Higgs Physics
Alex Pomarol, UAB (Barcelona)
& Englert, Brout 1 The 4th of July of 2012 marked a new milestone in particle physics
A Higgs-like state discovered:
LHC most relevant piece of data: m 125 GeV H ⇡
Really shook the theory community
2 What is the SM Higgs about?
What makes the SM Higgs exceptional?
3 Two achievements of the Higgs mechanism
I. Breaking the EW symmetry, giving masses and
providing the longitudinal component of the W
& Z II. Providing an excitation, the Higgs particle,
that makes the theory of massive W & Z consistent up to very high-energies
4 I
5 The Weak interaction is weak because mediators W, Z are massive
How to gain mass? (thinking contrary to dietitians!)
1) From compositeness (as a proton)? NO! Experiments tell us W, Z have properties of elementary gauge bosons at energies above their masses 2) From a condensate (Higgs mechanism): Already found Superconductivity in nature: Cooper’s pair
1) Weak Charge should not be conserved by the vacuum ➥ guarantees weak force is short-range = force-mediators get mass Q 0 = 0 W| i6 charged states can have 0 0 0 0 =0 overlapping with the | i/| i!h| | i6 vacuum state charged ↓ spin=0 Non-zero charged operator condensate = Higgs condensate
To avoid Noether’s theorem: Symmetry ⟺ Charge conservation ➥ Vacuum must break the electroweak symmetry
SU(2) x U(1) →7 U(1)EM ! 2) To become massive (W, Z), extra states are needed:
Massless gauge boson: Massive gauge boson:
AT = ( A+ , A- ) AT = ( A+ , A- ) AL
Must be provided by a new sector: The sector responsible for the Electroweak (EW) Symmetry Breaking 8 Non-zero charged condensate: e.g. U(1) case
Mexican-hat condensate potential
“Angular excitations” Massless: Goldstone ɸ hi ɸ hi Charge is not conserved interaction are short-range gauge bosons gets mass ... but where the extra state comes from?
The Goldstone boson corresponds to the longitudinal component
of the gauge9 boson AL Feynman-diagrammatically:
the condensate change the propagator of the gauge boson
x x x x G Aµ Aµ Aµ Aµ
Englet & Brout, PRL 13(1964)321
10 First beauty of the Higgs mechanism:
From 3 massless states, it delivers 3 massive states
G = Goldstone (A+, A-) = Gauge bosons
Higgs machine c Massive gauge boson
11 These new states WL , ZL (Goldstones) spoil the nice properties of gauge theories
Calculability is lost! Untitled-1.nb 1
M 0.5 WL WL 0.4 a) s 0.3 0.2 / v2 0.1 WL WL 200 400 600 800 1000 ps Amplitudes diverge
WL b) Loops are not finite!
WL Do not allow for precision calculations as in QED
12 II
13 Extra state(s) needed to make the theory consistent! ...but there are extra states in the EWS breaking sector:
condensate potential
“Radial excitation” H ɸ hi ɸ hi Second beauty of the Higgs mechanism: A very particular “radial excitation”, we call it the Higgs particle, can recovered calculability in massive gauge theories 14 Not all “radial excitations” of Mexican-hat potentials can make the theory consistent:
Only that of the Higgs Mexican-hat potential works:
