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Top Physics at the ILC: A (selective) Review

Top Physics at the ILC: A (selective) Review. Outline. Review of some basic aspects of top physics Top Threshold Scan Top Pair + Higgs QCD Factorization for Top Mass Reconstruction. New Physics EWSB Precision Test QCD. What we know …. Tevatron (Run I+II).

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Top Physics at the ILC: A (selective) Review

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  1. Top Physics at the ILC: A (selective) Review ILC Physics at Florence, GGI , Sept 12-14, 2007

  2. Outline • Review of some basic aspects of top physics • Top Threshold Scan • Top Pair + Higgs • QCD Factorization for Top Mass Reconstruction • New Physics • EWSB • Precision Test • QCD ILC Physics at Florence, GGI , Sept 12-14, 2007

  3. What we know … Tevatron (Run I+II) Room for “fancy” New Physics ideas Tev, LHC, ILC Room for lots of “hard work” Top quark is SM-like ! ILC Physics at Florence, GGI , Sept 12-14, 2007

  4. What ILC can/will do … Tevatron/LHC: • first incisive tests of SM-top • discovery potential for new physics: heavy resonances, FCNC decays,.. ILC: • high precision measurements • clean experimental environment • precise theoretical calculations • useful in any future scenario ILC Physics at Florence, GGI , Sept 12-14, 2007

  5. Top at the ILC EWSB New Physics • just a heavy quark ? • active role in EWSB ? • constraint on any model EWSB • Higgs mechanism Top Physics Precision Physics QCD Laboratory Summation of QCD effects and polarization essential! • 2nd part of talk ILC Physics at Florence, GGI , Sept 12-14, 2007

  6. Top at the ILC EWSB New Physics • just a heavy quark ? • active role in EWSB ? • constraint on any model EWSB • Higgs mechanism Top Physics Precision Physics QCD Laboratory ILC Physics at Florence, GGI , Sept 12-14, 2007

  7. Top FCNC’s Any signal clear indication for new physics! ILC luminosity range • production more sensitive than decay (larger phase space) • beam polarization improves sensitivity for production ILC Physics at Florence, GGI , Sept 12-14, 2007

  8. Top at the ILC Precision Physics: New Physics • top mass essential parameter for testing • small error and precise mass def. needed EWSB any model at the quantum level Top Physics Precision Physics QCD Laboratory more examples see: Heinemeyer etal. hep-ph/0306181 ILC Physics at Florence, GGI , Sept 12-14, 2007

  9. Top at the ILC Top, the QCD laboratory: New Physics • top mass extremely large: short-distance • top width: provides IR cutoff for low-energy EWSB processes have well convergent pert. exp. top quark dynamics Top Physics Precision Physics QCD Laboratory ILC Physics at Florence, GGI , Sept 12-14, 2007

  10. Top at the ILC Top, the QCD laboratory: New Physics EWSB Chetyrkin, Kuhn, Steinhauser Teubner, AH, etal; Bernreuther etal, Denner, Pozorini etal Penin etal, etc. etc. Jezabek, Kuhn, etal, Teubner, Stewart, Manohar, AH; Penin etal, Melnikov etal, Beneke, Signer etal, Sumino, Kiyo etal. Top Physics Dittmaier etal, Dawson etal,; Denner/Delanger/You etal Farrell, AH Precision Physics QCD Laboratory ILC Physics at Florence, GGI , Sept 12-14, 2007

  11. Top Mass from Threshold Scan Miquel, Martinez; Boogert, Gounaris Threshold Scan “threshold masses” Theoretical Tool: • NRQCD sums singularities ILC Physics at Florence, GGI , Sept 12-14, 2007

