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A Convenient Exception

A Convenient Exception. Woodcock Society Banquet May 7, 2008 Chris L. Davis. Elementary Particle Physics or High Energy Physics. The study of the building blocks of matter and, their interactions. Structure of Matter. Plus Anti-Particles (Anti-Matter). The Building Blocks.

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A Convenient Exception

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  1. A Convenient Exception Woodcock Society Banquet May 7, 2008 Chris L. Davis Woodcock Society Banquet

  2. Elementary Particle PhysicsorHigh Energy Physics • The study of the building blocks of matter and, their interactions Woodcock Society Banquet

  3. Structure of Matter Woodcock Society Banquet

  4. Plus Anti-Particles (Anti-Matter) The Building Blocks Woodcock Society Banquet

  5. The Interactions Woodcock Society Banquet

  6. Why High Energy ? • Resolution is defined by wavelength. You can’t see anything smaller than the wavelength of the “probe” you are using. • Visible light’s wavelength is about 0.5 millionth of a meter • Size of an atom is about 0.1 billionth of a meter • You can’t “see” atoms • Particles have a wavelength • Wavelength decreases with increasing energy (momentum). Woodcock Society Banquet

  7. CERN, Geneva, Switzerland Accelerators LHC 27km circumference Woodcock Society Banquet

  8. Fermilab, Chicago Main ring Circumference 4 miles Woodcock Society Banquet

  9. Stanford Linear Accelerator (SLAC) Two mile long linear accelerator Woodcock Society Banquet

  10. “Big” Science LHC centered on UofL Woodcock Society Banquet

  11. BaBar Collaboration at SLAC More than 600 PhD Physicists from 74 institutions in 9 countries In data acquisition mode since 1999 Woodcock Society Banquet

  12. Experimental Goals • Detailed measurement of asymmetry between matter and anti-matter known as CP-violation • C – electric charge • P – Parity (mirror image inversion) • CP violation first observed at CERN in 1964 at the level of 1 part in 1000 • Prior to this observation it was assumed there was a 100% symmetry between matter and anti-matter • The BaBar experiment was designed to verify and make detailed measurements of the asymmetry Why BaBar ? • We look for CP violation in particles containing a b quark and an anti-b quark - BBbar or BaBar. Collaboration mascot, BaBar the elephant in the children’s books by Laurent de Brunhoff Woodcock Society Banquet

  13. BaBar Detector BaBar has verified CP-violation and measured important parameters which characterize the asymmetry Woodcock Society Banquet

  14. So What ! What does CP violation do for you ? Everything ! Why ? A long, long time ago scientists believe there was a Big Bang ! Woodcock Society Banquet

  15. The Early Universe • Matter, anti-matter and energy (photons) exist in a sort of soup (primeval ?) undergoing continuous annihilation and creation. • If there was 100% symmetry between matter and anti-matter the end result would be a Universe entirely composed of energy. • This is clearly not the case ! • The Universe we inhabit contains only matter and energy • Expansion of the Universe causes cooling which quickly prevents creation of matter/anti-matter pairs from energy. • Annihilation of matter and anti-matter into energy continues. • There is no anti-matter ! Woodcock Society Banquet

  16. CP Violation to the Rescue • The fact that there is no anti-matter in the Universe is a clear indication of matter/anti-matter asymmetry • What is the origin of this asymmetry ? • One suggestion is the CP-violation observed in the BaBar experiment • During the matter/anti-matter creation and annihilation in the early Universe there was always a slight preference for matter creation. Woodcock Society Banquet

  17. Conclusion • Our existence, and that of the Universe we inhabit, could be the result of a “Convenient Exception” to the expected symmetry between matter and anti-matter. Woodcock Society Banquet

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