15 Higgs mediated processes recover calculability:
Untitled-1 1
3.5 L L W W WL WL 3 M 2.5 h 2 1.5 + 1 0.5 WL WL WL WL 500 1000 1500 2000 2500 3000 ps h Finite results!
Massive gauge theories become as good as massless gauge theories
16 To do this job, the Higgs couplings must take a particular value: W , Z
gMZ h = gMW , cos W W , Z f gM h = f 2MW f The couplings must be exactly these ones (at tree-level) to make the SM a consistent theory All couplings predicted by the Higgs mechanism! 17 Without a Higgs With a Higgs (100 GeV New Physics 10¹⁹ GeV (MP) New Physics Validity of Energy the SM ? Energy Magic Where is thewith the Higgs TeV all couplings MW Validity of MW are dimensionless the SM parameters 18 Very simple Lagrangian: Higgs must couple to particles that must get masses 2 2 4 = D H†D H +(y Hf f + h.c.) µ H + H L µ µ f L R | | | | { H is a 2 1 of SU(2)L ⊗ U(1)Y a a D = @ igT W ig0B µ µ µ µ = 0 •h i6 19 Very simple Lagrangian: Higgs must couple to particles that must get masses 2 2 4 = Dµ"H #†Dµ"H #+(yf"Hf # LfR + h.c.) µ H + H L | | | | { H is a 2 1 of SU(2)L ⊗ U(1)Y a a D = @ igT W ig0B µ µ µ µ = 0 In the vacuum, fermions and h i6 gauge bosons get masses • H is a (complex field) doublet = 4 d.o.f. = 3 Goldstones to become WL and ZL + Higgs 20 Very simple Lagrangian: Higgs must couple to particles that must get masses 2 2 4 = D H†D H +(y Hf f + h.c.) µ H + H L µ µ f L R | | | | a a D = @ igT W ig0B µ µ µ µ dimensionless couplings only grow/decrease logarithmically with the energy (due to quantum effects): ➥ remain small at high-energies that we know them from the masses: yf = mf /v from mW 2 2 = mh/8v 21 Very simple Lagrangian: Higgs must couple to particles that must get masses 2 2 4 = D H†D H +(y Hf f + h.c.) µ H + H L µ µ f L R | | | | a a D = @ igT W ig0B µ µ µ µ dimensionless couplings H 6 Add extra terms, | | , and this property is gone! ⇤2 Non-renormalizable theory: Inconsistent at E>Λ ! 22 Keystone state Z W Higgs G e u d c, s top Graviton Standard Model bottom of particles Either the Higgs or something else playing its role had to be discovered at the LHC (for consistency, as antimatter in 1932) 23 Although consistent, we think (and hope) the SM is not the full story New Physics 10¹⁹ GeV (MP) Not understandable the origin of such a small EW scale Validity of as compared to the the SM ? Planck scale Energy The problem is transferred MW to the Higgs condensate 24Is this a stable situation? Although consistent, we think (and hope) the SM is not the full story How can we keep the Higgs “light” New Physics in front of “fatty” states ? 10¹⁹ GeV Heavy states (MP) Strings/GUT Validity of the SM ? Energy MW Higgs = Scalar 25 Here is where the simplicity of the Higgs mechanism puts it into trouble Since not always simplicity is good: SIMPLICITY falls under quantum fluctuations! stable stable unstable “Vector” “fermion” “scalar” s=1 s=1/2 s=0 No spin, no “structure” to keep it light 26 The hierarchy problem in a nutshell Massless Massive Vector 2 dof 3 dof 2≠3 ✔ Massless vector Aµ (+,$) (+,0,$) are save Fermion 2 dof 4 dof 2≠4 ✔ Massless Ψ ΨL Ψ L , Ψ R fermions are save Scalar 1 dof 1 dof 1=1 Problem! h Massless (or light) scalars are not save! 27 Possibilities that theorists envisage to tackle this problem: 1) Keep the Higgs elementary, but protect it by symmetries: Supersymmetry Higss (boson) Higssino (fermion) 2) The Higgs is not elementary: Composite Higgs Higss made of fermions (as a pion in strong interactions) 28 Supersymmetry Composite Higgs New Physics New Physics 10¹⁹ GeV 10¹⁹ GeV (MP) (MP) Supersymmetric New strong