XXXIV International Meeting on Fundamental Physics

1. Physics at the Tevatron XXXIV International Meeting on Fundamental Physics From HERA and the TEVATRON to the LHC Rick Field University of Florida (for the CDF & D0 Collaborations) Real Colegio Maria Cristina, El Escorial, Spain 3nd Lecture Photons, Bosons, and Jets at the Tevatron CDF Run 2 Rick Field – Florida/CDF/CMS

2. Photons, Bosons, and Jets at the Tevatron • The Direct Photon Cross-Section. Some Cross Sections Measured at the Tevatron • The g + Heavy Quark Cross-Section. and comparisons with theory! • The g + g Cross-Section. • The Z-Boson Cross-Section. • The W-Boson Cross-Section. • The W+Jets, Z+Jets, and Z+b-Jet Cross-Sections. • The W+g and Z+g Cross-Sections. • The W+W Cross-Section. • The Higgs → W+W Cross-Section. • H → W+W with 100 times more data! • The W+Z and Z+Z Cross-Sections. • The Inclusive Jet and DiJet Cross-Sections. Rick Field – Florida/CDF/CMS

3. q g q  The Direct Photon Cross-Section • DØ uses a neural network (NN) with track isolation and calorimeter shower shape variables to separate direct photons from background photons and p0’s! Note rise at low pT! Highest pT(g) is 442 GeV/c (3 events above 300 GeV/c not displayed)! Rick Field – Florida/CDF/CMS

4. g + b/c Cross Sections (CDF) L = 67 pb-1 • b/c-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor. Rick Field – Florida/CDF/CMS

5. g + b/c Cross Sections (CDF) PYTHIA Tune A! L = 67 pb-1 g + b g + c • PYTHIA Tune A correctly predicts the relative amount of u, d, s, c, b quarks within the photon events. ET(g) > 25 GeV Rick Field – Florida/CDF/CMS

6. g + g Cross Section (CDF) L = 207 pb-1 QCD g + g g + gDf g + g mass • Di-Photon cross section with 207 pb-1 of Run 2 data compared with next-to-leading order QCD predictions from DIPHOX and ResBos. Rick Field – Florida/CDF/CMS

7. Z-boson Cross Section (CDF) L = 72 pb-1 QCDDrell-Yan • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF/CMS

8. Z-boson Cross Section (CDF) L = 337 pb-1 • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)! Rick Field – Florida/CDF/CMS

9. Channel for Z→ττ: electron + isolated track One t decays to an electron: τ→e+X (ET(e)> 10 GeV) . One t decays to hadrons: τ → h+X (pT > 15GeV/c). Remove Drell-Yan e+e- and apply event topology cuts for non-Z background. Signal cone Isolation cone The Z→tt Cross Section (CDF) • Taus are difficult to reconstruct at hadron colliders • Exploit event topology to suppress backgrounds (QCD & W+jet). • Measurement of cross section important for Higgs and SUSY analyses. • CDF strategy of hadronic τ reconstruction: • Study charged tracks define signal and isolation cone (isolation = require no tracks in isolation cone). • Use hadronic calorimeter clusters (to suppress electron background). • π0 detected by the CES detector and required to be in the signal cone. • CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of EM calorimeter. New Rick Field – Florida/CDF/CMS

10. 1 and 3 tracks, opposite sign same sign, opposite sign The Z→tt Cross Section (CDF) New • CDF Z→ττ (350 pb-1): 316 Z→ττ candidates. • Novel method for background estimation: main contribution QCD. • τ identification efficiency ~60% with uncertainty about 3%! Rick Field – Florida/CDF/CMS

11. Higgs → tt Search (CDF) events New 140 GeV Higgs Signal! 1 event • Data mass distribution agrees with SM expectation: • MH > 120 GeV: 8.4±0.9 expected, 11 observed. • Fit mass distribution for Higgs Signal (MSSM scenario): • Exclude 140 GeV Higgs at 95% C.L. • Upper limit on cross section times branching ratio. Rick Field – Florida/CDF/CMS

12. W-boson Cross Section (CDF) W Acceptance • Extend electron coverage to the forward region (1.2 < |h| < 2.8)! 48,144 W candidates ~4.5% background overall efficiency of signal ~7% Rick Field – Florida/CDF/CMS

13. 20 Years of Measuring W & Z Rick Field – Florida/CDF/CMS

14. W+Jets Production (CDF) • Background to Top and Higgs Physics. • Testing ground for pQCD in multi-jet environment. L = 320 pb-1 • Restrict sW : • W → e n, |he|< 1.1. • JETCLU jets (R=0.4): • ETjets>15 GeV, |hjet|< 2. • Uncertainties dominated by background subtraction and Jet Energy Scale. LO predictions normalized to data integrated cross sections:  Shape comparison only! Rick Field – Florida/CDF/CMS

