Alyssa Loos

• The Babar experiment

• Particles of matter

• CP Violation and Time asymmetry

• The positron-electron collision

• Babar Results

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Source: Tim Gershon

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Source: SLAC

• 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

• 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, 9-13-13 6 Source: Particle Central

• 15 billion years ago

• Anti-matter and matter existed in equal amounts

• Annihilated energy known as background cosmic radiation

• 1milifraction of a second

• Matter slightly outnumbered antimatter

• 1 second later…antimatter

disappears

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Source: Melbourne University

• Matter vs. Anti-Matter

• Same masses, different

charges

• CP Violation

• CPT=Time asymmetry

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Source: USAF

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• Time asymmetry describes when the transition from one state to

another takes a different amount of time than the reversed

process Source Physics Today

Source: Tim Gershon

• Y(4S) meson is made

up of a quark and

anti-quark

• B0 and B0 Bar

Pair

• Eigenstates

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Source: Gershon,Tim

• 1 in 10 tredecillion (10^43) or 14-sigma level of certainty

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

• “Time arrow” is different for macroscopic and microscopic

reality source: The Reference Frame

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• Plays a critical role in the early universe

• Important verification of quantum field theory

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Source: SLAC

• Babar made the first direct measurement

• B0 mesons exhibit T violation

• Direction of the “time arrow” in microscopic situations is

different than macroscopic source The Reference Frame

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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

Referance Frame(2012)

4. “Babar makes first direct measuresurement of time reversal

violation” Physics Today (2012)

5. SLAC National Linear Accelerator Website

6. USAF

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