1. The Standard Model of Particle Physics By: Sean Yeager Rutgers, The State University of New Jersey 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 A positively charged nucleus is surrounded by cloud of negatively charged electrons (e, -1)‏ Matter is made of atoms (Greek for indivisible)‏

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/c 2 )

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 + ν → p + e n

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 Z 0 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. F g = Gmm/r 2 F e = k ee/ r 2 F e / F g = kee/Gmm ~ 10 42

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 )‏ e μ

22. Third Generation u → c → Top (t)‏ d → s → Bottom (b)‏ e → μ → Tau ( τ )‏ ν e → ν μ → ν τ

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