15. W+Jets Production (CDF) • Important to study distributions and topological structure of W + Jets! di-jet DR distribution in the W+ ≥2 jet di-jet invariant mass distribution in the W+ ≥2 jet LO predictions normalized to data integrated cross sections:  Shape comparison only! More exhaustive comparisons expected soon!!! Rick Field – Florida/CDF/CMS

16. Z+Jets Production (DØ) • Same physics as W + jets s(Z) ~ s(W)/10, but Z→e+e- cleaner. • Central electrons (|h|<1.1). • MidPoint jets: (R = 0.5, pT > 20 GeV/c, |yjet|<2.5). L = 343 pb-1 PT distribution of the nth jet Z+j MCFM: NLO for Z+1p or Z+2p  good description of the measured cross sections. ME + PS: with MADGRAPH tree level process up to 3 partons  reproduce shape of Njet distributions (Pythia used for PS). Z+2j Z+3j Rick Field – Florida/CDF/CMS

17. Z + b-Jet Production (CDF & DØ) • Important background for new physics! • Leptonic decays for the Z. • Z associated with jets. • CDF: JETCLU, D0: MidPoint: • R = 0.7, |hjet| < 1.5, ET >20 GeV • Look for tagged jets in Z events. L = 335 pb-1 L = 180 pb-1 Extract fraction of b-tagged jets from secondary vertex mass distribution: NO assumption on the charm content. CDF DØ Assumption on the charm content from theoretical prediction: Nc=1.69Nb. Agreement with NLO prediction: Rick Field – Florida/CDF/CMS

18. W + g Cross Sections (CDF) ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF/CMS

19. Z + g Cross Sections (CDF) Note: (W)/(Z) ≈ 4 while (W)/(Z) ≈ 11 ET(g) > 7 GeV R(lg) > 0.7 Rick Field – Florida/CDF/CMS

20. The W+W Cross-Section Campbell & Ellis 1999 Rick Field – Florida/CDF/CMS

21. The W+W Cross-Section (CDF) L = 825 pb-1 We are beginning to study the details of Di-Boson production at the Tevatron! • WW→dileptons + MET • Two leptons pT > 20 GeV/c. • Z veto. • MET > 20 GeV. • Zero jets with ET>15 GeV and |h|<2.5. New Observe 95 events with 37.2 background! Missing ET! Lepton-Pair Mass! ET Sum! Rick Field – Florida/CDF/CMS

22. W+Z → trileptons + MET The Z+W, Z+Z Cross Sections Observe 2 events with a background of 0.9±0.2! Upper Limits Rick Field – Florida/CDF/CMS

23. Di-Bosons at the Tevatron W We are getting closer to the Higgs! Z W+g Z+g W+W W+Z Rick Field – Florida/CDF/CMS

24. Generic Squark and Gluino Search • Selection: • 3 jets with ET>125 GeV, 75 GeV and 25 GeV. • Missing ET>165 GeV. • HT=∑ jet ET > 350 GeV. • Missing ET not along a jet direction: • Avoid jet mismeasurements. • Background: • W/Z+jets with Wl or Z. • Top. • QCD multijets: • Mismeasured jet energies lead to missing ET. PYTHIA Tune A • Observe: 3, Expect: 4.1±1.5. Rick Field – Florida/CDF/CMS

25. Future Higgs & SUSY Searches • CDF and Tevatron running great! • Often world’s best constraints. • Many searches on SUSY, Higgs and other new particles. • Most currewnt analyses based on up to 350 pb-1: • We will analyze 1 fb-1 by summer 2006. • Anticipate 4.4 - 8.6 fb-1 by 2009. • If Tevatron finds no new physics it will provide further important constraints: • And hopefully LHC will then do the job! If we find something the real fun starts: What Is It? Rick Field – Florida/CDF/CMS

26. “Theory Jets” “Tevatron Jets” Jets at Tevatron • Experimental Jets: The study of “real” jets requires a “jet algorithm” and the different algorithms correspond to different observables and give different results! Next-to-leading order parton level calculation 0, 1, 2, or 3 partons! • Experimental Jets: The study of “real” jets requires a good understanding of the calorimeter response! • Experimental Jets: To compare with NLO parton level (and measure structure functions) requires a good understanding of the “underlying event”! Rick Field – Florida/CDF/CMS

27. Jet Corrections • Calorimeter Jets: • We measure “jets” at the “hadron level” in the calorimeter. • We certainly want to correct the “jets” for the detector resolution and effieciency. • Also, we must correct the “jets” for “pile-up”. • Must correct what we measure back to the true “particle level” jets! • Particle Level Jets: • Do we want to make further model dependent corrections? • Do we want to try and subtract the “underlying event” from the “particle level” jets. • This cannot really be done, but if you trust the Monte-Carlo models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models (use PYTHIA Tune A). • Parton Level Jets: • Do we want to use our data to try and extrapolate back to the parton level? • This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models. The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions. Rick Field – Florida/CDF/CMS

