The universal one-loop effective action

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: 55%

Fingerprints of heavy scales in electroweak effective Lagrangians

Pich

Rosell

Santos

et al. 2017

106

“…techniques exist for doing so up to one-loop level [18][19][20][21][22][23][24][25][26][27][28][29]. 2 In practice, functional methods have typically been overlooked in favour of the more traditional Feynman diagram approach, where many tools have been developed to ease otherwise complicated calculations.…”

Section: Jhep08(2017)054mentioning

confidence: 99%

“…The logical step is then to eliminate such unnecessary calculations by doing them once-and-for-all. The expression obtained in this way is the so-called Universal One-Loop Effective Action (UOLEA) [23,24]. It allows one to bypass the need for either Feynman diagram or functional methods entirely when deriving Wilson coefficients for operators up to dimension six.…”

Section: Jhep08(2017)054mentioning

confidence: 99%

Extending the Universal One-Loop Effective Action: heavy-light coefficients

Ellis

Quevillon

You

et al. 2017

Self Cite

115

The Universal One-Loop Effective Action (UOLEA) is a general expression for the effective action obtained by evaluating in a model-independent way the one-loop expansion of a functional path integral. It can be used to match UV theories to their low-energy EFTs more efficiently by avoiding redundant steps in the application of functional methods, simplifying the process of obtaining Wilson coefficients of operators up to dimension six. In addition to loops involving only heavy fields, matching may require the inclusion of loops containing both heavy and light particles. Here we use the recentlydeveloped covariant diagram technique to extend the UOLEA to include heavy-light terms which retain the same universal structure as the previously-derived heavy-only terms. As an example of its application, we integrate out a heavy singlet scalar with a linear coupling to a light doublet Higgs. The extension presented here is a first step towards completing the UOLEA to incorporate all possible structures encountered in a covariant derivative expansion of the one-loop path integral.

“…Therefore, we have adopted a top-down approach where there is a model and the aim has been to implement a systematic procedure for getting the low-energy theory, including all loop generated local operators. We have extended the covariant derivative expansion [9,10], taking into account SM extensions where heavy fields are coupled to (light) SM fields with linear (or higher) couplings that are proportional to the scale of new physics. Specific examples have been provided for the singlet extension of the SM and for THDM (I, II,X and Y) models [35].…”

Section: Discussionmentioning

confidence: 99%

“…A second problem, as observed in ref. [6], is that there are cases where the so-called covariant derivative expansion [7][8][9][10] (CDE) does not reproduce all the local operators in the lowenergy sector.…”

Section: Jhep05(2016)162mentioning

confidence: 99%

Low energy behaviour of standard model extensions

Boggia

Gómez-Ambrosio

Passarino

2016

The integration of heavy scalar fields is discussed in a class of BSM models, containing more that one representation for scalars and with mixing. The interplay between integrating out heavy scalars and the Standard Model decoupling limit is examined. In general, the latter cannot be obtained in terms of only one large scale and can only be achieved by imposing further assumptions on the couplings. Systematic low-energy expansions are derived in the more general, non-decoupling scenario, including mixed tree-loop and mixed heavy-light generated operators. The number of local operators is larger than the one usually reported in the literature.