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Prospects for sparticle reconstruction at new SUSY benchmark points Status report

Prospects for sparticle reconstruction at new SUSY benchmark points Status report. ADR for Massimiliano Chiorboli Universita’ and INFN Catania. Benchmark Points. Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204). The goal is to try to reconstruct sparticles

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Prospects for sparticle reconstruction at new SUSY benchmark points Status report

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  1. Prospects for sparticle reconstruction at new SUSY benchmark pointsStatus report ADR for Massimiliano Chiorboli Universita’ and INFN Catania

  2. Benchmark Points Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204) The goal is to try to reconstruct sparticles Last time we showed gluino and sbottom at point B (isajet, 10 fb-1, 300 fb-1), and point G (pythia, 300 fb-1) In mSUGRA scenario, Pythia overestimates the BR of the decay chain to be selected Only ISAJET results in this talk Massimiliano Chiorboli

  3. g 595.1 tL 392.9 bL 496.0 tR 575.9 bR 524.0 c40 361.1 qL 540 c30 339.9 qR 520 c20 174.4 lL 196.5 c2± 361.6 lR 136.2 c1± 173.8 c10 = LSP 95.6 Point B We use the isajet 7.58 parameters as input parameters to pythia 6.152 ISAPYTHIA masses and BR’s (17% bL, 10% bR) (37 % bL, 25% bR) (0.04 %) PYTHIA (16.4%) (60%) (83.2%) (38%) Massimiliano Chiorboli

  4. p b b p Sbottom and Gluino decay chain • Event final state: •  2 high pt isolated leptons OS •  2 high pt b jets • missing Et 10 fb-1 of SUSY events at point B produced with the “ISAPYTHIA” generator Detector simulation: fast simulation (CMSJET 4.801) SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW • 2 SFOS isolated leptons, pT>15 GeV, |h|<2.4 •  2 b-jets, pT>20 GeV, |h|<2.4 B-tagging performed with the FATSIM package of CMSJET: A jet is a b-jet if it contains at least two tracks with a significance sip> sbcut Massimiliano Chiorboli

  5. p ttll, not only b b p First step: c20 l+l- c10 SUSY only SUSY + SM Z+jet E(ll) > 100 GeV ttbar Massimiliano Chiorboli

  6. Dilepton edge fit Etmiss > 150 GeV Cut on the EmissT to have a clean SUSY sample Subtract OFOS lepton pairs to eliminate combinatorial bkg Fit in good agreement with the MC value Massimiliano Chiorboli

  7. p b E(ll) > 100 GeV Etmiss > 150 GeV Eb-jet 1 > 250 GeV b-tag: s>3 SM b p Sbottom reconstruction • 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 10 fb-1 Generated values Result of the fit Massimiliano Chiorboli

  8. p b b p E(ll) > 100 GeV Etmiss > 150 GeV Eb-jet 1 > 250 GeV b-tag: s>3 SM Gluino reconstruction Next step: reconstruct gluinosbottom I associate the reconstructed sbottom to the b-jet closest in angle to it 10 fb-1 Generated values Result of the fit We achieve a resolution better than 10% (still at CMSJET level!) Massimiliano Chiorboli

  9. Non-sbottom squarks: (16.4%) (22.4%) Squark reconstruction The right component is almost negligible I have to select non b-jets: more combinatorial Massimiliano Chiorboli

  10. p jet p jet p jet jet p jet p jet jet jet p jet Squark-gluino event topologies Massimiliano Chiorboli

  11. Event selection • 2 SFOS isolated leptons, pT>15 GeV, |h|<2.4 •  2 jets (not b), pT>20 GeV, |h|<2.4 • b-jet veto (I reject events having 1 jet with s>3) Main squark sources: Massimiliano Chiorboli

  12. SM backgrounds Massimiliano Chiorboli

  13. SM Dilepton edge Reproduce the same procedure as in the sbottom reconstruction method. Start from the dilepton invariant mass edge. E(ll) > 100 GeV Etmiss > 50 GeV Etmiss > 100 GeV Etmiss > 150 GeV It looks much better than the b-jet case. Probably a better understanding of the SM bkg’s is needed Wtb production? Massimiliano Chiorboli

  14. SM Squark reconstruction Etmiss > 50 GeV Etmiss > 100 GeV Etmiss > 150 GeV Selecting the most energetic jet to be combined with the leptons B-quark veto useful but not crucial Use minimum energy for cut for jet Massimiliano Chiorboli

  15. Etmiss > 150 GeV Ejet 1 > 200 GeV anti b-tag: s<2 b-veto SM Squark mass 10 fb-1 Result of the fit Generated values This assumes the mass of the neutralino-1 to be known Massimiliano Chiorboli