SM sector (new dof) Energy Energy new fermions (Higgsino,...) TeV and scalars (stops,...) TeV MW SM MW SM Higgs potential predicted in these theories ➥ Both imply changes in the Higgs sector 29 3) Possibility gaining supporters everyday among theorists mH~MP mH~0.3MP mH~MP mH~0.1MP mH~MP Only few mHH~100 GeV H where we mH~MP m ~MP can “live” mH~MP No new physics Multiverse at the LHC! 30 Supersymmetry = MSSM For consistency, an extra Higgs (doublet) is needed, sharing the “duties” of the SM Higgs Untitled-1 1 3.5 L L W W WL WL 3 M 2.5 h, H 2 1.5 + 1 0.5 WL WL WL WL 500 1000 1500 2000 2500 3000 ps Different couplings from the SM Higgs SM e.g. ghWW, gHWW < g hWW hVV couplings smaller than in the SM 31 Composite Higgs inspired by QCD where one observes that the (pseudo) scalar are the lightest states Spectrum of mesons: GeV 100 MeV Are Pseudo-Goldstone bosons (PGB) Mass protected by the global QCD symmetry! ⇥ ⇥ + 32 Can the light Higgs be a kind of a pion from a new strong sector? We’d like the spectrum of the new strong sector to be: TeV 100 GeV h Pseudo-Goldstone bosons (PGB) We do not know what the Higgs could be made of ! h = ? but we could study its properties at the LHC as in the 60s when pions, kaons, ... were discovered 33 Being Composite, the Higgs couplings are different from the SM values WL WL WL WL h + ● ● WL WL WL WL Untitled-1 1 partly-unitarize! different 3.5 from the SM Higgs M 3 2.5 2 1.5 A Composite Higgs 1 only partly 0.5 500 1000 1500 2000 2500 3000 ps does the job of a true Higgs 34 Being Composite, the Higgs couplings are different from the SM values WL WL WL WL h + ● ● WL WL WL WL Untitled-1 1 partly-unitarize! different 3.5 from the SM Higgs M 3 2.5 The rest of the new strong 2 1.5 sector (states of spin=0,1,2,...) 1 0.5 takes care of the fully 500 1000 1500 2000 2500 3000 ps unitarization: L WL W W (n) 35 WL WL After the 4th of July 2012 Plenty of new data on the “radial” excitation around the EWSB vacuum: CMS Preliminary s = 7 TeV, L = 5.05 fb-1 ; s = 8 TeV, L = 5.26 fb-1 12 7 TeV 4e, 4µ, 2e2µ Data 8 TeV 4e, 4µ, 2e2µ 10 Z+X In%summary% Z *,ZZ 8 mH=126 GeV Events / 3 GeV 6 4 2 H Combined results: consistency Characterization%of%the%excess:%0 mass%% of the global picture m4l [GeV] Evolution of the excess with time 80 100 120 140 160 180 Are the 4l and γγ observations m [GeV] consistent ? ! Likelihood%scan%for%mass%and%%4l signal%strength%in%three%high%% From 2-dim likelihood fit to signal Combined results: sharing of the excessmass and between strength years curves … show mass%resolution%channels% approximate 68% (full) and 95% SM (dashed) CL contours Energy-scale systematics Similar expected significances in both years not included ! results%are%selfVconsistent%and%%%%%%%%%%%% (more luminosity and larger cross-section 4μ candidate with m = 125.1 GeV can%be%combined% in 2012, but only two channels included) 4μ pT (muons)= 36.1, 47.5, 26.4, 71 .7GeV m12= 86.3 GeV, m34= 31.6 GeV 15 reconstructed vertices CMS Preliminary s = 7 TeV, L = 5.05 fb-1 ; s = 8 TeV, L = 5.26 fb-1 12 7 TeV 4e, 4µ, 2e2µ Max deviation ObservedData 8 TeV 4e, 4µ, 2e2(exp.)µ at m 10 significanceZ+X In%summary% H Z *,ZZ 8 2012theHiggsIncandela of TheStatus J. Search theCMSCOLLABORATION for mH=126 GeV th Events / 3 GeV 6 2011 data ATLAS: 126 Status GeV of SM Higgs searches, 4/7/2012 3.5 (3.1)Best σ -fit signal strengths, normalized48 to the 4 2012 data 127 GeV 4.0 (3.3)SM σ expectations, for all studied channels,July4 2 Compatibility%with%SM%Higgs%boson%% at mH = 126.5 GeV, 0 m4l [GeV] 2012theHiggsIncandela of TheStatus J. Search theCMSCOLLABORATION for event%yields%in%different%modes%(1)%th Fit to CV and CF 80 100 120 140 160 180 m [GeV] 4l July4 Group%the%Higgs%couplings%into%% 95 Vectorial %and% Fermionic %sets.