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Searches for New Physics

Searches for New Physics. Motivations Examples Searches so far Setting scene for LHC. 1/12. Status of the Standard Model. Perfect agreement with all confirmed accelerator data Consistency with precision electroweak data (LEP et al ) only if there is a Higgs boson

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Searches for New Physics

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  1. Searches for New Physics • Motivations • Examples • Searches so far • Setting scene for LHC 1/12

  2. Status of the Standard Model • Perfect agreement with all confirmedaccelerator data • Consistency with precision electroweak data (LEP et al) only if there is a Higgs boson • Agreement seems to require a relatively light Higgs boson weighing < ~ 200 GeV • Raises many unanswered questions: mass? flavour? unification?

  3. New Electroweak Physics? Check energy-dependence of radiative corrections Limit new contributions to vacuum polarization due, e.g., to new fermions

  4. Searches for New Gauge Bosons Limits on W’, Z’ from Tevatron

  5. Accelerator Evidence for New Physics? • The anomalous (?) anomalous magnetic moment of the muon • Disagrees with the SM @ 3.3  level if use e+e- annihilation data • But no discrepancy if use  decay data • Jury still out

  6. Open Questions beyond the Standard Model • What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) • Why so many types of matter particles? matter-antimatter difference? • Unification of the fundamental forces? at very high energy ~ 1016 GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings • Quantum theory of gravity? (super)string theory: extra space-time dimensions? LHC LHC LHC LHC

  7. A lot accessible directly to the LHC Some accessible only indirectly: Astrophysics and cosmology? At what Energy is the New Physics? Origin of mass Dark matter

  8. Where do the masses come from ? photon 0 W + Z 0 W - + 1 0 - 1 Some particles have mass, some do not Newton: Weight proportional to Mass Einstein: Energy related to Mass Neither explained origin of Mass Mass 0 Mass 80.419 91.188 80.419 Are masses due to Higgs boson? (yet another particle)

  9. Higgs Searches • What to look for in the SM: • No luck at LEP: • Nor at the Tevatron … • … so far!

  10. Progress in the Higgs Search @ Tevatron • Many measurements of other SM processes • Factor > 10 before SM Higgs sensitivity

  11. Theorists getting Cold Feet • Composite Higgs model? fermion masses? precision electroweak data? • Interpretation of EW data? consistency of measurements?Discard some? • Higgs + higher-dimensional operators? corridors to higher Higgs masses? • Little Higgs models? extra `Top’, gauge bosons, `Higgses’ • Higgsless models? strong WW scattering, extra D? Kraml et al: hep-ph/0608079

  12. Higgs field: <0|H|0> ≠ 0 Quantum loop problems Fermion-antifermion condensate Just like QCD, BCS superconductivity Top-antitop condensate? needed mt > 200 GeV Elementary Higgs or Composite? Cutoff Λ = 10 TeV • New technicolour force? consistency with precision electroweak data? • Cut-off Λ ~ 1 TeV with Supersymmetry?

  13. Searches for Technicolour

  14. What is Supersymmetry (Susy)? • The last undiscovered symmetry? • Could unify matter and force particles • Links fermions and bosons • Relates particles of different spins 0 - ½ - 1 - 3/2 - 2 Higgs - Electron - Photon - Gravitino - Graviton • Helps fix masses, unify fundamental forces

  15. Other Reasons to like Susy It enables the gauge couplings to unify It predicts mH < 150 GeV As suggested by EW data Erler: 2006 JE, Nanopoulos, Olive + Santoso: hep-ph/0509331

  16. Astronomers say that most of the matter in the Universe is invisible Dark Matter Lightest Supersymmetric particles ? We shall look for them with the LHC

  17. 3.3 σ effect in gμ – 2? Constraints on Supersymmetry • Absence of sparticles at LEP, Tevatron selectron, chargino > 100 GeV squarks, gluino > 250 GeV • Indirect constraints Higgs > 114 GeV, b → s γ • Density of dark matter lightest sparticle χ: WMAP: 0.094 < Ωχh2 < 0.124

  18. Classic Supersymmetric Signature Missing transverse energy carried away by dark matter particles

  19. Limits on Sparticles

  20. Focus-point region at large m0 Current Constraints on CMSSM Assuming the lightest sparticle is a neutralino Excluded because stau LSP Excluded by b  s gamma WMAP constraint on relic density Excluded (?) by latest g - 2 JE + Olive + Santoso + Spanos

  21. Sparticles may not be very light Full Model samples ← Second lightest visible sparticle Provide Dark Matter Detectable @ LHC Dark Matter Detectable Directly Lightest visible sparticle → JE + Olive + Santoso + Spanos

  22. Strategies for Detecting Supersymmetric Dark Matter • Annihilation in galactic halo χ – χ antiprotons, positrons, …? • Annihilation in galactic centre χ – χ γ + …? • Annihilation in core of Sun or Earth χ – χ ν + …  μ + … • Scattering on nucleus in laboratory χ + A  χ + A

  23. Search for Supersymmetric Dark Matter Limits on scattering of dark matter vs Predictions in some susy models

  24. Open Questions beyond the Standard Model • What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) • Why so many types of matter particles? matter-antimatter difference? • Unification of the fundamental forces? at very high energy ~ 1016 GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings • Quantum theory of gravity? (super)string theory: extra space-time dimensions?

  25. New Physics Constraints from B Mesons • Good consistency with CKM predictions • Start to constrain BSM, e.g., supersymmetry

  26. Searches for ‘Axions’ • Solve strong CP problem • Constraints from astrophysics • Laboratory searches begin to bite • Variants also considered

  27. Search for CPT Violation • Probes with neutral kaons • Look for mass, lifetime differences • Quantum gravity might yield decoherence? would violate CPT

  28. Open Questions beyond the Standard Model • What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) • Why so many types of matter particles? matter-antimatter difference? • Unification of the fundamental forces? at very high energy ~ 1016 GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings • Quantum theory of gravity? (super)string theory: extra space-time dimensions?

  29. Searches for Baryon Decay Compilation of limits on different decay modes

  30. New Gravitational Physics? Indirect evidence for gravitational waves Limits on deviations from Einstein/Newton

  31. String Theory • Candidate for reconciling gravity with quantum mechanics • Point-like particles → extended objects • Simplest possibility: lengths of string • Quantum consistency fixes # dimensions: • Bosonic string: 26, superstring: 10 • Must compactify extra dimensions, scale ~ 1/mP? • Or larger? Any way to test it?

  32. How large could extra Dimensions be? • 1/TeV? could break supersymmetry, electroweak • micron? can rewrite hierarchy problem • Infinite? warped compactifications • Look for black holes, Kaluza-Klein excitations @ colliders?

  33. And if gravity becomes strong at the TeV scale … Black Hole Production at LHC? Multiple jets, leptons from Hawking radiation

  34. Sometimes New Particles appear as they were expected … SEARCH FOR GLUONS IN e+ e- ANNIHILATION. John R. Ellis, Mary K. Gaillard, Graham G. Ross . CERN-TH-2161, Apr 1976, Nucl.Phys.B111:253,1976 … but sometimes not

  35. Haiku by Matsuo Basho In a way, it was quite fun not to see Mount Fuji in foggy rain • Interesting for theorists • But the politicians would rather we found something

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