Ruprecht Karls Universität Heidelberg

The formerly official SUSY-MadGraph page!

For the most recent version of Madgraph/Madevent please visit Louvain

Bug fix updates

SMadGraph is a supersymmetric extension to MadGraph, which generates Feynman diagrams for scattering processes at colliders (for example, the Tevatron, LHC and ILC, in likely chronological order) and writes a Fortran77 subroutine which calculates helicity amplitudes based on the famous HELAS library. (For more details, please read the manual. If you are an experimentalist or just not so good at programming simple Fortran77, there will soon be a SUSY version of the web-based event generator MadEvent. Note that there are two (identical) mirrors for this home page: in Edinburgh and in Rochester

If you use SMadGraph for a paper, please reference our official release paper to honor the pain we went through to build this tool for everyone.

At the heart of SMadGraph are six files:

The two .dat files specify the MSSM particle content and its interactions.
The two .inc files provide common blocks to transfer the masses and couplings between HELAS, Xcouplings_susy and the matrix element routines from MadGraph.
Xread_SLHA_rip.f reads the TeV-scale input parameters in the SUSY Les Houches Accord SLHA format.
Xcouplings_susy.f computes numerical values for all couplings from this input.

The SMadGraph MSSM model

We assume the R-parity conserving MSSM with two Higgs doublets and no additional CP violation. NO SUSY breaking scheme is assumed, because the spectrum is taken directly from the SLHA input file! Squark and sleptons mix only in the third generation. CKM and MNS matrices are diagonal.

Four-scalar couplings are not included, because we cannot conceive of any future collider which would be able to produce four SUSY scalars with any discernible rate, or three Higgs bosons for that matter.

Files to download:


To use SMadGraph, put the .dat files in the directory where you run the executable. The table of particles is (antiparticles in parenthesis):
u (u~), d (d~), c (c~), s (s~), t (t~), b (b~)
e- (e+), mu- (mu+), ta- (ta+)
ve (ve~), vm (vm~), vt (vt~)
EW & QCD gauge bosons
w- (w+), z, a, g
Higgs bosons
h1, h2, h3, h- (h+)
ul (ul~), ur (ur~), dl (dl~), dr (dr~)
cl (cl~), cr (cr~), sl (sl~), sr (sr~)
t1 (t1~), t2 (t2~), b1 (b1~), b2 (b2~)
el- (el+), er- (er+)
mul- (mul+), mur- (mur+)
ta1- (ta1+), ta2- (ta2+)
sve (sve~), svm (svm~), svt (svt~)
n1, n2, n3, n4
x1- (x1+), x2- (x2+)

Run the executable and simply specify the scattering process you want. For example:
u g -> ul go g
would give Feynman diagrams and Fortran output to calculate u quark--gluon scattering to an up-left squark, gluino and an extra gluon jet. After entering the process, you get to specify the order in QCD and QED (which includes the weak sector). For the example process, it's 3rd-order QCD (alpha_s^3), but for some processes it's useful to be able to restrict or require minimum order in the various couplings.

Note that the Majorana character of the neutralinos and gluino is handled internally and completely invisibly to the user. There are no additional gymnastics required to deal with these.

To use the output, you need to insert the matrix elements into your favorite Monte Carlo integrator package. For every phase space point generated, in the above example you would call the routine sug_ulgog(pmad,m2s) where pmad(0:3,5) is the momentum vector array for the 5 particles (same order as in the process definition), and m2s is the value returned, |M|^2, summed and averaged over helicities and color. But you also need to initialize everything at the beginning, which is done with something like this block.

Unfortunately, SUSY-MadEvent is not available at this time. We hope to make that public soon.

To produce an SLHA file, use one of the standard SUSY spectrum generators, SoftSusy, SuSpect or SPheno. Alternatively, some people have done some work for you.

If you need to include particle widths, which SMadGraph will also read in automatically from the SLHA format. To generate, use Sdecay. For consistency we recommend running it in leading-order mode.

To make sure SMadGraph is totally 100% bug-free as we formed the Comparison of Automated Tools for the Phenomenological Investigation of SuperSymmetry (CATPISS) collaboration, which verified this. Between Smadgraph, Whizard, and Sherpa we have compared more than 500 simple processes numerically and listed them for you and for eternity.

Tilman, Dave, and Tim

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