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Supersymmetry! The Cosmos … Time Space … and the LHC John ELLIS, CERN, Geneva, Switzerland 300,000 Formation years of atoms 3 Formation minutes of nuclei Formation 1 micro- of protons second & neutrons Origin of dark matter? 1 pico- Appearance second of mass? Origin of Matter? A Strange Recipe for a Universe Ordinary Matter The ‘Concordance Model’ prompted by astrophysics & cosmology Open Cosmological Questions • Where did the matter come from? LHC? 1 proton for every 1,000,000,000 photons • What is the dark matter? LHC? Much more than the normal matter • What is the dark energy? LHC? Even more than the dark matter • Why is the Universe so big and old? LHC? Mechanism for cosmological inflation Need particle physics to answer these questions The Very Early Universe • Size: a zero • Age: t zero • Temperature: T large T ~ 1/a, t ~ 1/T2 • Energies: E ~ T • Rough magnitudes: T ~ 10,000,000,000 degrees E ~ 1 MeV ~ mass of electron t ~ 1 second Need particle physics to describe earlier history DarkDark MatterMatter in in the the Universe Universe Astronomers say thatAstronomers most of tellthe matterus that mostin the of the Universematter in theis invisibleuniverse is Darkinvisible Matter „Supersymmetric‟ particles ? WeWe shallwill look look for for it themwith thewith LHC the LHC Where does the Matter come from? Dirac predicted the existence of antimatter: same mass opposite internal properties: electric charge, … Discovered in cosmic rays Studied using accelerators Matter and antimatter not quite equal and opposite: WHY? 2008 Nobel Physics Prize: Kobayashi & Maskawa Is this why the Universe contains mainly matter, not antimatter? Need physics beyond the Standard Model: objective of the LHC How to Create the Matter in the Universe? Sakharov • Need a difference between matter and antimatter observed in the laboratory • Need interactions that make matter present in unified theories not yet seen by experiment • Must break thermal equilibrium Possible in the early Universe Will we be able to calculate using laboratory data? Summary of the Standard Model • Particles and SU(3) × SU(2) × U(1) quantum numbers: • Lagrangian: gauge interactions matter fermions Yukawa interactions Higgs potential Parameters of the Standard Model • Gauge sector: – 3 gauge couplings: g3, g2, g ́ Unification? – 1 strong CP-violating phase • Yukawa interactions: – 3 charge-lepton masses Flavour? – 6 quark masses – 4 CKM angles and phase • Higgs sector: – 2 parameters: μ, λ Mass? • Total: 19 parameters 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 < ~ 180 GeV • Raises many unanswered questions: mass? flavour? unification? Precision Tests of the Standard Model Lepton couplings Pulls in global fit Open Questions beyond the Standard Model • What is the origin of particle masses? LHC due to a Higgs boson? • Why so many types of matter particles? LHC • What is the dark matter in the Universe? LHC • Unification of fundamental forces? LHC • Quantum theory of gravity? LHC Why do Things Weigh? Newton: Weight proportional to Mass Einstein: Energy related to Mass Neither explained0 origin of Mass Where do the masses come from? Are masses due to Higgs boson? (the physicists‟ Holy Grail) 2008 Nobel Physics Prize: Nambu Think of a Snowfield Skier moves fast: Like particle without mass e.g., photon = particle of light Snowshoer sinks into snow, moves slower: Like particle with mass e.g., electron The LHC will look for Hiker sinks deep, the snowflake: moves very slowly: The Higgs Boson Particle with large mass The State of the Higgs: May 2009 • Direct search limit from LEP: mH > 114.4 GeV • Electroweak fit sensitive to mt (Now mt = 173.1 ± 1.3 GeV) • Best-fit value for Higgs mass: +34 mH = 84 –26 GeV • 95% confidence-level upper limit: mH < 154 GeV, or 185 GeV including direct limit • Tevatron exclusion: mH < 160 GeV or > 170 GeV Higgs Search @ Tevatron Tevatron excludes Higgs between 160 & 170 GeV Combining the Higgs Information + 15.6 mH = 116.4 -1.3 GeV Supersymmetry? • Would unify matter particles and force particles • Related particles spinning at different rates 0 - ½ - 1 - 3/2 - 2 Higgs - Electron - Photon - Gravitino - Graviton (Every particle is a „ballet dancer‟) • Would help fix particle masses • Would help unify forces • Predicts light Higgs boson • Could provide dark matter for the astrophysicists and cosmologists Unify the Fundamental Interactions: Einstein‟s Dream … … but he never succeeded Maybe with extra dimensions of space? At what Energy is the New Physics? Dark matter Origin of mass A lot accessible Some accessible only via to the LHC