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W.Murray PPD 1 Bill Murray RAL, CCLRC WIN 07, Kolkata 15 th January 2007 What is E-W symmetry breaking What are the known knowns? What are the known unknowns? What about the unknown unknowns?

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W.Murray PPD 2 9 years ago.. “The LHC would certainly ferret out the Higgs by 2007”

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W.Murray PPD 3 What is E-W symmetry breaking? This gauge symmetry predicts γ,W,Z,gluons Requires them to be massless Symmetry breaking is needed for W/Z masses SU(3) x SU(2) x U(1)

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W.Murray PPD 4 How can it occur? Preserver underlying symmetry Spontaneous or dynamical breaking Preserves ρ=1 (Relative strength of neutral and charged current interactions) Higgs mechanism! Dr Bhattacharyya will cover this in detail.

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W.Murray PPD 5 Two experimental themes Precision Electroweak data Is ρ=1 true? Are the loop effects correctly seen? Can we predict the Higgs mass from them? Needs masses, couplings... Direct Higgs search What can we say about SM Higgs What does the future hold? And when? What about Super-symmetry?

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W.Murray PPD 6 Precision Electroweak Does the SM give M W, M t and Z properties correctly? Z properties Largely from LEP/SLC Final: “Phys Rept. 427 (2006) 257” W mass/width LEP II results Tevatron run I CDF Run II Top mass Tevatron: Runs I and II

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W.Murray PPD 7 Z Properties: LEP M z = ±0.0021GeV/c 2 Γ z =2.4952±0.0023GeV/c 2 Coupling example: ρ and sin 2 θ eff Leptons precise B quarks incompatible Non-universal EW corrections observed! Born level not quite correct – ρ close to 1 Born level

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W.Murray PPD 8 W mass LEP results are close to final M W = ±0.033 Run 1 Tevatron results: M W = ±0.059 Now: CDF Run II result Based on 200pb -1 Summary follows..

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W.Murray PPD 9 CDF lepton quality plots: Electron material modeling excellent As is muon tracking description Based on fitting ψ, φ data, validated at Z E/P, electrons Z mass muons

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W.Murray PPD 10 Measured Transverse mass Backgrounds very low Agreement of data with fit looks great For electrons, p(χ 2 )=5x10 -7 (stat only) But the data is really very impressive

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W.Murray PPD 11 Improvements since run I Huge improvements in ~all systematics

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W.Murray PPD 12 Combined W mass New result compatible with existing Most precise single result Only 200pb -1 : much more to come

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W.Murray PPD 13 Top Mass measurement A unique particle to the Tevatron Pair produced, top decays: The semileptonic are often 'golden' The other decay modes contribute too.

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W.Murray PPD 14 Semi-leptonic channel Clear leptonic signature With missing energy But enough constraints to calculate neutrino Two b jets All tops have these B tagging important W+jets is main backround

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W.Murray PPD 15 Mass Extraction Mass is fitted along with Jet Energy Scale M W fixes scale Using matrix element convoluted with resolution Uses all information in the event Biggest systematic: signal description Mass of jjj combination 166 b-tagged candidates

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W.Murray PPD 16 Comparison of channels Example from CDF All contribute But lepton plus jets dominates

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W.Murray PPD 17 Top by channel/experiment: CDF results based on much more data The lepton plus jets channels dominate the average M T =171.4±1.2±1.8 Systematics important – future gains will be hard work

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W.Murray PPD 18 Combined Electroweak The consistency of the data can be used to test the use of EW correction It also constrains the Higgs mass

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W.Murray PPD 19 The Electroweak fit: Note 0.2GeV range of scale Direct and indirect agree – predicting M top! Also suggests m H around 100GeV LEP said M H >114 5 th Jan 07 CDF M W

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W.Murray PPD 20 How is this χ 2 ? 18 observable Expect: sigma 1 2+ sigma See sigma 1 2+ sigma No problem! (Recent M W not included)

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W.Murray PPD 21 Why believe in a light Higgs? Electroweak fit (Z properties, W and top mass) give at 95%: M H <166GeV/c 2 (M H <153 with CDF M W ) M H <199GeV/c 2 (including LEP bound) (189GeV with new M W ) Summer 06

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W.Murray PPD 22 Direct Searches SM Higgs: Past: LEP Present: Tevatron Future: LHC Supersymmetry

