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 Agreement seems to require a relatively light Higgs boson weighing < ~ 200 GeV Raises many unanswered questions: mass? flavour? unification?

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

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

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

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 ~ GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions? LHC

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

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

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

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

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/

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

Searches for Technicolour

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 /2 - 2 Higgs - Electron - Photon - Gravitino - Graviton Helps fix masses, unify fundamental forces

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

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

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: < Ω χ h 2 < σ effect in g μ – 2?

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

Limits on Sparticles

Current Constraints on CMSSM WMAP constraint on relic density Excluded because stau LSP Excluded by b  s gamma Excluded (?) by latest g - 2 Focus-point region at large m 0 Assuming the lightest sparticle is a neutralino JE + Olive + Santoso + Spanos

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

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

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

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 ~ GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions?

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

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

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

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 ~ GeV? probe directly via baryon decay, neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions?

Searches for Baryon Decay Compilation of limits on different decay modes

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

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/m P ? Or larger? Any way to test it?

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 colliders?

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

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

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