Supersymmetric Particle Reconstructions at CMS Massimiliano Chiorboli INFN Catania

Massimiliano Chiorboli 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 7 May 2003 Massimiliano Chiorboli

SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets Massimiliano Chiorboli Decay Chains p b b p  2 high pt isolated leptons OS (leptons = e,m)  2 high pt b jets missing Et  2 high pt isolated leptons OS (leptons = e,m)  2 high pt non-b jets missing Et SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets 7 May 2003 Massimiliano Chiorboli

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 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli 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 7 May 2003 Massimiliano Chiorboli

Reconstruction Method At the end-point: p b 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 7 May 2003 Massimiliano Chiorboli

Reconstruction Method Once the sbottom (or the squark) is reconstructed: p b SM bkg can be reduced cutting on ETmiss The main problem is combinatorial 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli Results @ Point B sSUSY = 57.77 pb → dilepton edge well visible Sbottom Chain Squark Chain 10 fb-1 60 fb-1 300 fb-1 M(sbottom) 500±7 502±4 497±2 M(squark) 536±10 532±2 536±1 s(sbottom) 42±5 41±4 36±3 s(squark) 60±9 36±1 31±1 M(gluino) 594±7 592±4 591±3 592±7 595±2 590±2 s(gluino) 42±7 46±3 39±3 75±5 59±2 gluino 10 fb-1 sbottom chain 10 fb-1 squark chain 10 fb-1 sbottom 1 fb-1 squark 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: 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli 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 300 fb-1 10 fb-1 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli Results @ Point G sbottom gluino Sbottom Chain 300 fb-1 M(sbottom) 720±26 s(sbottom) 81±18 M(gluino) 851±40 s(gluino) 130±43 Squark Chain M(squark) 774±9 s(squark) 84±9 853±11 126±11 squark gluino 300 fb-1 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli Point I I G 300 fb-1 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 B Neutralino BR’s B G I BR(c20→ll) 16.44 2.26 0.25 BR(c20→tt) 83.22 75.88 98.13 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli 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 7 May 2003 Massimiliano Chiorboli

Massimiliano Chiorboli 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 7 May 2003 Massimiliano Chiorboli