Why can't a neutron be thought of as a proton plus an electron and neutrino?

[jcsd]

Originally posted by theriddler876
You're referring to rest mass

mass = rest mass

 

[theriddler876]

do these flavours have a charge, and if so, do they have a charge to mass ratio?

 

[jcsd]

No, neutrinoes are electrically neutral and possibly massless (if you look at a chart of elementary particles their mass will usually be given as zero, however a couple of experiments have suggested they may have a small but non-zero mass so the issue is still up in the air at the momen. It seems to me though that more people are coming down on the side that they have mass which is useful as they are a candidate for non-baryonic dark matter). They are generally cofined to weak interactions.

 

[Nereid]

Originally posted by jcsd
No, neutrinoes are electrically neutral and possibly massless (if you look at a chart of elementary particles their mass will usually be given as zero, however a couple of experiments have suggested they may have a small but non-zero mass so the issue is still up in the air at the momen. It seems to me though that more people are coming down on the side that they have mass which is useful as they are a candidate for non-baryonic dark matter). They are generally cofined to weak interactions.

At least one variety (mixture) must have mass ("rest mass"), otherwise there'd be no neutrino oscillations; these are now firmly established from observation. There's furious work going on to re-do core-collapse supernova models, to incorporate these oscillations.

Neutrinos are not likely to be more than a small fraction of non-baryonic dark matter as they're too hot; dark matter seems to be quite cold.

Here's an image of the Sun, in 'neutrino light'; it's fuzzy (image is >20^o cf <1^o actual) because we can't (yet) focus neutrinos as we can light:
http://antwrp.gsfc.nasa.gov/apod/ap980605.html

 

[jcsd]

It's still not 100% sure but IIRC neutrinoes cannot have both a well-defined flavour and a well-defined mass.

 

[Nereid]

This paper is a good, non-technical overview of neutrino oscillations, incorporating much of the most recent experimental results (thanks to SelfAdjoint):
http://arxiv.org/abs/physics/0303116

 

[theriddler876]

at some point something must have come from nothing,

I believe that nothing, fundamentally cannot exsist, we just can't detect it, take the neutrinos' for example, which "make up" sub atomic particles, well what makes them up?, you could keep asking that question, so would you ever truly have nothing?

 

[Floyd Flanigan]

Excellent point. It lends it's self to the theory of infinite halves. I like it.

 

[Nereid]

Originally posted by theriddler876
at some point something must have come from nothing,

I believe that nothing, fundamentally cannot exist, we just can't detect it, take the neutrinos' for example, which "make up" sub atomic particles, well what makes them up?, you could keep asking that question, so would you ever truly have nothing?

The Gordon Kane article, "The Dawn of Physics Beyond the Standard Model", in the June 2003 issue of Scientific American, is a good review of the current state of play - the successes of the Standard Model, and 'ten mysteries' which it cannot address.

BTW, neutrinos do not "make up" sub-atomic particles.

 

[quantumdude]

I took the cacophany on photon mass and split it off into a separate thread, which you can find here:

https://www.physicsforums.com/showthread.php?threadid=6616

A "real physicist" would know that--since a photon isn't even emitted in the beta decay of neutrons--that the subject of photon mass is, among other things, off topic.

Originally posted by chroot
Take your pseudoscientific blather somewhere else. Here at pf.com, we have a forum called "philosophy" just for this kind of discussion.

Not Philosophy, but Theory Development. We take our philosophy seriously here.

 

[PRodQuanta]

Floyd Flanigan,

I think by now, you have noticed chroot is this type of guy,"If it looks like an orange, smells like an orange, and there is mathematics that proves it is an orange; then it is an orange. That's all there is to it, no if, ands, or buts about it.

