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Supersymmetric Particle Reconstructions at CMS

Supersymmetric Particle Reconstructions at CMS. Massimiliano Chiorboli INFN Catania. Up to a couple of years ago, most of attention devoted to inclusive studies I started working in the Physics group on sparticle reconstruction Sbottom, squark ad gluino mass peaks in 3 mSUGRA points.

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Supersymmetric Particle Reconstructions at CMS

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  1. Supersymmetric Particle Reconstructions at CMS Massimiliano Chiorboli INFN Catania

  2. Up to a couple of years ago, most of attention devoted to inclusive studies • I started working in the Physics group on sparticle reconstruction • Sbottom, squark ad gluino mass peaks in 3 mSUGRA points Massimiliano Chiorboli

  3. Decay Chains p b b p •  2 high pt isolated leptons OS (leptons = e,m) •  2 high pt non-b jets • missing Et •  2 high pt isolated leptons OS (leptons = e,m) •  2 high pt b jets • missing Et SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets Massimiliano Chiorboli

  4. Generation and Simulation • SUSY events generated with ISAJET 7.51 + PYTHIA 6.158 • SM bkg events (tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets) generated with PYTHIA 6.158 • Detector simulated with CMSJET 4.801 Massimiliano Chiorboli

  5. Benchmark Points Proposed Post-LEP Benchmarks for Supersymmetry, M. Battaglia et al. (hep-ph/0106204) • Rather low m0 and m1/2 values in order to have high SUSY cross section • Three different tan b values (tan b = 10, 20, 35) since BR(c20 l+l- c10) depends on tan b Massimiliano Chiorboli

  6. p b b p Reconstruction Method At the end-point: • 2 isolated leptons, pT>15 GeV, |h|<2.4 •  2 b-jets, pT>20 GeV, |h|<2.4 • assuming M(c10) known • Selecting events “in edge” • Combining the c20 obtained from the two leptons with the most energetic b-jet in the event Massimiliano Chiorboli

  7. p b b p Reconstruction Method Once the sbottom (or the squark) is reconstructed: • SM bkg can be reduced cutting on ETmiss • The main problem is combinatorial Massimiliano Chiorboli

  8. → dilepton edge well visible 10 fb-1 10 fb-1 sbottom chain squark chain 1 fb-1 10 fb-1 squark sbottom Results @ Point B sSUSY = 57.77 pb gluino Result of the fit: Result of the fit: • Squark mass peaks can be reconstructed in the first few weeks (resolution ~12%) • Sbottom and gluino in the first year (resolution ~6÷8%) • Two independent gluino mass measurements • The resolution can be improved with larger statistics (~5÷6% at 300 fb-1) Generated values Generated value: Massimiliano Chiorboli

  9. 300 fb-1 10 fb-1 Results @ Point G With respect to the Point B: • Lower total SUSY cross section (8.25 pb) • Lower BR’s of useful decays • Higher BR’s of competitive decays • Lower BR of the last decay Massimiliano Chiorboli

  10. squark gluino gluino sbottom Results @ Point G 300 fb-1 Massimiliano Chiorboli

  11. B 300 fb-1 G I Point I • The tau channel is the main one also in the other points • Tau-pair edge is not as sharp as in the e and m case, but could help to cover points in which the reconstruction is problematic • It could be exploited in regions with too low leptonic BR Massimiliano Chiorboli

  12. Conclusions • Supersymmetric Spectroscopy has been attempted • CMS will be capable to reconstruct sparticles with favourable parameters • Point B • squark in the first few weeks (1 fb-1) • sbottom and gluino in the first year (10 fb-1) • Point G • squark, sbottom and gluino with 300 fb-1 • Point I • no recontruction possible with the lepton channel, but it could be useful to investigate other decay chains (e.g. c→tt) • CMS Note in preparation Massimiliano Chiorboli

  13. Future perspectives What can be done… • Re-run the analysis in full simulation • Try to look fo other sparticles in the same points • stop • non-strongly interacting sparticles • Investigate other decay channels • c→tt at Point I (high tan b points) • Explore reconstruction capability at different points Massimiliano Chiorboli

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