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Hunting the Last Missing Particle of the Standard Model

Hunting the Last Missing Particle of the Standard Model. Shufang Su • Caltech. smaller distance : higher energy. forces. Particles and Forces. -. Building blocks of matter -- elementary particles. Fundamental interactions Gravity Electromagnetic force

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Hunting the Last Missing Particle of the Standard Model

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  1. Hunting the Last Missing Particle of the Standard Model Shufang Su • Caltech

  2. smaller distance : higher energy forces Particles and Forces - • Building blocks of matter -- elementary particles • Fundamental interactions • Gravity • Electromagnetic force • Weak interaction nuclear -decay, burning of the sun … • Strong interaction -decay, holds proton and neutron … ? U. Arizona - Colloquium

  3. t  b Z c W • Electromagnetic  • Weak interaction Z,W • Strong interaction g Standard Model e   g n p Exp Discovery and Theory Development - 1 GeV = 109 eV=1.8x10-24 g  s d u e mass (GeV)  theory U. Arizona - Colloquium

  4. Standard Model - mW=80 GeV mZ=91 GeV Simply impose mass  theory not self-consistent Create mass for “gauge boson”  predict a Higgs particle However, we have not find this particle yet … Is there anything missing ? U. Arizona - Colloquium

  5. Outline - prediction  evidence  confirmation  establishment • Why need a Higgs ? • How to search the Higgs ? • Is it really a (Standard Model) Higgs ? • How to probe new physics using Higgs study ? U. Arizona - Colloquium

  6. Why need a Higgs ? U. Arizona - Colloquium

  7. Universe filled with background • Higgs field • Particle get mass via interaction • with the background Higgs field • Higgs mechanism • P.W. Higgs (1964, 1966) • Weinberg(1967), Salam (1968) Electroweak Symmetry Breaking - 2x10-18 m • Begin with a unified theory of EM and weak interaction We want something that • not disturb electromagnetic force • make weak interaction short-range • How to give mass to W and Z boson ? • How to give mass to quarks and leptons ? U. Arizona - Colloquium

  8. H0=v W,Z mass gauge transformation W degree of freedom eaten by W and Z  longitudinal modes  W,Z obtain mass H0=v X H g mW  gv  v=246 GeV W Higgs Mechanism (Particle Physics) - Potential V= - m2 H2 + ½  H4 left-over degree of freedom  physical Higgs particle minimize the potential mHSM2 v2  (100 GeV)2 Higgs U. Arizona - Colloquium

  9. f H0=v X H y f Higgs Property - • Advantage of Higgs mechanism • quark and lepton mass • SM (with Higgs) agrees well • with experiments mf  y v • Higgs propertyv=246 GeV • CP even scalar • coupling  mass • fermion mf/v • gauge boson mW/v , mZ/v • mass : mHSM2 v2  (100 GeV)2 • mass not predicted • Other model: • composite Higgs • hard to fit with • experimental data • hard to build model However, Higgs is still missing ... Go look for it! U. Arizona - Colloquium

  10. 116 GeV 105 GeV Theoretical Constraint on mHSM - V= - m2 H2 + ½  H4 mH2= v2 K. Riesselmann (1997) (ytyt  … Landau pole  = Mpl  1019 GeV 130 GeV < mH < 180 GeV potential unbounded from below SM valid up to scale  U. Arizona - Colloquium

  11. indirect direct without NuTeV indirect bounds: mt= 171-9 GeV direct search: mt=174.3  5.1 GeV +11 mHSM=81+52 GeV mHSM<193 GeV at 95% C.L. -33 Indirect Constraint from Electroweak Data - LEP EWWG U. Arizona - Colloquium

  12. How to search the Higgs ? • Decay right after it is produced • does not exist in nature anymore • produced it at high-energy colliders • look for its decay products at detectors U. Arizona - Colloquium

  13. mHSM  135 GeV mHSM  135 GeV BrHSM =  (HSM  final state)  (HSM  everything) gold-plated mode for LHC seaches: Ze+e- / +- Higgs Decay (SM) - Branching ratio mHSM (GeV) M. Spira (1998) U. Arizona - Colloquium

