(SM) Higgs Physics at the Tevatron Aidan Robson University of Glasgow UK TevFest, Manchester, 11 November 2011

Higgs Physics at the Tevatron 2 W+W+ W–W– Z/  W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– H H required to cancel high- energy behaviour

Indirect constraints Higgs Physics at the Tevatron e+e–e+e– ZHZH Z bbbb m H >114GeV m H <154GeV estimated final precision 3

Higgs Physics at the Tevatron Tevatron combination UK! SM Higgs excluded: 156<m H <177 GeV and 100<m H <108 GeV 4

Higgs Physics at the Tevatron First Tevatron exclusion? 5

Higgs Physics at the Tevatron First Tevatron exclusion! 6 PRD 41 (1990) 1717

Higgs Physics at the Tevatron First Tevatron exclusion! 7 PRD 41 (1990) 1717

Higgs Physics at the Tevatron First Tevatron exclusion! 8 Excluded 200 < m H < 1100 MeV at 90% CL PRD 41 (1990) 1717

9 W  Z   WW tt WZ t ZZ H → WW Tevatron Run 1: Heavy diboson production: only WW observed, 5 events above 1.2 expected bck obs 2007 obs 2008 Higgs Physics at the Tevatron

10 Higgs Physics at the Tevatron

q q’ W/Z H H t,b g g q q’ H W/Z SM Higgs searches m H /GeV gg  H qq  WH qq  qqH qq  ZH Br  / fb Higgs Physics at the Tevatron 11

12/54Higgs Physics at the Tevatron b-tagging Secondary vertex-finding algorithm Attempt to fit tracks to decay vertex Jet probability Compares track impact parameters to measured resolution functions  probability that there are no long-lived particles in jet cone Neural network filters n tracks in secondary vertex p T fraction carried by those tracks goodness of vertex fit vertex mass transverse decay length & significance … Imperial: Tim Scanlon, Stephen Robinson, Gavin Davies FNAL best thesis prize 2006 UK!

13/54Higgs Physics at the Tevatron b-tagging flavour decompositions  probability that there are no long-lived particles in jet cone Imperial: Amber Jenkins, Gavin Davies  (Z+b)/  (Z+jet)=2.24±0.24(stat)±0.27(sys) % (past) Liverpool: Andy Mehta, Beate Heinemann  (Z+b)/  (Z+jet)=1.92±0.22(stat)±0.15(sys) % Z → bb Z + b UK!

ZH → bb cut >0 removes 95% of the QCD background, 65% of the non-QCD background, and keeps 70% of signal most difficult final state among most sensitive channels UK! q q’ Z Z H b b 14 pre-tag single-tag double-tag pre-tag

ZH → bb EWK and jets control regions UK! Higgs Physics at the Tevatron 15 (an earlier iteration)

ZH → bb Exp 4.0xSM Obs 3.2xSM UK! Higgs Physics at the Tevatron 16 double-tag Imperial: Per Jonsson, Tim Scanlon, Michele Petteni, Lydia Lobo, Theodoros Christoudias, Gavin Davies; Manchester: Krisztian Peters, Remigius Mommsen

WH → l bb Results at mH = 115GeV: 95%CL Limits/SM World’s most sensitive low-mass Higgs search q q’ W W H b b l Key issue: estimating W+bb background Shape from MC with normalization from data control regions Higgs Events Exp. Limit Obs. Limit D0 WH →  bb Manchester: Phil Rich, Stefan Soeldner-Rembold

ZH → ll bb Results at mH = 115GeV: 95%CL Limits/SM Exp. Limit Obs. Limit q q’ Z Z H l b b l 18 Higgs Physics at the Tevatron Region I Region II Region III single tight tag double loose tag double tight tag electrons muons ⊗ (past) Liverpool: Andy Mehta D0: Imperial: Michele Petteni, Gavin Davies

