Alyssa Loos

• What is Time asymmetry

• CP Violation and Time asymmetry

• Particles of matter

• The Babar experiment

• The positron-electron collision

• Babar Results

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Source: Tim Gershon

• “Particle 1”

decays/combines

into “particle 2”

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• “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

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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

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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

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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

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Source: SLAC

Source: SLAC

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Source: SLAC

http://www.youtube.com/watch?v=KusaugMR5lU#t=01m08s

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Source: SLAC

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• Enables charged particle

momentum measurement

Source: SLAC

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• Measures the momentum

and the angles of charged

particles

Source: SLAC

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• Measures the positions of

charged particles

Source: SLAC

• Electron and

positron create a

Bº and Bº Bar

Pair

• Bº and Bº Bar

pair decay into

final states

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Source: Gershon,Tim

Final

States

Source: SLAC

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• 14-sigma level of certainty

• Difference in time measurement for B0 meson pairs is not zero

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• Plays a critical role in the early universe

• Important verification of quantum field theory

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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

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