# FlavorKit

## General

FlavorKit is a tool for the study of flavor observables beyond the standard model. We present a new kit for the study of flavor observables beyond the standard model. In contrast to previous flavor codes, FlavorKitis not restricted to a single model, but can be used to obtain predictions for flavor observables in a wide range of models (SUSY and non-SUSY). FlavorKitcan be used in two different ways. The basic usage of FlavorKitallows for the computation of a large number of lepton and quark flavor observables, using generic analytical expressions for the Wilson coefficients of the relevant operators. The setup is based on the public codes SARAHand SPheno, and thus allows for the analytical and numerical computation of the observables in the model defined by the user. If necessary, the user can also go beyond the basic usage and define his own operators and/or observables. For this purpose, a Mathematicapackage called PreSARAHhas been developed. This tool uses FeynArts/FormCalc to compute generic expressions for the required Wilson coefficients at the tree- and 1-loop levels. Similarly, the user can easily implement new observables. With all these tools properly combined, the user can obtain analytical and numerical results for the observables of his interest in the model of his choice. To calculate new flavor observables with SPhenofor a given model the user only needs the definition of the operators and the corresponding expressions for the observables as well as the model file for SARAH. All necessary calculations are done automatically.

## Approach

The critical step in the computation of a flavor observable is the derivation of analytical expressions for the Wilson coefficients of the relevant operators. This step, being model dependent, requires information about the model spectrum and interactions. However, generic expressions can be derived, later to be matched to the specific spectrum and interaction Lagrangian of a given model. For this purpose, we have created a new Mathematicapackage called PreSARAH. This package uses the power of FeynArtsand FormCalcto calculate generic 1-loop amplitudes, to extract the coefficients of the demanded operators, to translate them into the syntax needed for SARAHand to write the necessary wrapper code. PreSARAHworks for any 4-fermion or 2-fermion-1-boson operators and will be extended in the future to include other kinds of operators. The current version already contains a long list of fully implemented operators. The results for the Wilson coefficients obtained with PreSARAHare then interpreted by SARAH, which adapts the generic expressions to the specific details of the model chosen by the user and uses snippets of `Fortran`

code to calculate flavor observables from the resulting Wilson coefficients. As for the operators, there is a long list of observables already implemented. Finally, SARAHcan be used to obtain analytical output in LaTeX format or to create `Fortran`

modules for SPheno, thus making possible numerical studies.

## Using FlavorKit

- FlavorKit Download and Installation
- Basic usage of FlavorKit: making use of already defined observables in FlavorKit
- Advanced usage of FlavorKit: definition of new operators and observables

## Limitations

FlavorKit is a tool intended to be as general as possible. For this reason, there are some limitations compared to codes which perform specific calculations in a specific model. Here we list the main limitations of FlavorKit:

- Chiral resummation is not included because of its large model dependence
- Even though we have included some of the higher order corrections for the SM part of some observables in a parametric way, 2- or higher loop corrections, calculated in the context of the SM or the MSSM for specific observables, are not considered.