WW/WZ  l jj Higgs Physics at the Tevatron 19 σ(WW+WZ ) = 18.1 ± 3.3(stat) ± 2.5(sys) pb 5.2  significance σ(WW+WZ ) = pb 5.4  significance q q’ W W/Z W l j …

WZ/ZZ with V → bb Higgs Physics at the Tevatron 20 σ(WW+WZ  l cs/ l bb) = 1.08 x SM 3.0  significance –0.40 σ(VZ  bb) Multivariate analysis: 2.8σ Mass peak: 2.2σ

 lep  had : Br 45% lepton hadronic tau (1&3prong) 2 jets opposite charge 3 ANN: sig vs: Z , tt, QCD combined for fit Alpgen Z+jets M T (lep,E T ) / GeV/c H →  Higgs Physics at the Tevatron 21 D0 H →  → Jon’s talk Manchester: Mark Owen, Matthew Ford, Stefan Soeldner-Rembold

H →  Exp. Limit Obs. Limit Results at mH = 115GeV: 95%CL Limits/SM W W   W H Higgs Physics at the Tevatron 22/54

WH  l bb(NN) TagLeptonJet SecStx+SecVtxTight2 SecVtx+JPTight2 SecVtx+NntaggerTight2 SecVtx SingleTight2 SecStx+SecVtxIsoTrk2 SecVtx+JPIsoTrk2 SecVtx+NntaggerIsoTrk2 SecVtx SingleIsoTrk2 SecStx+SecVtxForward2 LooseSecVtx+JPForward2 SecVtx+NntaggerForward2 SecVtx SingleForward3 SecStx+SecVtxTight3 LooseSecVtx+JPTight3 SecVtx SingleTight3 SecStx+SecVtx Extend-  3 LooseSecVtx+JP Extend-  3 SecVtx Single Extend-  3 METbb(NN) WH  (l) bb: ZH  bb Tag SecStx+SecVtx SecVtx+JP SecVtx Single ZH  llbb(NN) TagLeptons SecStx+SecVtxHigh S/B SecVtx+JPHigh S/B SecVtx SingleHigh S/B SecStx+SecVtxLow S/B SecVtx+JPLow S/B SecVtx SingleLow S/B W/ZH  jjbb(NN) Tag SecStx+SecVtx WH  l bb(ME) Tag SecStx+SecVtx SecVtx+JP SecVtx Single SecStx+SecVtx SecVtx+JP SecVtx Single Many contributions Higgs Physics at the Tevatron 23 H  H 

Low mass Higgs searches Higgs Physics at the Tevatron 24 LLR b LLR s+b

H → WW discriminating variables: kinematics of 2 leptons; variables describing event topology eg LR with ME; multivariate techniques H t,b g g l l W W analysis strategy: split analysis into orthogonal channels and optimise separately jet multiplicity: different background compositions ETET ETET ee ee 10 3 DY Wj W  tt WZ ZZ DY WW HWWx10 Data kinematics of two leptons variables describing event topology 25 Glasgow: Rick St. Denis, Toby Davies, Peter Bussey, Stan Thompson, Aidan Robson Lancaster: Harald Fox, Scott Braithwaite Manchester: Kostas Petridis ee UK!

26/54Higgs Physics at the Tevatron Matrix element method  Use LO matrix element (MCFM) to compute event probability H  WW  l l WW  l l ZZ  ll W+parton  l +jet W  l +  E T model lepton energy resn pxpypzpxpypz lep1 LO | M | 2 : pxpypzpxpypz lep2 E x, E y parton  lepton fake rate  conversion rate x obs : (with true values y )  Compute likelihood ratio discriminator R = P s P s +  k b i P b i i k b is relative fraction of expected background contrib. P s computed for each m H  Fit templates (separately for high S/B and low S/B dilepton types)

H → WW >1 jet 1 jet tt 0 jet WW UK! Jet multiplicity: different background contributions S:12 S:16 Wj W  tt WZ ZZ DY WW HWW x10 Data S:26 Higgs Physics at the Tevatron 27 Hx10 low m ll S:3

