High Energy Physics Proton anti-proton collisions at Fermilab

1. High Energy Physics Proton anti-proton collisions at Fermilab Matthew Jones February 28, 2005

2. What is Physics? • Learning about Nature: • What is in the world around us? • What fundamental laws govern its behavior? • Examples: • Biology • Chemistry • Physics

3. Biology • van Leeuwonhoek • (1632-1723) Microscope

4. Chemistry Pieter Brueghel the Elder (1525-1569)

5. Physics • Biology does not reveal the most fundamental laws of nature: • Mostly influenced by chemistry • Neither does chemistry: • Influenced by physics (mostly electrostatics) • There turns out to be significant overlap • Particle physics: • What are the most fundamental constituents? • How do they interact?

6. What is matter? • Electrons: J.J. Thomson (1897)

7. What is matter? • Nuclei: particle Rutherford, Geiger, Marsden(1910)

8. Nuclear Physics • Protons, neutrons and electrons: • And neutrinos…

9. But there is more… • Muons and pions: • First observed in cosmic rays • Charged particles leave tracks in photographic emulsions • Kaons: • Produced by artificial particle accelerators • Studied using bubble chambers

10. A lot more!

11. A much simpler picture: • Fundamental constituents are quarks and leptons • Charged leptons: e-, -, - • Neutral leptons: e, ,  • Lightest quarks are labeled u, d, s • Baryons made from three quarks: Proton: (uud) Neutron (udd) • Mesons made from quark anti-quark pairs: Pions: + = (ud) Kaons: K+ = (us) • Direct observation of quarks in 1968-69.

12. Observation of quarks Electron Target quark (inside proton)

13. Fundamental Particles of Matter Quarks Leptons

14. Fundamental forces • Electricity and magnetism • Couple to electric charge carried by quarks and charged leptons • Strong nuclear force • Couples to color charge carried by quarks (3 colors) • Binds quarks together to form hadrons • Does not couple to leptons • Weak nuclear force • Couples to both quarks and leptons • Gravity?

15. Fundamental Forces • Quantum field theory: • Terms in a power series of small parameters, eg. , s, 1/mB,… • Decay of a B meson:

16. The Standard Model • Symmetries of matter predict the existence and properties of fundamental forces • Example: • Quarks can carry one of three “colors” (RGB) • The theory is invariant under a local redefinition of which color is which • Predicts existence and all properties of the gluon, which mediates the strong force • This is Quantum Chromodynamics (QCD).

17. The Standard Model • Matter: • Gauge bosons: • Photon () • Weak vector bosons (W§, Z0) • 8 gluons

18. Unanswered Questions • Why are there exactly 3 families of matter? • What determines their observed masses? • me = 0.511 MeV, m = 1777 MeV • mu = few MeV, mt = 174,000 MeV • m = very small but nonzero (relatively new discovery) • What is the relationship between quarks and leptons in the three families? • How do W§ and Z0 acquire mass? • There must be another particle: Higgs boson • But how does the theory keep mH finite? • Dark energy: What is it? Can we make it in the lab?

19. Beyond the Standard Model • One possible extension is Supersymmetry: • Example from 1931: Dirac proposes positron to fix up calculations involving electrons • Supersymmetry pairs all particles in the Standard Model with “Superpartners” differing by ½ unit of spin:

20. What Can We Measure? • Cross sections • What is the probability of making something happen? • Example: • Decay rates: • What is the probability of something decaying in a particular way after it has been produced? • Examples: • Includes lifetimes, angular distributions, …

21. Particle Physics Experiments • Massive particles need energy to produce: E = m c2 • Typical experiments involve collisions: Target particle Interaction Beam particle Beam particle Beam particle Decay products FIXED TARGET COLLIDING BEAMS

22. Particle Accelerators 2000 1931

23. HEP Laboratories

24. The Fermilab Accelerator Complex • Hydrogen ion source • 400 MeV Linac • 8 GeV synchrotron • 150 GeV synchrotron • Antiproton storage ring • 2 TeV collider • Two detectors

25. The CDF-II Detector • collision point • Vertex detector • Tracking chamber • Time-of-flight • Calorimeter • Muon chambers

26. The CDF-II Detector Energy in calorimeter Missing energy vector Jets of particles Production point (primary vertex) Displaced tracks

27. Too much data! • We can’t record every event… • Collisions every 396 ns (2.5 MHz) • Events can be read out at only 300 Hz • Data from one event is ~100 kBytes • Data can be recorded at only 60 Hz The trigger: Determines which events are interesting before reading them out and record them on tape.

