Supersymmetry (SUSY)

Image source: © Particle Data Group
  The theory of Supersymmetry (SUSY) assumes a new symmetry of nature. SUSY predicts for each fermion (matter particle with spin 1/2) a bosonic partner (force particle with integer spin) and vice versa. It is one of the best motivated extensions of the Standard Model and could solve many of its current problems. For instance, SUSY could explain the Higgs mass (hierarchy problem) and delivers a good candidate for the dark matter in our universe. If SUSY is realized in nature, there is a multitude of new particles that we can discover with the LHC. SUSY particles are produced in the strong interaction at the LHC which leads to large expected event yields. As a consequence, there is a good chance that SUSY will be one of the first new-physics signals at the LHC.

What we are working on

Analysis of final states with hadronically decaying taus

Supersymmetry is being searched for at the ATLAS experiment in many different final states, in order to cover a large part of the possible SUSY-parameter space. Final states with several leptons, few or no jets as well as high missing transverse energy are especially interesting in case of a direct electroweak production of gauginos or sleptons, the supersymmetric partners of gauge bosons and leptons in the standard model.
We work at the search for supersymmetry in events with at least 2 hadronically decaying tau leptons – the heaviest sister particles of electrons in the standard model. Hadronically decaying taus are basically narrow jets with special characteristics concerning tracks in the inner detector as well as energy depositions in the calorimeter. Due to the similarity to jets but also to electrons, the discrimination of taus from these objects is, however, a non-trivial task and poses special challenges to analyses using taus.
The analysis of final states with hadronically decaying taus, however, allows access to previously uncovered parameter regions of SUSY due to the underlying mass hierarchies of SUSY particles which are required for the increased production of taus.
Since the first SUSY analyses by ATLAS and CMS in 2010 and 2011 have shown that SUSY is not realized in nature as easily as predicted by the originally favoured SUSY models, only a full coverage of the SUSY parameter space will ensure that we don’t overlook the needle in the haystack.