3 –Tevatron -> LHC Physics

1. 3 –Tevatron -> LHC Physics • 3.1 QCD - Jets and Di - jets • 3.2 Di - Photons • 3.3 b Pair Production at Fermilab • 3.4 t Pair Production at Fermilab • 3.5 D-Y and Lepton Composites • 3.6 EW Production • W Mass and Width • Pt of W and Z • bb Decays of Z, Jet Spectroscopy • 3.7 Higgs Mass from Precision EW Measurements

2. Kinematics - Review Initial State

3. Review Kinematics - II Final State

4. Jet Et Distribution and Composites Simplest jet measurement - inclusive jet ET . Jet defined as energy in cone, radius R. Classical method to find substructure. Look for wide angle (S wave) scattering. Limits are  ~ s.

5. CDF Run II – Data Reach

6. Dijet Et Distribution – Run I As |3 - 4| increases MJJ increases and the cross section decreases. The plateau width decreases as ET increases (kinematic limit)

7. Dijet Mass Distribution Falls as 1/M3 due to parton scattering and ~ (1- M/s)12 due to structure function source distributions. Look for deviations at large M (composite variations or resonant structure due to excited quarks). Limits at Tevatron and LHC will increase as C.M. energy.

8. Initial, Final State Radiation The initial state has ~ no transverse momentum. Thus a 2 body final state is back-to-back in azimuth. Take the 2 highest Et jets in the 2 J or more sample. At the higher Pt scales available at the LHC ISR and FSR will become increasingly important – determined by the strong coupling constant at that Pt scale.

9. “Running” of s - Measure in 3J/2J Energy below which strong interaction is strong

10. Excited Quark Composites q q* g Look for resonant J - J structure, with a limit ~ C.M. energy

11. t Channel Angular Distribution If t channel exchange describes the dynamics, then  distribution is flat - as in Rutherford scattering. Deviations at large scattering angles would indicate composite quarks.

12. Diphoton, CDF Run II 2--> 2 processes similar to jets. Down by coupling and source factors Also useful in jet balancing for calibration. Important SM background in Higgs searches. Must establish SM photon signals u+g-->u+ (Lecture 2) u+u-->+

13. COMPHEP – Tree Only Tevatron, 2 TeV ||<1, ET>10 GeV

14. B Production @ FNAL d/dPT ~ 1/PT3 so (>) ~ 1/PT2 Spectrum is as expected withPT ~ M/2, g+g --> b + b. Adjustment in b -> B fragmentation function resolves the discrepancy. Establish a b jet signal and b tagging efficiency using 1 tag to 2 tag ratio. Many LHC searches and SM backgrounds (e.g. top pairs) require b tagging.

15. B Production – Rapidity Distribution Note rapidity plateau which extends to y ~ 5 at this low mass, ~ 2mb scale. At the LHC tracking and Si vertexing extends to |y| < 2.5.

16. B Lifetimes Use Si tracker to find decay vertices and the production vertex. (B) ~ (b). For Bc both the b and the c quark can decay ==> shorter lifetime. At LHC establish lifetime scale.

17. Weak Decay Widths Fermi theory Standard Model m W G2 2 body weak decay t -> W b

18. Top Mass and Jet Spectroscopy- Run I D0 - lepton + jets t-->Wb W-->JJ, l

19. Jet Spectroscopy - Top CDF - Lepton + jets (Si or lepton tags) t-->Wb so 2 b’s in the event

20. tt --> Wb+Wb, W--> qq or l CDF + D0 Top quark mass from data taken in the twentieth century

21. Top Mass @ FNAL Run I Run II

22. Top Production Cross Section > 100x gain in going to the LHC. The discovery at the Tevatron becomes a nasty background at the LHC. However, W-> J+J in top pair events sets the calorimeter energy scale at the LHC. Are the mass and the cross section consistent with a quark with SM couplings?

23. Run II Top Cross section No evidence for deviation from SM coupling of a heavy quark. At the LHC top pair events have jets, heavy flavor, missing energy and leptons. They thus serve as a sanity check that the detector is working correctly in many final state SM particles. The LHC experiments must establish a top pair sample before contemplating, for example, SUSY discoveries.

24. DY and Lepton Composites Run I Drell-Yan: Falls with the source function. For ud the W is prominent, while for uu the Z is the main high mass feature. Above that mass there is no SM signal, and searches for composite leptons or sequential W’, Z’ are made.

