Effective theory for a heavy scalar coupled to the SM via vector-like quarks

Abstract

We illustrate the application of the recently developed SCETBSM framework in the context of a specific model, in which the Standard Model (SM) is supplemented by a heavy scalar S and three generations of heavy, vector-like quarks Ψ. We construct the appropriate effective field theory for two-body decays of S into SM particles. We explicitly compute the Wilson coefficients of the SCETBSM operators appearing at leading and next-to-leading order (NLO) in an expansion in powers of v/MS, as well as for a subset of operators arising at NNLO, retaining the full dependence on the ratio MS/MΨ. For the phenomenologically most relevant decay channels of the heavy scalar, we study the impact of resummation effects of Sudakov logarithms on the decay rates.

Effective field theory for heavy vector resonances coupled to the Standard Model

“…With the generalization to heavy particles with non-zero spin and resonances carrying non-trivial SM charges, the present work constitutes two important generalizations of the SCET BSM approach, which was originally introduced to study the decays of a hypothetical spin-0 SM singlet resonance [5,6]. All that is missing now is the long-awaited discovery of some new heavy particle not contained in the SM of particle physics.…”

“…In refs. [5,6], the original formulation of SCET has been extended to an effective theory called SCET BSM , which describes light SM fields coupled to a field describing a hypothetical new heavy resonance with mass much above the electroweak scale. In these papers the operator basis was constructed up to third (and partially fourth) order in the expansion parameter λ for the case of a scalar resonance S transforming as a singlet under the SM gauge group.…”

Effective Field Theory after a New-Physics Discovery

“…Only numerical results will be shown here and none of the ingredients necessary to obtain them. They are detailed in the original papers and references therein 6,7 , including analytical solutions to the RG equations governing the scaling behavior of the various Wilson coefficients.…”

“…Furthermore, we comment on the matching procedure to a concrete UV completion and the size of the resummation effects. The full operator basis along with the anomalous dimensions up to next-to-next-to-leading order in the EFT power-counting can be found in the original paper 6 , whereas the in-depth treatment of the UV completion was presented in a later work 7 .…”

QCD and High Energy Interactions: MORIOND 2019 Theory Summary

“…In Ref. 65 SCET is used to describe a NP scenario with a new gauge-singlet heavy spin-0 particle with mass M S far above the EW scale v, which allows for the resummation of large logarithms of M S /v via RGE in predictions for its decay width to SM particles (see also 66 ).…”