Complementarity Redefine discriminant for WW hypothesis: R’ = P WW P WW +  k b i P b i i  exploit different sensitivities of matrix element / neural net  verify matrix element method: cycle signal – ME is leading order - remove variables that use jet information from neural net for comparison Higgs Physics at the Tevatron 28 σ(pp → WW) = 12.1 ± 0.9(stat) (sys) pb +1.6 –1.4 σ(pp → ZZ) = 1.45 (stat) (sys) pb – –0.42 SM, NLO: (1.4± 0.1) pb SM, NLO: (12.4± 0.8) pb UK!

No channel too small! Higgs Physics at the Tevatron q q’ W+W+ W+W+ H q’ q l+l+ l+l+ l–l– W+W+ W–W– S:3.1 S:1.0 WH S:0.3 ZH UK! trilepton same-sign dilepton NN Output 29 D0 same-sign leptons Manchester: Maiko Takahashi, Tianqi Zhao NN Output

Higgs Physics at the Tevatron Tevatron combination UK! SM Higgs excluded: 156<m H <177 GeV and 100<m H <108 GeV 30

Outlook Integrated luminosity (pb –1 ) On tape: ~ 10 fb -1 per experiment Results shown today : 1-7 fb Diboson Physics at the Tevatron 30 Sept 2011

Higgs Physics at the Tevatron 32 Leaps and bounds CDF WH only CDF high mass only Similar story for D0…

Higgs Physics at the Tevatron 33

To do Higgs Physics at the Tevatron 34 ♦ New methods / propagation of methods: Multivariate QCD rejection QCD modeling improvement More triggers added to loose lepton dataset More lepton categories New combined b-tagger More use of multivariate lepton ID More use of inclusive triggering / regression trigger modeling Clever flavour separation ♦ Exchanging ideas between CDF and D0 ♦ Need to be quick!

Outlook Higgs Physics at the Tevatron ♦ Creative analyses, excellent tools, outstanding measurements that form the basis of LHC Higgs physics programme ♦ A push for Higgs physics with 10/fb – competitive for just a little longer ♦ Higgs within reach! 35 Gavin Davies - Higgs convener TevNPHWG 2009– Jon Hays - TEVNPHWG 2008– Per Jonsson - Higgs group Trigger rep Higgs subgroup convener Krisztian Peters - Higgs convener Kostas Petridis - Higgs subgroup convener (ongoing) Tim Scanlon - Higgs subgroup convener 2009– - B-ID convener 2008– Rick St Denis - Higgs subgroup convener

Higgs Physics at the Tevatron 36

Higgs Physics at the Tevatron 37  Limit-setting  Analysis techniques  Analysis stability  Improving sensitivity  Motivation  Standard Model Basis and indirect searches  Higgs searches: Low mass / high mass channels  Tevatron Combination  Outlook and LHC

Tevatron Higgs Physics at the Tevatron   = 1.0  = 0.6  = 2.0 muon chambers D0  =2  = m tracker had cal hadronic cal EM cal had cal solenoid pre-radiatorshower max silicon E M cal  =1 CDF Fibre tracker to |  |<1.8 Calorimeter to |  |<4 Muon system to |  |<2 Drift chamber to |  |<1 Further tracking from Si Calorimeter to |  |<3 Muon system to |  |<1.5 38

Higgs Physics at the Tevatron Jets W/Z Higgs Susy quark top bottom quark  m s =17.77 ± 0.10 ± 0.07 dibosons 39

Higgs Physics at the Tevatron H g g p p 40

q q’ W/Z/  W/Z W/Z/  Dibosons photon E T (GeV) events Z Z Z    non-SM h 3, ZZ  |h 3 | < 0.037, |h 4 | < (  =1.2TeV) h 3, Z  SM non-SM W  Z   WW tt WZ t ZZ H → WW Higgs Physics at the Tevatron 41