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W.Murray PPD 23 Higgs then: LEP SM Higgs Final LEP result: M H >114.4GeV (95%CL) Excess at 115GeV would happen in 9% cases without signal Likelihood shown

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W.Murray PPD 24 Higgs now: The Tevatron Tevatron is running well, pp at 2TeV collision energy 2fb -1 delivered Records broken all the time CDF and D0 are in great shape Run II results coming out – top quality B tagging working well (B s oscillations!) Entering the region of sensitivity to SM Higgs

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W.Murray PPD 25 Higgs now: The Tevatron 2fb -1 enough for SM Higgs sensitivity

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W.Murray PPD 26 Tevatron Search channels M H, GeV/c 2

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W.Murray PPD 27 ZH→llbb search D0 plots of 0.9fb -1 Signal is ~50 times below background But well simulated and signal has mass peak Sensitivity possible

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W.Murray PPD 28 ZH→ννbb search; CDF Double tagged mass distribution: Overall small excess in data Signal 10% of background at peak This is the most powerful channel for light Higgs

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W.Murray PPD 29 WH→lνbb with CDF Small excess around 100GeV Signal 15 times below background 1 b tag 2 b tag

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H WW* : final selection ee M H =160GeV (x10) ee e 950pb -1

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W.Murray PPD 31 Combined Higgs boson CDF All low mass channels analyses use 1 fb -1 of data WH (lν bb) ZH (l + l - bb) ZH (ννbb) H→WW >~ 120 GeV For m H = 115 GeV, the 95%CL Limit/SM is 9 (expected) 13 (observed)

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W.Murray PPD 32 Tevatron SM Higgs Combination m H Limit/SM (GeV) Exp. Obs Essentially equivalent to one experiment with 1.3 fb -1, since the experiments have “complementary” statistics at low and high mass Tevatron is close to SM Higgs sensitivity All CDF and DØ results from summer 06 combined

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W.Murray PPD 33 Ingredients (DØ) Equiv Lumi gain Using ~330 pb Combine DØ and CDF2.0 NN b-Tagger/L NN analysis selections Dijet-mass resolution Increased Acceptance New channels Reduced Systematics ⇒ At 160 GeV needs ~5 fb -1 ⇒ At 115 GeV needs ~3 fb -1 Xsec Factor m H =115 GeV m H = 160 GeV Lumi = 2.0 fb-1 95% CL exclusion for m H = GeV with 8 fb -1 (assuming similar improvements at DØ and CDF) Improvements planned/expected

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W.Murray PPD 34 Tevatron Likelihood curve The Tevatron Higgs log- likelihood Small excess at 105GeV Small deficit at 165GeV Nothing to see here - move along.

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W.Murray PPD 35 Let's be naughty Log-likelihood curves can be added That's their great beauty So, if we ASSUME there is a Higgs, and just want to extract its mass, we can add: EW fit LEP Higgs search ll TeVatron Higgs search ll

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W.Murray PPD 36 Combined Likelihood A Higgs near 115GeV still best fit Very crude No systematics

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W.Murray PPD 37 Next: The LHC The 14TeV pp energy raises the Higgs cross section c/f 2TeV Tevatron Designed for luminosity c/f currently at Tevatron Decades of preparation for this search

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W.Murray PPD 38 LHC status 1000 th dipole in ring - Out of 1230 Collisions in 2007 planned But at 900GeV C-o-M

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W.Murray PPD 39 LHC Possible runs? Don't shoot me...just random guesses 30fb -1 often used: Nominal first 3 years

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W.Murray PPD 40 Rates? LHC backgrounds! Every event at a lepton collider is physics; every event at a hadron collider is background Sam Ting 10

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W.Murray PPD 41 Rates in channels used Rates in major channels No cuts, just branching ratios l: e or μ Thousands of events to look for... Far less will pass cuts LEP

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W.Murray PPD 42 Boson fusion: qq → qqH →ττ Two forward jets, P T like M W /2 Higgs products central No colourflow → suppressed central jets Z →ττ plus two jets main background Jet →l l' ', lν+jet final states ( hadronic ident.) mass reconstruction: need P T miss Low mass

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W.Murray PPD 43 qqH ( → ) via VBF Need to undestand tails in Z mass resolution But signal to background could be good S/√B~2.5 in one LHC year CMS: 40 fb -1 for discovery in m H = GeV range ATLAS: Maybe 20fb -1 Measures Yukawa coupling H mZmZ

