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

2. Talk Outline lIntroduction lDirect Search for Composite Quarks lContact Interaction Searches lQuark-Quark Compositeness: Dijet Events lQuark-Lepton Compositeness: Drell-Yan Events lRun II Prospects lConclusion

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

4. Effective Lagrangian M cos  

5. Dijet and Dielectron Variables lDijet and di-electron Event Measure the following: Jet, electron 2: E T 2,  2,  2 Jet, electron 1: E T 1,  1,  1  = 0

6. “Typical DØ Dijet Event” E T,1 = 475 GeV,  1 = -0.69, x 1 =0.66 E T,2 = 472 GeV,  2 = 0.69, x 2 =0.66 M JJ = 1.18 TeV Q 2 = 2.2x10 5

7. “Typical CDF Drell-Yan Event”

8. Dijet & Drell-Yan Production lTo search for compositeness we need a good prediction for Standard Model production lDijets: NLO event generator JETRAD, Giele, Glover, Kosower Nucl. Phys. B403, 633. lDrell Yan: NNLO Calculation Hamberg, Van Neerven, & Matsuura, Nucl. Phys. B359 343. lNeed to choose pdf lChoose Renormalization and Factorization scales (set equal) lJets: R sep : maximum separation allowed between two partons to form a jet (mimic exp. algorithm) R sep =1.3R (Snowmass: R sep =2.0R) 2R 1.3R

9. Compositeness Contact Predictions lCompositeness Calulations Eichten 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) l  = +1  + destructive interference  =  1  - constructive interference lOnly leading order calculation: Use to scale highest order QCD calculations. lDijets: Use NLO Jetrad prediction as basis lDrell-Yan Use Hamburg et al., NNLO calculation as a basis. M

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

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

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

13. Search for Excited Quarks lSelect data at central rapidity: DØ: |  jet | < 1.0, |  jet | < 1.6 104 pb -1 Use Bayes Theorem to fit Jetrad NLO QCD prediction + q* line shape to data CDF: |  jet | < 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.

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

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

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

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

18. Dijet Angular Limits Compositeness Limits DØ Coloron Mass Limits M c /cot  > 759 GeV  V8 > 2.1 TeV

19. Dijet Mass Spectrum at DØ lCalculate Ratio of Cross Sections. lAnalgous to R 

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

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

22. Drell-Yan Production lDØ measures the Drell-Yan Cross section at high dielectron mass. l120 pb-1 data |  | < 1.1, 1.5 < |  | < 2.5 lSubmitted to PRL hep-ex/9812010 lCDF measures the Drell-Yan Cross section at high dielectron and dimuon mass. 110 pb-1 data |  | < 1.0 lPhys. Rev. Lett. 79, 2198, 1997.

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

24. Quark-Electron Compositeness Limits

25. Run II Expectations lAssume that we will collect 2 fb -1 of data at 2 TeV lM >510 GeV 2 fb -1 lM >390 GeV 1 fb -1 lM >300 GeV 0.25 fb -1 lM >200 GeV 0.05 fb -1 Limits:  V8 > 3 TeV (cf 2.3) No Optimization lAssume Run 1 Systematics (~5%) lPlace limits using coloron model No optimization of bins (M > 500 GeV >550 events  800 events 0.5 <  < 1.0)

26. Conclusions lNo evidence for Compositeness found at the Tevatron lQCD in excellent agreement with the data lQuark-Quark Compositeness l  > 2 to 3 TeV depending on models lColorons: M c /cot  > 837 GeV lQuark-Electron Compositeness l  > ~ 3 to 6 TeV depending on model lVery Large Data Set in Run II: A Good Opportunity to find New Physics....