A Python package for flavour physics phenomenology in the Standard Model and beyond


State-of-the-art predictions for hundreds of observables, both in the Standard Model and for arbitrary new physics effects (parametrized as Wilson coefficients of dimension-6 operators)


Fit parameters or Wilson coefficients to a host of experimental data included in the package, or supplied by you


Visualize predictions or fit results in publication quality using flavio's predefined plot functions built on the power of matplotlib

Easy to install

Thanks to Python, no compilation is necessary, even when you make changes to the code

Easy to customize

By modifying simple text files, you can change input parameters or choose between different implementations, e.g. for hadronic form factors


Using Jupyter, you can access (or modify!) all the features of flavio in an interactive session (similar to Mathematica)

Featured processes

  • $B^0$, $B_s$, $K^0$, and $D^0$ mixing
  • $B\to K^{(*)}\mu^+\mu^-$ and other exclusive rare $B$ decays
  • Inclusive decays $B\to X_{s,d}\gamma$ and $B\to X_{s,d}l^+l^-$
  • Lepton flavour violating $B$ decays
  • $B\to D^{(*)}\tau\nu$ and other tree-level $B$ decays
  • $K\to \ell\nu$, $K\to \pi\ell\nu$, and $K\to \pi\nu\bar\nu$ decays
  • Lepton flavour violating $\tau$ and $\mu$ decays
  • Neutron EDM

License & disclaimer

The code is released under the MIT license. As such, it is provided “as is” without any warranty.

If you use flavio in a project, please cite:

D. Straub, “flavio: a Python package for flavour and precision phenomenology in the Standard Model and beyond” arXiv:1810.08132

This paper contains many references to results in the literature that went into the code. Please also consider citing the relevant original literature, where the real work was done.

The theme of this web site is based on devAid by Xiaoying Riley, licensed under CC BY 3.0.


Main developer: David Straub

Please file bug reports and make feature requests over at Github