  12. Top Mass from Threshold Scan Miquel, Martinez; Boogert, Gounaris Threshold Scan “threshold masses” Theoretical Tool: • NRQCD • Fixed order pert. theory: LL, NLL NNLL (partly) Manohar, Stewart, Teubner; Stahlhofen, AH; Pineda, Signer • RGE-improved pert. theory: LO, NLO, NNLO NNNLO (partly) Teubner AH; Melnikov Yelkovski; Yakovlev; Beneke, Signer Smirnov; Penin, Sumino, Kiyo; Schuller; ILC Physics at Florence, GGI , Sept 12-14, 2007

  13. Top Mass from Threshold Scan Miquel, Martinez; Boogert, Gounaris Threshold Scan “threshold masses” Main experimental problem: • monitoring (Babbha) • parametrization ILC Physics at Florence, GGI , Sept 12-14, 2007

  14. Top Mass from Threshold Scan Miquel, Martinez; Boogert, Gounaris Threshold Scan “threshold masses” “Official” ILC prospect: (Top/QCD working groups) ILC Physics at Florence, GGI , Sept 12-14, 2007

  15. Top Mass from Threshold Scan Miquel, Martinez; Boogert, Gounaris Threshold Scan “threshold masses” Outlook: (Top/QCD working groups) • needed for measurements of • completion of NNLL (RGE-improved) and NNNLO (fixed-order) total cross section • Monte-Carlo for top threshold (total cross section + distribution) • finite life-time corrections (non-factorizable, interference, distributions) • application to squark pair production, etc. ILC Physics at Florence, GGI , Sept 12-14, 2007

  16. Top at the ILC Top, the QCD laboratory: New Physics EWSB Chetyrkin, Kuhn, Steinhauser Teubner, AH, etal; Bernreuther etal, Denner, Pozorini etal Penin etal, etc. etc. Jezabek, Kuhn, etal, Teubner, Stewart, Manohar, AH; Penin etal, Melnikov etal, Beneke, Signer etal, Sumino, Kiyo etal. Top Physics Dittmaier etal, Dawson etal,; Denner/Delanger/You etal Farrell, AH Precision Physics QCD Laboratory ILC Physics at Florence, GGI , Sept 12-14, 2007

  17. Top Yukawa Coupling • very sensitive to CP property of Higgs Bhupal, Djuadi, Godbole, etal • Top quarks are nonrelativistic • Fixed order perturbation theory breaks down • NRQCD treatment necessary • very sensitive to CP properties of Higgs ILC Physics at Florence, GGI , Sept 12-14, 2007

  18. Top Yukawa Coupling Farrell, AH NLL 1-loop tree hard Wilson coeff soft Green fct • factor 2 from summation of terms • factor 2 from polarization • essential for realistic studies Juste ‘02, ‘06 tree-level, no polarization ILC Physics at Florence, GGI , Sept 12-14, 2007

  19. Top at the ILC Top, the QCD laboratory: New Physics EWSB Bernreuther, Brandenburg, etal, Parke, Shadmi etal., etc Bernreuther, Bonciani, Gehrmann, Heinesch, Leineweber, Mastrolia, Remiddi etal., Huber Top Physics Fadin, Khoze; Reisser, AH Beneke, Signer, Zanderighi, etal., Reisser AH Precision Physics QCD Laboratory Denner, Dittmaier, Roth, Wieders; Beenakker etal; Jadach etal. ILC Physics at Florence, GGI , Sept 12-14, 2007

  20. Top Mass Measurements Miquel, Martinez; Boogert, Gounaris ILC Threshold Scan “threshold masses” Tev +LHC + ILC Invariant Mass Reconstruction • data available soon • uncertainties (much) more involved • many different methods available • error around 1 GeV challenging • What mass is measured? • How to quantify a theory error? ILC Physics at Florence, GGI , Sept 12-14, 2007

  21. ILC: Ideal Study Case • No beam remnant : all soft radiation can be assigned to top or antitop Resonance region: ILC at large c.m. energy: • Dijet limit: QCD factorizationá la Korchemsky/Sterman • related to thrust and heavy jet mass event shapes • set up similar to Chekanov/Morgunov analyis except for use of k_T ILC Physics at Florence, GGI , Sept 12-14, 2007

