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THE DARK UNIVERSE

THE DARK UNIVERSE. Jonathan Feng Department of Physics and Astronomy UCI Distinguished Faculty Lecture 26 October 2004. What is the universe made of?. An age old question, but we live at a particularly interesting time:. We know how “big” the universe is.

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THE DARK UNIVERSE

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  1. THE DARK UNIVERSE Jonathan Feng Department of Physics and Astronomy UCI Distinguished Faculty Lecture 26 October 2004

  2. What is the universe made of? • An age old question, but we live at a particularly interesting time: • We know how “big” the universe is. • We have no idea what most of it is made of. UCI Distinguished Faculty Lecture

  3. Alexandria Syene Historical Precedent Eratosthenes measured the size of the Earth in 200 B.C. • Much bigger than expected • Accurate to 10% • Led to more questions than answers UCI Distinguished Faculty Lecture

  4. NGC 2403 CL0024+1654 Now again, but with Earth  universe First evidence from rotation of galaxies and galactic clusters in 1930’s • Expect vc ~ R -1/2 beyond luminous region • Instead find vc ~ constant • Discrepancy resolved by postulating dark matter UCI Distinguished Faculty Lecture

  5. Since 1998, these data have been supplemented by additional cosmological observations These measurements imply: Dark Matter: 23% ± 4% Dark Energy L: 73% ± 4% The universe is 96% dark! • Much bigger than expected • Accurate to 10% • Leads to more questions than answers UCI Distinguished Faculty Lecture

  6. earth, air, fire, water stars, planets, dark matter, dark energy UCI Distinguished Faculty Lecture

  7. Stable • Cold (slow) • Non-baryonic Dark Matter: What is it? Known DM properties Dark matter requires new kinds of particles Particle physics ↔ Cosmology UCI Distinguished Faculty Lecture

  8. Dark Matter Candidates • Many different kinds of new particles are possible. • But independent of cosmology, new particles are required to solve one of the biggest problem in particle physics: electroweak symmetry breaking. • These particles are often WIMPs, weakly-interacting massive particles, with masses ~ 100 GeV. Could these be dark matter? UCI Distinguished Faculty Lecture

  9. 1) Initially, DM is in thermal equilibrium: cc↔ f f 2) Universe cools: N = NEQ ~ e-m/T 3) cs “freeze out”: N ~ const Thermal Relic DM Particles 1 2 3 UCI Distinguished Faculty Lecture

  10. Final N fixed by annihilation cross section: WDM ~ 0.1 (sweak/sA) Remarkable! 13 Gyr later, Martha Stewart sells ImClone stock – the next day, stock plummets Exponential drop Freeze out Coincidences? Maybe, but worth serious investigation! UCI Distinguished Faculty Lecture

  11. New Possibilities for Dark Matter Supersymmetry predicts a partner particle for every known particle. The partner of the photon is generally an excellent DM candidate, but different models have different implications for detection. Feng, Matchev, Wilczek (2000) Conventional models Focus point models UCI Distinguished Faculty Lecture

  12. cc neutrinos in the Sun cc positrons in the halo Steve Barwick AMANDA in the Antarctic Ice AMS on the International Space Station Focus point dark matter predicts enhanced detection rates UCI Distinguished Faculty Lecture

  13. Extra spatial dimensions could be curled up into small circles. • Particles moving in extra dimensions appear as a set of copies of normal particles. … 4/R 3/R 2/R Garden hose mass 1/R 0 Extra Dimensional Dark Matter Cheng, Feng, Matchev (2002) UCI Distinguished Faculty Lecture

  14. Dark Matter Detection CDMS in the Soudan mine ½ mile underground in Minnesota DM UCI Distinguished Faculty Lecture

  15. SuperWIMP Dark Matter Feng, Rajaraman, Takayama (2003) • Both supersymmetry and extra dimensions predict partner particles for all known particles. What about the partners of the graviton? • Such partners interact only through gravity, that is, extremely weakly. • Can they have the right relic density? UCI Distinguished Faculty Lecture

  16. SuperWIMP Dark Matter • Early universe behaves as usual, WIMPs freeze out with desired thermal relic density • A year passes…then WIMPs decay to graviton partners WIMP MPl2/MW3 ~ year ≈ G̃ Graviton partners inherit the right density, but escape most searches – they are superweakly-interacting “superWIMPs” UCI Distinguished Faculty Lecture

  17. Andy Lankford Dark Matter at Colliders Large Hadron Collider at CERN, Geneva If dark matter is WIMPs or superWIMPs, we will know soon after the LHC turns on in 2007 UCI Distinguished Faculty Lecture

  18. Acknowledgments Physics and Astronomy Department staff Szu Wang UCI Distinguished Faculty Lecture

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