28. Inclusive Jet Cross Section (DØ ) • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5) • L= 378 pb-1 • Two rapidity bins • Highest PT jet is 630 GeV/c • Compared with NLO QCD (JetRad, No Rsep) Note that DØ does not make any corrections for hadronization and the “underlying event”!? They compare the NLO parton level directly to their hadron level data! Log-Log Scale! Rick Field – Florida/CDF/CMS

29. Di-Jet Cross Section (DØ) • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5) • L= 143 pb-1 • |yjet| < 0.5 • Compared with NLO QCD (JetRad, Rsep = 1.3) • Update expected soon! Rick Field – Florida/CDF/CMS

30. CTEQ4M PDFsCTEQ4HJ PDFs Run I CDF Inclusive Jet Data(Statistical Errors Only)JetClu RCONE=0.7 0.1<||<0.7R=F=ET /2 RSEP=1.3 CTEQ4HJ CTEQ4M Inclusive Jet Cross Section (CDF) • Run 1 showed a possible excess at large jet ET (see below). • This resulted in new PDF’s with more gluons at large x. • The Run 2 data are consistent with the new structure functions (CTEQ6.1M). Rick Field – Florida/CDF/CMS

31. Inclusive Jet Cross Section (CDF) • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.75) • Data corrected to the hadron level • L= 1.04 fb-1 • 0.1 < |yjet| < 0.7 • Compared with NLO QCD (JetRad, Rsep = 1.3) Sensitive to UE + hadronization effects for PT < 200 GeV/c! Rick Field – Florida/CDF/CMS

32. KT Algorithm • kT Algorithm: • Cluster together calorimeter towers by their kT proximity. • Infrared and collinear safe at all orders of pQCD. • No splitting and merging. • No ad hoc Rsep parameter necessary to compare with parton level. • Every parton, particle, or tower is assigned to a “jet”. • No biases from seed towers. • Favored algorithm in e+e- annihilations! KT Algorithm Will the KT algorithm be effective in the collider environment where there is an “underlying event”? Raw Jet ET = 533 GeV Raw Jet ET = 618 GeV CDF Run 2 Only towers with ET > 0.5 GeV are shown Rick Field – Florida/CDF/CMS

33. KT Inclusive Jet Cross Section (CDF) • KT Algorithm (D = 0.7) • Data corrected to the hadron level • L= 385 pb-1 • 0.1 < |yjet| < 0.7 • Compared with NLO QCD (JetRad) corrected to the hadron level. Sensitive to UE + hadronization effects for PT < 300 GeV/c! Rick Field – Florida/CDF/CMS

34. MidPoint Cone Algorithm (R = 0.7) Hadronization and “Underlying Event” Corrections • Compare the hadronization and “underlying event” corrections for th KT algorithm (D = 0.7) and the MidPoint algorithm (R = 0.7)! Note that DØ does not make any corrections for hadronization and the “underlying event”!? • We see that the KT algorithm (D = 0.7) is slightly more sensitive to the underlying event than the cone algorithm (R = 0.7), but with a good model of the “underlying event” both cross sections can be measured at the Tevatrun! The KT algorithm is slightly more sensitive to the “underlying event”! Rick Field – Florida/CDF/CMS

35. KT Inclusive Jet Cross Section (CDF) NLO parton level theory corrected to the “particle level”! D = 0.5 D = 1.0 Data at the “particle level”! 7 8 7 Correction factors applied to NLO theory! Corrections increase as D increases! Rick Field – Florida/CDF/CMS

36. from Run I Big uncertainty for high-x gluon PDF! High x Gluon PDF • Forward jets measurements put constraints on the high x gluon distribution! Uncertainty on gluon PDF (from CTEQ6) x Rick Field – Florida/CDF/CMS

37. KT Inclusive Jet Cross Section (CDF) • KT Algorithm (D = 0.7). • Data corrected to the hadron level. • L = 385 pb-1. • Five rapidity regions: • |yjet| < 0.1 • 0.1 < |yjet| < 0.7 • 0.7 < |yjet| < 1.1 • 1.1 < |yjet| < 1.6 • 1.6 < |yjet| < 2.1 • Compared with NLO QCD (JetRad) with CTEQ6.1 Excellent agreement over all rapidity ranges! Rick Field – Florida/CDF/CMS

38. Df Jet#1-Jet#2 Jet#1-Jet#2 Df Distribution Jet-Jet Correlations (DØ) • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5) • L= 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005)) • Data/NLO agreement good. Data/HERWIG agreement good. • Data/PYTHIA agreement good provided PARP(67) = 1.0→4.0 (i.e. like Tune A, best fit 2.5). Rick Field – Florida/CDF/CMS