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Old Oct 1st 2019, 08:15 PM   #81
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Originally Posted by neila9876 View Post
That dragon's theory seems complicated and poetic enough, but can it explains the phenominon of mass oscillation of the neutrino as well as the 1/3 phenominon of solar neutrino in ONE way?
@woody:
What's regrettable is that the posts about explanation of experiments are not here...otherwise > 60percent. haha...
If I had access to an actual Journal I would be happy to look up some of these experiments. However I do not as they are very expensive.

These are not my theories! Why would you say that they are? The "complicated" parts are there whether I can explain them simply or not. QM is not something that you can really just pick a text up and master easily. There is nothing I can do about that. The Math is simply nasty.

Particles will oscillate between one or more different states as a part of their time evolution. The new thing (to me) is that the neutrinos oscillate by changing what are known as "families." (There are three: electron, muon, and tau.) Unfortunately I haven't done a search for this effect because of the Journal cost. (arXive doesn't seem to have it, unless I somehow missed the paper.) I don't have any details on it.

I usually keep to the Standard Model when I answer questions. More often than not that's what the students here need for thier education. On occasion I will address other possibilities, but I always try to mention that when I'm branching out. As far as I know neutrino oscillation does not fit in with the Standard Model.

-Dan
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Old Oct 2nd 2019, 02:10 AM   #82
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Red face theory vs experiment

@dragon:
People now just set out to find a way to "describe" the mass oscillation of neutrino.
.................
The theory of "standard" model seems to be "incontinuous" with experiment?
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Old Oct 2nd 2019, 03:29 AM   #83
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Originally Posted by neila9876 View Post
@dragon:
People now just set out to find a way to "describe" the mass oscillation of neutrino.
.................
The theory of "standard" model seems to be "incontinuous" with experiment?
All I know about the oscillation is that someone went looking for it. So there must have been some kind of theory that I haven't yet looked at, but I doubt it's in the Standard Model.

The Standard Model, as I'm using the term, is something that can be described as a collection of different theories kind of smashed all together. If one aspect of the Model, say something as simple as the rate at which a free neutron decays (or whatever), turns out not to be right most of the rest of the SM will still be good to use, just not in that area until someone can explain it.

It's actually a bit of a pain to keep straight all the theories that are in the SM and which aren't. But hey, it's the best we've got at the moment.

-Dan
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Old Oct 2nd 2019, 03:54 PM   #84
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Talking boson vs fermion vs dragon

"... but I doubt it's in the Standard Model."
This semi-tramp heard that it is just because SM can not describe the mass of neutrino that scientists has to establish another model for neutrino. It's something outside SM. Actually, I know not much about SM,haha...
"It's actually a bit of a pain to keep straight all the theories that are in the SM and which aren't."
That's true.
.................
This semi-tramp often heard of "boson" and "fermion". I only know a bit characters of them: the method of classification for them is "spin"...
But that dragon's opinion about "spin" is as below:

“When we say that an electron has a quantity called "spin" we aren't talking about something rotating about an axis. Spin is a result of Quantum Mechanics merged with SR. (For non-Relativistic systems we can add a factor to the solution of the Schrodinger equation. You can see this most vividly by the solution of an electron orbiting a nucleus, hydrogen specifically. The solution simply does not work without spin included.) The spin is not in "real space", but in an "internal space." In fact, the electron has spin 1/2 and thus has to go around twice in order to get back to its original orientation!

The reason the term spin is used is because it does share similar Mathematical properties with the spin of an object in real space. It's unfortunate that rotation and spin have similar uses. The reason it has survived is because, while spin is not the same thing as a rotation, it still contributes to the angular momentum of the electron. So the notation will live on.

Ever since QM was born Physicists have tried to explain what's happening by analogy and many of those analogies don't do a good job of explaining it. Spin and orbital are terms that should probably be revamped. But we've been doing it for over 100 years so I doubt anything is going to change.”
“Unfortunately after I just went on a rant about making analogies I'm now going to make an analogy! Sorry.

Let's use a rotation in real space for simplicity. Say that we have a particle that is moving along the, say, +z axis and that the particle has a spin. Use your right hand "grab" the velocity vector (pointing in the +z direction) with your thumb in the direction of the velocity. Now, if the particle is rotating in the direction your fingers curl then the spin is "right handed." If the spin is in the opposite direction then it's "left handed." Most particles are either right handed or left handed depending on the reference frame of the observer, just like you would expect. But a neutrino is only left handed and an anti-neutrino is always right handed no matter what the reference frame is. Unfortunately there is no simple picture I can give you for the neutrino.

