Where has all of the Antimatter Gone?. Kevin Pitts University of Illinois September 26, 2001. Outline. Why do we think the antimatter is missing? Quarks, gluons and all that the early universe The Fermilab Tevatron The CDF Detector
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University of Illinois
September 26, 2001
E = mc2
Soviet physicist Andrei Sakarhov put forth three conditions required for a matter/antimatter asymmetry in the universe:
CP violation is jargon for a force that doesn’t treat matter and antimatter the same.
In the 1960’s, everybody thought CP was conserved (not violated)
Then in 1964, CP violation was (unexpectedly) observed in the decays of mesons containing strange quarks.
More than 35 years later, we still don’t really understand this phenomena,
but now we have a new system to study CP violation
the strange quark has a heavy brother: bottom
1964:CP violation was (unexpectedly) observed in the decays of mesons containing strange quarks.
Since the bottom quark is a heavy version of a strange quark, should see CP violation in B decays, too.
Also, the bottom is quite interesting (unique) for other reasons:
1. It wants to decay to top, but can’t.
2. It has a long lifetime. (It lives on average .45mm)
3. It can “mix” with it’s anti-partner (B /B mixing)
particle is massive
mB = 5mp
doesn’t occur “naturally”
at least in a detectable way
accelerator produce it via high energy collisions
Need a detector
must measure the collisions
B’s are more rare than most things, less rare than others (like top, W/Z, Higgs?)
Need lots of readout electronics and data acquisition
require fast processing
Need lots of computing power and storage
data sizes in PetaByte range
lots of cpu cycles to process large data samples
Need lots of people!
To make it all happenHow to Measure B Decays
Wilson Hall and accelerator complex
Aerial view of the laboratory
Central + Endplug detectors
Detector rolling off of the beamline
Silicon strips surround the
Provide VERY precise measurements (~50m) at
at distance of 2-10 cm from the beam line.
of charged particles
COT = Central Outer Tracker
70,000 wires strung between
Measures trajectory of charged tracks as the pass through the chamber.
A high energy collision as seen by the previous version of the CDF detector
Lines represent reconstructed trajectories
Charged particles bend in magnetic field
big bendlow momentum
2.5M collisions per second
can write data from 50-100 collisions per second
must decide which 2.4999M events to discard each second in real time !
What if the B decays aren’t part of the 100?
“Trigger” is the fast logic used to make these decisions
Response time is too short to use standard computers
We build dedicated electronics for these purposes
utilize memory, processors, fast logic
not arbitrarily programmableTriggering and Readout
XTRP test stand
Tape robot in computing center
Raeghan Byrne and
hard at work on the
CDF muon systems
CDF made one of the first measurements
Now, BaBar and Belle have made more precise measurements
Ultimate goal: make very precise measurements of CP violation in many different ways. We then can test the theory for
Standard model Higgs branching ratio versus mass
2. For exercise, you can run around your experiment.
3. Collaborate with institutions like Harvard and Yale and then ask them about their sports teams.
4. 4500 Amps of current and 1000 cubic meters of flammable gas.
5. Two words: “beam dump.”
6. Create more W bosons before 9am than most people do in a whole day.
7. Seven truckloads of LN2 per day.
8. Al Gore didn’t invent the internet….we did!
9. Find out if irradiated objects really glow!
10. Actually have to worry about the speed of light.Top 10 Great Things About Particle Physics