The Nobel Prize in Physics 2015

Neutrino oscillations present a curious physical puzzle.

To see what this puzzle is, I will summarize masses and mixing angles.

Mass unit = 1 GeV, a little more than a proton's mass.
Particle | Charge | WIS | Gen 1 | Gen 2 | Gen 3
Up quark | +2/3 | +1/2 | 1.9*10^(-3) | 1.32*10^(0) | 1.727*10^(2)
Down quark | -1/3 | -1/2 | 4.4*10^(-3) | 8.7*10^(-2) | 4.24*10^(0)
Neutrino | 0 | +1/2 | ~0 | ~9*10^(-12) | ~5*10^(-11)
Electron | -1 | -1/2 | 5.11*10^(-4) | 1.057*10^(-1) | 1.78*10^(0)
(Standard ModelWP, Neutrino oscillationWP, normal hierarchy, first neutrino mass assumed << the two others' masses)
(WIS = weak isospin, a quantum number that gets flipped by charged weak interactions)

So neutrinos' masses ought to be somewhat greater than corresponding charged-lepton masses, but they are much smaller.

Quark mixings (Cabibbo–Kobayashi–Maskawa matrixWP magnitudes):
Flavor | d | s | b
u | 0.97437 | 0.22534 | 0.00351
c | 0.22520 | 0.93744 | 0.0412
t | 0.00867 | 0.0404 | 0.999146
Nearly diagonal.

Neutrino mixings (Pontecorvo–Maki–Nakagawa–Sakata matrixWP, v1.3: Three-neutrino results after the 'Neutrino 2014' conference | nu-fit magnitudes)
Flavor | 1 | 2 | 3
e | 0.801 - 0.845 | 0.514 - 0.580 | 0.137 - 0.158
mu | 0.225 - 0.517 | 0.441 - 0.699 | 0.614 - 0.793
tau | 0.246 - 0.529 | 0.464 - 0.713 | 0.590 - 0.776
(3-sigma ranges)
This matrix is much farther from being a diagonal matrix.
 
If the Higgs mechanism makes the neutrinos' masses, then it has a very serious oddity. The neutrinos' low masses translate into very low Higgs-particle couplings for them.

The Higgs-particle field's vacuum value is about 246 GeV. Calculating Higgs-particle couplings for the elementary fermions, the top quark has 0.7 and the electron has 2*10^(-6), but the heaviest neutrino has 2*10^(-13).

That is rather bizarrely tiny.

But there is a possible solution, the Seesaw mechanismWP. It states that neutrinos have an additional kind of mass, their "Majorana masses". This kind of mass is alongside the masses induced by the Higgs particle, the "Dirac masses". These masses then mix, with some of the resulting masses being the very low observed masses:

m(observed) = m(Dirac)^2 / m(Majorana)

If m(Dirac) is about 10 GeV, then to get 5*10^(-11) GeV, one needs m(Majorana) = 2*10^(12) GeV.

That's close to Grand Unified Theory mass scales of around 2*10^(16) GeV (gauge unification: Standard Model + TeV-scale SUSY).

So there may be some connection with GUT's.

-

The neutrino masses form this 5*5 matrix:
(0 m')
(m M)
with 0, m, and M being 3*3 ones. m' is the hermitian conjugate of m. The 3 comes from the 3 generations. The 6 comes from including both left-handed and right-handed neutrinos.

Multiply on the right by (I, -M^(-1).m), and one gets (-m'.M^(-1).m, 0)

Thus, one gets mass matrix -m'.M^(-1).m

The up-like quarks, the down-like quarks, and the electronlike leptons also have 3*3 mass matrices.

The mass matrices for the up-like quarks and the down-like quarks are almost aligned, as is evident from their near-diagonal generation mixing, while that is clearly not the case for the electronlike leptons and the neutrinos. If the neutrinos' Dirac matrices are almost aligned, then their Majorana masses must be rather badly misaligned.
 
wogoga said:
A summary:
Click to expand...
A better summary of Neutrinos questioned:
  • Questions about beta decay revealing the ignorance of the author about beta decay.
    A "Bryan W. Reed" answers but the author just dismisses the answers.
  • Reading "Constructing quarks: a sociological history of particle physics" rather than a physics textbook.
  • The implied ignorance of thinking that neutrino experiments stopped in 1984 (the date of the book)!
  • The physicists at the time of the discovery of the neutrino actually knew the physics that we know today that points to the existence of neutrinos, e.g. the conservation of energy!
  • Unsupported assertion: "Most elementary particles are inferred from very complicated statistical interpretations of photomultiplier data".
    Most of the elementary particles are quarks and they were detected by looking at scattering.
  • Ignorance about the Nobel Prize (in Physics): "The rules for the Nobel Prize in Physics require that the significance of achievements being recognized has been "tested by time". In practice it means that the lag between the discovery and the award is typically on the order of 20 years and can be much longer."
  • More ignorance: There has been no "deficit of solar neutrinos" since 2001.
    The convincing evidence for solar neutrino oscillation came in 2001 from the Sudbury Neutrino Observatory (SNO) in Canada. It detected all types of neutrinos coming from the Sun,[6] ...
This actually boils down to "I do not know much about nuclear physics and neutrinos but neutrinos do not exist anyway", wogoga.
 
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Bob McDonald in the latest Quirks and Quarks podcast has a very interesting and layman friendly interview with the Canadian astrophysicist, Dr. Art McDonald (no relation I assume), about his neutrino research for which he shared the Nobel Prize. He talks about the Kamiokande, Super K H2O, and the Canadian SNO D2O (pronounced "snow") experiments.

Interview begins at about 47:00.
http://www.cbc.ca/player/Radio/Quirks+and+Quarks/Full+Episodes/ID/2676830043/


The Homestake Gold Mine experiment designed by Nobel laureate Raymond Davis, Jr. in the 60s used a 100,000 gallon tank of perchloroethylene, dry cleaning fluid, almost a mile underground. From what I understand, only a third of the predicted neutrinos were detected, and this was the motivation for the search for the "missing neutrinos" coming from the sun.

According to Dr. McDonald, since the standard model predicted a massless neutrino, it is a difficult to incorporate these findings into the theory.
My take on all this is that the significance of the nature of neutrinos is that they hold implications for explaining the imbalance between matter and anti-matter and for other fundamental questions of how the universe has evolved. The post-doc research discussed in the lecture I attended the other day was looking into the possibility that the neutrino is its own anti-particle.

The SNO-Plus conversion, according to Dr. McDonald, will hopefully enable their group to observe vestiges of the matter/anti-matter asymmetry that occurred in the early universe, and possibly to establish a base mass for the neutrino.


http://www.cbc.ca/player/Radio/Quirks+and+Quarks/Full+Episodes/ID/2676830043/
 
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aleCcowaN said:
...what boils down to "I don't know what you're talking about, but it's controversial!".

Wolfgang, this thread is about why Kajita and McDonald -who belong to a profession you clearly don't- got the Nobel Prize, not about why you will never be allowed even to cater that ceremony. Besides, it is supposed to contain scientific explanations and not story telling, which is what you basically do.
Click to expand...
:thumbsup::D:D:D:D:D:thumbsup:

Congratulations!! Two in one day and in the same thread!!!!!!!
 
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