  14. Ecm  189 GeV 2461 Pb-1 Ecm  206 GeV 536 Pb-1 e+e- ZHSM e- e+ LEP Search : Current mHSM Limit - • Large Electron Positron Collider (CERN) 1 pb= 10-12 b; 1b=10-28 m2 Add plot • possible signal mHSM 116 GeV • signal+background 37% C.L. • background 8% C.L. exclusion bound mHSM 114.4 GeV 95% C.L. U. Arizona - Colloquium

  15. huge background W,Z  leptons mHSM  135 GeV HSM bb mHSM  135 GeV HSM W+W- Higgs Prodcution at Tevatron (Run II) - - / Ecm = 2 TeV L= 2 fb-1 / year events/year • Tevatron (Fermilab) pp collider CDF, D0 2x104 2x102 cross section (pb) 2 M. Spira (1998) U. Arizona - Colloquium

  16. Higgs Search at Tevatron (Run II) - • Tevatron (Fermilab)Ecm = 2 TeV, L= 2 fb-1 / year If no Higgs is found 95% C.L. exclusion limit (15 year) (5 year) (1 year) Run II Higgs working group U. Arizona - Colloquium

  17. 20 fb-1 130 Higgs Search at Tevatron (Run II) - • Tevatron (Fermilab)Ecm = 2 TeV, L= 2 fb-1 / year Discovery reach (15 year) (5 year) (1 year) Run II Higgs working group U. Arizona - Colloquium

  18. mHSM  135 GeV HSM  mHSM  135 GeV HSM W+W-, ZZ p HSM  , , W+W-, ZZ 120 GeV HSM  180 GeV p Higgs Producction at LHC - • Large Hadron Collider (CERN) pp ATLAS, CMS events/year Ecm = 14 TeV L= 10 fb-1 / year 106 102 ggH 10 104 1 cross section (pb) 10-1 102 10-2 10-3 M. Spira (1998) 1 10-4 mHSM (GeV) U. Arizona - Colloquium

  19. Higgs Search at LHC - • Large Hadron Collider (CERN) pp L=10 fb-1 / year ggH ggHtt 5  • cover entire Higgs mass region of SM with • more than 5  significance. CMS, ATLAS (2002) U. Arizona - Colloquium

  20. Need precise study of Higgs properties at a e+e- collider • basic properties: mass, width, spin and CP quantum number • origin of particle mass  Higgs coupling  particle mass • reconstruct Higgs potential: Higgs self-coupling • If we see something at LHC looks like a Higgs … Is it really a Higgs ? Is it the Standard Model Higgs ? U. Arizona - Colloquium

  21. Higgs Prodcution at LC - Linear Collider e+e- clean environment Ecm = 500 GeV / 1 TeV ; L= 500 / 1000 fb-1 / year H HZ H cross section (fb) HZ Hee Hee mHSM (GeV) LC source book copiously produced, thousands of events U. Arizona - Colloquium

  22. Higgs decay width:HSM/HSM = 6% • HSM =  (HSM  W+W-) • Br (HSM  W+W-) H e- e+ Z Higgs production H Higgs decay HSM  W+W- Higgs Mass, Decay Width and JPC - Miller et. al. (2001) Garcia et al. (2001) • Higgs mass: mHSM = 40 MeV • reconstruct Higgs in ZH production • compare with indirect bounds from global fit • final state angular distribution • angular and polarization asymmetry e+e- Z U. Arizona - Colloquium

  23. v reconstruct Higgs potential Higgs Coupling - • mHSM  150 GeV • Higgs decay branching ratio • Higgs production cross section • mHSM  150 GeV • HSM cc, gg,  • too small • HSM W+W-,ZZ • precisely measured • HSM bb • precision reduced when • mHSM  200 GeV • HSM tt • possible when mHSM  2 mt Carena et. Al. (2002) mHSM = 120 GeV U. Arizona - Colloquium

