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Search for Compositeness at the Tevatron

Search for Compositeness at the Tevatron. Iain A. Bertram Northwestern University/D Ø. Talk Outline. Introduction Direct Search for Composite Quarks Contact Interaction Searches Quark-Quark Compositeness: Dijet Events Quark-Lepton Compositeness: Drell-Yan Events Run II Prospects

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Search for Compositeness at the Tevatron

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  1. Search for Compositeness at the Tevatron Iain A. Bertram Northwestern University/DØ

  2. Talk Outline • Introduction • Direct Search for Composite Quarks • Contact Interaction Searches • Quark-Quark Compositeness: Dijet Events • Quark-Lepton Compositeness: Drell-Yan Events • Run II Prospects • Conclusion

  3. Three quark and lepton generations suggests that quark and leptons are composites. Composed of PREONS. Preons interact via a new strong interaction (Metacolour). Below a characteristic energy scale , the preons form metacolour singlets: quarks and leptons. Strength of interactions related to Introduction Atom Nucleus Nucleon Quark

  4. Effective Lagrangian cos M

  5. Dijet and Dielectron Variables • Dijet and di-electron Event Measure the following: Jet, electron 1: ET1, h1, 1 Jet, electron 2: ET2, h2, 2 h = 0

  6. “Typical DØ Dijet Event” ET,1 = 475 GeV, h1 = -0.69, x1=0.66 ET,2 = 472 GeV, h2 = 0.69, x2=0.66 MJJ = 1.18 TeV Q2 = 2.2x105

  7. “Typical CDF Drell-Yan Event”

  8. Dijet & Drell-Yan Production • To search for compositeness we need a good prediction for Standard Model production • Dijets: NLO event generator JETRAD, Giele, Glover, Kosower Nucl. Phys. B403, 633. • Drell Yan: NNLO CalculationHamberg, Van Neerven, & Matsuura, Nucl. Phys. B359 343. • Need to choose pdf • Choose Renormalization and Factorization scales (set equal) • Jets: Rsep: maximum separation allowed between two partons to form a jet (mimic exp. algorithm)Rsep=1.3R (Snowmass: Rsep=2.0R) 1.3R 2R

  9. Compositeness CalulationsEichten et al., Rev. Mod. Phys. 56, 579 (84) Eichten et al., Phys. Rev. Lett 50, 811 (83)Chivukula et al., Phys. Lett. B 380, 92 (96)Lee, Phys. Rev. D 55, 2591 (97)Lane, hep-ph/9605257 (96)  = +1 + destructive interference  = -1 - constructive interference Only leading order calculation:Use to scale highest order QCD calculations. Dijets: Use NLO Jetrad prediction as basis Drell-YanUse Hamburg et al., NNLO calculation as a basis. Compositeness Contact Predictions M

  10. Colorons (R.S. Chivukula,A.G. Cohen and E.H. Simmons, hep-ph/9603311,Phys. Lett. B380 92 (1996) Produces similar effects to compositeness. Motivated by technicolor Add additional SU(3) QCD type group. Symmetry breaking between this and standard QCD SU(3) leads to an additional set of massive gluons called colorons Can be modeled in a similar way to compositeness: Colorons

  11. Search for excited quarks in dijet mass spectrum motivated by UA2’s observation of W,Z  JJ (Zeit. Phys. C49)In proton anti-proton collisions. Search for Excited Quarks M

  12. PYTHIA, f=f’=fs=1.0, L*=Mq*, Contact terms only.Smeared with Jet Resolutions, CTEQ3L PDF.Baur et al Phys. Rev. D42, 815 (90) Search for Excited Quarks

  13. Select data at central rapidity: DØ: |hjet| < 1.0, |Dhjet| < 1.6 104 pb-1 Use Bayes Theorem to fit Jetrad NLO QCD prediction + q* line shape to data CDF: |hjet| < 2.0, cos < 2/3 106 pb-1 Phys. Rev. D55, 5263 (1997) Phys. Rev. Lett. 74, 3539 (1995) Fit data with Ansatz Function + q* line shape. Search for Excited Quarks

  14. Search for Excited Quarks CDF: Exclude Mq*up to 570 GeV between 580 & 760 GeV DØ: Mq* > 725 GeV

  15. Search for Excited Quarks Combined Limits Mq* > 760 GeV

  16. Dijet Angular Distribution Search for Quark-Quark Compositeness Compositeness produces excess of events at small  and large mass

  17. Define: Optimize for compositeness:DØ: X=4 CDF: X=2.5 Search for Quark-Quark Compositeness CDF: Phys. Rev. Lett.77, 5336, 1996, Erratum-ibid.78, 4307, 1997 DØ: Phys. Rev. Lett. 80, 666,1998.

  18. Dijet Angular Limits Compositeness Limits DØ Coloron Mass Limits Mc/cot > 759 GeV LV8 > 2.1 TeV

  19. Calculate Ratio of Cross Sections. Analgous to R Dijet Mass Spectrum at DØ

  20. DØ Dijet Mass Spectrum Accepted by PRL: hep-ex/9807014 LL=+1 LL=-1  TeV -4 TeV

  21. Quark-Quark Compositeness Limits Coloron Limit: Mc/cot > 837 GeV (hep-ph/9809472)

  22. DØ measures the Drell-Yan Cross section at high dielectron mass. 120 pb-1 data |h| < 1.1, 1.5 < |h| < 2.5 Submitted to PRL hep-ex/9812010 Drell-Yan Production • CDF measures the Drell-Yan Cross section at high dielectron and dimuon mass. • 110 pb-1 data |h| < 1.0 • Phys. Rev. Lett. 79, 2198, 1997.

  23. High Mass Drell-Yan: Compositeness CDF Data DØ Data

  24. Quark-Electron Compositeness Limits

  25. Assume that we will collect 2 fb-1 of data at 2 TeV M >510 GeV 2 fb-1 M >390 GeV 1 fb-1 M >300 GeV 0.25 fb-1 M >200 GeV 0.05 fb-1 Run II Expectations • Assume Run 1 Systematics (~5%) • Place limits using coloron model • No optimization of bins(M > 500 GeV>550 events |h| < 0.5, >800 events 0.5 < |h| < 1.0) Limits: LV8 > 3 TeV (cf 2.3) No Optimization

  26. Conclusions • No evidence for Compositeness found at the Tevatron • QCD in excellent agreement with the data • Quark-Quark Compositeness •  > 2 to 3 TeV depending on models • Colorons: Mc/cot > 837 GeV • Quark-Electron Compositeness •  > ~ 3 to 6 TeV depending on model • Very Large Data Set in Run II: A Good Opportunity to find New Physics....

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