Where has all of the Antimatter Gone?

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Where has all of the Antimatter Gone?

• Kevin Pitts
• University of Illinois
• September 26, 2001

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Outline

• Why do we think the antimatter is missing?
• Quarks, gluons and all that
• the early universe
• The Fermilab Tevatron
• The CDF Detector
• What its like to collaborate
  with 500 others
• What the future holds

I. Physics II. Technology III. Sociology
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The Standard Model

• 6 quarks
• quarks combine to make hadrons
• puud, ?ud
• 6 leptons
• free particles
• electron, electron neutrino
• Bosons carry force
• W,Z,?,g

baryons
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Masses

• Masses are heirerarchical
• strange heavier than down
• bottom heavier than strange
• More massive particles more difficult to produce
  in accelerators
• converting energy to matter
• more energy more difficult
• Aside in Standard Model, neutrinos are massless.
• Experimental evidence indicates that neutrinos do
  have mass

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Mass/Energy

• Einstein was right
• the speed of light, c, is a constant
• therefore, we have an equivalence between mass
  and energy
• Implications
• the kinetic energy of the collisions can be
  converted to mass!
• Example pp ? tt X
• kinetic energy of proton/antiproton gets
  converted into top quark mass
• Massive particles can decay to products with less
  mass
• Example t ? b ??
• m(top) gtgt m(b) m(?) m(?)
• the remaining mass/energy of the top goes into
  kinetic energy of the b, ?, and ?

E mc2
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Universal Evolution

• The early universe (tlt1sec) was quite hotso hot
  that there was a soup of quarks, photons and
  gluons
• reaction ?? ? qq proceeded in both directions
• photons creating matter/antimatter (need
  high-energy photons)
• matter/antimatter annihilation (can be low
  energy quarks)
• these types of reactions are quite frequent in
  particle accelerators and are well measured
• The universe cooled ? lower energy ?
• cool universe qq ? ?? and not the opposite
  direction!
• Produce equal amounts of matter and antimatter.
  Annihilation requires equal amounts of matter and
  antimatter.
• Q Why isnt the universe full of photons?
• Q Why arent there equal amounts of matter and
  antimatter left?

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Today

• First experiment
• do you know of anyone or anything that has
  annihilated?
• Locally, we are quite sure that there is
  virtually no antimatter
• exception small amounts of antimatter are
  produced when cosmic rays interact in the
  atmosphere
• Non-locally, astronomers see no evidence for
  annihilating stars or galaxies
• if there is antimatter, then it has to be
  isolated
• unlikely, because there would have to have been a
  segregation in the early universe.
• Actually, our universe is full of photons
• N?/Nbaryon 109
• after annihilations 100000001 quark for every
  1000000000 antiquark

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Sakarhovs Conditions

• Soviet physicist Andrei Sakarhov put forth three
  conditions required for a matter/antimatter
  asymmetry in the universe
• Baryon number violation
• example proton decay (not seen)
• CP violation
• some force of nature treats matter and antimatter
  differently!
• Phase transition
• at some point, a phase transition froze out
  this asymmetry

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CP Violation

• CP violation is jargon for a force that doesnt
  treat matter and antimatter the same.
• In the 1960s, 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 dont really
  understand this phenomena,
• but now we have a new system to study CP
  violation
• the strange quark has a heavy brother bottom

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Why Study Bs

• 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 cant.
• 2. It has a long lifetime. (It lives on
  average .45mm)
• 3. It can mix with its anti-partner (B /B
  mixing)

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How to Measure B Decays

• Need an accelerator
• particle is massive
• mB 5mp
• doesnt occur naturally
• at least in a detectable way
• accelerator produce it via high energy collisions
• Need a detector
• must measure the collisions
• Bs are more rare than most things, less rare
  than others (like top, W/Z, Higgs?)

