For Postdocs:

  o Search for Supersymmetry with stau final state
  o Search for Supersymmetry in the single-lepton final state
     using machine learning
  o Search for physics beyond the SM with long-lived particles

For PhD Students:

1. Search for Supersymmetry with focus on search for (in)direct stau production
A favorite SUSY scenario contains the SUSY partners of the tau lepton as second lightest particle, and this stau will then decay to a tau lepton and the lightest SUSY particle. The search for direct stau production is very challenging since the targeted signal has an extremely low cross section. The DESY group is currently leading the search with the following final states: electron+hadronic tau decay, muon+hadronic tau decay, electron+muon. While the cut-based approach is already approved, the next step is to improve the sensitivity using multivariate methods in the final states with two hadronic stau decays and decays to a muon or electron and one hadronic stau decay.

2. Search for new physics beyond the standard model leading to long-lived particles
A field that is currently under-represented by CMS analyses are searches for long-lived particles. These include searches for disappearing or kinked tracks and dE/dx measurements. Long-lived particles are expected in many different models for physics beyond the Standard Model. Particles can be long-lived if they can decay only to a particle that is very close in mass, as predicted in some SUSY models. But while in SUSY the coupling is fixed, other BSM models predict long-lived particles due to very small couplings between a BSM particle and its decay products.
Existing analyses are inclusive, and we are planning to categorize searches for long-lived particles systematically in different categories, e.g. in bins of the number of additional jets. Such scenarios can be described by simplified models, such that results can then be interpreted in different full models. The thesis will also contain work on track reconstruction and the use of multivariate methods will improve the sensitivity of such a search.

3. Search for supersymmetry using machine learning methods
SUSY searches are often characterized by the number of leptons in the final state. Final states with a single isolated lepton allow for a quite inclusive search, since one of the main backgrounds in full-hadronic searches, QCD multijet events, are suppressed by the lepton requirement. This final state has been investigated with cut-based analyses, and the next step is to develop a generic search with machine learning methods.

Technical tasks currently done in the group:
  o MET Scanning (search for events with large missing energy and
     characterization of these events within the JetMET group)
  o MET Tail analysis (on W+jets events)
  o HCAL upgrade with uTCA technology

For Master Students:

There are several SUSY topics possible for master theses. For more information please contact our group leader.