The Standard Model of Particle Physics -- where we are at

Trakk · Sep 3, 2015

Awfully ingenious.

But I'm so entranced with Grand Unified Theory simplification that I'll show how it works.

The smallest simple-group GUT that includes the (Minimal Supersymmetric) Standard Model is the Georgi-Glashow SU(5) model. Its multiplets break down into the unbroken (MS)SM ones as follows:

Gauge (spins 1 and 1/2)
24 -> (gluons) + (electroweak W) + (electroweak B) + (-5/6,2,3) + (5/6,2,3*)

Higgs (spins 0 and 1/2)
5 -> (L up Higgs) + (L,-1/3,1,3)
5* -> (L down Higgs) + (L,1/3,1,3*)
5* -> (L up Higgs)* + (R,1/3,1,3*)
5 -> (L down Higgs)* + (R,-1/3,1,3)

Elementary fermions (spins 1/2 and 0)
1 -> (R neutrino)*
5 -> (R down) + (L lepton)*
10 -> (L quark) + (R up)* + (R chgd lepton)*
10* -> (L quark)* + (R up) + (R chgd lepton)
5* -> (R down)* + (L lepton)
1' -> (R neutrino)

Note that the EF's multiplicity numbers are binomial-theorem values, coefficients of powers of x in (1+x)^5. The 10 is the antisymmetric combination of two 5's, the 10* three 5's, the 5* four 5's, and the 1' five 5's. The 1 is zero 5's, of course. The 5 and its mirror image 5* are called "fundamental representations" of SU(5). There's also this nice alternation between left and right handedness:
1 L, 5 R, 10 L, 10* R, 5* L, 1' R

This suggests further unification.

But for now, I note that there are some new particles that have appeared, a (-5/6,2,3) and its antiparticle (5/6,2,3*), and a (-1/3,1,3) and its antiparticle (1/3,1,3*). These particles make low-energy particles with quarklike QCD behavior and electric charges -4/3 and -1/3. These particles can also cause isolated protons to decay. Since that decay has yet to be observed, these particles' masses must be pushed up to GUT scales by symmetry breaking, about 10^(16) GeV.

Trakk · Sep 3, 2015

Next up is the Fritzsch-Minkowski-Georgi SO(10) model. It breaks down into SU(5) * U(1), where the second group is related to a chargelike quantity related to (B-L), (baryon number) - (lepton number). Its multiplets are (SU(5) multiplet, U(1) "charge").

Gauge:
45 -> (24,0) + (1,0) + (10,-1) + (10*,1)

Higgs (both L and R):
10 -> (5,-1/2) + (5*,1/2)

Elementary fermions:
L: 16 -> (1,5/4) + (10,1/4) + (5*,-3/4)
R: 16* -> (1',-5/4) + (10*,-1/4) + (5,3/4)

The (10,-1) and its antiparticle (10*,1) also cause isolated-proton decay.

-

The next biggest one after that is E6, and it breaks down into SO(10) * U(1) the latter group related to yet another chargelike quantity.

Gauge:
78 -> (45,0) + (1,0) + (16,-1) + (16*,1)

EF's, Higgs (in the same kind of multiplet):
L: 27 -> (16,1/3) + (10,-2/3) + (1,4/3)
R: 27* -> (16*,-1/3) + (10,2/3) + (1,-4/3)

-

Finally, E8 -> E6 * SU(3)

Gauge -> gauge, EF's, Higgs (all of the Standard Model's multiplets in one E8 multiplet):
248 -> (78,1) + (1,8) + (27,3) + (27*,3*)

-

There are several other symmetry-breakdown routes besides E8 -> E6 -> SO(10) -> SU(5) -> SM SU(3)*SU(2)*U(1)

nebulaJP · Sep 12, 2015

sfs said:
That's pretty bad -- bosons do collide in the Standard Model.

Not generally:

"But W-boson scattering was incredibly rare: It occurs only once in 100 trillion proton-proton collisions,..."

sfs · Sep 12, 2015

nebulaJP said:
Not generally:

"But W-boson scattering was incredibly rare: It occurs only once in 100 trillion proton-proton collisions,..."

