arXiv subjects

Krzysztof Rolbiecki

Publications and source records attributed to Krzysztof Rolbiecki.

44 records · Page 3Linked to original sources

arXiv2011

Momentum reconstruction at the LHC for probing CP-violation in the stop sector

We study the potential to observe CP-violating effects in SUSY stop cascade decay chains at the LHC. Asymmetries composed by triple products of momenta of the final state particles are sensitive to CP-violating effects. Due to large boosts that dilute the asymmetries, these can be difficult to observe. If all particle masses in a cascade decay are known, it may be possible to reconstruct all momenta in the decay chains on an event-by-event basis even when we have missing momentum due to a stable LSP. After the reconstruction, the non-diluted CP-violating signal can be recovered and gets significantly enhanced so that an observation may become feasible. A fully hadronic study has been completed to define the areas of the mSUGRA parameter space that may yield a 3-sigma observation with 500 fb^(-1) at the LHC.

hep-ph↗

arXiv2011

Early spin determination at the LHC?

If signals of new physics are discovered at the LHC it will be crucial to determine the spin structure of the new model. We discuss a method that can help to address this question with a low integrated luminosity, L=1 fb^-1, at sqrt{s}=14 TeV. Based on the differences in angular distributions of primarily produced particles we show that a significant difference can be observed in the final state jet-pairs rapidity distance. An additional advantage of the method is that it does not rely on any particular structure of the couplings in the decay chain. We simulate samples for models with supersymmetric and UED-like spin structure and show that a distinction can be made early on.

hep-ph↗

arXiv2011

Towards Measuring the Stop Mixing Angle at the LHC

We address the question of how to determine the stop mixing angle and its CP-violating phase at the LHC. As an observable we discuss ratios of branching ratios for different decay modes of the light stop ~t_1 to charginos and neutralinos. These observables can have a very strong dependence on the parameters of the stop sector. We discuss in detail the origin of these effects. Using various combinations of the ratios of branching ratios we argue that, depending on the scenario, the observable may be promising in exposing the light stop mass, the mixing angle and the CP phase. This will, however, require a good knowledge of the supersymmetric spectrum, which is likely to be achievable only in combination with results from a linear collider.

hep-ph↗

arXiv2010

Tau-Sneutrino NLSP and Multilepton Signatures at the LHC

In models with gravitino as the lightest supersymmetric particle(LSP), the next to lightest supersymmetric particle (NLSP) can have a long lifetime and appear stable in collider experiments. We study the leptonic signatures of such a scenario with tau-sneutrino as the NLSP, which is realized in the non-universal Higgs masses scenario. We focus on an interesting trilepton signature with two like-sign taus and an electron or a muon of opposite sign. The neutralinos and charginos are quite heavy in the model considered, and the trilepton signal comes mostly from the slepton-sneutrino production. We identify the relevant backgrounds, taking into account tau decays, and devise a set of cuts to optimize this trilepton signal. We simulate signal and backgrounds at the LHC with 14 TeV center-of-mass energy. Although the sleptons in this model are relatively light, O(100 GeV), discovery is more demanding compared to typical neutralino LSP scenarios. The trilepton signal requires large amount of accumulated data, at least ~80 fb^-1, at the CM energy of 14 TeV.

hep-ph↗

arXiv2008

CP violation in the chargino/neutralino sector of the MSSM

The CP-violating effects in the neutralino sector of the MSSM can be observed in event-counting type experiments, i.e. without the need of exploiting variables sensitive to beam or neutralino polarization. On the other hand, such CP-odd effects in the chargino sector can be generated only at the loop level. We contrast the two sectors and present results of full one-loop analysis of the CP-odd asymmetry in the non-diagonal chargino pair production in e+e- collisions.

hep-ph↗

arXiv2007

One-loop corrections to three-body leptonic chargino decays

We calculate full one-loop corrections to the genuine three-body decays of the light chargino χ_1^\pm to χ^0_1 l^\pm νin the Minimal Supersymmetric Standard Model. We find that the corrections to the decay width can be of the order of a few percent. We show also how radiative corrections affect energy and angular distributions of the final lepton.

hep-ph↗

arXiv2007

CP violation in chargino production in e+e- collisions

We present the analysis of CP-violating effects in non-diagonal chargino pair production in e+e- collisions. These effects appear only at the one-loop level. We show that CP-odd asymmetries in chargino production are sensitive to the phases of mu and A_t parameters and can be of the order of a few %.

hep-ph↗

arXiv2007

Polarization-independent CP-odd Observable in e^+e^- Chargino Production at One Loop

We discuss CP violation in the process e^+e^- \to \tildeχ^+_i\tildeχ^-_j with unpolarized beams. When the scalars are heavy, the box-diagram results constitute a major part of the full result. However, there are situations when the vertex and self-energy corrections dominate over the box diagrams. We also comment on CP violation in the final chargino decay.

hep-ph↗