What Particle Physicists Want to Know Hitoshi Murayama Letters & Science Forum December 2, 2002

L&S Forum2 We are interested in things we don’t see

L&S Forum3 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 ~10 62 %??

L&S Forum4 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 Forum5 Einstein’s Dream 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)

L&S Forum6 History of Unification gravity electric magnetic  -decay  -decay  -decay planets apple electromagnetiesm atoms Quantum mechanics mechanics Special relativity Quantum ElectroDynamics Weak force Strong force Electroweak theory Grand Unification? GR String theory?

L&S Forum7 We are just about to achieve another layer of unification 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 EM weak

What are they?

L&S Forum9 “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 cm 3 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 Forum10 Neutrinos from backstage to center stage Pauli postulated neutrinos in order to save the energy conservation in nuclear  - 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

L&S Forum11 Neutrinos Have Mass SuperKamiokande

L&S Forum12 Raised More Questions 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?  ~m /15eV Are neutrinos and anti- neutrinos the same? How do we extend the Standard Model to incorporate massive neutrinos?

L&S Forum13 Evidence for Dark Matter 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=10 12 eV (or T=10 16 degrees): the correct energy scale to produce them Giacconi 2002 Nobel Father of X-ray astronomy

L&S Forum14 Type-IA Supernovae 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

L&S Forum15 Accelerating Universe 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  has the equation of state w=p/  =–1 Generically called “Dark Energy”

L&S Forum16 Embarrassment with Dark Energy A naïve estimate of the cosmological constant in Theory:   ~M Pl 4 =G N –2 ~ 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 Forum17 Cosmic Coincidence Problem 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   ~ G N 2 (TeV) 8, coincidence natural Arkani-Hamed, Hall, Kolda, HM

L&S Forum18 What is the Dark Energy? We have to measure w For example with a dedicated satellite experiment Domain wall Friedland, HM, Perelstein SNAP

L&S Forum19 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 Forum20 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 Forum21 Cosmology and Particle Physics meet at TeV scale Dark Matter m WIMP ~TeV Fermi (Higgs) scale v~1/4 TeV Dark Energy   ~(2meV) 4 vs G N –1/2 (TeV) 2 ~0.5meV Neutrino  (  m 2 LMA ) 1/2 ~7meV vs G N –1/2 (TeV) 2 ~0.5meV  TeV-scale physics likely to be rich

L&S Forum22 LHC 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

L&S Forum23 LC Linear e + e – Collider 0.5–1.5 TeV International Project Planning stage Tests if Higgs Boson is the “Mother of Mass”

L&S Forum24 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

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Where Did Anti-Matter Go?

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L&S Forum28 Matter and Anti-Matter Early Universe 10,000,000,00110,000,000,000

L&S Forum29 Matter and Anti-Matter Current Universe The Great Annihilation 1 us

L&S Forum30 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  (  B>0) >  (  B<0) Possible new consequences in –Matter instability –CP violation

L&S Forum31 Do We Exist Thanks to Neutrino Mass? Plans to shoot neutrino beams over thousands of kilometers to see this CP-violation may be observed in neutrino oscillation It’s of course completely safe!

L&S Forum32 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