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Compelling Questions of High Energy Physics?

Compelling Questions of High Energy Physics?

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Compelling Questions of High Energy Physics?

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  1. Compelling Questions of High Energy Physics? What does the future hold? Persis S. Drell Physics Department Cornell University

  2. Physics: “The knife that cuts into the grain of nature” -Jacob Bronowski “The rules of the game are what we mean by fundamental physics…” -Richard Feynman

  3. Fundamental Questions of Particle Physics • What are the fundamental constituents of matter? How many are there? Can we understand why they have the masses that they do? • What are the fundamental forces? Can we understand why some are weak and some are strong? Can they be unified? • What is the structure of spacetime? • How did the Universe evolve in the first seconds after the big bang?

  4. ??

  5. Building Blocks Forces and Force Carriers

  6. The decay of the muon via the weak interactions e - nm ne W- - m

  7. Ingredients of the Standard Model • Local Gauge Invariance • Symmetries Generate Interactions • Spontaneous Symmetry Breaking • Gives mass to force carriers • Predicts a Higgs • Non-Abelian • The force carriers can have charge • Add in the matter fields of the quarks and leptons, lots of extra parameters, bake at 350 for 30 minutes • Correctly predict the results of every high energy physics experiment for the last 30 years.

  8. Top Features of the Standard Model • Every experiment for last 30 years has either agreed with the model or the experiment is wrong. • Unification of 3 of 4 forces • Explains HEP to the TeV scale (10-18 m) • Predicted the existence and mass of the Z boson • Makes flavor mixing in the quark sector understandable to a 1st year physics grad • CKM • Leaves us with lots of unanswered questions! Weak EM Strong Gravity Vud Vus Vub Vcd Vc sVcb Vtd Vts Vtb d d = s s b b strong weak

  9. Quark Flavor Mixing • Eigenstates of the strong interactions (states of quark flavor u,d,s,c,b,t) are not eigenstates of the weak interactions • Flavor a symmetry of the SI • Flavor not a symmetry of the WI • Weak Interaction diagonal on a different basis • WI basis and SI basis related by rotation matrix (CKM) • Phenomenology of flavor mixing Vud Vus Vub Vcd Vc sVcb Vtd Vts Vtb d d s = s b b weak strong

  10. Worst “bugs” in the Standard Model • Too many free parameters • Different bases for strong and weak interactions • Where do the masses come from? • Parity violation of the weak interactions added by hand • Fundamental Scalar (spin 0) Higgs • Fine tuning problems • Only works to 1TeV • Doesn’t include gravity • Leaves us with lots of unanswered questions

  11. Compelling Questions for the Next Decade-Going beyond the SM- • What is the right description of gravity? • Can all the forces be unified? • What is the origin of mass? • What is the new physics beyond the SM? • Can we understand flavor mixing and where does CP violation come from? • Can we explain the Universe?

  12. Current Probes of SM-The high energy frontier- • LEP: MH > 100GeV • Possible signal at MH = 114GeV ?? • FNAL: May discover Higgs if light enough • LHC: Will discover the Higgs!

  13. -High Density Frontier-(Nucleon+Nucleon)BNL

  14. -High Precision Frontier- • Rare K and B decays • Masses and mixing of n • Flavor oscillations

  15. -Precision Frontier-Neutrino Oscillations • Lepton Flavor Mixing • No neutrino mass => no lepton flavor mixing • Finite neutrino mass => expect lepton flavor mixing just like we have quark flavor mixing • Simplest solution: leptons mix just like quarks • Problem with simplest solution: very unnatural. • Once allow neutrino to have mass: • Dirac mass like quarks • Majorana mass (unique to particles without electric charge) • Rule of QFT: be as generic as possible ne ne Lepton Mixing Matrix = nm nm nt nt weak mass

  16. -Precision Frontier-CP Violation • What happened to the anti-matter? • Studies of CP Violation in K and B decays • Studies of rare processes that are highly suppressed in the SM so new physics has a chance to compete favorably. Big Bang Matter=Antimatter Now Matter only

  17. Be Broad Warning: focus on the problem at hand, but still be a student of problems in other fields

  18. Be Critical Warning: Always temper your criticism with judgement

  19. Three of these plots show statistical fluctuations. One shows a real signal. Can you pick out the real signal?

  20. Be Bold ‘Truth emerges more readily from error than from confusion’ -Francis Bacon 1561-1626

  21. Be Optimistic!