Not really relevant: either they do or they don't. To be sure, photon-photon scattering has played a larger role in particle physics, but that's boson-boson scattering too.

nebulaJP · Sep 12, 2015

sfs said:
Not really relevant: either they do or they don't. To be sure, photon-photon scattering has played a larger role in particle physics, but that's boson-boson scattering too.

One can say that generally speaking, "[The Standard Model] sees all reality as particles that divide into light-like bosons that don’t collide and matter-like fermions that do."

sfs · Sep 12, 2015

nebulaJP said:
One can say that generally speaking, "[The Standard Model] sees all reality as particles that divide into light-like bosons that don’t collide and matter-like fermions that do."

Well, yes, one can say that, but one will be wrong if one does. In particle physics, events are either forbidden or allowed. Boson-boson scattering is allowed.

nebulaJP · Sep 19, 2015

sfs said:
Well, yes, one can say that, but one will be wrong if one does. In particle physics, events are either forbidden or allowed. Boson-boson scattering is allowed.

From what I understand, only protons, neutrons, electrons and atoms are accelerated in particle accelerators for the purpose of collision. Why aren’t photons used?

sfs · Sep 19, 2015

nebulaJP said:
From what I understand, only protons, neutrons, electrons and atoms are accelerated in particle accelerators for the purpose of collision. Why aren’t photons used?

Because the other particles are charged, and you can use electric fields to accelerate them up to high energies. How are you going to generate extremely high energy photons?

Black Dog · Sep 21, 2015

Uncle Mikey said:
Dark Energy...

So if we had called it "other matter", the bible would have been wrong?

Uncle Mikey · Oct 8, 2015

Black Dog said:
So if we had called it "other matter", the bible would have been wrong?

Good question.

The answer is no.

Dark Energy is destroying the Universe, therefore it fits the name.

Maybe it was a coincidence or Familiar Spirits at work.

Dark Matter on the other hand, is not destroying the Universe, but rather nurturing it.

Dark Matter is an example of a name that doesn't fit Scripture.

It is however mentioned in Scripture as Transparent Gold, related to New Jerusalem and Wisdom.

Black Dog · Oct 9, 2015

Uncle Mikey said:
Good question.

The answer is no.

Dark Energy is destroying the Universe, therefore it fits the name.

Maybe it was a coincidence or Familiar Spirits at work.

Dark Matter on the other hand, is not destroying the Universe, but rather nurturing it.

Dark Matter is an example of a name that doesn't fit Scripture.

It is however mentioned in Scripture as Transparent Gold, related to New Jerusalem and Wisdom.

You will have to forgive me if I don't buy into this. The words in the bible, or any book that long, can be twisted into whatever you want. I'm pretty sure I can go through songs and stories about Santa and find where they prophesied all sorts of things, so long as I know what I'm belatedly looking to prophesy. The trick is to show where the bible, or the books about Santa, tell us something before science discovers it.

Uncle Mikey · Oct 12, 2015

Black Dog said:
The trick is to show where the bible, or the books about Santa, tell us something before science discovers it.

I've done that so many times now, I've lost count.

Black Dog · Oct 12, 2015

Uncle Mikey said:
I've done that so many times now, I've lost count.

I'm new to the forum, and haven't seen any. Could you please provide a link?

Black Dog · Oct 12, 2015

Trakk said:
The Standard Model has been very successful so far, but there are lots of things that don't fit.

Empirical

Neutrino masses

Matter-antimatter asymmetry

Gravity

Dark matter

Dark energy

Inflation

Theoretical

Sources of neutrino masses -- seesaw mechanism?

Strong CP violation -- why isn't it observed?

Higgs-particle instability at around GUT energies

Elementary-fermion unification at GUT energies

Gauge unification at GUT energies

GUT = Grand Unified Theory

There is a lot of work being done to resolve these problems. Here is some:

Neutrino-oscillation experiments, searches for neutrinoless beta decay

Nucleon electric-dipole moments

Proton decay and bound-neutron decay

Dark-matter direct detection

Detection of dark-matter annihilation radiation

Continued search for supersymmetric and other BSM particles at the Large Hadron Collider

Cosmic Microwave Background: search for evidence of inflation-generated gravitational waves

Post-Newtonian gravitational effects, the best-known tests of general relativity and similar theories

...

Some of these experiments could well give us some interesting results in coming years.

What's your opinion on the likelihood of supersymmetry?

The Standard Model of Particle Physics -- where we are at

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