  22. Factorization Theorem Fleming, Mantry, Stewart, AH hep-ph/0703207 SOFT QCD JET JET SCET HQET SOFT LO factorization theorem SOFT JET JET ILC Physics at Florence, GGI , Sept 12-14, 2007

  23. Factorization Theorem Jet functions: • perturbative, any mass scheme • depends on → “jet” mass • Breit-Wigner at tree level Soft function: • non-perturbative • renormalized due to UV divergences • also governs massless dijet thrust and jet mass event distributions Short distance top mass can (in principle) be determined to better than . Korshemsky, Sterman, etal. Bauer, Manohar, Wise, Lee ILC Physics at Florence, GGI , Sept 12-14, 2007

  24. Closing Remarks .. ILC is a precision machine … .. I only touched a few interesting issues … .. plenty of interesting conceptual things to work on … .. QCD aspects of top are no free lunches, needs hard work … .. even in the beyond-SM era… ILC Physics at Florence, GGI , Sept 12-14, 2007

  25. Backup Slides ILC Physics at Florence, GGI , Sept 12-14, 2007

  26. LO Numerical Analysis Single differential distribution: Non-perturbative effects shift the peak to higher energies and broaden the distribution. ILC Physics at Florence, GGI , Sept 12-14, 2007

  27. LO Numerical Analysis Different invariant mass prescriptions/soft functions: Fairly precise determination of jet mass from determination of Q-dependence of the peak position and extrapolation Q to zero ILC Physics at Florence, GGI , Sept 12-14, 2007

  28. Short-distance Top Jet Mass • One-loop: shift in the pole scheme 300 MeV • shift in the pole scheme contains renormalon • jet mass scheme: defined such that peak located at the mass to all orders What mass is measured? Answer: the one that gives the best convergence in the theoretical expansion. Top Jet mass is the scheme where we expect that a LO analysis contains the least theoretical uncertainties. ILC Physics at Florence, GGI , Sept 12-14, 2007

  29. ILC Top Mass Reconstruction Chekanov, Morgunov hep-ex/0301014 All-hadronic channel ILC special every particle is assigned to top or antitop (fully inclusive !!) Event Selection • k_T (Durham) jet algorithm all particles are assigned to exactly 6 jets reduces events for massless quark pair production selects hadronic events Top Reconstruction • 6 jets with momenta • group in pairs of 3: • b-tagging • massless jet pair mass: both invariant masses close to selects back-to-back events reduces combinatorics Analysis: ILC Physics at Florence, GGI , Sept 12-14, 2007

  30. Event Shapes e.g. Thrust distribution on the peak region: Chekanov; Morgunov hep-ex/0301014 ILC Physics at Florence, GGI , Sept 12-14, 2007

  31. Theory Issues for • definition of jet observables • initial state radiation • final state radiation • underlying events • color reconnection & soft gluon interactions • beam remnant • parton distributions • summing large logs • relation to Lagrangian short distance mass Can be addressed in the framework of the ILC. Requires extensions of ILC concepts and other known concepts Hadron event shapes ILC Physics at Florence, GGI , Sept 12-14, 2007

  32. Lepton + Jets ATLAS Reconstruction Methods Plain Method: • W reconstruction + b tagging • Inv. mass from • 100.000 events after cuts Major error sources: • b jet energy scale: • FSR jets: Kinematic Fit: • reconstruct entire event • impose constraints ( e.g. ) • vary unknows freely • b jet energy scale: • FSR jets: Continuous Jet Definition: • plain method for varying cone size: • take weighted average • FSR error reduced Large Events: • select events with • top pair back-to-back decay products in different hemispheres • large cone size around top/antitop jet axes: • and from in-cone momenta • strong sensitivity to soft jets + Underlying Events • Mass scale calibrations (W mass) • UE: • calibration ILC Physics at Florence, GGI , Sept 12-14, 2007

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