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Hunting the Last Missing Particle of the Standard Model

Delve into the quest for the elusive Higgs particle, a crucial missing piece of the Standard Model in particle physics. Explore the building blocks of matter, fundamental interactions, and the mechanisms behind mass generation. Unravel the mysteries of the universe with this comprehensive overview.

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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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