Post-LHC8 SUSY Benchmarks for the ILC

We constantly review the impact of LHC results on the prospects for Supersymmetry at the ILC. Recently we defined a new set of SUSY Benchmark Models in the light of LHC 8TeV Results.

Simplified SUSY at the ILC

At the ILC, one has the possibility to search for SUSY in an model-independent way: The corner-stone of SUSY is that sparticles couple as particles. This is independent of the mechanism responsible for SUSY breaking. Any model will have one Lightest SUSY Particle (LSP), and one Next to Lightest SUSY Particle (NLSP). In models with conserved R-parity, the NLSP must decay solely to the LSP and the SM partner of the NLSP. Therefore, studying NLSP production and decay can be regarded as a "simplified model without simplification": Any SUSY model will have such a process. The NLSP could be any sparticle: a slepton, an electroweak-ino, or even a squark. However, since there are only a finite number of sparticles, one can systematically search for signals of all possible NLSP:s. This way, the entire space of models that have a kinematically reachable NLSP can be covered. For any NLSP, the "worst case" can be determined, since the SUSY principle allows to calculate the cross-section once the NLSP nature and mass are given. We are investigating the regions in the LSP-NLSP mass-plane where the "worst case" could be discovered or excluded experimentally for various LSP-NLSP combinations.

Light Higgsinos at the ILC

A basic requirement for natural, ie. only minimally fine-tuned SUSY are light higgsinos. If the Bino and the Winos are heavy, then the light chargino and the lightest two neutralinos are nearly pure higgsino states and very close in mass, with a few or even sub-GeV mass splittings. We're investigating the prospects for resolving such near-degenerate states at the ILC.

Bilinear R-Parity Violating SUSY the ILC

Supersymmetry (SUSY) with bilinearly broken R parity offers an attractive possibility to explain the origin of neutrino masses and mixings. Thereby neutralinos become a probe to the neutrino sector since studying neutralino decays gives access to neutrino parameters at colliders. We study the ILC performance in SUSY models with bRPV parameters determined from current neutrino data.

SUSY with stau-coannihilation the ILC and LHC

Simplified models have become a widely used and important tool to cover the more diverse phenomenology beyond constrained SUSY models. However, they come with a substantial number of caveats themselves, and great care needs to be taken when drawing conclusions from limits based on the simplified approach. To illustrate this issue with a concrete example, we examine the applicability of simplified model results to a series of full SUSY model points which all feature a small stau-LSP mass difference, and are compatible with electroweak and flavor precision observables as well as current LHC results. Together with the Helmholtz Young Investigator Group of Isabell Melzer-Pellmann , we're studying various channels using the Snowmass Combined LHC detector implementation in the Delphes simulation package, as well as the Letter of Intent or Technical Design Report simulations of the ILD detector concept at the ILC.
  • Most recent publication on this topic: M. Berggren, A. Cakir, D. Krücker, J. List, A. Lobanov and I. A. Melzer-Pellmann, Non-Simplified SUSY: stau-Coannihilation at LHC and ILC, arXiv:1307.8076 [hep-ph]
  • Most recent presentation on this topic: Poster at EPS-HEP 2013
  • Detailled publication on prospects for measurements in the stau-sector at the ILC: P. Bechtle, M. Berggren, J. List, P. Schade and O. Stempel, Prospects for the study of the stau-system in SPS1a' at the ILC, Phys.\ Rev.\ D {\bf 82} (2010) 055016, arXiv:0908.0876 [hep-ex]

Slepton and gaugino mass reconstruction techniques the ILC

In the presence of two invisible LSPs, the decay chains can only be fully reconstructed in special cases, eg. in this one . Another very clean possibility to determine masses are threshold scans. In the continuum, masses can be reconstructed from kinematic endpoints and edges, eg. in the energy spectrum of the SM daughter particle in the decay. This however depends not only on the detector performance, but also on the beam energy spectrum and on the lineshape of the SM daughter particle if it decays further. Therefore a realistic estimate of achievable precisions requires approriate reconstruction techniques, which we investigate using various examples.

SUSY Parameter Fits in the pMSSM

We're using Fittino to study how well pMSSM parameters can be reconstructed from prospective ILC and LHC measurements.