1. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 1 53 Search for a SM Higgs boson in the ZH→e + e - bb bar final state with the DØ detector at the Tevatron Thesis defense Betty Calpas supervised by Elemér Nagy

2. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 2 53 Outline Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - b-tagging - Multivariate analysis - Results Summary

3. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 3 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

4. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 4 53 The Higgs mechanism was introduced to give SM particles masses (except neutrino). The SM does not predict the H mass, but it is constrained by electroweak measurements and direct searches performed at LEP and Tevatron: - LEP: 114 GeV < M H < 168 GeV at 95% CL. Introduction

5. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 5 53 The main Higgs search channels at the Tevatron at low masses Low mass m H < 135 GeV W/Z associate production

6. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 6 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

7. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 7 53 The Tevatron

8. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 8 53 y θ z x From the center to the exterior: a tracker system (silicon vertex detector and fiber tracker), in a 2T solenoid field, for charged track reconstruction; preshower detectors (CPS) help identify electrons, photons and hadronic jets; a liquid argon calorimeter for electron, photon, and hadronic jet reconstruction; a muon system for muon detection, using scintillators and drift tubes in a 1.2 T toroidal field. The DØ detector P P b ar φ η det = - ln[tan(θ/2)]

9. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 9 53 Run IIa Run IIb 1 Run IIb 2 Apr.02 - Feb.06 Jun.06 - Aug.07 Oct.07 – Jun.09 4.2 fb -1

10. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 10 53 The goal is to look for the Higgs production in association with a Z. The ZH→e + e - bb bar channel is very interesting at the Tevatron. I performed my first service task on the timing of the calorimeter. I did my second service task on the certification of the electrons in the calorimeter. To increase the Z acceptance, I carried out my third service task on the certification of the electrons in the intercryostat region. Finally, my service tasks were used for the Higgs search. 3 years of thesis study

11. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 11 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

12. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 12 53 1- Timing of the calorimeter E ≠ L E = L Goal - the timing of the calorimeter read-out may shift in time; - so we need to verify the correct timing of the calorimeter read-out, - and calculate possible correction factor. The Triple Timing method - the signals are read 3 times (normal - early - late) with 132 ns in interval, - those 3 signals are fit to a simulated signal, - correction factors are calculated. Amplitu de correctio n

13. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 13 53 Calorimeter electronics read-out divided into 12 crates

14. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 14 53 Correction factors for all 55 296 channels

15. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 15 53 (1 - correction factors) for all crates

16. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 16 53 Summary of service task 1 Correction factors for the calorimeter read-out have been calculated. They are negligible in most cases. The calorimeter read-out is stable. Work summarized in the internal note 5495.

17. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 17 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

18. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 18 53 2- Electron identification in the calorimeter

19. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 19 53 - EMfrac : fraction of energy deposit in the EM calorimeter, ; - Hmx : characterise the e shape, based on EM shape of the cluster; - Trackmatch : probability that the e have a track (using ΔR btw the cluster and the track); - Iso : indicate the activity around the e, ; - HoR : likelihood variable based on track, CPS and E T information; - Lhood : likelihood variable based on track information, give the probability that the e is a real e; - NNe : this Neural Net work variable, based on CPS informations, = 0 (if fake) or = 1 (if real e). Cuts for electron identification NNe EMfrac

20. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 20 53 Problem with the increased luminosity Between Run IIa and Run IIb, the instantaneous luminosity has increased by a factor 5, so more background events have been collected. → the Run IIa cuts are not suitable for the Run IIb cuts: Data MC Run IIaRun IIb Data MC

21. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 21 53 Electron identification for CC region New set of definitions have been determined to select electrons in the CC and EC calorimeter at high luminosity. The performance of each cut and their correlation have been studied.

22. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 22 53 Efficiency has been calculated as a function of p T, η, φ,... for different definitions, and for the CC and EC. The Tag and Probe method - Tag e selected with tight cuts to cut down bkg; - Probe e selected with appropriate cuts to optimized signal / bkg. Efficiency calculation

23. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 23 53 Efficiency at high luminosity Efficacite vs pT (VLoose)‏Efficacite vs pT (Tight)‏

24. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 24 53 Efficiency correction Efficiency scale factors (data / MC) have been determined. Scale factors vs pT (VLoose)‏ Scale factors vs pT (Tight)‏ Scale factor ± 1σ uncertainty Scale factor ± 1σ uncertainty

25. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 25 53 Run IIa cuts Run IIb cuts studied Efficiency vs background CC p T = 40 GeV

26. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 26 53 In order to maintain high efficiency for data collected at the increased luminosity, the selection requirements for electrons in the calorimeter have been re-optimized. Efficiencies have been calculated for data and simulation. Efficiency scale factors have been determined so that the simulation matches the data. Work summarized in the internal note 5761. Summary of service task 2

27. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 27 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

28. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 28 53 3- Electron identification in the intercryostat To increase the Z event acceptance - Determine e identification efficiency in the intercryostat region (ICR); - Calculate scale factor. ICD |η det | = 1.1 |η det | = 1.5

29. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 29 53 Specificity of the ICR - because of partial electromagnetic calorimeter coverage in the icr, the e are identified as a tau objets; Type 1 tau: have 1 track and no EM cluster: Type 2 tau: have 1 track and an EM cluster: (found at the edges of ICR). Adequate tau cuts for e identification: - the tau cluster should be in the ICR 1.1 < |η det | < 1.5; - have at least 1 track with hight p T > 20 GeV; - the extrapolation of the track should be in the ICR; - IsoHc4 < 3.0 GeV: total track p T in a hollow cone 0.05 < R < 0.4 around the tau cluster; - NN τ > 0.7 : Neural Net Work cut (using E T, EMfrac, ICDfrac,..); - LHood τ > 0.15 : likelihood cut specific for tau objet (using Emfrac, ICDfrac,...);

30. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 30 53 The efficiency calculation is broken into 3 parts - Tracking efficiency (≈ 80%): probability that a cluster pointing towards the ICR produces a track in the tracking system. - Tau efficiency (≈ 97%): probability that a cluster that has produced a track pointing towards the ICR also produces a Tau object. - Neural Net Work efficiency (≈ 97%): probability that cluster that has produced both a track and a Tau object also passes the NNτ selection cut. The total efficiency is the product of those 3 efficiency (≈ 75%).

31. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 31 53 Summary of service task 3 To increase the Z acceptance, cuts have been defined to select electrons in the intercryostat region. Efficiency of detecting the electron in the ICR is around 80%. To achieve data and simulation agreement, scale factors have been calculated. The Z acceptance increased by 17%. Work summarized in the internal note 5939.

32. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 32 53 Introduction Experimental aspects - The Tevatron - The DØ detector Service tasks 1 - Timing of the calorimeter 2 - Electron identification in the calorimeter 3 - Electron identification in the intercryostat Search for ZH → e + e - bb bar - Data sample and event selection - Background - B-tagging - Multivariate analysis - Results Summary Outline

33. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 33 53 ZHllbb team

34. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 34 53 Event selection (I)‏ Electron selection Events are selected with 2 e in the calorimeter with at least 1 e in the CC: To increase the Z acceptance The dielectron selection is extended to include events with 1 e in the calorimeter plus 1 e reconstructed in the ICR (e icr ) : Z boson selection - the invariant mass of the lepton pair for the 2 channels should be in [60 – 150] GeV; - the z distance between the electron track and the primary vertex should be less than 1 cm. - in 1.1 < |η det | < 1.5; - at least 1 track w/ p T > 20 GeV; - isoHc4 < 3 Gev; - NN τ > 0.7 - LHood τ > 0.15. - in CC |η det | < 1.1 or EC 1.5 < |η det | < 2.5 ; - p T > 15 GeV; - isolation 0.95; - Hmx7(8) < 35 (20) in CC (EC); - NNe 7(3) > 0.2 (0.4) in CC (EC)‏ - have a track in CC.

35. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 35 53 b jet identification: At least one of jets should be tagged as b quark, using the fact that b hadron have long life time: - search for Secondary Vertex L xy ; - calculate jet lifetime probability from the impact parameters d 0 ; - combine these information in a Neural Network. Event selection (II)‏ Jet selection: Events are selected by requiring at least 2 jets: - |η det | < 2.5; - 1st leading jet p T > 20 GeV; - 2nd leading jet p T > 15 GeV; - at least 2 tracks (Run IIb data).

36. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 36 53 OP VT OP L Required 2 orthogonal b jets data set with 2 operating points: 1 and only 1VT jet (OP VT) or 2L jets (OP L).

37. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 37 53 Simulation Electroweak background‏ - Z production with jets light and heavy flavor quarks (Alpgen+Pythia)‏ - Dibosons WW, WZ or ZZ (Pythia) - tt bar (Alpgen+Pythia)‏ Signal - ZH (Pythia), for M H = 100, 105,...150 GeV Correction - Zero bias events have been added to the simulation - Efficiency scale factor, Zp T, jet energy, higher order cross section, jet topology modeling,...

38. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 38 53 Multijet background selection Multijet (from data)‏ - Coming from jets misidentified as leptons - The multijet bkg shape has been obtained by inverting selection cut (Hmx for ee or NN τ for ee icr ) - The number of multijet events has been determined with a fit performed on data and simulation on the M Z distribution: g q q D ij m : nb. data event ; α ij : QCD normalisation factor ; Q ij m : nb. QCD event k ι, k ε : luminosity and efficiency factor ; k Z j : cross section Z+j-jet Z m ij : nb. Z+j-jet event ; O m ij : nb. other bkg (dibosons, tt bar ) ; k X =1 ± σ X.

39. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 39 53 Dilepton invariant mass (inclusive)‏ ee ee icr

40. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 40 53 Combined (ee, ee icr )‏ Di-jet mass before b-tagging (at least 2 jets + Z 60-150 GeV cut )‏

41. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 41 53 Di-jet mass after b-tagging Combined (ee, ee icr ) 2L Combined (ee, ee icr ) 1T

42. Run IIa Cut-flow table ee icr Run IIb

43. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 43 53 Kinematical fit Constraints: M ll = M Z ± 2.5 GeV, Σp x (y) (ZH) = 0 ± 7 GeV. Post-fit, combined (ee, ee icr ) 2LPre-fit, combined (ee, ee icr ) 2L

44. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 44 53 Final discriminant To further separate signal and bkg, a multivariate discriminant analysis tool called Random Forest of binary boosted decision trees (RF), is used (using p T Z, M j1j2...). RF gives a variable btw 0 (bkg) and 1 (signal), which is then used for the limit setting. RF (115 GeV), combined (ee, ee icr ) 2LRF (115 GeV), combined (ee, ee icr ) 1T

45. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 45 53 Systematic errors Flat systematics: do not change the form of the RF distribution: - QCD normalization - higher order cross section, - luminosity, - efficiencies factors Shape systematics: do change the shape of the RF distribution: - Zp T, - jet energy, - jet topology modeling...

46. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 46 53 Bkg subtracted RF distribution of the data (115 GeV), combined (ee, ee icr )‏ after the “profiling” of the systematic errors

47. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 47 53 Signal-bkg separation The upper limit on the Higgs production cross section is calculated at 95% CL with a Poisson log-likelihood ratio (LLR) as test statistics: LLR = -2ln P(N|H S+B ) / P(N|H B ): H S+B and H B : test hypotheses of background with and without signal N : number of events P : poissonian pdf of N: P = e -μ μ N / N! Limit calculation Profiling method: LLR is minimized wrt the nuisance parameters. Confidence level: CL S+B = p(LLR S+B > LLR Obs | H S+B )‏ CL B = P(LLR B > LLR Obs | H B ) CL S = CL S+B / CL B A signal R = (σ Obs ×BR) / (σ Obs ×BR) SM is excluded at 95% CL if CL s (R) = 0.05. S+ B B

48. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 48 53 Limit at 115 GeV exp (obs): 35.5 (27.2) Limits results: ee icr

49. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 49 53 Limit at 115 GeV exp (obs): 12.6 (10.1) Limits results: ee

50. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 50 53 Limit results: combined (ee, ee icr )‏ Limit at 115 GeV exp (obs): 11.5 (8.2) ee icr channel improves the expected limit by 9% wrt that obtained with the ee.

51. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 51 53 Limit results: combined (electrons, muons)‏ Limit at 115 GeV exp (obs): 7.52 (4.83)

52. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 52 53 Result of the ZH→e + e - bb bar search with 4.2 fb -1 has been presented. 1st analysis using the electrons in the ICR, which increase the Z acceptance by 17%, and improves the expected limit by 9% wrt that obtained with the ee. No Higgs signal has been observed, and 95% CL limits on the ZH cross-section x BR(H→bb) for different Higgs masses were set. The shown results are under review for publication. Analysis summary

53. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 53 The stability of the calorimeter read-out has been studied. Good stability have been found. Due to the increased luminosity, selection cuts have been re-optimized to identify electrons in the calorimeter. They show high efficiency. To improve the Z acceptance (17%), the event selection has been extended to include the electrons in the ICR with high efficiency. 95% CL limits on the ZH→l + l - bb bar for different Higgs masses were set with 4.2 fb -1. Those results are under review for publication. 3 years thesis summary

54. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 54 53 Back up slides

55. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 55 53 The Standard Model (SM) uses gauge symmetry which has a consequence that particles are massless, but this is in contradiction with the experiments. The Higgs mechanism was introduced to give particles masses, and this theory can be proven by finding Higgs bosons (H). The SM doesn't predict the H mass, but it is constrained by theory and (in)direct experimental searches performed at LEP and Tevatron: - LEP: 114 GeV< M H <186 GeV Introduction

56. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 56 53 The main Higgs search channels at the Tevatron at low masses σ(pp bar ) = 61 mb

57. Typical Higgs σ x BR < 1 pb. It is hidden by ~ 10 9 x larger bkg. Important SM bkg: W/Z+jets (+ HF)‏ t and tt, WW,WZ,ZZ has been measured. Last benchmark before detecting the Higgs is still to come W Z / Z Z → W / Z (Z→ ) bb hopefully soon

58. Higgs at the LHC

59. ATLAS: calo EM a echantillonnage, structure en mille feuille de plomb et argon liquide. : calo HAD compose de plaque de fer (abs.) et de plaque de scintillateur (actif) CMS: calo EM = cristaux de tungstate de plomb (PbW0 4 ). Calo had = plaque de cuivre (abs.) et plaque de scintillateur (actif.)‏

60. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 60 53 Back up ST1

61. dt (ns) vs scale factor Mean of the scale factor for all crate

62. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 62 53 Back up EMid

63. Based on EM info: - 4 EM energy fractions, - the total EM energy, - vertex z-position transverse shower width in φ and z.

64. using ΔR btw the cluster and the track: Total track pT (>0.5GeV) in a hollow cone 0.05<R<0.4 around the EM cluster Based on CPS info NN7: - EM1frac, - nb cells in EM1 in R cone =0.2, and 0.2<R cone <0.4, - IsoHc4, -nb. Trace in R cone =0.05, - nb cluster in the CPS in R cone =0.1, - a combination of the nb of hit and the energy in the CPS NN3: - IsoHc4, - Hmx8, - nb cells in EM1 in R cone =0.2.

65. Hit & road Likelihood variable using EM3 and primary vertex to define the 3D road, considering the charge of the particles, 2 such roads are defined named left and right road. Counting the number of hits deposited in CFT and SMT along the 4 sigma road. Shower widths of the EM cluster at 3 rd layer of the EM calorimeter in (R, φ). Likelihood using track informations,P traces T, E t traces /p T traces, Hmx.