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W.Murray PPD 44 H →γγ Very rare (10 -3 ) decay mode – top loop But trigger is good Large backgrounds of γγ, γ -jet and jet jet Jet rejection 10 3 required Need energy and angle resolution in calorimeter Primary vertex! CMS resolution 0.5GeV best Production mechanism may improve s/b

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W.Murray PPD 45 H → ZZ → l + l - l + l - Golden channel m H >140GeV/c 2 Above ~200 two real Z's Good mass resolution, trigger Backgrounds: Irreducible QCD ZZ to llll Reducible Zbb, tt Multivariate (p t, η ) methods for low m H ATLAS toroids help

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W.Murray PPD 46 H WW (*) Important for M H ~170 GeV, Higgs mass not fully reconstructed, sensitive to systematics bck Isolated leptons WW (*) →l l (l=e,μ) Missing transverse energy E T miss Background t ( Wb) t ( Wb) -Request central jet veto -WW spin correlations for the signal - small l + l - opening angles VBF qqH→qqWW Presence of forward jets allows purer signal most low-mass range accessible ATL-PHYS

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W.Murray PPD 47 SM Discovery With 30 fb -1, more than 7 for the whole range A 200GeV Higgs can be found with 2fb -1

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W.Murray PPD 48 Measuring the Higgs mass MSSM Higgs m/m (%) h, A, H 0.1 0.4 H 4l 0.1 0.4 H/A h bb 1 2 hh bb 1-2 Zh bbll 1 2 H/A 1-10 precision of <0.3% for m H < 400 GeV no theoretical error included

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W.Murray PPD 49 Branching ratio information 3 channels for almost all m H <200GeV Comparison of rates gives coupling info. e.g. glue/W rate to 25% Hard to measure better than 10% Quark couplings rarely accessible (ttH, H to bb)

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W.Murray PPD 50 Higgs Total Width Width: Above 200GeV large width can be measured Below there is no possibility ILC can do better A muon collider would be very useful here

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W.Murray PPD 51 Higgs Spin/Parity Spin? Parity? ZZ and maybe ttH allow parity reconstruction Spin 0 established if VVH seen – should be for all masses

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W.Murray PPD 52 LHC Higgs Extended Higgs sectors ???? Nobel Prize: Peter Higgs Nobel Prize: Peter Higgs LHC can definitively test the SM Higgs sector This model is falsifiable! Mass measurements to per cent level Cross section x Branching ratio 10's percent Self coupling probably not addressable

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W.Murray PPD 53 Extended Higgs sectors? All previous discussion relates to simplest model; one Higgs doublet Many more complex possibilities fit EW data SUSY is an obvious example Requires two doublets Can accommodate more complex possibilities

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W.Murray PPD 54 Supersymmetry EW fit result favours SUSY region: Heavy SUSY SUSY has two Higgs doublets 5 Higgses Two parameters: M A, tanβ Including Run II CDF M W

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W.Murray PPD 55 LEP SUSY Higgs limit: LEP limits in M h max Reduced M top extends tanβ exclusion Tanβ > ~2.5 for 174 Benchmark – not absolute limit. Reduced by: CPV scenarios nMSSM models Invisible decays 179GeV M top

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W.Murray PPD 56 e.g. CPX Scenario at LEP Designed to have h/H/A mixing M SUSY 500GeV M 2 200GeV μ2000GeV m g 1000GeV arg(A) 90 o No mass limits for moderate tanβ Hard at LHC too

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W.Murray PPD 57 TeVatron MSSM reach TeVatron currently sensitive to modes with enhanced couplings (w.r.t. SM) tanβ in Bbφ→bbbb φ→ττ Therefore large tanβ and moderate mass

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W.Murray PPD 58 Other MSSM searches: γγγ Fermio-phobic Higgs D0, 0.83fb -1 No sign of signal Exclude fermio-phobic Higgs below 66GeV if H + mass 100GeV

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W.Murray PPD 59 LHC expectations: H/A similar shape to TeVatron But hugely expanded HH can be found for most of plot But not all CPV scenarios all Higgs may escape

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W.Murray PPD 60 Conclusions Incredible new results from Tevatron m W precision improving Higgs mass below 150GeV seems clear Direct Higgs searches close to sensitive LHC will start this year There is a real race happening NOT Do NOT assume the unknown is true But in 2010 electroweak symmetry breaking of the SM will be established – or clearly wrong A lepton collider will be required to explore properties

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