The Eighteen Parameters of the Standard Model in Your Everyday Life

1
The Eighteen Parameters of the Standard Model in
Your Everyday Life
Twenty-seven

• Robert N. Cahn
• Lawrence Berkeley National Lab

2
A Polemic
Asserting that particle physics addresses the
question What makes the everyday world the way
it is?
3
Voices from the Past
On Fermilab The money and brains which go into
such an object as the Batavia accelerator are
very likely to be wasted. P.W. Anderson, 1971
On the SSC If we decide that cheap ignorance is
better than an investment in the future of
science, then we will have shaped for our
children and our grandchildren a real weakness..I
urge a vote in favor of the supercollider. Rep.
Newt Gingrich, June, 1992
4
A Muonic World
What happens?
Matter shrinks
Light becomes soft x rays.
5
No. Remember muonic atoms.
Muon would be stable, but hydrogen isnt
Universe neutrons and neutrinos!
6
Todays theory has 27 (1) dials.
One is
.
7
The dials appear to be independent, arbitrarily
set. Probably they are linked.
8
Increase u-quark mass by 0.8 MeV
hydrogen disappears
by only 0.16 MeV and nitrogen disappears
9
Fundamental Fermions
Electric charge
Mass (GeV)
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Other worlds
As long as the masses of the quarks and leptons
appear arbitrary, there are plausible alternative
worlds.
As long as we dont understand why there are
three generations, we can imagine other
possibilities.
11
Suppose we had only the second generation
Only one quark survives
No isotopes.
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A Strange World
One stable baryon
No nuclei? Lightest meson is
Probably too heavy to bind
to
A single atom
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18 Parameters
Quark masses
Charged lepton masses
Coupling strengths
Quark mixing
Electroweak Symmetry Breaking
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Coupling Constants
Theyre not constant vacuum polarization
quarks, leptons
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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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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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Evolution of ?em
For t quark, Q2/3. Multiply by 3 for color.
18
If the t quark mass were 17 GeV
?em would decrease by 0.5
19
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.
20
QCD scale depends on mt
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mt and the protons mass
Protons mass determined by not quark
masses.
(u and d quark masses are about 1 of a protons)
If top quark mass were 10 times smaller,
protons mass would be reduced by factor 0.84.
22
Weak Decays
Cabibbo hypothesis
Discovery of charm quark made this just a
rotation
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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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Mixing Amplitudes
What if 0.97 had been 0.25? We will see.
Actual elements are complex ? CP violation
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CP Violation and Baryon-Antibaryon Asymmetry
Andrei Sakharov (1967) Why were here Baryon
number violation. Non-equilibrium. CP violation.
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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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Neutrino Masses and Mixing

• Oscillations atmospheric and solar
  neutrinos

0.06 eV

0.009 eV
0.0 eV
e
?
?
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Majorana Neutrinos

• Electron has four degrees of freedom
• Massive particle needs L and R.
• Cant have just
• Cant use
• For neutrinos can use (Majorana)

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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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Electroweak Symmetry Breaking
Weak isospin
Breaking this symmetry gives mass to fermions, W,
and Z.
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Higgs Litany
To minimize potential energy
Three degrees of freedom eaten to make W, W-, Z0
massive.
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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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Problem 13.9

• Calculate what the suns 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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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!
35
Changing Vud
can only decrease. Reducing it to 0.25
is equivalent to doubling .
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What about Higgs boson mass?

• Doesnt affect much. Thats why its so hard to
  find!
• There could be several Higgs bosons, as in
  supersymmetry.

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Supersymmetry

• For every particle, there is partner with spin
  differing by half a unit
• Requires at least three neutral,two charged Higgs
  bosons.

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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, not
  without it.

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Grand Unification or Not?
Standard Model
Minimal Supersymmetric Standard Model
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What if the lightest particles were selectrons?

• Atoms would lose their individuality.
• Molecules would lose their integrity.
• Matter would fuse into an undifferentiated blob.

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Binding energy of matter

• For ordinary matter with N atoms
• For bosonic atoms (F. J. Dyson, 1967)
• Watch out!

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• 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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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.