Abstract
We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wave-function corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a overline{text {DR}} (or overline{text {MS}}) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop-induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infrared divergences for such cases, which is achieved through an infrared counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiatively induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described.
Highlights
While the large hadron collider (LHC) has completed the standard model (SM) of particle physics with the discovery of a scalar which has all expected properties of the long searched for Higgs boson [1,2,3], there is no indication for new physics up to now
We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models
Whereas wave-function corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a dimensional reduction (DR) scheme
Summary
While the large hadron collider (LHC) has completed the standard model (SM) of particle physics with the discovery of a scalar which has all expected properties of the long searched for Higgs boson [1,2,3], there is no indication for new physics up to now. The available codes to study decays at the oneloop level in the MSSM are SDECAY [79], SUSY_HIT [49] and SFOLD [80] for sfermion decays, FVSFOLD for flavour violating squark as well as gluino decays, and SloopS [76] and CNNDecays [75,77] for neutralino and chargino decays without and with R-parity violation This limited number of codes and supported models has to be seen in contrast to the increasing number of models which are currently studied. Since many particle species receive significant higher-order corrections to their masses and mixing beyond tree level, we allow the inclusion of mass and mixing corrections for the involved external states This needs a careful treatment of the infrared divergences, for which we add an infrared counter-term making use of modified Goldstone boson vertices. The appendix contains all relevant generic expressions for virtual and real corrections as well as a derivation of the employed Goldstone boson vertices
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