astrophysics & cosmology To answer these questions: The Large Hadron Collider (LHC) Several thousand billion protons Each with the energy of a fly Primary targets: •Origin of mass 99.9999991% of light speed •Nature of Dark Matter Orbit 27km ring 11 000 times/second •Primordial Plasma A billion collisions a second •Matter vs Antimatter The Emptiest Space in the Solar System Vacuum similar to interplanetary space: the pressure in the beam-pipes will be ten times lower than on the Moon. Colder than Outer Space LHC 1.9 degrees above absolute zero = - 271 C Outer space 2.7 degrees above zero = - 270 C First Beam on Sept. 10th A billion people watched on TV Temporary Halt since Sept. 19th • Electrical fault in connection between two magnets • Ohmic heating broke cryostat, vacuum pipe • Repairs ongoing during shutdown • Precursor diagnostic identified • Simple rewiring to avoid recurrence • Relief valves being installed Last repaired Magnet being lowered Pressure Release Valves Residual potential Concern Safe operating Conditions GeneralVista General View delof LHC y& sus itsExperimentos Experiments 27km in circumference ~ 100m deep ALICE: Primordial cosmic plasma ATLAS: Higgs and supersymmetry CMS: Higgs and supersymmetry LHCb: Matter-antimatter difference The ATLAS Detector Diameter 25 m Over 2000 scientists and engineers Total length 46 m Nearly 40 countries Overall weight 7000 tons More components than a moon rocket Assembling ATLAS The CMS detector: search for Higgs and supersymmetry Heavier than the Eiffel Tower: would sink in water 2500 physicists 180 institutes 37 countries Construction of CMS The LHC Physics Haystack(s) Interesting cross sections • Cross sections for heavy particles ~ 1 /(1 TeV)2 • Most have small couplings ~ α2 • Compare with total cross section ~ 1/(100 MeV)2 • Fraction ~ 1/1,000,000,000,000 Susy • Need ~ 1,000 events for signal • Compare needle ~ 1/100,000,000 m3 Higgs • Haystack ~ 100 m3 • Must look in ~ 100,000 haystacks A Simulated Higgs Event A la recherche du Some Sample Higgs Signals Higgs perdu … γγ ZZ* -> 4 leptons ττ When will the LHC discover the Higgs boson? 1 „year‟ @ 1033 „month‟ @ 1033 „month‟ @ 1032 Blaising, JE et al: 2006 Theoretical Constraints on Higgs Mass • Large → large self-coupling → blow up at low energy scale Λ due to renormalization • Small: renormalization due to t quark drives quartic coupling < 0 at some scale Λ → vacuum unstable • Bounds on Higgs mass depend on Λ Vacuum Stability vs Metastability • Dependence on scale up to which Standard Model remains – Stable – Metastable at non-zero temperature – Metastable at zero temperature What is the probable fate of the SM? Confidence Levels (CL) Confidence Levels (CL) for different fates without/with Tevatron exclusion Blow-up excluded at 99.2% CL CL as function of instability scale Espinosa, JE, Giudice, Hoecker, Riotto The LHC will tell the fate of the SM Examples with LHC measurement of mH = 120 or 115 GeV Espinosa, JE, Giudice, Hoecker, Riotto How to Stabilize a Light Higgs Boson? • Top quark destabilizes potential: introduce introduce stop-like scalar: • Can delay collapse of potential: • But new coupling must be fine-tuned to avoid blow-up: • Stabilize with new fermions: – just like Higgsinos • Very like Supersymmetry! JE & D. Ross The Stakes in the Higgs Search • How is particle symmetry broken? • Is there an elementary scalar field? • What is the fate of the Standard Model? • Did mass appear when the Universe was a picosecond old? • Did Higgs help create the matter in the Universe? • Did a related inflaton make the Universe so big and old? • Why is there so little dark energy? Comments on Dark Energy • Many orders of magnitude smaller than expected contributions from „known‟ physics: 10-48 GeV4 4 -4 4 QCD: ΛQCD ~ 10 GeV 4 8 4 Higgs: mW ~ 10 GeV 4 12 4 Broken susy: msusy ~ 10 GeV 4 64 4 GUT: mGUT ~ 10 GeV 4 76 4 Quantum Gravity: mP ~ 10 GeV • Need new physics! The Higgs and Vacuum Energy • Must add a constant to the effective potential so that net value in true vacuum ~ 0 • Physical value ~ 10-60 • Will light be cast by discovery of Higgs? Theorists getting Cold Feet • Composite Higgs model? conflicts with 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? Elementary Higgs or Composite? • Higgs field: • Fermion-antifermion <0|H|0> ≠ 0 condensate • Quantum loop problems • Just like QCD, BCS Cutoff superconductivity Λ = 10 TeV • Top-antitop condensate? needed mt > 200 GeV • New technicolour force? inconsistent with • Cut-off Λ ~ 1 TeV precision electroweak data? with Supersymmetry? Supersymmetry? • Would unify
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