67. Electron definition p17

72. Back up ICRid

73. ICR cut The NNτ, which exists for all 3 tau types, is designed to distinguish taus from jets; Taus have a NN_h of ~1, while jets have a NN_h of ~ 0. Electrons are much more like taus than jets, so they also tend to have NN_h of close to 1. We cut on NN_h of >02 (loose), >0.7 (Medium), and >0.9 (Tight) in our ICR electron definitions. The LHoodτ was developed by me because we had some electrons reconstructed as type 3 taus and the NN_h for type 3s is does quite poorly at distinguishing electrons from jets. This variable was designed to supplement the NN_h; values close to 0 are jets, with large valuse being more electron-like. The LH_type3 and NN_h are correlated; the problem is that the NN_h was optimized to find real type 3 taus, which have a very different detector signature than electrons.

74. Tau identification in the ICR

75. Tracker efficiency

76. Tau efficiency

77. NN efficiency Loose

78. NN efficiency Medium

79. NN efficiency Tight

80. Back up Analyse

81. Event selection Dimuon Selection (µµ)‏ At least 2 Loose muons in the region |η| < 1.1 p T µ > 10 GeV A central track ΔZ (PV, µ) < 2cm Muon-plus-Track Selection (µµ trk )‏ Exactly one µ, plus additional muons plus track (µ trk )‏ should pass the following cuts: To be in |η| < 2.0, with At least 1 SMT hit p T µtrk > 20 GeV ΔR(µ trk, µ) > 0.1, and ΔR(µ trk, jet) > 0.5 ΔZ (PV, µtrk) < 2cm Scaled Isolation I(µ trk ) < 0.3 Reconstructed Z →µµ 60 < M µµ <150 GeV Opposite sign muons Anticosmics pseudo-acolinearity > 0.05 |PV Z |< 40 cm, and Δ Z (PV, µ) < 2 cm Dielectron Selection (ee)‏ At least 2 electrons in CC |η| < 1.1 or EC 1.5< |η| <2.5 p T e > 15 GeV Isolation 0.95 Good shape in CC or EC, and track in CC ΔZ (PV, e) < 1cm Electron plus ICR Selection (eeicr)‏ Exactly one e, plus additional electron reconstructed as Tau in the ICR should pass the following cuts: To be in 1.1 < |η| < 1.5, with At least 1 SMT hit p T µtrk > 20 GeV NNh > 0.7 Lhood > 0.15 Reconstructed Z →ee 60 < M ee <150 GeV |PV Z |< 40 cm

82. QCD normalisation fit results

83. Corrections apply to MC 1) Lepton energy corrections - the EM resolution is improved by applying a calibration based on the H-Matrix value and mod of the EM shower. We use a processor to correct electron energies in both data and the MC. Subsequently, the energies of MC electrons are smeared using the another. - The energy of the ICR electron is calculated from the track momentum. We apply over-smearing to the track pT. 2) Lepton identification corrections all correction derived for ee and eeicr have been used. 3) Z pT correction The Z boson pT distribution is corrected in MC by reweighting the Z-pT distribution to match the data. The correction is derived from the pT distribution at the generator level and the observed spectrum in the unfolded data. It is then applied with a processor.

84. 4.a) Jet identification - Emfrac 0.05< Emfrac<0.95; - HADfrac< 0.4 for electronic noise in the had. Calo.; - 90% of the jet energy should be in at least 2 tower, to avoid noisy tower; - be confim at L1: pT(jet) / E(tower in a cone[R 0.5. to reduce elec. noise; - MC jets are corrected by the Jet Shifting, Smearing, and Removal (JSSR) processor. The smearing parameters are obtained by fitting the pT imbalance of the photon plus single jet events for both data and the MC.