Now this is a topic I have argued before, that the photon has a mass. And if you ask me, I think it is very possible it does, like expressed in this book here: Photon :
Old Problems in Light of New Ideas
(A Volume in Contemporary Fundamental Physics - Valerie V. Dvoeglazov - Editor)
Nova Science Publishers, Inc.; ISBN 1560728108

What chroot is saying, is that according to the mathematics, the fact that a photon has a mass isn't very probable. Which brings me to one of my favorite sayings:
"It's possible, but not probable."
Paden Roder

 

[jcsd]

It's possible because you cannot detrimine the mass of light exactly by experiment, so the best any experiment, even an idealized one can do is place an upper limit on it.

But if light has mass then much of quantum physics and the standard modle go straight out of the window.

 

[chroot]

Originally posted by jcsd
But if light has mass then much of quantum physics and the standard modle go straight out of the window.

That's the ticket, jcsd.

What you don't realize, PRodQuanta, is that an enormous amount of theory and experiment depends upon the mass of light being zero. Were it not zero, none of our theories would agree with any of the experiments done in the last, oh, 50 years or so. QED is the most successful scientific theory of all time, and has predicted experimental results to the precision of, IIRC, parts per 100 billion. It would be hard to swallow that all this agreement between theory and experiment is nothing but coincidence!

- Warren

 

[Nereid]

Originally posted by chroot
That's the ticket, jcsd.

What you don't realize, PRodQuanta, is that an enormous amount of theory and experiment depends upon the mass of light being zero. Were it not zero, none of our theories would agree with any of the experiments done in the last, oh, 50 years or so. QED is the most successful scientific theory of all time, and has predicted experimental results to the precision of, IIRC, parts per 100 billion. It would be hard to swallow that all this agreement between theory and experiment is nothing but coincidence!

- Warren

In other words, alternative theories have a lot of heavy lifting to do just to get to the starting line. If you have a pet theory which proposes something as radical as a non-zero (rest) mass for the photon, you have to show that your theory can explain (is consistent with) all the experiments which have been, up till now, explained with a zero mass photon. Not a task for the faint-hearted.

 

[neutroncount]

I must mention that the engineering behind some of what we take for granted today are built from the pure theory and prediction of quantum mechainics. If the theory doesn't hold as you say, most of that research wouldn't have produced squat for products.

 

[theriddler876]

Originally posted by chroot
That's the ticket, jcsd.

What you don't realize, PRodQuanta, is that an enormous amount of theory and experiment depends upon the mass of light being zero. Were it not zero, none of our theories would agree with any of the experiments done in the last, oh, 50 years or so.
- Warren

Perhaps all experiments have a slight margin of error, Perhaps the mass of light is so small that the values attained by the experiments do and will continue to work, we have limited technology, it would be trying to get the exact measurement of a rock, by weighing it with a balance measuring only in whole Kg

 

[jcsd]

As I said you cannot verify the mass of light exactly even in an idealized experiment only place upper limits on it.

The thing is though the fact that light has no mass is axiomatic in theories like Q.E.D., it's a key assumption and one which if fals invalidates the whole theory.

 

[bdkeenan00]

Wouldn't the electromagnetic force be reduced to a short range force if the photon had a mass according to QED?

 

[chroot]

bdkeenan00,

Indeed. We would no longer be able to see those quasars...

- Warren

 

[Jeebus]

These are all mechanical scenarios for the reaction occurrence, right?

http://xxx.arXiv.org/abs/physics/0205057

"Small perturbations of averaged ideal turbulence reproduce the electromagnetic field. A hollow cavity models the neutron. The cavity stabilized via a perturbation of the turbulence energy serves as a model of the proton. An isle of quiescent fluid models a localized electron. The antineutrino corresponds to a positive disturbance of the turbulence energy needed in order to compensate the difference in perturbations of the energy produced by the electron and proton." --arXiv

The Neutron mass exceeds the sum of the Proton and Electron masses. Thus the decay can conserve energy, right?

Isn't this decay commonly involved in fission of radioactive nuclei in the nuclear reactors that are used to generate electricity for the detonation of nuclear weapons?