28. 132 ns 5.5  s The CDF-II Trigger • Three level trigger: • Level 1 pipeline: tracks, muons, energy • A decision is made every 132 ns, but it takes 5.5 s for a particular event. • Level 2 pipeline: precise tracking from silicon detector. • Level 3: Full event reconstruction on a farm of ~250 PC’s running Linux. • O(100 Terra Bytes) of raw data per year

29. The CDF Physics Program proton • QCD at high energies • Production and properties of the top quark • Electroweak interactions: W§, Z0 • Searches: Higgs, supersymmetry, ??? • Heavy flavor physics: bottom and charm quarks Anti-proton

30. Bottom Quarks at CDF • Large cross section for • One out of every 2000 collisions produces b-quarks in the detector acceptance • Current production rate is ~3 kHz • We record only the ones we can analyse: • 2 leptons in final state: • 1 lepton in final state: • No leptons in final state:

31. Heavy Flavor Physics • All types of B hadrons are produced • Trigger on B’s that decay to hadrons: • B0! D-+, B0s! D-s+ where D-s! K+K--

32. Graduate Studies in Experimental High Energy Physics Three key aspects: • Hardware • Build part of the detector • Also software: use part of the detector • Analysis • Use the hardware to learn something • Service contribution • Keep the experiment running!

33. Detector Hardware: An example • Level 1 track trigger (XFT) • Identifies tracks in less than 396 ns • Uses limited information  eXtremely Fast Tracker • Complications • At high luminosities there can be more than one interaction per bunch crossing. • Overlapping hits in tracking chamber confuse the XFT • Trigger rate from fake tracks is too large • XFT upgrade: (Baylor University, Fermilab, Ohio State University, Purdue, University of Illinois)

34. eXtremely Fast Track Trigger Upgrade • High momentum tracks  interesting events • XFT finds the tracks in an event every 132 ns

35. XFT Trigger Upgrade • Identify track segments in stereo superlayers. • Confirm presence of tracks with matching stereo track segments. • Additional benefit: 3d momentum measurements in the Level 1 trigger.

36. 2nd Example: The CDF-II TOF Detector • Precise (100 ps) measure of time at which particles leave the tracking chamber • Provides kaon and proton identification • Many applications in heavy flavor physics

37. Time-of-Flight Detector • Still learning how to use it • Calibrations • Reconstruction algorithms • Simulation (parametric, single photon, SPICE)

38. Physics Analysis • A few key measurements: • Eg. B0s oscillation frequency • Many related measurements: • B production mechanisms • Properties of B0s and b: • Lifetimes, masses, branching ratios • Rare decays • Charm physics • Some unanticipated opportunities: • X(3872)! J/+-

39. Example: Heavy Quark Fragmentation • Quarks do not exist as free particles • Just like a stretched rubber band, the strong force gets stronger at large distances • When too much energy is stored in the “string”, a quark-antiquark pair appears • Eventually form bound states of mesons and baryons • When a B0s = (b s) meson is produced, what happens to the s-quark?

40. Example: Heavy Quark Fragmentation • Look for B0s (b s) production in association with a K+ (u s)… • But the B0s oscillates: • Instead, study using D+s decays which do not oscillate… • But some are produced in B-decay… • Use geometric information to find the prompt D+s decays.

41. Service to the Experiment • Detector operations: • Data acquisition • Starting and stopping runs • Recording calibration data • Identifying problems • Detector safety monitoring • Monitoring beam conditions • Turning on/off parts of the detector • Data quality monitoring • Is the detector really working?

42. Shifts on CDF

43. Where Next? • Pure research based at a university or international laboratory. • Opportunities from hardware development: • Hands on electrical engineering experience • Medical physics instrumentation • Experience with large software projects • Opportunities from data analysis: • Excellent background in statistics: anyone with large data samples (pharmaceutical companies, medical fields, economic and financial data, etc…)

44. Summary • High Energy Physics: • Studying nature at its smallest scale • Studying the most fundamental laws of nature • The Fermilab Tevatron collider: • World’s highest energy collider • Unique physics program • Good preparation for the LHC at CERN • The CDF-II experiment • Opportunities in detector instrumentation • Many important measurements possible