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Slides for TOP-12-10

Slides for TOP-12-10. D. Barge, C. Campagnari, D. Kovalskyi, V. Krutelyov (UCSB)W. Andrews, G. Cerati, D. Evans, F. Golf, I. MacNeill, S. Padhi, Y. Tu, F. Wuerthwein, A. Yagil, J. Yoo (UCSD)L. Bauerdick, K. Burkett, I. Fisk, Y. Gao, O. Gutsche, B. Hooberman,

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Slides for TOP-12-10

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  1. Slides for TOP-12-10 D. Barge, C. Campagnari, D. Kovalskyi, V. Krutelyov (UCSB)W. Andrews, G. Cerati, D. Evans, F. Golf, I. MacNeill, S. Padhi, Y. Tu, F. Wuerthwein, A. Yagil, J. Yoo (UCSD)L. Bauerdick, K. Burkett, I. Fisk, Y. Gao, O. Gutsche, B. Hooberman, S. Jindariani, J. Linacre, V. Martinez Outschoorn (FNAL)

  2. Documentation Talks: https://indico.cern.ch/getFile.py/access?contribId=1&resId=0&materialId=slides&confId=180584 http://indico.cern.ch/getFile.py/access?contribId=8&sessionId=0&resId=0&materialId=slides&confId=180655 http://indico.cern.ch/getFile.py/access? contribId=1&resId=0&materialId=slides&confId=187624 https://indico.cern.ch/getFile.py/access?contribId=2&resId=0&materialId=slides&confId=190610 https://indico.cern.ch/getFile.py/access?contribId=3&resId=0&materialId=slides&confId=191553

  3. Definition of Observables • We measure the following asymmetry variables in the dilepton final states, inspired by this theory paper: http://arxiv.org/abs/1105.3743 by D. Krohn, T. Liu, J. Shelton, L.T. Wang • lepton charge asymmetry (does not require top reco) • Top charge asymmetry of top • Any significant differences from the SM expectation could be a signal of new physics

  4. Event selection (inclusive) • Event cleaning: if >= 10 tracks; at least 25% purity; at least 1 good DA vertex (not isFake, ndf > 4, rho < 2 cm, z < 24 cm) • 2 opposite sign isolated leptons: pT > 20 GeV, |eta| < 2.5 (2.4) for e (µ) • ≥2 pf jets with pT > 30 GeV, |eta| < 2.5 • loose pfjet ID (L1FastL2L3 corrected) • ∆R > 0.4 from all leptons passing analysis selection • ≥1b tags: CSVM (tighter requirement which suppresses DY significantly) • MET > 30 GeV • Z veto: 76<mll<106 GeV veto (for SF leptons) • mll>12 GeV to veto low mass resonances (SF leptons)

  5. In the following slides, we use pythia-powheg ttbar sample and normalize the ttbar yields such that the total MC yields equal data yields in the inclusive region.

  6. Results in the Inclusive Region PAS reconstructed unfolded No significant discrepancy is observed compared to the SM prediction in the inclusive region

  7. M_ttbar Dependence No significant discrepancy is observed compared to the SM prediction in the high mass region too

  8. Systematics • Systematics for the inclusive measurements • Systematics for the measurement of M_ttbar dependence

  9. Back up

  10. Data-MC comparison • We compare data to sum of MC in the preselection region, using the 3 different ttbar samples for the ttbar->dilepton component • TTJets_TuneZ2_7TeV-madgraph-tauola:madgraph sample, no spin correlations between top and tbar • TTTo2L2Nu2B_7TeV-powheg-pythia6: powheg dilepton sample, with spin correlations • TT_TuneZ2_7TeV-mcatnlo: MC@NLO sample, with spin correlations • All other background samples (including tt->other) are kept the same • All distributions are normalized to unity (shape comparison only) • asymmetry measurements are only sensitive to the shape • K-S calculated using bins of 0.2* plotted width

  11. Shape Comparison

  12. Summary for the Shape Comparison • Asymmetry values and K-S vs data, for preselection region • for variables requiring top reconstruction, only events with solution are used • powheg dilepton ttbar sample seems to best represent the data for these variables

  13. Reconstruction of Top kinematics • In dilepton channel, each event yields two neutrinos. • There is an ambiguity of combining b-jets and leptons from the same top quark. • It is a challenge to reconstruct top mass in the dilepton channel. • We currently use the analytical matrix weighting technique (AMWT) described in http://arxiv.org/abs/arXiv:1105.5661 • Each events is reconstructed using a series of input M_top values between 100-300 GeV with one GeV step. • In order to determine a preferred value of M_top, a weight is assigned to each solution. For each event, the M_top hypothesis with the maximum averaged weight (over solutions) is taken as the reconstructed top mass. • Events without solutions are discarded.

  14. Reconstructed Top Mass About 17% events without solutions. Looks reasonably well

  15. Other distributions in preselection region

  16. Data-driven BG estimates: DY • Estimate for high region: 47.6 ± 10.6 events (stat. uncertainty only) • consistent with MC predictions of 39.9 ± 4.8 events • Estimate for inclusive region: 142.4 ± 15.0 events (stat. uncertainty only) • consistent with MC prediction 126.7 ± 8.7 events

  17. Data-driven BG estimates: Fakes • Estimate for high mass region: 45.9 +108.5-45.9 events (stat. uncertainty only) • consistent with MC prediction of 47.1 ± 5.4 events • Estimate for inclusive region: 138 + 281-138 events (stat. uncertainty only) • consistent with MC prediction 100.1 ± 6.7 events

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