 

[mormonator_rm]

neutrinos, then back to neutron decay

A neutrino and anti-neutrino will have opposite lepton number, which is critical in studying leptonic decay modes. Also, it should be noted that the electron and its anti-neutrino will couple from the W- massive vector boson of the weak force. The positron and electron-neutrino from the W+. Hence the defined direction for neutron decay into proton, electron, and anti-neutrino. It actually conserves lepton number in the process because the electron has L = 1 and the anti-neutrino has L = -1, cancelling to zero. And of course, baryon number is conserved.

I think it may be important to this discussion to mention that the neutron decay proceeds via W- decay as a result of the up quark being changed to a down quark. You could treat it as;

udd -> uud + d(-u)

where the d(-u) term is going to effectively result in the formation of W-. Because the down quark has isospin -1/2 and the anti-up quark also the same isospin, the resulting W- will carry off an isospin of -1, leaving your proton with the opposite isospin from the original neutron. The W- has a very large width, and thus decays very soon after emmission into e- and -(v~e). The full process becomes;

n -> p + W- -> p + e- + -(v~e)

where -(v~e) is the electron anti-neutrino.

 

[mormonator_rm]

Whoops

Um... I didn't realize there were five pages to this thread. My reply was intended for the last message on the first page. Whoops, sorry about that.

Okay, reply to Jeebus' message. I would imagine that such neutron decay is a regular occurrence in nuclear reactors, as Cerenkov radiation is very common in reactor pools.

The result of the decay conserves energy. However, in the process you have to make your 940 MeV neutron emit a W- particle with mass 80.41 GeV! Either there is some serious contribution from temporary energy conservation violation (which is permissible for short moments of time: Heisenberg Uncertainty Principle) i.e. vacuum energy, or the W- must be a virtual particle only. In either case, the result is an electron and anti-neutrino, with the electron having considerable momentum (enough to travel faster than light in water, hence the Cerenkov effect being visible).

 

[jcsd]

Originally posted by mormonator_rm
Um... I didn't realize there were five pages to this thread. My reply was intended for the last message on the first page. Whoops, sorry about that.

Okay, reply to Jeebus' message. I would imagine that such neutron decay is a regular occurrence in nuclear reactors, as Cerenkov radiation is very common in reactor pools.

The result of the decay conserves energy. However, in the process you have to make your 940 MeV neutron emit a W- particle with mass 80.41 GeV! Either there is some serious contribution from temporary energy conservation violation (which is permissible for short moments of time: Heisenberg Uncertainty Principle) i.e. vacuum energy, or the W- must be a virtual particle only. In either case, the result is an electron and anti-neutrino, with the electron having considerable momentum (enough to travel faster than light in water, hence the Cerenkov effect being visible).

mormonator, wouldn't temporary energy conservation violation mean the W^- has to be a virtual particle.

 

[mormonator_rm]

W- virtual or real

I would imagine that is the case, but I have been informed that the W- in neutron decay is often a real particle, not virtual. Personally, I would think that the violation requires it to be a virtual particle, but this is apparently not always the case. What I think is by no means what is true.

 

[mormonator_rm]

Alright, I went looking for references to real W- decay in n --> p + e- + -(v~e) and found absolutely nothing. I guess I was fed a bunch of BS by some profs and a textbook with misinformation. So yeah, the W- must always be virtual, which made perfect sense all along.

 

[turin]

Originally posted by chroot
There is no way for a composite particle of more than three quarks to be color neutral. There is also no way for a single quark to be color-neutral. Therefore, there are no particles with more than three quarks, or fewer than two. Quarks cannot be found in isolation.

I can't think of a counter example for "quarks cannot be found in isolation," but, what rules out a 5-quark hadron with red, blue, green, and another of these colours with its anti-colour?

How do the protons stay so close to each other in the nucleas inspite of the emmense electrostatic repulsion?

 

[mormonator_rm]

That's one of the latest things going on right now with the finding of X(3872) and other proposals. We are seeing very serious evidence of just the kind of thing you are talking about; hadrons with four or more quarks/antiquarks in combination seem to be turning up suddenly. And yes, they would have to be color neutral.

