Session X11: SUSY

Interpretation of Searches for Supersymmetry with Simplified Models

The results of CMS searches for Supersymmetry are interpreted in the context of Simplified Models. These results are based on data samples with a corresponding integrated luminosity of up to $4.98 fb^{-1}$ produced in proton-proton collisions at a centerof-mass energy of 7 TeV collected by the CMS experiment at the LHC. This analysis provides a compilation of acceptance predictions and cross section upper limits for a range of Simplified Models and mass parameters. The results provide information that can be used to constrain other theoretical models. They also provide a comparison of different CMS search strategies.   

Triggering and signal optimization in a search for SUSY with bottom-quark jets in pp collisions at 8 TeV with CMS

A search is presented for physics beyond the standard model based on events with significant missing transverse energy (MET), at least three jets, and at least one identified bottom-quark jet. The bottom-quark-jets plus MET signature arises in models of so-called natural supersymmetry and is expected to be one of the most accessible SUSY final states at the CERN Large Hadron Collider (LHC). The study is based on a sample of 19 fb-1 collected at 8 TeV with the CMS detector at the LHC in 2012. Particular emphasis is given to the trigger, event selection, and optimization of the analysis selection criteria. The background-determination methods and limits on new physics signatures are described.   

Prediction of top-quark and W boson backgrounds in a search for supersymmetry with b-tagged jets at CMS

Data-driven methods are presented for predicting major sources of standard model backgrounds in a search for supersymmetry at CMS. The data sample is selected from proton-proton collisions with significant hadronic transverse energy, one or more b-tagged jets, and missing transverse energy (MET). Such events can arise in SUSY models with production of top or bottom squarks. The main SM backgrounds for this search involve the production of top-quarks and W bosons where a charged lepton was produced but not observed or identified. We describe methods for predicting the MET spectrum of these backgrounds. These predictions are compared with observations in data and with simulations of gluino production.   

Data-driven estimation of Z-boson backgrounds to new physics with the b-jet and missing transverse energy signature

We present a search for new physics using 19 $\textrm{fb}^{-1}$ of data collected at the Large Hadron Collider (LHC) using the Compact Muon Solenoid (CMS) detector. Events were selected that contained at least three jets, at least one b-quark jet, and large missing transverse energy. A detailed description of a background arising from a Z-boson decaying to a pair of neutrinos ($Z \rightarrow\nu\bar{\nu}$) is presented. Results from our analysis are presented with a discussion on our sensitivity to the $Z\rightarrow\nu\bar{\nu}$ background estimate.   

Search for new physics using events with two same-sign isolated leptons in the final state

Although same-sign di-lepton final states are very rare in the SM context, they appear naturally in many different new physics scenarios such as SUSY where two same-sign leptons can be produced in the decay chain of supersymmetric particles. Same-sign di-leptons accompanied by b-quarks can arise from SUSY processes where 3rd generation quark superpartners are lighter that other squarks, resulting in an abundance of top and bottom quarks produced in the cascade decays. In general, same-sign di-leptons can be particularly sensitive to SUSY models with compressed spectra where the mass of the LSP is very close to the mass of the produced supersymmetric particle, either if it is produced via strong production (squarks or gluinos) when it is accompanied with high hadronic activity or if it is produced via EWK production (charginos or neutralinos) when almost no hadronic activity is present. In all cases, the SUSY decay chain ends with the LSP, which escapes undetected and therefore contributes strongly to the missing E$_{T}$ of the event. We therefore search for SUSY using same-sign di-lepton events with hadronic activity and large missing E$_{T}$, using the full 2012 integrated luminosity and we interpret our results in the context of various SUSY models.   

Search for supersymmetry using events with three leptons, multiple jets, and missing transverse momentum in 8 TeV proton-proton collision data with the ATLAS detector

We describe a search for new physics using events with three leptons, multiple jets, and missing transverse momentum. The search utilizes proton-proton collisions at 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The recorded dataset corresponds to an integrated luminosity of 13 fb$^{-1}$. The rates and kinematic distributions of the observed data are found to be in agreement with Standard Model expectations. Therefore, limits for the production cross-sections are established for two simplified supersymmetry models. The first model is pair production of gluinos that decay into top squarks and quarks. The second model is pair production of bottom squarks decaying into top quarks and charginos.   

Search for chargino and slepton pair production using the $M_{\mathrm{CT}\perp}$ variable

We perform a search for chargino pair-production in 2012 LHC data at $\sqrt{s}$ = 8 TeV with the CMS detector. We search for events with two leptons, missing energy, and no b-tagged jets. We then use the $M_{\mathrm{CT}\perp}$ variable to discriminate against Standard Model backgrounds. Background is estimated using a shape fit to the distribution using data-driven and Monte Carlo template shapes. The data is well-described by the background-only fit, and we observe no evidence of new physics. We interpret these results in terms of limits on two simplified models, one modeling chargino pair-production and the other slepton pair-production.   

Search for Electroweak production of changino and neutralinos

We present the results of a search for electroweak production of charginos and neutralinos at CMS using a dataset collected in 2012. The search uses several final state signatures including multileptons, dileptons$+$dijets, and same-sign dileptons without significant jet activity as well as opposite-sign dileptons. Each of these final states are designed to either target different productions, chargino or neutralino pair or chargino-neutralino pair, or probe difficult regions of phase-space. For example, the same-sing dileptons can extend the sensitivity to chargino-neutralino pair production with subsequent decays to three leptons where one of the leptons is soft and cannot be detected. Such a scenario is likely to happen if the mass difference between the supersymmetric particles produced in the decay chain is small. The results are interpreted using simplified models of electroweak production of charginos and neutralinos.   

Searches for supersymmetry in final states with a Z boson with the ATLAS detector

This talk presents searches for supersymmetry in the final state with events containing a $Z$ boson ($Z\to\ell\ell$, $\ell=e,\mu$), large missing transverse momentum and jets. Two ATLAS analyses are presented, one using a data sample of 1 fb$^{-1}$ collected at $\sqrt{s}=7$ TeV and the other using 6 fb$^{-1}$ collected at $\sqrt{s}=8$ TeV. No excesses above the Standard Model background expectation were observed. The results were interpreted in the context of a general gauge mediation (GGM) scenario, where the lightest supersymmetric particle is the gravitino and the next-to-lightest supersymmetric particle is a Higgsino-like neutralino.