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Tutorial - Part 1: Our First Model Point Test

The Model

In this part of the tutorial you will use CheckMATE to test a given Supersymmetry model point. As the model, we will use the famous constrained Minimal Supersymmetric Standard Model (cMSSM): It is defined by five parameters (do not worry: you do not need to understand what they mean, they are just mentioned for completion):

  • a universal scalar mass m0 (here: 2 TeV),
  • a universal gaugino mass m12 (here: 900 GeV),
  • a universal trlinear coupling A0 (here -3.5 TeV),
  • the ratio of the two Higgs vacuum expectation values tanBeta = vu/vd (Here: 20) and
  • the sign of the Higgsino mass parameter sgn(mu) (Here: +)

Supersymmetry predicts that each Standard Model particle p has a 'supersymmetric' partner particle ~p which differs in spin and mass. The gluon, as an example, has a partner called the gluino, which is a spin 1/2 particle (whereas the gluon is spin 0). The masses depend on the parameters of the model. The SUSY particles are usually heavy and - if they are produced - decay into lighter particles. However, a SUSY particle can (in most models) only decay into another SUSY particle and that makes the lightest particle automatically stable. This provides a nice dark matter candidate and produces large amounts of missing transverse energy - a signature which distinguishes it well from the Standard Model.

Using one of the many so-called spectrum generators on the market, one can find the masses and decays of all SUSY particle for the above model point. We have used SoftSUSY[1] for the spectrum and SUSYHIT[2] to find the decay tables. These tools use a common format to store their results, called SUSY Les-Houches Accord (slha).

Please have a quick look at the slha file that corresponds to the above model here.

What are the two lightest colored SUSY particles in the spectrum and what are their masses?
[Show Answer]

What does the gluino predominantly decay into and why?
[Show Answer]

In this first tutorial, we will try to find out whether this model point has been exluded by the 13 TeV LHC run or not.