  16. Generator level cos(a) Gluino reconstruction try to reconstruct the gluino in squark decay chain with the same method. associate the jet closest in angle to the reconstructed squark Etmiss > 50 GeV Etmiss > 100 GeV Etmiss > 150 GeV Massimiliano Chiorboli

  17. Gluino combinatorial suppression Generator level Un upper cut on the energy of the second jet can suppress jets coming from squarks Associate the jet closest in angle to the reconstructed quark E parton (GeV) 1 jet 2 jet CMSJET E jet (GeV) E jet (GeV) E jet (GeV) Massimiliano Chiorboli

  18. Etmiss > 150 GeV Ejet 1 > 200 GeV anti b-tag: s<2 b-veto Ejet 2 < 80 GeV SM Gluino mass peak 10 fb-1 Result of the fit Generated value Worse resolution but better statistics than the gluino from the sbottom chain Massimiliano Chiorboli

  19. Etmiss > 150 GeV Ejet 1 > 200 GeV anti b-tag: s<2 b-veto Ejet 2 < 80 GeV SM M(gluino)-M(squark) The difference of masses is independent from the neutralino 1 mass 10 fb-1 Result of the fit Generated value Massimiliano Chiorboli

  20. Etmiss > 200 GeV Eb-jet 1 > 150 GeV b-tag: s>3 E(ll) > 100 GeV cos f(b1-gluino) > 0.4 cos f(b1-sbottom) > 0.2 Point B: Sbottom and Gluino 300 fb-1 Result of the fit 300 fb-1 Generated values 300 fb-1 Result of the fit Generated value Massimiliano Chiorboli

  21. Squark and Gluino at 300 fb-1 Result of the fit 300 fb-1 Generated values 300 fb-1 Result of the fit Generated value Massimiliano Chiorboli

  22. Questions of the last meeting • Influence of pile-up at 300 fb-1? • Can bL and bR be distinguished? • Effect of the neutralino 1 mass • Effect of the calo energy scale (syst.) • Precision on •BR (stat: sbottom ~ 5%, squarks ~ 2%) Massimiliano Chiorboli

  23. Effect of the pile-up on the sbottom and gluino reconstruction No pile-up 100 fb-1 Pile-up The background increases and the peaks are shifted on the left Massimiliano Chiorboli

  24. Separation of the two sbottoms Even at high integrated luminosities, it doesn’t seem possible to separate the two sbottoms I try to perform a double gaussian fit on the peak 300 fb-1 Both the mass values and the coefficient seem to be in agreement with the MC Massimiliano Chiorboli

  25. p b b p Sparticle reconstruction Problem c10 measurement! Mass to ~15-25%from study of various decays Gluino Massimiliano Chiorboli

  26. Sensitivity to M(c1) At 300 fb-1 we can perhaps have the M(c1) as input from a LC. To evaluate the effect the error on M(c1) on the sbottom and gluino mass measurements, I reconstruct the peaks changing the M(c1) Since we have a statistical error of 3 GeV at 300 fb-1, to have an uncertainty on the gluino and sbottom mass given by the M(c1) uncertainty smaller than this statistical error, we should know M(c1) with an error less than 3/1.6 = 1.9 GeV Massimiliano Chiorboli

  27. ttll, not only (2.5%) (64%) Point G: dilepton edge ran point G using ISAJET BR’s: E(ll) > 100 GeV 300 fb-1 Massimiliano Chiorboli

  28. SM Point G: dilepton edge 300 fb-1 Etmiss >1 50 GeV Etmiss > 200 GeV Etmiss > 250 GeV Massimiliano Chiorboli

  29. Point G: squark and gluino reconstruction The squark channel seems more efficient than the sbottom one 300 fb-1 Etmiss > 250 GeV Eb-jet 1 > 250 GeV Etmiss > 250 GeV Eb-jet 1 > 250 GeV Eb-jet 2 < 100 GeV Massimiliano Chiorboli

  30. (0.25%) (98%) Point I: dilepton chain 300 fb-1 In this point it’s impossible to reconstruct the decay chain Massimiliano Chiorboli

  31. Results: Direct reconstruction @ POINT B • Squark, sbottom and gluino reconstruction possible even at low integrated luminosity (10 fb-1) with • Resolution <10% • Errors  5-6% if approximate M(c10) M(llmax) (this approximation is valid only in a mSUGRA scenario for which M(c20)  2M(c10)) • Precision on mass 1-2% if M(c10) would be known • Sbottom (L,R) separation possible? • At 300 fb-1 and assuming M(c10) measured from a LC, we can have errors of  0.5% (if not limited to a few %). Systematics? @ POINT G • Sbottom and gluino reconstruction possible only athigh luminosity • At 300 fb-1 we can reconstruct sbottoms and gluino with resolution 7%, errors 1-2%, assuming M(c1) known from a LC Massimiliano Chiorboli

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