% … and over channels ATLAS: Status of SM Higgs searches, 4/7/2012 36 ATLAS: Status of SM! Higgs %Event%yields%in%different% searches, 4/7/2012 % 47 production%times%decay% Attach%a%modifier%to%the%SM% Sensitivity (expected and observed) driven by “high-resolution” channels (γγ, 4l). modes%are%selfV prediction%% “Low-resolution” channels (lνlν, bb, ττ) consistent% %to%each%of%those%%(CV%and%CF).% 2012 The Status of the Higgs Search J. Incandela for the CMS COLLABORATION 2012theHiggsIncandela of TheStatus J. Search theCMSCOLLABORATION for crucial to understand the nature of the th % !July4 albeit%many%modes%have% “signal”, measure its properties, and Use%LO%theoretical%prediction%for% not%yet%reached%sensitivity% assess consistency of the overall picture loopVinduced%%H% %γγ,%H% %gg% to%distinguish%SM%from% ATLAS: Status of SM Higgs searches, 4/7/2012 Background% couplings.% 46 % In%agreement%with%the%SM%within%the% %95%%confidence%range%% 2012 The Status of the Higgs Search J. Incandela for the CMS COLLABORATION 2012theHiggsIncandela of TheStatus J. Search theCMSCOLLABORATION for th %"%Need%more%data!% solid contour: 68% CL 2012 The Status of the Higgs Search J. Incandela for the CMS COLLABORATION 2012theHiggsIncandela of TheStatus J. Search theCMSCOLLABORATION for th July4 dashed contour: 95% CL % 9999 July4 36 The path to discovery… 37 All Higgs couplings are predicted in the SM as a function of Masses W , Z gMZ h = gMW , cos W W , Z f gM h = f 2MW f We can predict how the Higgs can be produced at the LHC and how it will decay as a function of its mass (unknown before the 4/7/12) 38 Main production mechanism at the LHC Gluon fusion: Largest cross-section Vector Boson Fusion (VBF) Associated production (VH) tth production 39 40 2.1 Decays to quarks and leptons 2.1.1 The Born approximation In the Born approximation, the partial width of the Higgs boson decay into fermion pairs, Fig. 2.1, is given by [111,145] GµNc 2 3 ΓBorn(H ff¯)= MH m β (2.6) → 4√2π f f 2 2 1/2 with β 2.2=(1 Decays4mf /MH ) intobeing electroweak the velocity gauge of the fermions bosons in the final state and Nc the Most −important decay channels at the+ LHC color factor2.2.1Nc Two=3(1)forquarks(leptons).Intheleptoncase,onlydecaysi body decays nto τ τ − pairs and, to a much lesser extent, decays into muon pairs are relevant. Above the WW and ZZ kinematical thresholds, the Higgs boson will decay mainly into pairs of massive gauge bosons; Fig. 2.9a. The decayf widths are directly proportional to the HV V H hcouplings → bb, givenττ in eq. (2.2) which, as discussed in the beginning of this chapter, correspond to the J PC =0++ assignment of the• SM Higgs boson spin and parity quantum numbers. ¯ These are S–wave couplings, !" !" in thef laboratory frame, and linear in sin θ,withθ ∼ 1 · 2 beingFigure the 2.1: angle The between Feynman the diagram Higgs and for one the of Higgs the vector boson bosons decays. into fermions. 