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Left and Right: Matter and Antimatter
Transcript of Left and Right: Matter and Antimatter
Matter and Antimatter
Matter and antimatter and the Universe
The K particle
Intensive studies at LEP 1989-2000
Mass 80.2 GeV
Many properties measured
Responsible for beta decay
North Pole South Pole
If a human hand were the only thing to exist in a universe, would it be a left hand or a right hand?
How can you explain
'left' and 'right' over the
What is the
difference between left and right?
W particles only interact with lefthanded electrons
What is the absolute difference between an electron and a positron?
For every species of particle there is a species of aniparticle with opposite charge (etc) and identical mass (etc)
electron - positron
proton - antiproton
up quark - anti-up quark
How can you explain 'positive charge' and 'negative charge' over the telephone??
Q. What is the absolute difference between an electron and a positron?
A (2). The world and the universe contain many electrons and very few positrons.
Decay rates to electron + positive pion and positron+negative pion are different
Difference (0.332 +- 0.006) %
"The charged lepton produced more often in decays of the long lived neutral kaon is what we earthlings call a positron. "
Then nothing happened for ~30 years...
Use several accelerators to generate positive muons, which decay giving muon antineutrinos
muon antineutrinos mix to electron antineutrinos, which make positrons in a large underground detector
Measuring this rate can determine the CP violating phase delta
These accelerators (1 GeV, ~10 MW) are also needed for Accelerator Driven Thorium Reactors
What about the lepton sector?
Charged leptons couple to neutrinos through W particles
Is there CP violation here too?
Could this explain why we're here?
A 2/3 quark (u,c,t) can change into a 1/3 quarks (d,s,b) by interacting with a W particle
K and M showed that these 9 numbers have real and imaginary parts.
process uses the
As late as 2001, the two particle detectors BaBar at Stanford, USA and Belle at Tsukuba, Japan, both detected broken symmetries independently of each other. The results were exactly as Kobayashi and Maskawa had predicted almost three decades earlier.
Like the neutral kaons, but with a b quark instead of an s quark so much more massive:
Many decay channels, lots of things to measure
Much more difficult to produce
Hundreds of papers
Billions of B particles
Thousands of measurements
Many more CP violating effects:
Some large : K+ pi- and pi+ K- rates differ by 10%
All agree with the Standard Model: no large surprises
How did we get here?
How can you tell whether you're looking at the real world, or a mirror reflection?
Also muons, taus, neutrinos, and quarks
Are these answers related?
Not obviously: Ws give electrons and positrons equally.
The fact that they are LH and RH is soon lost
Is there an absolute difference between LH particles and RH antiparticles?
Quark and antiquark processes have the same amplitude but different phases.
If two are combined, interference can lead to different results
We understand CP violation in quarks.
And now know that it does
explain what happened in the big bang to make the universe habitable.