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269B class organizational meeting

269B class organizational meeting. LHC and Geneva. Main CERN Campus; ATLAS. CMS. Today (good timing  ). 7 TeV collisions, but miniscule luminosity (50 Hz of proton-proton collisions). Tomorrow:. Classes of Topics. Fundamental physics E.g. Higgs, Supersymmetry, large extra dimensions

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269B class organizational meeting

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  1. 269B class organizational meeting

  2. LHC and Geneva Main CERN Campus; ATLAS CMS ASDF

  3. Today (good timing ) • 7 TeV collisions, but miniscule luminosity (50 Hz of proton-proton collisions)

  4. Tomorrow:

  5. Classes of Topics • Fundamental physics • E.g. Higgs, Supersymmetry, large extra dimensions • “Phenomenology” – the interplay between theory and experiment • E.g. partons in protons, hard scattering, “ordinary” particles, jets • General experimental issues • E.g. accelerators, measuring momentum and energy • Specific experimental issues • E.g. pixel detectors, CMS versus ATLAS • The future of physics at the energy frontier • E.g. muon colliders, plasma wakefield acceleration

  6. Fundamental physics Higgs Supersymmetry (several types) Z’ and W’ particles Techniparticles Large extra dimensions, Kaluza-Klein particles, black holes Compositeness Magnetic monopoles b’ and t’ quarks Massive charged stable particles “Phenomenology” – the interplay between theory and experiment Partons in protons Elastic and diffractive scattering Hard scattering “ordinary” particles Heavy quarks (b and t) jets General experimental issues Accelerators Luminosity Measuring momentum(tracking) Measuring energy (sampling calorimeters) -Muon systems “Particle flow” Specific experimental issues Pixel, Si strip tracking detectors CMS versus ATLAS Data analysis techniques Examine past discoveries, measurements The future of physics at the energy frontier Upgrades to LHC ILC and CLIC electron positron colliders muon colliders plasma wakefield acceleration Laser acceleration More detailed list of topics

  7. Organizational issues: • What is expected? • Kind of apprenticeship experience, tailored to individual • Grading scheme (attendance, participation, talk or paper) • Who is enrolled? • When to meet?

  8. A Superficial Introduction

  9. Known Particle Physics Assume relativisticquantum mechanics (field theory) The Standard Model (1974) has two basic principles: Symmetry at every point in space-time Symmetry breaking Only the 1st principle is beautiful…

  10. Symmetry aka SU3xSU2xU1: a rotation symmetry at every point in space-time: Explains the Strong (SU3) and weak (SU2) nuclear forces Explains Electromagnetism (U1)

  11. Symmetry breaking Simple classical example: vertical pencil Introducing the Higgs mechanism: A special particle that has a strange potential energy function in the vacuum: Massive electrons, quarks, neutrinos, W and Z, and other particles

  12. Standard Model: (too much) Success! 1974 Standard Model emerged with the “November revolution” 1979 I became a grad student For 34 years no discrepancy has been found All of the known fundamental particles are listed below. The Higgs is the fundamental particle that allows Electroweak unification. The only missing piece. The only scalar (Spin 0) particle. 12

  13. Tevatron vs. LHC: Higgs Low-mass (<130 GeV): Favored by precision data fits Experimentally very difficult LEP-TeV working group fit: mH< 157 GeV (95% CL)

  14. Here’s what a Higgs particle might look like (H ZZ4) • A simulation • Muons in green. • The “golden” discovery mode for H mass >135 GeV

  15. Technicolor Theories beyond the Standard Model (sometimes, but not always, GUTs) which do not have a scalar Higgs field. Details (see Wikipedia): Instead, they have a larger number of fermion fields than the Standard Model and involve a larger gauge group. This larger gauge group is spontaneously broken down to the Standard Model group as fermion condensates form. 15

  16. GUTs and the Higgs particle GUTs=Grand Unified Theories Einstein tried but failed… The SU3xSU2xU1 symmetries come from one big symmetry A beautiful idea Forces of nature merge into one force eventually (at high energy) ? 16

  17. GUTs seem incompatible with Higgs… “Fine corrections” to the Higgs mass tend to become huge (~1015 GeV/c2 or more), this cannot be Known as the hierarchy problem 17

  18. Supersymmetry (SUSY) SM particles have supersymmetric partners: Differ by 1/2 unit in spin Sfermions (squarks, selectron, smuon, ...): spin 0 Gauginos (chargino, neutralino, gluino,…): spin 1/2 g ~ G G 18

  19. Supersymmetry: A symmetry that relates spins (fermions to bosons): One new superpartner for every known elementary particle. The superpartner differs only by half a unit of spin, and its mass. The lightest supersymmetric particle is the best candidate for Dark Matter If supersymmetry exists close to the TeV energy scale, it Solves the hierarchy problem The early universe should have produced just about the right amount of Dark Matter Supersymmetry is also a consequence of most versions of string theory though it can exist in nature even if string theory is wrong. 19

  20. Supersymmetry=Particles Galore Mass [GeV] Example: a whole new spectrum waiting at a few hundred GeV mass? 20

  21. SUSY also fixes GUTs details Standard Model only • A simple SUSY model

  22. Large extra dimensions, R-S: Large extra dimensions (1998): To explain the weakness of gravity relative to the other forces. Fields of the Standard Model are confined to a four-dimensional membrane, while gravity propagates in several additional spatial dimensions that are large compared to the Planck scale Production of black holes at the LHC?? Randall-Sundrum models (1999): our Universe is a five-dimensional anti de Sitter space and the elementary particles except for the graviton are localized on a (3+1)-dimensional brane or branes 22

  23. Modern Particle Accelerators The particles are guided around a ring by strong magnets so they can gain energy over many cycles and then remain stored for hours or days The particles gain energy by surfing on the electric fields of well-timed radio oscillations (in a cavity like a microwave oven)

  24. CERN Accelerator Complex LHC is designed for 14 TeV energy (7 TeV per proton in each beam)

  25. Add >1500 dipole and quadrupole magnets, liquid helium services …

  26. ..and Two Large Detectors Beams collide 40 million times producing 1 billion proton-proton collisions every second Typical data run will last 9 months ATLAS CMS

  27. Context • See http://www.nature.com/nature/journal/v448/n7151/full/nature06076.html • 1987 (Reagan) the U.S. proposed to build a 40 TeV collider (the SSC) in Texas. • 1991 CERN proposed to re-use an existing accelerator tunnel to build a “wimpy” 14 TeV collider. • UCLA Prof. Dave Cline was one of a handful of (unfunded) U.S. physicists involved in LHC. • 1993 the SSC was killed by Congress (Clinton) • 1994 UCLA and other U.S. institutions joined the LHC effort • Then >14 years of planning, prototyping, and construction… • Dec. 2009 collisions at 0.9 & 2.36 TeV • Mar. 2010 collisions at 7 TeV (Fermilab 1.96 TeV)

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