Abstract
In this study we present a universal effective action for one-loop matching of all scalar leptoquarks. We use both the Universal One-Loop Effective Action (UOLEA) and covariant diagrams to evaluate the Wilson coefficients directly in the Green basis for up to dimension-6 operators. On the technical side, we use the newly developed method of evaluating supertraces, to further validate the results stemming from the use of covariant diagrams. As an application, we perform a fully functional matching onto Standard Model Effective Field Theory (SMEFT) of a model with two scalar leptoquark fields: a weak isospin singlet and a doublet. We demonstrate its use by calculating several observables, such as lepton magnetic and electric dipole moments, neutrino masses, proton decay rate, while we comment upon fine tuning issues in this model. Apart from its phenomenological interest, this model generates the majority of dimension-6 operators and provides an EFT benchmark towards future matching automation.
Highlights
Effective field theory (EFT) [1,2,3] is an important part of our understanding of nature, it constitutes a robust way of dealing with new physics phenomena for Beyond the Standard Model (BSM) physics
We demonstrate its use by calculating several observables, such as lepton magnetic and electric dipole moments, neutrino masses, proton decay rate, while we comment upon fine tuning issues in this model
We have chosen to study the decoupling of heavy scalar leptoquark fields for two main reasons: first, there is a plethora of interesting BSM phenomena associated to them, i.e. from neutrino masses and proton decay [38], to possible interpretation of recent flavour anomalies and enhanced anomalous magnetic moment of the muon [39,40,41,42,43,44], and second, leptoquark fields are naturally embedded in Grand Unified Theories (GUTs) which may be in turn linked to even more fundamental theories
Summary
Effective field theory (EFT) [1,2,3] is an important part of our understanding of nature, it constitutes a robust way of dealing with new physics phenomena for Beyond the Standard Model (BSM) physics. Very recently the fermionic UOLEA was constructed [13, 14] and the completion of the fermionic and scalar UOLEA was developed [15] taking mixed statistics into account Another approach to functional matching, which was used to derive the heavy-light part of the UOLEA, are the covariant diagrams [16], which mimic the usual Feynman diagrams but are at all steps gauge-covariant. Finding the X-matrix, and evaluating the Supertrace functional at the desired order in the EFT Lagrangian is what is required for the master formula of eq (1.5) to work This is the functional approach mainly of refs. We have chosen to study the decoupling of heavy scalar leptoquark fields for two main reasons: first, there is a plethora of interesting BSM phenomena associated to them, i.e. from neutrino masses and proton decay [38], to possible interpretation of recent flavour anomalies and enhanced anomalous magnetic moment of the muon [39,40,41,42,43,44], and second, leptoquark fields are naturally embedded in Grand Unified Theories (GUTs) which may be in turn linked to even more fundamental theories
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