25. Extract V,A Coupling to Fermions F/B asymmetry allows an extraction of the A and V couplings, gA, gV of fermions to the Z at high mass – compare to SM. If a Z’ is seen at the LHC, use the F/B distribution to try to extract the A and V couplings.

26. Run II – DY High Mass

27. Run II – DY High Mass Whole “zoo” of new Physics candidates – all still null. At LHC establish muon and electron momentum scale and resolution with Z mass and width. Explore tail when backgrounds are under control.

28. W - High Transverse Mass Run I Search DY at high mass for sequential W’. Mass calculated in 2 spatial dimensions only using missing transverse energy.

29. W - SM Mass and Width Prediction Mass: W Width; Color factor of 3 for quarks. 9 distinct dilepton or diquark final states.

30. COMPHEP – W BR Check that the naïve estimates are confirmed in COMPHEP for W and Z into 2*x.

31. W,Z Production Cross Section Cross section x BR for W is ~ 4 pb for Tevatron Run II

32. Lumi with W, Z ? At present in Run II, using W,Z is more accurate than Lumi monitor. Use W and Z at LHC as “standard candles”. Test of trigger and reco efficiencies – cross-check minbias trigger normalization.

33. W and Z - Width and Leptonic B.R. Expect 1/9 ~ 0.11 Expect 9 (0.21 GeV) = 1.9 GeV

34. Direct W Width Measurement Far from the pole mass the Breit – Wigner width (power law) dominates over the Gaussian resolution decay widths of 1.5 to 2.5 GeV Monte Carlo

35. W Transverse Mass D0 and CDF: Transverse plane only. Use Z as a control sample. At large mass dominated by the BW width, since falloff is slow w.r.t the Gaussian resolution.

36. W Mass – Colliders, Run I Hadron WW (LEP II) production near threshold (Lecture 1 )

37. W Mass - All Methods Direct Precision EW measurements

38. I.S.R. and PTW u d W+ g 2-->1 has no F.S. PT. Recall Lecture 2 - charmonium production. Scale is set by the FS mass in 2 -> 1.

39. COMPHEP - PTW Basic 2 --> 2 behavior, 1/PT3. . Gluon radiation from either initial quark.

40. Lepton Asymmetry at Tevatron

41. CDF – Lepton Asymmetry Positron goes in antiproton direction Electron goes in proton direction  Charge asymmetry, constrains PDF. Recall u > d at large x.

42. COMPHEP - Asymmetry COMPHEP generates the asymmetry in pbar-p at 2 TeV. Can use the PDF that COMPHEP has available to check PDF sensitivity. Generate your own asymmetry and look for deviations.

43. Z --> bb, Run I Dijets with 2 decay vertices (b tags). Look for calorimetric J-J mass distribution. Mass resolution, dM ~ 15 GeV. This exercise is practice for searches of J-J spectra such as Z’ decays into di-jets, or H decays into b quark pairs.

44. Run II Mass Resolution Using tracker information to replace distinct energy deposit in the calorimetry for charged particles with the tracker momentum – which is more precisely measured. Seems to gain ~ 20%. This is quite hard – at LHC we will use W->J+J in top pair events.

45. VV at Tevatron - W from D0 The WW  vertex as measured at Run II is consistent with the SM, as it is at LEP II. Transverse mass in leptonic W decays with additional photon.

46. WW at D0 – Run II Look at dileptons plus missing transverse energy. Tests the WWZ and WW  vertex as at LEP - II

47. WW Cross Section Measured at CDF Extrapolate to LHC energy. COMPHEP gives a D-Y WW cross section at the LHC of 72 pb. At LHC will be able to begin to explore W-W scattering independent of Higgs searches.

48. W Mass Corrections Due to Top, Higgs Klein-Gordon Dirac W mass shift due to top (m) and Higgs (M)

49. What is MH and How Do We Measure It? • The Higgs mass is a free parameter in the current “Standard Model” (SM). • Precision data taken on the Z resonance constrains the Higgs mass. Mt = 176 +- 6 GeV, MW = 80.41 +- 0.09 GeV. Lowest order SM predicts that MZ = MW/cosW.. Radiative corrections due to loops. • Note the opposite signs of contributions to mass from fermion and boson loops. Crucial for SUSY and radiative stability. b t H W W W W W

50. CDF D0 Data Favor a Light Higgs