A Convenient Exception Woodcock Society Banquet May 7
A Convenient Exception Woodcock Society Banquet May 7, 2008 Chris L. Davis May 7, 2008 Woodcock Society Banquet
Elementary Particle Physics or High Energy Physics § The study of the building blocks of matter and, their interactions Chris L. Davis May 7, 2008 Woodcock Society Banquet
Structure of Matter Chris L. Davis May 7, 2008 Woodcock Society Banquet
The Building Blocks § Plus Anti-Particles (Anti-Matter) Chris L. Davis May 7, 2008 Woodcock Society Banquet
The Interactions Chris L. Davis May 7, 2008 Woodcock Society Banquet
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). Chris L. Davis May 7, 2008 Woodcock Society Banquet
Accelerators CERN, Geneva, Switzerland LHC 27 km circumference Chris L. Davis May 7, 2008 Woodcock Society Banquet
Fermilab, Chicago Main ring Circumference 4 miles Chris L. Davis May 7, 2008 Woodcock Society Banquet
Stanford Linear Accelerator (SLAC) Two mile long linear accelerator Chris L. Davis May 7, 2008 Woodcock Society Banquet
“Big” Science LHC centered on Uof. L Chris L. Davis May 7, 2008 Woodcock Society Banquet
Ba. Bar Collaboration at SLAC More than 600 Ph. D Physicists from 74 institutions in 9 countries Chris L. Davis May 7, 2008 In data acquisition mode since 1999 Woodcock Society Banquet
Communication World Wide Web Invented by particle physicist Tim Berners-Lee at CERN in 1990 to ease communication and information transfer between collaborating institutions in experiments. Chris L. Davis May 7, 2008 Woodcock Society Banquet
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 antimatter The Ba. Bar experiment was designed to verify and make detailed measurements of the asymmetry Why Ba. Bar ? § We look for CP violation in particles containing a b quark and an anti-b quark - BBbar or Ba. Bar. Collaboration mascot, Ba. Bar the elephant in the children’s books by Laurent de Brunhoff Chris L. Davis May 7, 2008 Woodcock Society Banquet
Ba. Bar Detector Ba. Bar has verified CP-violation and measured important parameters which characterize the asymmetry Chris L. Davis May 7, 2008 Woodcock Society Banquet
So What ! What does CP violation do for you ? Everything ! Why ? A long, long time ago scientists believe there was a Big Bang ! Chris L. Davis May 7, 2008 Woodcock Society Banquet
The Early Universe § Matter, anti-matter and energy (photons) exist in a sort of soup (primeval ? ) undergoing continuous annihilation and creation. § Expansion of the Universe causes cooling which quickly prevents creation of matter/anti-matter pairs from energy. Annihilation of matter and antimatter into energy continues. § § § If there was 100% symmetry between matter and anti-matter the end result would be a Universe mostly of energy, but with small equal amounts of matter and anti-matter. This is clearly not the case ! The Universe we inhabit contains only matter and energy There is no anti-matter ! Chris L. Davis May 7, 2008 Woodcock Society Banquet
CP Violation to the Rescue § The fact that there is no anti-matter in the Universe is a clear indication of matter/antimatter asymmetry § What is the origin of this asymmetry ? § One suggestion is the CP-violation observed in the Ba. Bar experiment § During the matter/anti-matter creation and annihilation in the early Universe there was always a slight preference for matter creation. Chris L. Davis May 7, 2008 Woodcock Society Banquet
Conclusion § Our existence, and that of the Universe we inhabit, could be the result of a “Convenient Exception” (Apologies to Al Gore) to the expected symmetry between matter and anti-matter. Chris L. Davis May 7, 2008 Woodcock Society Banquet
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