IdeasOfParticlePhysics

The Ideas of Particle Physics (Coughlan, Dodd, and Gripaios)

  • Three varieties of radiation result from the three main fundamental forces of nature effective within atoms.
  • QM + SR makes it necessary to invent spin. (If electron spin had not been proposed and discovered experimentally, it would be been proposed theoretically.)
  • In non-relativistic QM, g=2 is an experimental fact. With the Dirac equation it is a prediction.
  • Anti-matter => that fundamental particles cannot be thought of as immutable fundamental entities. They can be created and destroyed.
  • Four forces, only two relevant for most of the world.

  • Intrinsic parity has meaning only because particles can be created or destroyed. If particles where conserved, then the product of intrinsic parities would always be the same.

    Physics

  • Can determine pion spin from p+ p->d + pi and pi + d -> p +
  • Spin splitting from B-field is like mass splitting of isospin from charge.
  • 1st massive accelerator experiment: In 25 days produced 1014 nus and got 51 muons
  • Kaons produced by strong interactions (ks or \bar{k}) but they decay as kL or kS

  • K1 = (K + \bar(k)) (Up to normalization) K2 = (K - \bar(k)) (Up to normalization)

    KL = K2 + epsilon x K1 and Ks = K1 - epsilon x K2

    epsilon is due to higher-order weak process => very small

  • sigma(nu + e -> e + nu) = sigma0 x (Enu)/me where sigma0 ~ 10-44 cm2 ~ (10-7 GeV-1) ^2
  • The reversion to the simplicity of the point-like scattering after a relatively more complicated transitional phase is taken to indicate that we have broken through to a new, more basic level of matter with in the nucleon.
  • Deep inelastic lepton-nucleon scattering has been an extremely useful tool for probing the structure of hadrons. Learned:
    • the nucleon contains point-like constituents (partons), as evidenced by the approximate scale invariance of structure functions F(nu, q2) = F(x)
    • partons have spin 1/2 is clear from the observed relation between the electromagnetic structure functions: 2F1(x) = F2(x)
    • behavior of the electro-weak cross sections strongly suggests the identification of these spin 1/2 partons with fractionally charged quarks
    • partons only account for about half of the nucleon momentum (at the energies that were originally probed)
  • pi0 -> gamma gamma support for three colors. Calculation off by factor of 9 with only one color.
  • Asymptotic freedom requires a non-Abelian interaction, <= 16 quarks, no Higgs breaking
  • p158: nice explanation of pdf variation with q2.
  • Unusual lifetime of J/psi: preferred decay modes inhibited. Obvious J/psi -> D0 + \bar{D_0} not possible b/c of D mass. More complicated (3 gluon) decay to non-charmed hadrons takes longer.
  • Number of fundamental particles in SM: 45 spin-1/2: 15 * 3(families) = (1 nu (L-only) + 2 charged-leps (Land R) + 3(colors)*2(flavors)*2(helicities))x 3 12 gauge bosons: (27 DoF) 8 gluons + W+ W- Z + gamma 8*2 + 3x3 + 2 = 27 1 Higgs boson

  • Question: How to think about anomalies in an EFT ?

    Questions

  • 19 Free parameters in the SM 18 + 1 (theta QCD ~0) Claim with nu mass now 27 + 1

    18: 9 masses + 3 coupling strengths + 4 quark mixing parameters (How to see 4?) + 2 EWK symmetry breaking (v and mH) 27: 18 + 3 nu masses + 4 mixing parameters + 2 phases if Majorana

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