2.3 Loop induced decays into γγ, γZ and gg The partial decay widths exhibit a strong suppression near threshold, Γ(H fff¯)1 a)Since gluons and2.3 photons Loopb) are induced massless decays particles, into theyγγ, doγcZ) notandcouplegg to the Higgs→ boson∼ β3 0forM 2m .ThisistypicalforthedecayofaHiggsparticlewithascala¯ r f → directly.H % Nevertheless,f V the Hgg and Hγγ Vvertices, as well as the HZγ coupling, canf2 be coupling eq. (2.3).H If theSince Higgs gluons boson andH were photons a pseudoscalar are massless particles,A boson theyH withdo not couplingscouple to the given Higgs in boson generated VV* at→ thedirectly. Vff quantum Nevertheless, level with theloopsHgg involvingand Hγγ massivevertices,[and as colored well as the or charged]HZγ coupling, particles can be h → • • V* f¯ • eq. (2.5), thewhich partial couple decay togenerated the width Higgs at would boson. the quantum have The H level beenγγ withand suppresse loopsHZγ involvingcouplingsdonlybyafactor massive are mediated[and colored byβ orWf charged][146]bosonand particles V f3 which couple to the Higgs boson. The Hγγ and HZγ couplings are mediated by W boson and charged fermions loops, while the HggGcouplingN is mediatedf only by quark loops; Fig.¯ 2.14. charged fermions loops,¯ whileµ thec Hgg coupling2 is mediated only by quark loops;f Fig.4 2.14. For fermions, onlyΓBorn the( heavyA f topf)= quark and,M toH a lessermf βf extent,thebottomquarkcontribute(2.7) For fermions,→ only the heavy4√ top2π quark and, to a lesser extent,thebottomquarkcontribute substantially for Higgs boson masses M > 100 GeV. Figure 2.9: Diagrams for the Higgs bosonH decays into> real and/or virtual gauge bosons. substantially for Higgs boson masses∼ MH 100 GeV. More generally, and to anticipate the discussions that∼ we will have on the Higgs CP– a) γ(Z) γ(Z) properties,The for partial a Φ boson width with fora) a Higgs mixed boson CP–even decaying andγ( intoZ CP–odd) two real coupl gauingsge bosons,g ¯ γH(Za) +VVibγwith, Φff ∝ → 5 H H H ¯ H the diffVerential= W or rateZ,aregivenby[32,145] for the fermionicW decayWΦ(p+)+ f(p,+ s)f(¯p,F s¯)whereF s ands ¯ denote the h → γγ • → • polarization vectors of the fermions• and the four–momenta a•re such that p = p p¯,isgiven G M 3 M 2 µ H γ√ γ 2 ±γ V ±γ by [see Ref. [147] forΓ(H instance]VV)= δV 1 4x (1 4x +12x ) ,x= 2 (2.27) → 16√2π − − g M g H b) dΓ βf 2 2 1 2 H 2 2 with δW =2andδZ =1.ForlargeenoughHiggsbosonmasses,whenthephasespaceb) Q factors (s, s¯)= 2 ( a + b )H MΦ mf + mf s s¯ dΩ 64π MΦ | | | | 2 Q− • · can be ignored, the decay! width into WW" •bosons is two times# larger than the decay width 2 2 1 2 g2 2 into ZZ bosons and the branching+( a ratiosb ) p for+ sp the+ decayss¯ M wouldΦsg s¯ be,+ m respf s ectively,s¯ mf 2/3 and 1/3 | | − |41| · · − 2 · · − if no other decay channelFigure 2.14: is kinematically Loop induced Higgs open. boson decays into a) two photons (Zγ)andb)twogluons. " µ ν ρ σ # Figure 2.14: Loop inducedRe( Higgsab∗)%µ bosonνρσp+ decaysp s s¯ into a)2Im( twoab phot∗)monsf p+(Z(γs)andb)twogluons.+¯s) (2.8) For large Higgs masses,For masses− the much vector larger bosons than− the are Higgs longitudinall− boson mass,ypolarized[159] these virtu· al particles do not decouple since their couplings to the Higgs boson grow with the masses,thuscompensatingtheloop$ The terms proportionalFor masses to much Re( largerab∗)andIm( than the Higgsab∗)representtheCP–violatingpartofthecou- boson mass,2 these virtual particles do not decouple ΓL 1 4x +4x MH MV mass suppression. These= decays are thus extremely! interest1(2.28)ing since their strength is sensitive plings. Averagingsince their over couplings the polarizations to the Higgs of boson the− two grow fermion with2 thes, masses these,thuscompensatingtheloop two terms disappear and to scalesΓ farL beyond+ ΓT the1 Higgs4x boson+12 massx and−→ can be used as a possible probe for new charged 1 2− 2 2 2 1 2 2 2 2 we are left withmass the suppression. two contributionsand/or These colored decays particles area thus whose(M extremely masses2m are interest2 