85. 4.b) Jet correction (data)‏ O: est l'energie dans le cone du jet mais non associee a l'interaction dure comme: - les bruits de fond de l'electronique et de l'uranium, et les effets d'empilement. Ces 3 energies sont mesurees a partir des evenements de bias nul (collectes durant les croisements de faisceaux, mais sans aucune condition de declenchement), et pour lesquels aucun vertex primaire n'a ete reconstruit. - les interactions multiple. Cette energie est mesuree a partir des evenements de biais minimum (collecte durant les croisements de faisceaux mais sans aucune condition de declenchement), et pour lesquels aucun vertex primaire n'a ete reconstruit. En pratique on mesure la densite d'energie moyenne par tour calorimetrique de ces contributions pour differentes multplicite de vertex et en differents intervalles de luminosite instantanee. L'energie O est ensuite calculee en ajoutant l'estimation de la densite d'energie moyenne de toutes les tours calorimetique appartenant au cone de jet. R: est la reponse corrigee du calorimetre. elle tient compte de la perte d'energie dans les materiaux avant le calorimetre (pour eta_det = 0 l'epaisseur est d'environ 3.5 X0), ou dans les zones peu instrumente (l'epaisseur de l'ICR est de 1.1 X0), ou les inhomogeneit d'un module a l'autre. R est mesure a avec des evenements "photon + jet" dos a dos, a partir d'une methode basee sur la conservation de l'energie dans le plan transverse. S: est la fraction d'energie du jet qui a ete deposee a l'exterieur du cone, et de la fraction d'energie deposee dans le cone par des particules n'appartenant pas initialement au jet de particule. D'abord, avec la simulation, on calcule la densite d'energie (ou profil d'energie des jets) en fonction de la distance radiale (dans le plan eta-phi) a l'axe du jet. Ce profile est calcule pour les particules appartenant au jet de particule (E_jet_MC) ainsi que pour toutes les autres particules de l'evenement (E_particule_MC). Ces profiles sont ensuite ajustes au profil global mesure dans les donnees. S est alors le rapport entre l'energie dans le cone du jet (E_jet_MC + E_particule_MC) et l'energie de toutes les particules du jet de particules E_jet_MC.

86. 4.c) Jet correction (MC)‏

87. 4.c) η, ΔR jet correction (MC)‏ Reweighting factors are determined in the Z=+1j and Z=+2j samples. These reweighting functions are then applied to the Z=+nlp, Z=+bb+nlp, and Z=+cc+nlp MC samples.

88. 5) Vertex confirmation correction (Run IIb) Reweighting factors are determined in the Z=+1j and Z=+2j samples. These reweighting functions are then applied to the Z=+nlp, Z=+bb+nlp, and Z=+cc+nlp MC samples. 6) cross section correction (N(N)LO / LO)‏ - Z+light: jet 1.30, - Z+bb: 1.96, - Z+CC: 2.15; - ZZ: 1.03, - WZ: 1.06, - WW:1.01, - tt bar : 1.43 7) Corrections to the Alpgen parameters Possible corrections to the Alpgen parameters used in the simulation, such as renormalization (factorization) scale, k-factor used to determine the scale of s at each vertex, parton matching cluster pT threshold and cluster radius, have been studied. Only the correction for the pT threshold is applied, but the remaining effects are sources of systematic uncertainty. 8) Trigger corrections The trigger effect has been estimate in data, and take into account in MC with processor.

89. 9) Luminosity reweighting After correction 10) Primary vertex reweighting After correction

90. Cut-flow table ee

91. Cut-flow table ee icr

92. 20 variables list used in RF trainning

93. Limit table

94. Betty Calpas Thesis Defense 06/11/2010 Search for a SM Higgs boson 94 53 Systematic errors Flat systematics: do not change the form of the RF distribution like luminosity, cross section, or efficiencies factors Shape systematics: do change the shape of the RF distribution like JES, Jet ID, ZpT reweighting...

95. Limit improvement Tevatron: 163 < M H < 166 GeV @ 95% CL.

96. Perspectives of the SM Higgs searches at the Tevatron Integrate luminosity fb -1 vs time Lowest lum Highest lum Running through FY11 would yield ~10 fb –1 of data for analysis

97. - Add new channels - Increase acceptance - Increase efficiencies using looser event selection - Better object identification (leptons, jets) using MVA - Better signal/bkg separation using MVA - Improve signal and bkg simula theory: higher order corrections experiment: better parameterization of detector effects (resolution, etc.)‏ - Experimental determination of different bkg processes ….. Projected expected limits including improvements

98. 10fb -1 analyzed data allows to… …either exclude the Higgs in the full mass range 100-180 GeVat 95% CL… …or discover it by 3σ evidence with 50% probability at M H =115 GeV