ZZ seen in 4 lepton at 5.7σ All now observed! Dibosons W  Z   WW tt WZ t ZZ H → WW q q’ W Z/  W Z Z q q’ UK! 42 Higgs Physics at the Tevatron σ(pp → WZ) = (4.1 ± 0.7) pb σ(pp → ZZ ) = ( (stat) ± 0.2 (syst)) pb

Limit setting Higgs Physics at the Tevatron 43 background suppression signal separation Background Higgs signal x 10 events X X = some observable H 1 =SM+Higgs (of mass m H ) H 0 =SM only  Construct test statistic Q = P(data|H 1 )/P(data|H 0 ) –2lnQ =  2 (data|H 1 ) –  2 (data|H 0 ), marginalized over nuisance params except   H  Find 95 th percentile of resulting   H distribution – this is 95% CL upper limit.  When computed with collider data this is the “observed limit”  Repeat for pseudoexperiments drawn from expected distributions to build up expected outcomes  Median of expected outcomes is “expected limit” Expected outcomes 95% CL Limit/SM Median = expected limit  H (pb) 95%  H /  SM 95% rescale PDF

Limit setting (2) Higgs Physics at the Tevatron 44 95% CL Limit / SM m H / GeV Repeat for different values of m H  build up exclusion plot median 1212 illustrative m H =160

What have we found? Higgs Physics at the Tevatron 45 95% CL Limit / SM m H / GeV expected limit observed limit illustrative expected limit observed limit illustrative DeficitExcess

Low mass projections Higgs Physics at the Tevatron equivalent luminosity gain charm discrimination30% improved b-tagging20% improved dijet mass resolution15% extra final states5–10% improved lepton id5–10% total : 1.4x in the limit (~ 2x in effective luminosity) Probability of 95% CL Exclusion Probability of 3  evidence 46

ZH → bb Higgs Physics at the Tevatron cut at 0.6 removes 95% of the QCD background, 65% of the non-QCD background, and keeps 70% of signal most difficult final state among most sensitive channels UK! q q’ Z Z H b b 47

ZH → ll bb Results at mH = 115GeV: 95%CL Limits/SM Higgs Events Exp. Limit Obs. Limit q q’ Z Z H l b b l 48 Higgs Physics at the Tevatron

And so many other results: ♦ SUSY limits ♦ limits on new heavy bosons ♦ observations of new baryons ♦ new jet measurements ♦ measurements of  s ♦ diffraction … 49

50/54Higgs Physics at the Tevatron H  WW H0H0 W+W+ l+l+ W–W– l–l– ee, e ,  ; E T Isolation m ll > 16 Z and top suppression Dilepton sample composition Drell-Yan dominated WW dominated Higgs enhanced B ZZ tt WW HHH H signal separation H0H0 W+W+ l+l+ W–W– l–l– W+W+ W–W– q q’ q 90% 10%

Stability  convergence Assessing NN stability  rogue variables – had checked data-simulation agreement in as many regions as possible Drell Yan-richWW-rich Met – applicability? training epoch successful trainingunsuccessful training training estimator  control regions… Higgs Physics at the Tevatron 51

H → WW Higgs Physics at the Tevatron Bkg uncertainty does not wash out signal D0: Expect 35 Signal Events CDF: Expect 32 Signal Events 52 (winter 2010 publication)

Individual combinations UK! 53 Higgs Physics at the Tevatron

54 High mass Higgs combination UK! PRL (2010) PRL (2010) PRL (2010) Exp 0.87xSM Obs 0.93xSM Winter SM Higgs excluded: 163<m H <166 GeV

