SUSY-HIT for Flavour-Violating Stop Decays

released by Ramona Gröber, Margarete Mühlleitner, Eva Popenda, Alexander Wlotzka

A Fortran package for the calculation of the decay widths and branching ratios of the light stop including tree-level FCNC couplings. This calculation applies for scenarios, where the lightest SUSY particle is the lightest neutralino and the next-to-lightest SUSY particle is the lightest squark, which is mostly stop-like, and where the mass difference between these two particles is below the threshold of the stop 3-body decay into the lightest neutralino, the W boson and a bottom quark.
New since 22 Feb 2015 is the extension of the three-body decay into W b neutralino1 to the FV case and the proper treatment of the threshold region between this three- and the four-body decay as well of the threshold region between this three-body decay and the two-body decay into top neutralino. For both threshold regions the respective off-shell decay is calculated up to 30 GeV above the corresponding threshold. From then on the respective on-shell decay is given out.


In order to install and run the code download and unpack the file susyhit.tar.gz. Type 'make' in order to compile the program. An executable called 'run' is created. Type './run' to run the executable.

Note, that flavour violation has only been implemented for the light stop decays and not for other SUSY particle nor Higgs decays. Also the spectrum calculator SuSpect has not been changed to include flavour violation.

For the computation of the flavour violating stop decays the user has to provide an input file in the SLHA2 format! Furthermore, this file has to be called ''. The output is in the SLHA2 format and called 'susyhit_slha2.out'.

In the '' file the option '1' for flavour violation has to be chosen. In this case the FCNC 2-body decay and also the 4-body decay including FCNC couplings are calculated. In the 4-body decay, the user has the choice to sum up all final states that contribute to the 4-body decay (set the related option to '0') or to give out the invidual final state decay widths (set the related option to '1').

The FV 2-body decay into a charm quark and neutralino is evaluated by keeping the charm quark mass dependence at tree-level but neglecting it in the SUSY-QCD corrections. In the SUSY-QCD corrections alpha_s is used in the DRbar scheme at the scale of the stop mass. The computation of the 4-body decay takes roughly 15 min.

In case the FV stop decays are calculated, neither HDECAY nor SuSpect are linked. It therefore does not matter if the first flag in is set equal to '1' or to '2'.


In case of problems related to the SUSY-HIT package including flavour violation please email to Ramona Gröber, Margarete Mühlleitner

Last modified: Wed Aug 21 06:03:24 CEST 2014