics beyond the SM to which aμ may be pointing. While from the effective field theory (EFT) point of view no direct correlations exist, this changes in specific new physics models. In particular, in the case of explanations involving heavy new particles above the electroweak (EW) scale with chiral enhancement, which are preferred to evade exclusion limits from direct searches, correlations with other observables sensitive to EW symmetry breaking are expected. Such scenarios can be classified according to the SU(2)L representations and the hypercharges of the new particles. We match the resulting class of models with heavy new scalars and fermions onto SMEFT and study the resulting correlations with h → μμ and Z → μμ decays, where, via SU(2)L symmetry, the latter process is related to Z → νν and modified W-μ-ν couplings.


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