• Need lots of readout electronics and data
  acquisition
• high rates
• require fast processing
• Need lots of computing power and storage
• data sizes in PetaByte range
• kB,MB,GB,TB,PB
• lots of cpu cycles to process large data samples
• Need lots of people!
• To make it all happen

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The Fermilab Tevatron

• Collides proton-antiprotons
• Energy
• 2.0 TeV 2000 mp
• highest energy in the world
• Rate
• collisions occur every 396ns
• 2.5M collisions/second!
• 1000 Bs /second!
• Technology
• superconducting magnets
• Size
• 4 miles in circumference

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Fermi National Accelerator Laboratory (Fermilab)
Wilson Hall and accelerator complex
Aerial view of the laboratory
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Accelerator Components
Linear accelerator (LINAC)
Tevatron tunnel
Antiproton ring
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Antimatter

• Antiprotons are indeed antimatter
• We use part of the accelerator chain to produce
  and store antiprotons
• Antiprotons constantly cycled through another ring

Antiproton source
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The CDF Detector

• Specifically designed to measure Tevatron
  collisions
• Size
• 4 stories tall
• 5000 tons
• Sensitivity
• 1 million channels
• each channel 1 piece of info
• Detector is cylindrical in shape
• need to cover entire interaction region

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The CDF Detector
Central Endplug detectors
Detector rolling off of the beamline
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Detector Strategy
CDF II Detector cross section

• Precise measurements close-in
• track trajectories, vertices
• Coarse measurements further out
• calorimeters measure total energy
• Muon detectors last
• muons penetrate deeply
• High speed DAQ and trigger electronics

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Assembly of Vertex Detector
Silicon strips surround the beampipe. Provide
VERY precise measurements (50?m) at at distance
of 2-10 cm from the beam line.
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Schematic of CDF Detector
Measures trajectory of charged particles
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Stringing the COT
COT Central Outer Tracker 70,000 wires strung
between endplates. Measures trajectory of
charged tracks as the pass through the chamber.
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A High Energy Collision
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 bend?low momentum
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Triggering and Readout

• Need to reduce rate
• 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 arent 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
• hardware computers
• utilize memory, processors, fast logic
• not arbitrarily programmable

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Illinois XTRP Trigger System

• Dedicated system to combine info from other
  system
• tracks
• energy clusters
• muons
• The XTRP system brings this info together
• Pipelined system
• new data every 33ns
• 4 events in the boards at a time

XTRP test stand
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Computing and Data Rates

• Rates
• Each event about 250kB
• Write 100 events/sec?disk
• 25MB of data every second
• Acquire data at a higher rate
• 250MB/sec sustained rate
• burst rates higher
• Incoming data processed by a farm of PCs running
  Linux (300 dual-processor machines)

Tape robot in computing center
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UIUC Students at Work
Graduate students Raeghan Byrne and Trevor
Vickey hard at work on the CDF muon systems
H40feet
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The CDF Collaboration

• 500 physicists
• students, postdocs, faculty
• 35 institutions
• US, Italy, Japan, Korea, Great Britain, France
• many support personnel
• engineers
• technicians
• support staff

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Sociology

• Although the experiments are big, the work gets
  done in small groups (2-4 people).
• Its also a great environment and opportunity to
  be constantly interacting with physicists from
  around the world.
• I like the variety, too. In addition to physics,
  we dabble in things like
• computing, mechanical engineering, electrical
  engineering
• budgets, conflict management

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Other Experiments

• ee? ? b b
• Different accelerators/ environment
• Many techniques are similar
• Three accelerators
• Cornell
• Stanford (SLAC)
• Japan (KEK)

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Experimental Status

• 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
• 1. Results
• 2. Self-consistency

Standard model Higgs branching ratio versus mass
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Summary--Final Thoughts

• This is an exciting time for particle physics
• There are many other interesting subjects and
  measurements that we perform
• CDF has published well over 100 papers on a
  variety of topics, such as
• top quark physics
• Quantum Chromodynamics (QCD)
• Electroweak phenomena (W/Z production and decay)
• bottom quark physics
• searches for new phenomena (supersymmetry,
  technicolor, quantum gravity)
• the list goes on

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Top 10 Great Things About Particle Physics

• 1. You straight can use the words, squarks,
  gluinos, WIMPs and technirho with a face.
• 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 didnt invent the internet.we did!
• 9. Find out if irradiated objects really glow!
• 10. Actually have to worry about the speed of
  light.