Where has all of the Antimatter Gone?

1. Where has all of the Antimatter Gone? Kevin Pitts University of Illinois September 26, 2001

2. Outline • Why do we think the antimatter is missing? • Quarks, gluons and all that • the early universe • The Fermilab Tevatron • The CDF Detector • What it’s like to collaborate with 500 others • What the future holds I. Physics II. Technology III. Sociology

3. The Standard Model • 6 quarks • quarks combine to make hadrons • p=uud, +=ud • 6 leptons • “free particles” • electron, electron neutrino • Bosons carry force • W,Z,,g baryons

4. 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

5. 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) >> m(b) + m() + m() • the remaining mass/energy of the top goes into kinetic energy of the b, , and  E = mc2

6. Universal Evolution • The early universe (t<1sec) was quite hot…so 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 isn’t the universe full of photons? • Q: Why aren’t there equal amounts of matter and antimatter left?

7. 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

8. Sakarhov’s 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

9. CP Violation 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

10. Why Study B’s 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)

11. Need an accelerator 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 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 How to Measure B Decays

12. 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 B’s /second! • Technology • superconducting magnets • Size • 4 miles in circumference

13. Fermi National Accelerator Laboratory (Fermilab) Wilson Hall and accelerator complex Aerial view of the laboratory

14. Accelerator Components Linear accelerator (LINAC) Tevatron tunnel Antiproton ring

15. 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

16. 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

17. The CDF Detector Central + Endplug detectors Detector rolling off of the beamline

18. 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 Detector Strategy CDF II Detector cross section

19. 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.

20. Schematic of CDF Detector Measures trajectory of charged particles

21. Stringing the COT COT = Central Outer Tracker 70,000 wires strung between endplates. Measures trajectory of charged tracks as the pass through the chamber.

22. 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

23. 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 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 “hardware” computers utilize memory, processors, fast logic not arbitrarily programmable Triggering and Readout

24. 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

25. 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

26. UIUC Students at Work Graduate students Raeghan Byrne and Trevor Vickey hard at work on the CDF muon systems H=40feet

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

28. Sociology • Although the experiments are big, the work gets done in small groups (2-4 people). • It’s 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

29. Other Experiments • e+e bb • Different accelerators/ environment • Many techniques are similar • Three accelerators: • Cornell • Stanford (SLAC) • Japan (KEK)

30. 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

31. 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

32. 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 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