generatedm )anding by since the their Hbiggs(M strength mechanism2m is sensitiveand+2m which) are ∝ 2 | | Φ − f − f ∝ 2 | | Φ− f f whileto the scalesL, T farpolarization3 beyondtoo heavy the Higgs to states be produced boson are democratically mass directly. and can be used populated as a possible near probethe threshold, for new charged at x = which reproduce the β and βf threshold behaviors of the pure CP–even (b =0)andCP–odd 1/4. Since the longitudinalf wave functions are linear in the energy, the width grows as the (a =0)statesnotedabove.and/or colored particlesUnfortunately, whose massesbecause are of the generated suppression by bythe the Higgs additiona mechanismlelectroweakorstrongcou- and which are third power of thepling Higgs constants, mass, Γ these(H loopVV decays) areM 3 important.Asdiscussedin only for Higgs1.4.1, masses a below heavy130 Higgs GeV too heavy to be produced directly. H ∼ when the total Higgs→ decay width∝ is rather small. However,§ these partial widths will be boson wouldUnfortunately, be obese since because its of total the decay suppression74 width by becomes the additiona complelectroweakorstrongcou-arable to its mass very important when we will discuss the Higgs production at hadron and photon colliders, pling constants, these loop decays are important only for Higgs masses below 130 GeV where the cross sections will be directly proportional to,3 respectively, the gluonic and pho- Γ(H WW + ZZ) 0.5TeV[MH /1TeV] ∼ (2.29) when the totaltonic Higgs partial→ decay decay width widths. is rather Since∼ the small. entire However, Higgs boson th masesesrangecanbeprobedinthese partial widths will be very important when we will discuss the Higgs production at hadron and photon colliders, and behaves hardlyproduction as a resonance. processes, we will also discuss the amplitudes for heavy Higgs bosons. where the cross sectionsIn this section, will be we directly first analyze proportional the decays to, widths respectively, both at lea theding gluonic order (LO)and pho- and then tonic partial decayincluding widths. the next–to–leading Since the entire order Higgs (NLO) boson QCD mas correctionssrangecanbeprobedinthese.ThediscussionoftheLO production processes,electroweak we corrections will also discuss and the the82 higher–order amplitudes QCD for correcti heavyons Higgs will be bosons. postponed to the next section. In this section, we first analyze the decays widths both at leading order (LO) and then including the next–to–leading order (NLO) QCD corrections88 .ThediscussionoftheLO electroweak corrections and the higher–order QCD corrections will be postponed to the next section. 88 HiggsSM Boson Higgs Branching Decays Ratios: ✦ 1 The Nature has WW chosen the bb Higgs boson -1 gg ZZ mass (~125.5 10 LHC HIGGS XS WG 2013 GeV) maximally rich, but quite cc challenging 10-2 experimentally 0.16% Z ✦ The “big five”: [%] Uncert Total + BR Higgs ๏ H(bb) - 57% 10-3 ๏ H(WW) - 22% 0.02% Greg Landsberg - Higgs Bosons in the SM and Beyond EPS 2013 ๏ H(ττ) - 6.2% µµ µµ -4 14 ๏ 10 H(ZZ) - 2.8% 80 100 120 140 160 180 200 ๏ H(γγ) - 0.23% MH [GeV] Slide The luck of a125 GeV Higgs is that most of the decay modes are visible 42 Looking for gg → h → γγ : 43 Looking for gg → h → ZZ* → 4f : 44 Aleandro Nisati - LHCP2014 Experimental Summary Aleandro Nisati - LHCP2014 ExperimentalAleandro Nisati - SummaryLHCP2014 Experimental Summary TheThe Higgs Higgs boson boson mass: mass: HH!!