There is a way to do this just using Mathematics but unless you've worked with the Dirac equation it would likely confuse you. Let's leave it at the level of there is a way to do it. (By the way, the Dirac equation is a spin 1/2 relativistic equation, much like the Schrodinger equation is a spin 0 non-Relativistic equation.)”
“"m" comes in whenever we are using spherical harmonics, as in the derivation of the electron wavefunction for a hydrogen atom. m gives a measure of the angular momentum and often ends up quantized, even Classically. Without showing you the Math I don't know what else I can say about it. As for the Stern-Gerlach, only spin is measured, not m.

Spin comes out naturally by combining QM and SR. One of the problems in the early days of QM was to find a way to incorporate spin into the Schrodinger equation. It had to be added in manually. Dirac was the first to write down an equation that includes spin automatically. Oddly enough we call this the Dirac equation and it holds for massive particles with spin 1/2. (Schrodinger's equation isn't relativistic and thus spin was missing from the formalism.)

One of the big weird things in Physcis is spin. Mathematically it is treated like an "extra" angular momentum. But it has some weird properties, the most telling of which is, for example, an electron with spin 1/2. If we were to take spin as an actual angular momentum we would find that the electron has to go around twice to make one full revolution. Clearly this is ridiculous and we so can't treat spin as an angular momentum, though the Mathematics are otherwise the same.

Why is there such a thing as spin? I have no idea. It's just a property that falls out of the Mathematics.”
...
So, this semi-tramp feels that the method of classification itself for "boson" and "fermion" is a bit inexplicit and even a bit mist?
And actually what's the use of this method of classification in physics?
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Old Oct 10th 2019, 03:52 PM   #85
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Talking theory vs experiment

This semi-tramp heard Mr. muon said that "..Interaction with a proton (emitting a positron in the process, and converting the proton to a neutron)..." ahead. I also heard that free proton is very stable. Is it theory? Did experiment detect the "interaction"/ or say "reaction"?
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Old Oct 10th 2019, 08:21 PM   #86
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Originally Posted by neila9876 View Post
This semi-tramp heard Mr. muon said that "..Interaction with a proton (emitting a positron in the process, and converting the proton to a neutron)..." ahead. I also heard that free proton is very stable. Is it theory? Did experiment detect the "interaction"/ or say "reaction"?
I'm pretty sure it's a real interaction, antineutrino absorption. An antineutrino, when it encounters a proton, can emit a W- boson, while itself turning into a positron. The W- boson then converts the proton into a neutron. That doesn't mean the proton isn't stable, stable particles interact all the time. The neutrino and antineutrino are themselves stable. Even the positron is stable, yet it annihilates with an electron almost immediately.

Even though I can't find a source for this now, I don't see why it couldn't happen. It conserves charge at all steps, lepton number (-1), lepton family number, and baryon number.

Here's a further demonstration that weak isospin and weak hypercharge are also each conserved at both steps of the process:

Part 1: Antineutrino Emits a W- and converts itself into a Positron
starting particle:
electron antineutrino (right-chiral, in order to be able to participate in a charged weak interaction since it's an antiparticle):
-1/2 weak isospin
+1 weak hypercharge
-----------------------
ending particles:
W- boson (left-chiral, as always observed)
-1 weak isospin
0 weak hypercharge
positron (left-chiral; it is a product of the interaction rather than participating in it so I believe this is possible)
+1/2 weak isospin
+1 weak hypercharge
-----------------------
-1/2 = -1 + +1/2
(weak isospin is conserved)
+1 = 0 + +1
(weak hypercharge is conserved)
Part 2: W- joins with the Proton to form a Neutron
starting particles:
W- boson (left-chiral, as always observed)
-1 weak isospin
0 weak hypercharge
Up Quark of Proton (left-chiral, in order to be able to participate in a charged weak interaction)
+1/2 weak isospin
+1/3 weak hypercharge
-----------------------
ending particle:
Down Quark of Neutron (left-chiral, though it doesn't matter since it's a product rather than a participant of the interaction)
-1/2 weak isospin
+1/3 weak hypercharge
-----------------------
-1 + +1/2 = -1/2
(weak isospin is conserved)
0 + 1/3 = +1/3
(weak hypercharge is conserved)

Last edited by muon; Oct 10th 2019 at 11:29 PM.
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Old Oct 12th 2019, 06:23 PM   #87
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Red face theory vs experiment

If this semi-tramp can pay for a telescope, he will watch the Sun. There are so many protons there for billions of years...
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