PHYS 3446 – Lecture #22Spontaneous Symmetry BreakingEW Potential and Symmetry BreakingThe Higgs MechanismHiggs Production Processes at Hadron CollidersHadron Collider SM Higgs Production sSM Higgs Branching RatioHow do we find the Higgs particle?What do we know as of Winter 06?How do we make a Neutrino Beam?How can we select sign of neutrinos?How can there be wrong sign of neutrinos in a sign selected beam?4. QCD Factorization TheoremHow is sin2qW measured?Slide 15Neutrino OscillationNeutrino Oscillation FormalismOscillation Probabilityn Sources for Oscillation ExperimentsOscillation DetectorsAtmospheric Neutrinos & Their FluxSNO Experiment ResultsImportance of the Zenith AngleSuper-K Atmospheric Neutrino ResultsAccelerator Based ExperimentsLong Baseline Experiment Concept (K2K)Different Neutrino Oscillation StrategiesExclusion PlotsFuture: Neutrino FactoryWhat do we know now?What do we not know?Issues in SMFeynman RulesFeynman Diagram ComponentsFeynman Diagram RulesA Few Example Feynman DiagramsA Few Feynman Diagram ExercisesWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu1PHYS 3446 – Lecture #22Wednesday, Nov. 29, 2006Dr. Jae Yu1. The Standard Model Symmetry Breaking and the Higgs particleHiggs Search StrategyNeutrino OscillationsIssues in the Standard Model2. Feynmann DiagramsWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu2Spontaneous Symmetry BreakingWhile the collection of ground states does preserve the symmetry in L, the Feynman formalism allows to work with only one of the ground states through the local gauge symmetry Causes the symmetry to break.This is called “spontaneous” symmetry breaking, because symmetry breaking is not externally caused.The true symmetry of the system is hidden by an arbitrary choice of a particular ground state. This is the case of discrete symmetry w/ 2 ground states.Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu3EW Potential and Symmetry Breaking42224121Symmetric about this axisNot symmetric about this axisWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu4The Higgs Mechanism•Recovery from a spontaneously broken electroweak symmetry gives masses to gauge fields (W and Z) and produce a massive scalar boson–The gauge vector bosons become massive (W and Z) –The massive scalar boson produced through this spontaneous EW symmetry breaking is the Higgs particle•In SM, the Higgs boson is a ramification of the mechanism that gives masses to weak vector bosons, leptons and quarksThe Higgs MechanismWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu5Higgs Production Processes at Hadron CollidersGluon fusion: Hgg WW, ZZ Fusion: HZZWW ,Higgs-strahlung off W,Z: HZWZWqq , ,**Higgs Bremsstrahlung off top: Httggqq ,Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu6Hadron Collider SM Higgs Production LHCTevatronWe use WHe+bb channel for search for Higgs at TevatronWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu7SM Higgs Branching Ratio 140GeV/c2We use WHe+bb channel for search for HiggsWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu8How do we find the Higgs particle?•Look for WHl++b b-bar•Use the finite lifetime of mesons containing b-quarks within a particle jets.b vertexSiliconDetectorsBeampipe1”Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu9LEP EWWG: http://www.cern.ch/LEPEWWG 114.4<MH<199GeVWhat do we know as of Winter 06?Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu10How do we make a Neutrino Beam?•Use large number of protons on target to produce many secondary hadrons (, K, D, etc) and focus as many of them as possible•Let and K decay in-flight for beam in the decay pipe– + 99 99 K 6 •Let the beam go through shield and dirt to filter out and the remaining hadrons, except for –Dominated by pGood targetGood beam focusingLong decay regionSufficient dumpWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu11How can we select sign of neutrinos?•Neutrinos are electrically neutral•Need to select the charge of the secondary hadrons from the proton interaction on target•Sets of Dipoles are used to select desired charges of the secondary hadronsdi-polesWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu12How can there be wrong sign of neutrinos in a sign selected beam?•Interaction of correct sign secondary hadrons with beamline elements, including dump and shields–Act as if a fixed target is hit by hadron beam•Back-scatter of unused protons into the beamline•CP violating neutrino oscillationsWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu134. QCD Factorization TheoremNon-perturbative, infra-red partk k’W+(W-)p, }EHadPq=k-k’q, (q)xPPartonic hard scatter=f*pfpFactor the whole interaction into two independent parts!!Allow QCD perturbation theory to work and physical observables calculable.Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu14How is sin2W measured?•Cross section ratios between NC and CC proportional to sin2W•Llewellyn Smith Formula:•Define experimental variable to distinguish NC and CC•Compare the measured ratio with MC prediction)(CC)(CCW4W22)(CC)(NC)(σσ1θsin95θsin21ρσσRWEMweakQIc oupling2)3(sin)3(weakIcoupling Wednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu15Charged Current EventsNeutral Current EventsHow Can Events be Separated?x-viewy-viewx-viewy-viewNothing is coming in!!!Nothing is coming in!!!Nothing is going out!!!Event LengthWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu16Neutrino Oscillation•First suggestion of neutrino mixing by B. Pontecorvo at the K0, K0-bar mixing in 1957•Solar neutrino deficit in 1969 by Ray Davis in Homestake Mine in SD. Called MSW effect•Caused by the two different eigenstates for mass and weak•Neutrinos change their flavor as they travel Neutrino flavor mixing•SM based on massless neutrinos•SM inconsistent•Oscillation probability depends on–Distance between the source and the observation point–Energy of the neutrinos–Difference in square of the massesWednesday, Nov. 29, 2006 PHYS 3446, Fall 2006Jae Yu17Neutrino Oscillation Formalism•Two neutrino mixing case:sin cosmn q n q n=- +1 2where
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