New CDF HWW Higgs Physics at the Tevatron UK! 4.8 → 5.9 fb -1 : 11% better from statistics Optimized e - selection Added Trileptons, Low M ll, VH, VBF for 0 Jet Added  modes All together: 17% better! Results at m H = 165GeV: 95%CL Limits/SM Exp eventsExp.Obs. Publication New Wj W  tt WZ ZZ DY WW HWWx10 Data 55

Higgs Physics at the Tevatron

Higgs Physics at the Tevatron Low mass projections equivalent luminosity gain charm discrimination30% improved b-tagging20% improved dijet mass resolution15% extra final states5–10% improved lepton id5–10% total : 1.4x in the limit (~ 2x in effective luminosity) 57

PDFs Higgs Physics at the Tevatron Tevatron y = LHC H g g p p  pp → H =  gg → H f g/p (x 1,Q=M H ) f g/p (x 2,Q=M H ) + … 58

Low mass Higgs searches Higgs Physics at the Tevatron 59

60/54Higgs Physics at the Tevatron Neural network method NN score 0 1 var1 var2 var n Background Higgs  Various versions. Current:  Apply preselection (eg E T to remove Drell-Yan)  Train on {all backgrounds / WW} against Higgs m H =110,120…160…200 { possibly separate ee,e ,  x10  Pass signal/all backgrounds through net  Form templates NN 0 1  Pass templates and data to fitter E T  E T m ll E lep1 E lep2 E T sig Data HWW WW DY Wg WZ ZZ t fakes E T jet1  R leptons  leptons  E T lep or jet E T jet2 N jets Most recent CDF “combined ME/NN” analysis also uses ME LRs as NN input variables

Higgs Physics at the Tevatron 61 log(Λ/GeV) m t =174 GeV Planck scale GeV Altarelli PLB m H (GeV) Implications

4 th generation Higgs Physics at the Tevatron H t,X g g Low-mass scenario: masses close to experimental limits m l4 =100GeV m 4 =80GeV m u4 =256GeV m d4 =128GeV 62

MSSM H →  Key issue: understanding  ID efficiency Large calibration samples: W for ID optimization Z for efficiency confirmation UK! Benchmark scenario UK! No Evidence for SUSY Higgs  sensitive at high tan  in future will include b  b , b  bbb tan  Cross section x Br 95%CL (pb) Higgs Physics at the Tevatron 63

Ones to watch?  b jets.Br is factor 2 too large Higgs Physics at the Tevatron 64

mWmW Higgs Physics at the Tevatron UK! m W : CDF: m W = ± 48 MeV/c 2 D0: m W = ± 43 MeV/c 2 Tev: m W = ± 31 MeV/c 2 (includes Run 1) LEP: m W = ± 33 MeV/c 2 Heading to CDF 25MeV/c 2 measurement CDF  m Z (stat) published (200/pb)43 MeV expected (2.3/fb)13 MeV 65

WW Higgs Physics at the Tevatron Tev error improves from 62 to 49 MeV UK! m W : CDF: m W = ± 48 MeV/c 2 D0: m W = ± 43 MeV/c 2 Tev: m W = ± 31 MeV/c 2 (includes Run 1) LEP: m W = ± 33 MeV/c 2 Heading to CDF 25MeV/c 2 measurement change to mW 66

mtmt Matrix element-based top mass measurement Lepton+jets with 4.8fb -1 NN for background discrimination Likelihood fit over variables sensitive to top mass Simultaneous constraint of jet energy scale using W in lepton+jets m t =172.8 ± 1.3 total GeV (0.7 stat 0.6 JES 0.8 sys ) More precise than CDF 2009! Expect 1GeV precision achievable E T model lepton energy resn pxpypzpxpypz lep1 pxpypzpxpypz jet1 E x, E y x obs : (true values y ) etc. Higgs Physics at the Tevatron 67

Single top Single top observed u W l g b b b t W d u W l b b t W d t-channel s-channel t-channel cross section [pb] s-channel cross section [pb] Higgs Physics at the Tevatron 68

Higgs Physics at the Tevatron 69 LHC projections