  24. Photon Collider - • e+e-collider operating in  modeEcm=0.8 Ecmee • measure  (HSM  ) •  bb (HSM  ) Br(HSM  bb) • sensitive to heavy states • Higgs decay width HSM =  (HSM  ) / Br(HSM   ) • mHSM  200 GeV , directly measure HSM • photon polarization  CP quantum number every particle (get mass from Higgs) contributes U. Arizona - Colloquium

  25. There must be new physics beyond minimal Standard Model • What is it ? • How to probe it using Higgs study ? • If we find deviation from Standard Model prediction … What can we learn ? U. Arizona - Colloquium

  26. H - 2 precise cancellation up to 1034 order -(1019 GeV)2 (1019 GeV)2 • Supersymmetry Spin differ by 1/2 SM particle superpartner What New Physics ? - • SM is an effective theory below some energy scale  • Hierarchy problem:MEW100 GeV , Mplank 1019 GeV ? • Naturalness problem: mass of a fundamental scalar (like Higgs) receive huge quantum corrections: • (mH2)physical  (mH2)0 + 2 (100 GeV)2 H Minimal Supersymmetric Standard Model (MSSM) U. Arizona - Colloquium

  27. Higgs Sector in MSSM - • CP-even Higgs h0 • decoupling limit: mA0  mZ • h0 similar to SM Higgs • h0 mass • tree level: mh0mZ • loop corrections: mh0 135 GeV gauge coupling SM Higgs searches at low mass region could be applied to the light MSSM Higgs h0 MSSM Higgs sector determined bytan andmA0 U. Arizona - Colloquium

  28. e+e- Zh0 e+e- A0h0 mA0 91.9 GeV mh0 91.0 GeV 0.5  tan  2.4 LEP Search Limit (MSSM) - cos2(-eff)  sin2(-eff) A0h0 Zh0 U. Arizona - Colloquium

  29. h0 coupling mZ2 HSM coupling mA02 -1  mA0 650-800 GeV Bounds on mA0 From Higgs Coupling Measurements -  Br(HW+W-)=5% mA0 controls the degree of decoupling • mA0  mZ • decoupling region • no deviation • non-zero deviation •  • constraints on mA0 Carena et. al. (2002) U. Arizona - Colloquium

  30. gauge interaction anomaly gravity low energy MSSM (visible sector) 105 parameters SUSY-breaking (hidden sector) a few parameters • gravity-mediated SUSY breaking (SUGRA) • gauge-mediated SUSY breaking (GMSB) • anomaly-mediated SUSY breaking (AMSB) Three SUSY Breaking Scenarios - • supersymmetry must be broken • electron: m=0.511 MeV, no scalar-electron • MSSM:105 new SUSY breaking parametersout of control • mechanism for SUSY breaking: (flavor blind) • greatly reduce SUSY parameters something U. Arizona - Colloquium

  31. Distinguish SUSY Breaking Scenario mA0 500 GeV mA0 1000 GeV - • LEP search bound Dedes, Heinemeyer, SS, weiglein (2001, 2002) • deviation from SM Higgs coupling  constrains on mA0 U. Arizona - Colloquium

  32. mA0 1100 GeV mA0 1300 GeV GMSB and AMSB - U. Arizona - Colloquium

  33. Distinguish SUSY Breaking Scenario - 500 GeV  mA0  600 GeV , tan  30 AMSB • if we know ranges of • mA0, tan from LHC • if we see deviations • of coupling at LC • Can we distinguish various SUSY breaking scenario? GMSB SUGRA U. Arizona - Colloquium

  34. Conclusion - Higgs mechanism provides a simple and elegant way to explain the origin of the mass • Why need a Higgs ? • How to search the Higgs ? • Is it really a (Standard Model) Higgs ? • How to probe new physics using Higgs study ? • Tevatron Run II exclude Higgs up to 180 GeV (10 fb-1) • LHC would find the Higgs if it is there • detail study at Linear Collider • measure Higgs mass, decay width, coupling… at high precision • Minimal Supersymmetric Standard Model (MSSM) • constrain parameter space (mA0) • distinguish various SUSY breaking scenarios • Heavy Higgs search U. Arizona - Colloquium

  35. p - p p p Tevatron LHC 2007-- Now -- The hunting is continuing … U. Arizona - Colloquium

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