1. The Eighteen Parameters of the Standard Model in Your Everyday Life
Twenty-seven
The Eighteen Parameters of the Standard Model in Your Everyday Life
Robert N. Cahn
Lawrence Berkeley National Lab
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2. A Polemic Asserting that particle physics addresses the question
What makes the everyday world the way it is?
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3. A Muonic World μ e What happens? Matter shrinks:
Light becomes soft x rays.
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4. No. Remember muonic atoms.
“Muon” would be stable, but “hydrogen” isn’t:
Universe = neutrons and neutrinos!
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5. Today’s theory has 27 (+1) dials.
One is .
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6. The dials appear to be independent, arbitrarily set
The dials appear to be independent, arbitrarily set. Probably they are linked.
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7. Increase u-quark mass by 0.8 MeV
hydrogen disappears
by only 0.16 MeV and nitrogen disappears:
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8. Fundamental Fermions u +2/3 0.005 c +2/3 1.5 t +2/3 172 d -1/3 0.010
0.15
b -1/3
4.5
Electric charge
Mass (GeV)
e 0 ?
 0
 0
e -1
0.0005 
0.106
 -1
1.78
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9. Other worlds
As long as the masses of the quarks and leptons appear arbitrary, there are plausible alternative worlds.
As long as we don’t understand why there are three generations, we can imagine other possibilities.
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10. Suppose we had only the second generation:
Only one quark survives:
No isotopes.
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11. A Strange World One stable baryon: No nuclei? Lightest meson is
Probably too heavy to bind to
A single atom:
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12. 18 Parameters Quark masses: Charged lepton masses: Coupling strengths:
Quark mixing:
Electroweak Symmetry Breaking:
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13. mt and the proton’s mass
Proton’s mass determined by QCD coupling strength not quark masses.
(u and d quark masses are about 1% of a proton’s)
If top quark mass were 10 times smaller, the proton’s mass would be reduced by factor 0.84, if we believe in Grand Unification.
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14. CP Violation and Baryon-Antibaryon Asymmetry
Andrei Sakharov (1967):
Why we’re here:
Baryon number violation.
Non-equilibrium.
CP violation.
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15. Is there CP violation in leptons?
Neutrinos have mass.
Neutrinos mix as quarks do.
Neutrinos can be their own antiparticles.
1827
3 neutrino masses
4 mixing parameters
2 extra phases if “Majorana neutrinos”
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16. Majorana Neutrinos Electron has four degrees of freedom:
Massive particle needs L and R.
Can’t have just :
Can’t use
For neutrinos can use (Majorana)
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17. Which CP violation makes us happen?
Quarks? No. Too small.
Light neutrinos? No. Too small.
Heavy neutrinos? Maybe!
Need more parameters. CP violation for light neutrinos would be hint.
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18. GF in your everyday life.
drives the sun.
Increasing v increases mW and decreases GF
Decreases heat at center of sun. Sun contracts.
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19. Problem 13.9
Calculate what the sun’s spectrum would be if the mass of the W boson were decreased by a factor of two and what it would be if the mass of the W boson were increased by a factor of two.
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20. Solution by J.D.Jackson
Doubling would cause the radius to shrink by 33% and increase the surface temperature by 22%.
Be sure to use sunblock!
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21. What about Higgs boson mass?
Doesn’t affect much. That’s why it was so hard to find!
There could be several Higgs bosons, as in supersymmetry.
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22. Supersymmetry
For every particle, there is partner with spin differing by half a unit:
Requires at least three neutral,two charged Higgs bosons.
quark
squark
electron
selectron
gluon
gluino
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23. Why should we believe in supersymmetry?
“Supersymmetry has withstood the test of time, although
there is no evidence to support it.”
From an introduction for Bruno Zumino as colloquium speaker at Berkeley.
Theoretical esthetics.
Half the particles required by supersymmetry have been found.
Grand unification works with supersymmetry, but not without it.
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24. Grand Unification or Not?
Standard Model
Minimal Supersymmetric
Standard Model
U(1)
U(1)
SU(2)
SU(2)
SU(3)
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25. What if the lightest particles were selectrons, that is, bosons?
Atoms would lose their individuality.
Molecules would lose their integrity.
Matter would fuse into an undifferentiated blob.
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26. Binding energy of matter
For ordinary matter with N atoms
For bosonic atoms (F. J. Dyson, 1967)
Watch out!
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27. It teaches us how much we actually have to explain about the world.
The greatness of the Standard Model is not the questions it answers but the questions it lets us ask.
It teaches us how much we actually have to explain about the world.
It demands that we learn how our world was chosen (by symmetry breaking) from many equally plausible and quite different alternatives.
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28. Without addressing the fundamental questions of particle physics we cannot fully explain the world of atoms and molecules, or even why there are atoms and molecules.
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29. Extra Slides
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30. Coupling Constants: They’re not constant: vacuum polarization:
quarks, leptons
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31. Grand Unification?
We know weak and electromagnetic interactions are one.
Can we combine electroweak with strong interactions?
If we “evolve”
do they converge to a single value?
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32. Unification Philosophy
High-energy values fixed.
Low-energy values of couplings:
“evolve” (even in Kansas)
not fundamental
depend on fermion masses
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33. Evolution of em For t quark, Q=2/3. Multiply by 3 for color.
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34. If the t quark mass were 17 GeV
em would decrease by 0.5%
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35. Evolution of strong
nf is the number of quark flavors with mass below M.
11 comes from gluon self-interaction.
Integration constant sets mass scale.
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36. QCD scale depends on mt
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37. Weak Decays Cabibbo hypothesis:
Discovery of charm quark made this just a rotation:
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38. Six Quarks Kobayashi and Maskawa showed that three doublets
lead to complex mixing matrix:
Only four independent parameters, but still complex.
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39. Mixing Amplitudes What if 0.97 had been 0.25? We will see….
M. Kobayashi
T. Maskawa
2009 Nobel Prize
What if 0.97 had been 0.25? We will see….
Actual elements are complex:  CP violation
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40. Neutrino Masses and Mixing
Oscillations: “atmospheric” and “solar” neutrinos:
0.06 eV
0.009 eV
0.0 eV e  
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41. Electroweak Symmetry Breaking
Weak isospin:
Breaking this symmetry gives mass to fermions, W, and Z.
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42. Higgs Litany To minimize potential energy:
2009 Nobel Prize
Three massless bosons eaten to make W+, W-, Z0 massive.
Y. Nambu
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43. Changing Vud
can only decrease. Reducing it to 0.25 is equivalent to doubling
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