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The Standard Model of Particle Physics

By: Sean Yeager Rutgers, The State University of New Jersey. The Standard Model of Particle Physics. 1 July 2009. Objective. Find the most basic constituents of nature These will be the building blocks from which everything is made. Starting off.

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The Standard Model of Particle Physics

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  1. By: Sean Yeager Rutgers, The State University of New Jersey The Standard Modelof Particle Physics 1 July 2009

  2. Objective • Find the most basic constituents of nature • These will be the building blocks from which everything is made

  3. Starting off Matter is made of atoms (Greek for indivisible)‏ A positively charged nucleus is surrounded by cloud of negatively charged electrons (e, -1)‏

  4. Bingo! • As far as we can detect, the electron does not have a substructure • It is the first of our building blocks

  5. Examining the Nucleus • Thousands of times more massive than an e • Occupies a much smaller volume than e cloud • Made of protons (p, +1) and neutrons (n, 0)‏ • Neutrons are slightly bigger (938.3 vs. 939.6 MeV/c2)

  6. A Step Further • Turns out protons and neutrons also have a substructure • They are made of three quarks each

  7. Quarks • Name comes from Joyce's Finnegans Wake • Subject to confinement, which means that they are never alone • Come in packs of two or three • Matter is made of two varieties: Up (u, +2/3) and Down (d, -1/3)‏ • Protons (uud) and neutrons (udd)‏

  8. Available to anyone who can mathematically prove quark confinement.

  9. Quark Color Quarks are fermions. Subject to Pauli principle 3 Quarks in proton → can't all have same quantum numbers Introduce color → red, green and blue Will only ever see colorless combintion (RGB add up to white)

  10. Taking a Jump: Beta Decay n + ν → p + e

  11. ν? That's Odd • ν was introduced by Pauli to conserve energy and spin • Named the neutrino (Italian pun: Thanks Fermi)‏ • Our last candidate for particles • Carries no charge • Tiny mass • Until recently, many thought it was massless

  12. Exploring the Forces • Photon “mediates” the Electromagnetic Force • Opposites attracting • This covers the majority of the day to day forces we feel.

  13. Wait a second... • Electromagnetic Force alone would blow apart the positively charged protons in the nucleus! • There must be an even more powerful force holding them together!

  14. A Very Original Name... • Strong Force • Mediated by the gluon • Holds quarks together • Extremely strong at short (~10-15 m) ranges • Corresponds to nucleus radius • Negligible at anything bigger

  15. Back to Betas • Actually an example of a Weak Force interaction • Mediated by the W+, W-, and Z0 Bosons • Way for heavy particles to decay into smaller ones (free neutron unstable)‏

  16. Something is Missing • Gravity: the mystery force • Counter intuitive, since it was the first force to be described classically • Mediated by the graviton? Mediated by the graviton?

  17. Most Importantly... Gravity is NOT part of the Standard Model

  18. Fg = Gmm/r2 Fe = k ee/ r2 Fe / Fg = kee/Gmm ~ 1042

  19. Review • 4 particles (u, d, e, ν)‏ • 4 forces (Electromagnetic, Strong, Weak, and gravity)‏ • Mediators (photon, gluon, W/Z, graviton)‏

  20. I Am A Liar (sort of)‏ • These particles make up all of normal matter • They are the “First Generation” • Two more generations • Each heavier than the last • These make up weird stuff that you never see • Each generation contains “cousins” of the first generation

  21. Second Generation • Up (u) → Charm (c)‏ • Down (d) → Strange (s)‏ • Electron (e) → Muon (μ)‏ • Neutrino (ν ) → Neutrino (ν )‏ μ e

  22. Third Generation • u → c → Top (t)‏ • d → s → Bottom (b)‏ • e →μ→ Tau (τ)‏ • νe→νμ→ντ

  23. Weird Names? • Strange → new particles were... strange • Charm → balance to strange • Top/Truth and Bottom/Beauty • Took a while to realize that neutrinos across generations were distinct

  24. At Last! The Standard Model!

  25. The Higgs Boson (July 4, 2012) Nothing so far explains why all the different particle have such different masses. That's where the Higgs comes in. Imagine a crowded party, all of the people there are like Higgs. Imagine Bill Nye shows up, everyone wants to talk to him and clusters around – powerful interaction with Higgs, has large mass Imagine a smelly person walks in, no one gathers around – low interaction with Higgs, has low mass

  26. Higgs Continued Pool of water Water is Higgs Shark – sleek, moves quickly, low mass Zack Galifianakis – chucky, moves slowly, high mass

  27. Antimatter! • All particles have an antimatter equivalent with equal mass but opposite properties (i.e. charge)‏ • When a particle collides with its antiparticle, they explode.

  28. WRONG!!! • The Standard Model is an excellent description of the universe, but it is incomplete

  29. Gravity • Gravity is NOT explained by the standard model • Attempts have been made to reconcile it with the Standard Model • This is why people are making a big deal about string theory

  30. Supersymmetry (SUSY) Fermions have a boson spartner Bosons have a fermion spartner Really weird names, neutralino, squark, gaugino, wino Solves a couple messy problems

  31. Summary • Despite being incomplete, it's the best we've got • Provides a solid description of the Electromagnetic, Weak, and Strong Forces • Wraps up the particles into a nice little table

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