Krzysztof Rolbiecki

CheckMATE 2: From the model to the limit

We present the latest developments to the CheckMATE program that allows models of new physics to be easily tested against the recent LHC data. To achieve this goal, the core of CheckMATE now contains over 60 LHC analyses of which 12 are from the 13 TeV run. The main new feature is that CheckMATE 2 now integrates the Monte Carlo event generation via Madgraph and Pythia 8. This allows users to go directly from a SLHA file or UFO model to the result of whether a model is allowed or not. In addition, the integration of the event generation leads to a significant increase in the speed of the program. Many other improvements have also been made, including the possibility to now combine signal regions to give a total likelihood for a model.

Analysis of the neutralino system in three–body leptonic decays of neutralinos

Neutralinos

Can R-parity violation hide vanilla supersymmetry at the LHC?

\tilde{\chi}^0

Constraining compressed supersymmetry using leptonic signatures

in supersymmetric theories, the spin–1/2 Majorana–type superpartners of the U(1) and SU(2) neutral electroweak gauge bosons and SU(2) neutral Higgs bosons, are expected to be among light supersymmetric particles so that they can be produced copiously via direct pair production and/or from cascade decays of other sparticles such as sleptons at the planned Large Hadron Collider and the prospective International Linear Collider. Considering the prospects of having both highly polarized neutralinos and possibility of reconstructing their decay rest frames, we provide a systematic investigation of the three–body leptonic decays of the neutralinos in the minimal supersymmetric standard model and demonstrate alternative ways for probing the Majorana nature of the neutralinos and CP violation in the neutralino system.

Towards measuring the stop mixing angle at the LHC

A bstractCurrent experimental constraints on a large parameter space in supersymmetric models rely on the large missing energy signature. This is usually provided by the lightest neutralino which stability is ensured by R-parity. However, if R-parity is violated, the lightest neutralino decays into the standard model particles and the missing energy cut is not efficient anymore. In particular, the U DD type R-parity violation induces the neutralino decay to three quarks which potentially leads to the most difficult signal to be searched at hadron colliders. In this paper, we study the constraints on R-parity violating supersymmetric models using a same-sign dilepton and a multijet signatures. We show that the gluino and squarks lighter than TeV are already excluded in the constrained minimal supersymmetric standard model with the R-parity violation if their masses are approximately equal. We also analyze constraints in a simplified model with the R-parity violation. We compare how the R-parity violation changes some of the observables typically used to distinguish a supersymmetric signal from standard model backgrounds.

Probing CP violation with and without momentum reconstruction at the LHC

A bstractWe study the impact of the multi-lepton searches at the LHC on supersymmetric models with compressed mass spectra. For such models the acceptances of the usual search strategies are significantly reduced due to requirement of large effective mass and

Early spin determination at the LHC

E_T^{\mathrm{miss}}

CP violation at one loop in the polarization-independent chargino production in e+ e-collisions

. On the other hand, lepton searches do have much lower thresholds for

Combined LHC/ILC analysis of a SUSY scenario with heavy sfermions

E_T^{\mathrm{miss}}

Pinning down the Invisible Sneutrino

and pT of the final state objects. Therefore, if a model with a compressed mass spectrum allows for multi-lepton final states, one could derive constraints using multi-lepton searches. For a class of simplified models we study the exclusion limits using ATLAS multi-lepton search analyses for the final states containing 2-4 electrons or muons with a total integrated luminosity of 1-2 fb−1 at