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What Particle Physicists Want to Know

What Particle Physicists Want to Know. Hitoshi Murayama Letters & Science Forum December 2, 2002. We are interested in things we don’t see. Energy budget of Universe. Stars and galaxies are only ~0.5% Neutrinos are ~0.3–10% Rest of ordinary matter (electrons and protons) are ~5%

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What Particle Physicists Want to Know

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  1. What Particle PhysicistsWant to Know Hitoshi Murayama Letters & Science Forum December 2, 2002

  2. We are interested inthings we don’t see L&S Forum

  3. Energy budget of Universe • Stars and galaxies are only ~0.5% • Neutrinos are ~0.3–10% • Rest of ordinary matter (electrons and protons) are ~5% • Dark Matter ~30% • Dark Energy ~65% • Anti-Matter 0% • Higgs condensate ~1062%?? L&S Forum

  4. The Cosmic Questions • What is Dark Matter? • What is Dark Energy? • How much is Neutrino component? • Is Higgs Boson really there? • Where did Anti-Matter go? L&S Forum

  5. Is there an underlying simplicity behind vast phenomena in Nature? Einstein dreamed to come up with a unified description But he failed to unify electromagnetism and gravity (GR) Einstein’s Dream L&S Forum

  6. Special relativity GR Quantum ElectroDynamics Weak force Electroweak theory Strong force String theory? Grand Unification? History of Unification electric magnetic planets atoms apple electromagnetiesm Quantum mechanics gravity mechanics g-decay b-decay a-decay L&S Forum

  7. HERA ep collider Unification of electromagnetic and weak forces  electroweak theory Long-term goal since ‘60s We are getting there! The main missing link: Higgs boson We are just about to achieveanother layer of unification EM weak L&S Forum

  8. What are they?

  9. “Wimpy and Abundant”Neutrinos are Everywhere • They come from the Big Bang: • When the Universe was hot, neutrinos were created equally with any other particles • They are still left over: ~300 neutrinos per cm3 • They come from the Sun: • Trillions of neutrinos going through your body every second • They are shy: • If you want to stop them, you need to stack up lead shield up to three light-years L&S Forum

  10. Pauli postulated neutrinos in order to save the energy conservation in nuclear b-decay in 1930 Finally discovered by Cowan and Reines using a nuclear reactor in 1958 Massless Neutrinos in the Standard Model (‘60s) Evidence for neutrino mass from SuperK (1998) and SNO (2002) First evidence that the minimal Standard Model of particle physics is incomplete! 2002 Nobel to pioneers: Davis and Koshiba Neutrinosfrom backstage to center stage L&S Forum

  11. Neutrinos Have Mass L&S Forum SuperKamiokande

  12. Why do neutrinos have mass at all? Why so small? At least million times smaller than the lightest particle: electron We have seen mass differences. What are the masses? Wn~mn/15eV Are neutrinos and anti-neutrinos the same? How do we extend the Standard Model to incorporate massive neutrinos? Raised More Questions L&S Forum

  13. Galaxy and cluster of galaxies are held together by mass far bigger than all stars combined Crucial ingredient in the “standard cosmology” and structure formation It is not dim small stars (e.g., MACHOs) WIMPs (Weakly Interacting Massive Particle) strongly favored Stable heavy particle produced in early Universe, left-over from near-complete annihilation TeV=1012eV (or T=1016 degrees): the correct energy scale to produce them Giacconi 2002 Nobel Father of X-ray astronomy Evidence for Dark Matter L&S Forum

  14. Type-IA Supernovae “standard candles” Brightness not quite standard, but correlated with the duration of the brightness curve Apparent brightness  how far (“time”) Know redshift  expansion since then Expansion of Universe is accelerating Type-IA Supernovae L&S Forum

  15. Einstein’s equation: If the energy dilutes as Universe expands, it must slow down Need something that gains in energy as Universe stretches i.e, negative pressure The cosmological constant L has the equation of state w=p/r=–1 Generically called “Dark Energy” Accelerating Universe L&S Forum

  16. Embarrassment with Dark Energy • A naïve estimate of the cosmological constant in Theory: rL~MPl4=GN–2~10120 times observation The worst prediction in theoretical physics! • People had argued that there must be some mechanism to set it zero • But now it seems finite??? L&S Forum

  17. Why do we see matter and cosmological constant almost equal in amount? “Why Now” problem Actually a triple coincidence problem including the radiation If there is a deep reason for rL~ GN2(TeV)8, coincidence natural Cosmic Coincidence Problem Arkani-Hamed, Hall, Kolda, HM L&S Forum

  18. We have to measure w For example with a dedicated satellite experiment Domain wall Friedland, HM, Perelstein What is the Dark Energy? SNAP L&S Forum

  19. Mystery of the “weak force” • Gravity pulls two massive bodies (long-ranged) • Electric force repels two like charges (long-ranged) • “Weak force” pulls protons and electrons (short-ranged) acts only over 10–16 cm [need it for the Sun to burn!] L&S Forum

  20. Something is in the Universe • There is something filling our Universe • It doesn’t disturb gravity or electric force • It does disturb weak force and make it short-ranged • No longer go with speed of light, acquire a mass • “Mother of mass” of all elementary particles • Electron, quarks, muon, … • What is it?? L&S Forum

  21. Cosmology and Particle Physicsmeet at TeV scale • Dark Matter mWIMP~TeV • Fermi (Higgs) scale v~1/4 TeV • Dark Energy rL~(2meV)4vs GN–1/2(TeV)2~0.5meV • Neutrino • (Dm2LMA)1/2~7meV vsGN–1/2(TeV)2~0.5meV • TeV-scale physics likely to be rich L&S Forum

  22. Large Hadron Collider 14 TeV pp CERN (Geneva) Under construction LHC would discover Standard Model Higgs boson of any mass within 3 years! Measure mass, some ratio of couplings LHC L&S Forum

  23. Linear e+e– Collider 0.5–1.5 TeV International Project Planning stage Tests if Higgs Boson is the “Mother of Mass” LC L&S Forum

  24. Dark Matter:The Missing Link? • Dark Matter likely to be TeV-scale electrically neutral weakly interacting particle (e.g., LSP, Lightest KK) • Then accessible at accelerators (LHC & LC) • Precision measurement at LC of its mass, couplings in order to calculate its cosmic abundance • If it agrees with cosmological observations, we understand Universe back to 10–10 sec after the Big Bang L&S Forum

  25. L&S Forum

  26. Where Did Anti-Matter Go?

  27. L&S Forum

  28. Matter and Anti-MatterEarly Universe 10,000,000,001 10,000,000,000 L&S Forum

  29. Matter and Anti-MatterCurrent Universe us 1 The Great Annihilation L&S Forum

  30. Baryogenesis • What created this tiny excess matter? • Necessary conditions for baryogenesis (Sakharov): • matter number non-conservation • CP violation (subtle difference between matter and anti-matter) • Non-equilibrium  G(DB>0) > G(DB<0) • Possible new consequences in • Matter instability • CP violation L&S Forum

  31. Plans to shoot neutrino beams over thousands of kilometers to see this CP-violation may be observed in neutrino oscillation Do We Exist Thanks to Neutrino Mass? It’s of course completely safe! L&S Forum

  32. Conclusion • What is Universe made of? • Einstein’s Dream towards unified description • Physics at TeV scale likely to be rich • LHC & LC: major assault on physics at TeV-scale • Many cosmic questions accessible experimentally • Dark Matter, Dark Energy, Higgs Condensate, Anti-Matter L&S Forum

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