babar's confirmation of time asymmetryboson.physics.sc.edu/~gothe/730-f13/talks/loos-2.pdf ·...
TRANSCRIPT
• What is Time asymmetry
• CP Violation and Time asymmetry
• Particles of matter
• The Babar experiment
• The positron-electron collision
• Babar Results
A. Loos, Seminar 730, 11-8-13 2
Source: Tim Gershon
• “Particle 1”
decays/combines
into “particle 2”
A. Loos, Seminar 730, 11-8-13 3
• “Particle 1”
decays/combines
into “particle 2”
• The time durations
are not equal
• CP Violation
• “states that fundamental processes remain unchanged when particles are replaced by their antimatter counterparts (C), left and right are reversed (P)” …(The
Reference Frame)
• CPT violation=Time asymmetry
• Asymmetry Example: Matter vs. Anti-Matter
• Same masses, different charges
A. Loos, Seminar 730, 11-8-13 4
Source: USAF
• 15 billion years ago
• Anti-matter and matter existed in equal amounts
• Annihilated energy known as background cosmic radiation
• 10s after the big bang matter slightly outnumbered antimatter
• Soon after…antimatter disappears
A. Loos, Seminar 730, 11-8-13 5
Source: Melbourne University
• Quarks= elementary
particles
• Interact with the strong nuclear
force
• Leptons
• Do not interact with the strong
nuclear force
• Electrons and electron neutrinos
A. Loos, Seminar 730, 11-8-13 6
Source: Particle Central
• Baryons
• stable
• Made up of 3 quarks
• Neutrons and Protons
• Mesons
• short-lived
• Made up of 1 quark and one
antiquark
A. Loos, Seminar 730, 11-8-13 7 Source: Particle Central
• Located at SLAC in Menlo Park, California
• Took data between 1999 and 2008
• Billions of positron/electron collisions took place
• Designed to sort out properties of matter and anti-matter
A. Loos, Seminar 730, 11-8-13 8
Source: SLAC
Source: SLAC
A. Loos, Seminar 730, 11-8-13 9
Source: SLAC
http://www.youtube.com/watch?v=KusaugMR5lU#t=01m08s
A. Loos, Seminar 730, 11-8-13 12
• Measures the momentum
and the angles of charged
particles
Source: SLAC
• Electron and
positron create a
Bº and Bº Bar
Pair
• Bº and Bº Bar
pair decay into
final states
A. Loos, Seminar 730, 11-8-13 14
Source: Gershon,Tim
Final
States
Source: SLAC
• 14-sigma level of certainty
• Difference in time measurement for B0 meson pairs is not zero
A. Loos, Seminar 730, 11-8-13 17
• Plays a critical role in the early universe
• Important verification of quantum field theory
A. Loos, Seminar 730, 11-8-13 18
Source: SLAC
1. “Elementary www.particlecentral.com/particle_page.html
2. Gershon,Tim . “A Triangle that Matters” PhysicsWorld.com.
(2007)
3. Pilsen, Lubos. “Babar directly measures time violation” The
Reference Frame(2012)
4. “Babar makes first direct measurement of time reversal
violation” Physics Today (2012)
5. SLAC National Linear Accelerator Website
6. USAF
A. Loos, Seminar 730, 11-8-13 19