γγ4l • ATLAS: Improved calibration of electrons and Combined• photonsMuon mass calibration with Z and J/ψ • –Electron Calorimeter calibration non-uniformities described and layer in inter- previous page calibration corrected using e/γ/µ – EM cluster energy correction via MVA regression – Energy scale and resolution with Z!ee ATLAS: • Selection: isolated photons, PT/mγγ > 0.35, 0.25 – Events split according to γ conversions, ηγ and Ptt: ATLAS mH = 125.98 ± 0.42 (stat) ± 0.28 (sys) GeV Systematic uncertainties reduced by a factor 2.5 Signal strength @ best-fit mass: µ =Strong%reduc6on%of%the%systema6c% 1.29 ± 0.30 uncertainty% CMS:ATLAS m mHH = = 125.4 124.51 ± 0.5± 0.52 (stat) (stat) ± 0.6 ± 0.04(sys) (sys)GeV GeV CMS: mH = 125.6 ± 0.4 (stat) ± 0.2 (sys) GeV 34"33" ATLAS mH = " the H!γγ and H!4l mass consistency is now reduce to 2σ CMS: 125.6 ±0.4 (stat) ±0.2 (sys) GeV 45 35" strengths of the five channels and the SM expectation of one is about 8%. The compatibility between the combined best-fit signal strengthµ ˆ and the best-fit signal strengths of the five channels is 13%. The dependence of the combined value ofµ ˆ on the assumed mH has been investigated and is relatively weak: changing the mass hypothesis between 124.5 and 126.5 GeV changes the value ofµ ˆ by about 4%. Table 2: Summary of the best-fit values and uncertainties for the signal strength µ for the individual channels and their combination at a Higgs boson mass of 125.5 GeV. µ Higgs Boson Decay (mH=125.5 GeV) VH Vbb 0.4 1.0 → − ± H ττ 0.8 0.7 → ± H WW( ) 1.0 0.3 → ∗ ± H γγ 1.6 0.3 → ± TheH ZZLHC( ) 1first-run.5 0.4 legacy: → ∗ ± The(signal(Strength( ( Combined 1.30 0.20 µ ± ATLAS (stat) Total uncertainty s = 7 TeV, L ≤ 5.1 fb-1 s = 8 TeV, L ≤ 19.6 fb-1 (sys) SM m = 125.5 GeV Tevatron Run II, L 10 fb-1 H (theo) ± 1 on µ CMS Preliminary m = 125.7 GeV int m = 125.5 GeV Combined H ATLAS Preliminary + 0.23 arXiv:1307.1427 H µ = 0.80 ± 0.14 2 - 0.22 p = 0.65 m =125 GeV/c H SM H + 0.17 W,Z H → bb +0.33 - 0.13 SM Combined (68% C.L.) s = 7 TeV: Ldt = 4.7 fb-1 µ = 1.55 + 0.17 ∫ -0.28 - 0.12 s = 8 TeV: Ldt = 13 fb-1 H bb ∫ + 0.35 arXiv:1307.1427 → Single channel H ZZ* 4l - 0.32 µ = 1.15 ± 0.62 H → ττ + 0.20 s = 7 TeV: ∫Ldt = 4.6 fb-1 +0.40 - 0.13 -1 µ = 1.43 + 0.17 s = 8 TeV: ∫Ldt = 13 fb -0.35 - 0.10 (*) H + 0.20 arXiv:1307.1427 H → WW → lνlν - 0.21 H → ττ H WW*-1 l l s = 7 TeV: ∫Ldt = 4.6 fb + 0.23 µ = 1.10 ± 0.41 -1 - 0.19 + - s = 8 TeV: ∫Ldt = 20.7 fb +0.31 µ = 0.99 + 0.15 H W W H → γγ -0.28 - 0.09 s = 7 TeV: Ldt = 4.8 fb-1 + 0.13 arXiv:1307.1427 ∫ Combined - 0.14 H → γγ -1 + - s = 8 TeV: ∫LdtH = 20.7 fb, ZZ*, WW* + 0.17 H (*) +0.21 - 0.13 µ = 0.77 ± 0.27 H → ZZ → 4l µ = 1.33 + 0.12 -0.18 0.10 s = 7 TeV: ∫Ldt = 4.6 fb-1 - s = 8 TeV: ∫Ldt = 20.7 fb-1 ATLAS-CONF-2013-0 7 9 H → WW VH Vbb W,Z H bb ±0.5 µ = 0.68 ± 0.20 Preliminary Combined µ = 1.30+0.7 ±±0.4 0.20 New( s = 7 TeV: ∫Ldt = 4.6 - 4.8 fb-1µ = 0.2 -0.6 <0.1 0 1 2 3 4 5 6 7 8 9 10 s = 8 TeV: ∫Ldt = 13 - 20.7 fb-1 H (8TeV: 13 fb-1) ATLAS-CONF-2012-160 H → ZZ Best Fit ( × Br)/SM Preliminary µ = 0.92 ± 0.28 0.7 µ = 0.7+ -1 0 +1 -0.6 Signal strength (µ) 0 0.5 1 1.5 2 2.5 s = 7 TeV Ldt = 4.6-4.8 fb-1 -0.5 0 0.5 1 1.5 2 Best fit σ/σ ( SM s = 8 TeV Ldt = 13-20.7 fb-1 Signal strength (µ) Figure 1: Measurements of the signal strength parameter µ for mH =125.5 GeV for the individual chan- nels and their combination. ➥quite compatible with the SM Higgs ! In the SM, the production cross• sections Combined( are completely fixedµ once(!mH(Best(accuracy(is specified. The best-fit valuebut(no(strong(physics(mo&va&on:( for the global signal strength factor µ(thanksdoes not give to any ATLAS direct information and CMS on the results relative contributions“dancing” around the SM values) from different production modes. Furthermore,– fixing the ratios of the production cross sections to the ratios predicted by the SM may conceal tension betweenATLAS the data((γγ and,( theWW*( SM. Therefore,and(46 inZZ* addition)(((((((((((((((((( to µ =((1.33(±(0.20)(((1.23±0.18(including(bb(and(ττ)( the signal strength in different decay modes, the signal strengths of different Higgs production processes contributing to the same final state are determined.