Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 398.882 LHC PhysicsExperimental Methods and MeasurementsHiggs Physics and Other Essentials[Lecture 22, April 29, 2009]C.Paus, LHC Physics: Higgs Physics and Other Essentials 2OrganizationNext week lectures:●Monday 2pm and Tuesday 9:30am (which room?) Project 3●remember, due May 2 Conference Schedule●worked outC.Paus, LHC Physics: Higgs Physics and Other Essentials 3C.Paus, LHC Physics: Higgs Physics and Other Essentials 4Outline Higgs Search and Other Essentials●the fundamental question●state-of-the-art●Higgs boson production and decay @ LHC●closer look at specific channels●beyond the Standard Model (BSM)●in 5 years from now - Higgs Boson PropertiesC.Paus, LHC Physics: Higgs Physics and Other Essentials 5The Fundamental QuestionWhat is the origin of elementary particle masses?C.Paus, LHC Physics: Higgs Physics and Other Essentials 6The Fundamental QuestionWhat is around us?proton mass:mp = 938 MeVquark masses:mu = 1.5-4.5 MeVmd = 5.0-8.5 MeVrest mass:kinetic energy &QCD effectsC.Paus, LHC Physics: Higgs Physics and Other Essentials 7The Fundamental QuestionHow are we effected by elementary particle mass? electron mass (105 MeV) (Bohr radius r = 1/ em me ): massless electrons would result in no atomic bindingu, d quark mass (~1-10MeV): massless quark or mu=md would result in proton decays, different nucleosynthesis, ... W mass: massless or small masswould result in rapid fusion in stars ---------------------------------------------------------------------------------------------------mass values for electron, u quark, d quark, W boson are fine tuned for thecreation of the universe and life on our planet.principle of mass creation: Higgs mechanism (our best guess)origin of elementary particle mass: completely unknownC.Paus, LHC Physics: Higgs Physics and Other Essentials 8The Fundamental QuestionElectroweak Symmetry Breaking (hep-ph/9803257):- consistent description of nature seems to be based gauge symmetries - problem: SU(2)l x U(1)Y gauge symmetry no masses for W / Z boson- ad hoc mass terms spoil theory- incorporated in the Standard Model using a complex scalar field (4 components)- self interaction creates potential- vacuum break symmetry spontaneously - three components absorbed by Z/W bosons. - one scalar field component is not absorbed resulting in physical particle:Higgs BosonC.Paus, LHC Physics: Higgs Physics and Other Essentials 9The Fundamental QuestionfermiongfxW/Z bosong gaugeHiggsHiggsv2- interaction of particles with Higgs generates mass- couplings are proportional to massesv ~ 246 GeV (vacuum expectation value)Fermions (Yukawa coupling): Higgs boson (self coupling):m f ~ gf v M2 = v2g top ~ 1 ! W/Z bosons (gauge coupling): M ~ g v HiggsC.Paus, LHC Physics: Higgs Physics and Other Essentials 10The Fundamental QuestionW and Z masses result from couplings to the Higgs fieldGluon and photon have no such couplings masslessQuark and lepton masses are determined by the strength of their coupling to the Higgs fieldWhat about neutrinos? Do they have the same nature?Couplings determine quark mixing, CP violation, ...Is the Higgs field responsible for matter dominance? We have no understanding of the origin of those couplingsC.Paus, LHC Physics: Higgs Physics and Other Essentials 11State-Of-The-ArtWhat do we know about the Standard Model Higgs Boson?theory: unitarity in WW scattering requires MH < 1 TeVdirect searches at LEP: MH < 114.4 GeV excluded with 95%CL(talk by itself: ALEPH candidate events; end of LEP data taking in 2000)indirect prediction in SM: MH > 144 GeV excluded with 95% CL … mt + … ln(MH)MW(Phys) = MW(Born) +2WW WWHtbWC.Paus, LHC Physics: Higgs Physics and Other Essentials 12State-Of-The-Art, 2007What do we know about the Standard Model Higgs Boson?2007 sensitivity:4-12 time SM cross section. 1fb-1 analyzed by CDF400pb-1 analyzed by D0< 50% of available data.~ 8fb-1 needed to excludeSM ~ 160GeVC.Paus, LHC Physics: Higgs Physics and Other Essentials 13State-Of-The-Art, 2008What do we know about the Standard Model Higgs Boson?Winter 2008 first tangible results on the Higgs from the TevatronDedicated effort combines CDF and D0 and finds first new exclusion 'point' since the LEP2 experiments (finished 2001).C.Paus, LHC Physics: Higgs Physics and Other Essentials 14State-Of-The-Art, 2009What do we know about the Standard Model Higgs Boson?Winter 2009 brought exciting new resultsDedicated effort combines CDF and D0 and finds first new exclusion area since the LEP2 experiments (finished 2001).C.Paus, LHC Physics: Higgs Physics and Other Essentials 15Higgs Boson Production and DecayJob Description ( for experimentalist ):Discover the Higgs Boson and explore its properties.In more Detail:Does the Higgs Boson exist? One or more?Is the Higgs Boson a scalar boson?Does the Higgs Boson generate the masses of gauge bosons and fermions?Does the Higgs Boson couple to itself?C.Paus, LHC Physics: Higgs Physics and Other Essentials 16Higgs Boson Production and DecayProtonProtonLHC:pp collisions @ 14 TeVWhat is this?C.Paus, LHC Physics: Higgs Physics and Other Essentials 17Higgs Boson Production and DecayK ~ 1.1K ~ 1.4K ~ 1.2K ~ 2K = (N)NLO / LOC.Paus, LHC Physics: Higgs Physics and Other Essentials 18Higgs Boson Production and DecaySome more words on K-factors - K = (N)NLO / LOLeading Order O(2s):Next to Leading Order O(3s):gg  Hgg  Hgg  gH, gq  qH, ...~ 4-15% +  ~ 5-15% from PDFC.Paus, LHC Physics: Higgs Physics and Other Essentials 19Higgs Boson Production and DecayHff ~ mf2HVV ~ mV4~ mH3mH < 135 GeV:bb,  dominantmH > 135 GeV:WW, ZZ dominantC.Paus, LHC Physics: Higgs Physics and Other Essentials 20Higgs Boson Production and DecayBranching fraction reminder:W boson decays:in e, ,, 3*ud, 3*sc BR(l) ~ 11%BR(hadrons) ~ 68%Z boson decays: in ee, , , , hadronicBR(ll) ~ 3.3%BR() ~ 20 % BR(hadrons) ~ 70 %decays: in e, , hadronic+BR(l) ~ 18 % BR(hadrons) ~ 64 %C.Paus, LHC Physics: Higgs Physics and Other Essentials 21Higgs Boson Production and DecaymH= 150 GeV: S/B ~ 10-10trigger: 10-7