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The Next Step

The Next Step. DOE Site Visit Aug 21, 2006. João Guimarães da Costa Harvard University. tt+X Search. tt+E T Search. Top Cross Section. Higgs Search. Top Rare Decays (FCNC). (see Ingyin’s talk). Top sample kinematics. Little Higgs. SUSY: Stop. Improvements in Top Cross Section.

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The Next Step

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  1. The Next Step DOE Site Visit Aug 21, 2006 João Guimarães da Costa Harvard University The Next Steps ---- DOE Visit 2006

  2. tt+X Search tt+ET Search Top Cross Section Higgs Search Top Rare Decays (FCNC) (see Ingyin’s talk) Top sample kinematics Little Higgs SUSY: Stop

  3. Improvements in Top Cross Section Relative Uncertainty (%) Luminosity (pb-1) • Reduce major systematic uncertainties • B-tagging efficiency (see Daniel’s talk) • Background: W + heavy flavor • Smaller improvements • Better treatment of mistags • Improvements in Non-W background estimation • Complementary B-tagging technique • Soft Electron Tagger (see John Paul’s talk) Systematic limited Projections

  4. B-tagging Efficiency Systematic (see Daniel’s talk) Similar technique will be used at LHC

  5. Background: W + Heavy Flavor ~35% of top background is W+HF W+bbX W+cX W+ccX Current uncertainty: ~30%

  6. Cross Section using Jet Spectrum Fit Checking the W + heavy flavor prediction in W+jets data Fit Results W + HF underestimated by 26%

  7. Background: W + Heavy Flavor W+bbX W+cX W+ccX • Difficult to model • W+heavy flavor cross section has large uncertainties • Depend on PDF, hadronization and fragmentations scales and mass of b,c quarks • Heavy flavor fractions cancel most uncertainties Get these from Monte Carlo

  8. Background: W + Heavy Flavor • Calibrate using generic jet data • In Run I, the MC underestimated the gluon splitting component • Measure gluon splitting in data Distance between dijets in ,  space Double Tagged Direct production Gluon splitting Flavor excitation

  9. W+HF Fractions Measurement Run II: • Run 2: Measurement was done with low Et sample ~ 27% uncertainty Gluon splitting Work in Progress Distance between dijets in ,  space

  10. Top Cross Section with Soft Electron Tags Lifetime b-tagger Most decays happen quickly Probability to remain(t) (see John Paul’s talk) e,μ ~ 60% of top events gbct 940 m 470 • Advantages: • Recover b-tagging efficiency • SecVtx: 48% efficient per b-jet • SLT: Extra ~10% per b-jet in top events • Sensitive to different new physics • Discrepancy on cross section would be indication of new physics • Interesting events seen in run I (superjets) • Excess of SecVtx + SLT tagged events ~ 1 mm b P.V. secondary vertex Soft Lepton Tagger primary vertex impact parameter

  11. tt + X: Is there new physics in the top sample? “The most likely place to find new physics is in the tt + X sample……” Nima Arkani-Hamed Top Sample: 408 single tag events 119 double tag events Heavy objects decaying into tt+X would distort the kinematics distributions Event Kinematics Analysis: Double Tag Sample

  12. New Physics in the Large Top Sample? Event Kinematics Analysis KS Probabilities

  13. Heavy Tops: Generic Analysis Heavy pair-produced particles decaying into tt + ET • Heavy Top “T”: • Little Higgs theories • Fermionic particle • Cross Section: ~1pb at 300 GeV • Stop: • Small cross section • Collaborating: • With our colleagues in the theory group • With Kevin and Verena on ATLAS • Massive particle: T • More central events SM top • Larger acceptance Same final state as tt but different kinematics

  14. Heavy Top Search: Kinematics • No killer variable • Large correlations Advance analysis technique Missing Energy (GeV) HT (GeV) W Transverse Mass (GeV)

  15. Heavy Top Search: Neural Net Technique Takes care of correlations automatically • Work in progress: • Cover full range of possible masses • Investigate MC sample with TT production • Look at data Expected Limit

  16. Search for the SM Higgs Measurement done in the W+Jets sample

  17. W+jets Background (W+HF) • W + heavy flavor is major background for Higgs W+HF

  18. Search for the SM Higgs

  19. Conclusions • Top Physics • Transition from statistics limited analysis to systematic limited analysis • Explore new large top sample searching for new physics • Soft electron tagger • Kinematics studies • Search for heavy particles decaying into tt • Higgs Physics • Too early to see SM Higgs at CDF • However, we can establish the ground work for a possible discovery Lots of exciting things to do at CDF

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