– CMS Such a separation(((γγ, avoidsττ,(bb model,( assumptionsWW*(and( needed ZZ*)(((((((µ =((0.80(±(0.14)( – TEVATRON((bb,(γγ, ττ,(WW*)((((((((((((µ =((1.44(±(0.60)(( 5 CompaCble(with(SM(Higgs(boson(expectaCon:(Accuracy(~(15%(( 5/22/13( F.(Ceru4(LBNL(N(EPSNHEP(Stockolm((2013( 15( ConclusionsBetter perspective to understand how close to a SM Higgs: CMS Preliminary s = 7 TeV, L 5.1 fb-1 s = 8 TeV, L 19.6 fb-1 ✦ ≤ ≤ Higgs physics remains the apex of the LHC 1/2 couplings 68% CL program t aligned 1 95% CL ✦ Amazing progress since the discovery of a W Z with the mass ! or (g/2v) Higgs boson just a year ago: λ ๏ Seen beyond any doubts in three bosonic 10-1 channels b ๏ Looks more and more like the SM Higgs boson τ -2 ๏ No evidence for non-SM decays yet Higgs coupling 10 ๏ No evidence for additional Higgs bosons at higher or lower mass so far 1 2 3 4 5 10 20 100 200 ✦ Coupling to the top quarks has been established mass (GeV) via gluon fusion production mechanism ✦ Couplings to the down-type third-generation fermions are established at >3 sigma level, thanks to the Tevatron and the LHC efforts 47 ✦ The spin and the mass of a new state have been determined (see next talk) ✦ Greg Landsberg - Higgs Bosons in the SM and Beyond EPS 2013 Many new directions of studies, with an exciting LHC program that will last some two decades 50 ๏ Cf. nearly 20 years of beautiful top physics since its discovery in 1995 ✦ The goal is to shrink the error bars to dots on the “Regge plot” above and fill it in Slide ConclusionsBetter perspective to understand how close to a SM Higgs: CMS Preliminary s = 7 TeV, L 5.1 fb-1 s = 8 TeV, L 19.6 fb-1 ✦ ≤ ≤ Higgs physics remains the apex of the LHC 1/2 68% CL program t 1 95% CL ✦ Amazing progress since the discovery of a W Z or (g/2v) Higgs boson just a year ago: λ ๏ Seen beyond any doubts in three bosonic 10-1 channels b ๏ Looks more and more like the SM Higgs boson τ -2 ๏ No evidence for non-SM decays yet Higgs coupling 10 Other scalar would have ๏ No evidence for additional Higgs bosons at couplings to SM higher or lower mass so far particles 1 2 3 4 5 10 20 100 200 in other trajectories ✦ mass (GeV) Coupling to the top quarks has been established of this plane ! via gluon fusion production mechanism ✦ Couplings to the down-type third-generation fermions are established at >3 sigma level, thanks to the Tevatron and the LHC efforts 48 ✦ The spin and the mass of a new state have been determined (see next talk) ✦ Greg Landsberg - Higgs Bosons in the SM and Beyond EPS 2013 Many new directions of studies, with an exciting LHC program that will last some two decades 50 ๏ Cf. nearly 20 years of beautiful top physics since its discovery in 1995 ✦ The goal is to shrink the error bars to dots on the “Regge plot” above and fill it in Slide ttH Measurements ❖ Direct studyOne&of&the&difficult&channels:&WH&with&H&to&bb of top Yukawa coupling! ❖ Exploring all accessible Higgs decay modes! ❖ Approaching SM sensitivity in 8 TeV data New recent data constraining the htt coupling: CMS 26 Daniel'Froidevaux,'CERN rd LHCP'Conference,'NY,'349 'of'June'2014 25 mercredi 4 juin 2014