Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session W14: Searches II |
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Sponsoring Units: DPF Chair: Robert Cahn, Lawrence Berkeley National Laboratory Room: Plaza Court 4 |
Tuesday, May 5, 2009 10:45AM - 10:57AM |
W14.00001: Finding Supersymmetry without using Missing Transverse Energy Jeff Haas Missing transverse energy (MET) is a measure of the transverse momentum of particles that escape detection. One needs a complete understanding of the characteristics of the detector to obtain an accurate measurement of MET. Experience at the Tevatron suggests that it may take considerable time and effort to gain such an understanding. Therefore, it is of interest to investigate strategies to search for supersymmetry that do not rely on MET. I will investigate the supersymmetric (SUSY) parameter space accessible with rather low integrated luminosity, 0.1-1.0 fb$^{-1}$, at the Compact Muon Solenoid (CMS) experiment. If SUSY particles are relatively light, then the production cross sections can be huge, in the range $10^{5-6}$ fb, and a discovery in the early stages of running the Large Hadron Collider (LHC) may be possible. For gluino and squarks with masses $m_{\tilde{g}}$ $\sim$ $m_{\tilde{q}}$ $\sim$ 400-750 GeV the expected production cross sections are of the order $10^{4-6}$ fb for a signal with $>$ 3 jets and $>$ 2 isolated leptons. [Preview Abstract] |
Tuesday, May 5, 2009 10:57AM - 11:09AM |
W14.00002: ATLAS sensitivity to leptoquarks and heavy Majorana neutrinos in final states with high-pt dileptons and jets with early LHC data. Vikas Bansal Dilepton-jet final states are used to study physical phenomena not predicted by the standard model. ATLAS discovery potential to leptoquarks and Majorana neutrinos is presented with fully-simulated ATLAS detector at the Large Hadron Collider (LHC) at CERN. The study is motivated by leptoquarks' role in Grand Unification of fundamental forces and the See-saw mechanism that explains the masses of the observed neutrinos. The analysis algorithms are presented, background sources are discussed and the estimates of sensitivity and discovery potential to these processes are reported. [Preview Abstract] |
Tuesday, May 5, 2009 11:09AM - 11:21AM |
W14.00003: Searching for 100 GeV Majorana Neutrinos at the LHC Using Same Sign Dilepton Final State Warren Clarida, Yasar Onel, Taylan Yetkin, Rick Vidal, Weimin Wu, Tao Han, Haifeng Pi, Efe Yazgen The Standard Model can be extended to include massive neutrinos as observed in the recent oscillation experiments. One model introduces a new neutrino with a Majorana nature with an unknown mass. In this study we presented the potential for the discovery of a Majorana neutrino during the first year of data collection from the Large Hadron Collider. We considered the production of a muon and Majorana neutrino that subsequently decays into a muon and W boson. Since the muons have the same sign and there is no missing energy this signal's signature is a lepton number violating final state, which cannot occur in the Standard Model. The signal and background events were produced and analyzed by using CMS software. In the analysis we used muon triggers, muon isolation, jet energy corrections, b-tagging, and an examination of the combinatorial background. The neutrino mass was found by using one of the muons with the partons from the W decay. We found that the mass can be reconstructed reasonably well using one of the isolated muons and two jets with proper jet corrections; whereas the contribution from the various backgrounds was small. We concluded that discovery potential can be reached in the first year of running at the LHC. [Preview Abstract] |
Tuesday, May 5, 2009 11:21AM - 11:33AM |
W14.00004: Trigger study for GMSB with photons Shi-Lei Zang, Uriel Nauenberg, Bernadette Heyburn We present a trigger study for the gauge-mediated SUSY breaking (GMSB) searches at CMS. As a result of the study, we propose to use two new high level triggers based on the electromagnetic calorimeter: EM-high-$E_T$ and EM-very-high-$E_T$, along with the existing double-photon trigger. As a result of the study, we developed a new method for optimization of the trigger thresholds, which uses $log(\epsilon)/log(b)$ as the optimization criteria, where $\epsilon$ ($b$) is the trigger efficiency for signal (background). [Preview Abstract] |
Tuesday, May 5, 2009 11:33AM - 11:45AM |
W14.00005: MUSiC - A Generic Search for Deviations from Monte Carlo Predictions in CMS Carsten Hof We present a model independent analysis approach, systematically scanning the data for deviations from the Standard Model Monte Carlo expectation. Such an analysis can contribute to the understanding of the CMS detector and the tuning of the event generators. Furthermore, due to the minimal theoretical bias this approach is sensitive to a variety of models of new physics, including those not yet thought of. Events are classified into event classes according to their particle content (muons, electrons, photons, jets and missing transverse energy). A broad scan of various distributions is performed, identifying significant deviations from the Monte Carlo simulation. We outline the importance of systematic uncertainties, which are taken into account rigorously within the algorithm. Possible detector effects and generator issues, as well as models involving supersymmetry and new heavy gauge bosons have been used as an input to the search algorithm. [Preview Abstract] |
Tuesday, May 5, 2009 11:45AM - 11:57AM |
W14.00006: Triggering for Hadronically Decaying Tau Leptons at CMS in the Super-LHC Era Michael Mason, Alexei Safonov Signals involving hadronically decaying taus in the final state will remain very important for physics reach of the Large Hadron Collider in the SUPER-LHC era. Greatly increased instantaneous luminosity will lead to an average of up to 200-400 pile-up events per bunch crossing making triggering extremely challenging. To address these challenges, we study various options for extending existing CMS Level-1 tau trigger setup to achieve acceptable trigger rates while preserving high triggering efficiency in the high pile-up environment. We use simulations to evaluate performance of the extended algorithms and compare it to the existing schema. We also discuss potential improvements to trigger performance if tracking capabilities were to become available in the upgraded CMS Level 1 trigger. [Preview Abstract] |
Tuesday, May 5, 2009 11:57AM - 12:09PM |
W14.00007: ATLAS Jet Calibration: layer/cell weighting Belen Salvachua The LHC will provide a very rich jet phenomenology for both standard model and beyond the standard model physics. Jet calibration is essential for understanding the present SM limits and claims on future discoveries. The jet energy scale uncertainty sets the largest constraint on the ATLAS sensitivity to new physics in hadronic channels. As part of its function, the jet calibration accounts for the intrinsic difference between the hadronic and the electromagnetic cascade development. We present a Monte Carlo based jet calibration that combines two different approaches: the so called H1 method which is based on the jet energy density distribution and the so called sampling method, which is based on the longitudinal energy distribution of the jets. First results show good performance for both jet energy resolution and linearity. [Preview Abstract] |
Tuesday, May 5, 2009 12:09PM - 12:21PM |
W14.00008: CMS Detector Sensitivity for the Discovery of Supersimmetry with Two Same-sign Muons, Jets and MET Yuriy Pakhotin Expecting launch of the Large Hadron Collider (LHC) in 2009 the preparations are underway to search for signatures of Supersymmetry (SUSY) or other possible extensions of Standard Model (SM) in the inclusive topology with 2 same-sign muons in final state, using the Compact Muon Solenoid (CMS) experiment. This talk reports on the discovery potential of the CMS with first collected collision data. The CMS performance based on the most recent full detector simulation with start-up 5 TeV proton beams energy of LHC. Strategy to reduce SM background, both from the online CMS High-Level trigger and from offline data analysis is presented. Data driven methods to estimate SM background are reviewed. [Preview Abstract] |
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