Still, quarks cannot be found in isolation since the energy to free a single quark would be infinite. The strong potential is approximatley proportional to the distance between the quarks, so it will increase as quarks are brought further apart. Someone pointed this out in another thread I think, that the potential created as quarks are pulled further apart tends to create quark/antiquark pairs, destroying any chance of actually deconfining a quark.

Protons are still attracted to each other through the residual strong force, which is mediated by mesons rather than gluons. Basically, the protons have a "sea" of quarks and anti-quarks in addition to their three commonly known valence quarks (uud). Any quark/antiquark pair from this "sea" of quarks can interact with the other protons, attracting them together even though they are color-neutral in the gluonic strong field regime. Hence it is called the residual strong force, and it is able to hold together color-neutral nucleons of any type (and that includes hyperons in hypernucleii as well).

 

[turin]

Originally posted by mormonator_rm
Someone pointed this out in another thread I think, that the potential created as quarks are pulled further apart tends to create quark/antiquark pairs, destroying any chance of actually deconfining a quark.

This is something that totally confuses me. Why does high potential generate particle/antiparticle pairs? I often hear, in the context of particle physics, that, if something can happen, it will happen (i.e. 1.022 MeV gamma turning into an electron and positron). I don't like that, but I'll deal with it for now if that's the contemporarily acceptable answer.

Originally posted by mormonator_rm
... the protons have a "sea" of quarks and anti-quarks in addition to their three commonly known valence quarks (uud).

How does this get around contributing a huge amount of mass to the baryon?

Originally posted by mormonator_rm
Any quark/antiquark pair from this "sea" of quarks can interact with the other protons, attracting them together even though they are color-neutral in the gluonic strong field regime.

But doesn't the interaction still have to be mediated by bosons (if it's attractive anyway)? I don't yet see how gluons exchange can be ignored in this scheme.

 

[mormonator_rm]

Originally posted by turin
This is something that totally confuses me. Why does high potential generate particle/antiparticle pairs? I often hear, in the context of particle physics, that, if something can happen, it will happen (i.e. 1.022 MeV gamma turning into an electron and positron). I don't like that, but I'll deal with it for now if that's the contemporarily acceptable answer.

Nothing likes to be in a state of higher energy, it will always find a state where it has the least energy. Energy also has a tendency to form massive bodies to carry it off. So as the potential grows, it seeks to bring it back down by creating a quark-antiquark pair. This allows the energy to be released in the form of mass, and also brings the potential back down to where you started.

Originally posted by turin
How does this get around contributing a huge amount of mass to the baryon?

The total energy within the baryon should remain fairly constant as long as it does not decay. Basically, the quark-antiquark "sea" and the potential will trade off, but always add up to the total energy that we see as the baryon's rest mass. More "sea" quarks may be formed and the potential will relax a bit, or more of these "sea" quarks may be released/annihilated and the potential will increase in response.

Originally posted by turin
But doesn't the interaction still have to be mediated by bosons (if it's attractive anyway)? I don't yet see how gluons exchange can be ignored in this scheme.

Mesons are in effect bosons. They have integer spin just like the Gauge Bosons do. This was the foundation of Yukawa's hypothesis on nuclear interactions, when he discovered the pion and measured its mass using the nuclear binding potential. Gluons will not couple to any particle that does not have color charge, so color neutral particles will not couple to gluons, i.e. a gluon can affect a quark within a proton, but it will not effect the whole proton, and because the gluon is colored it is not as likely to bridge the gap between two orbiting protons as a pion would.

 

[turin]

Originally posted by mormonator_rm
Energy also has a tendency to form massive bodies to carry it off.

Is this something like a postulate of particle physics?

Originally posted by mormonator_rm
So as the potential grows, it seeks to bring it back down by creating a quark-antiquark pair. This allows the energy to be released in the form of mass, and also brings the potential back down to where you started.

But the energy is still there, just in a different form (instead of potential energy which I'm assuming to be synonymous with virtual bosons, it is now in the form of fermions). So is mass like the most stable form of stress-energy?

I've also heard that matter and energy are just excitations of a field (I think something like this particle/antiparticle sea). Is there some postulate that says the exitations like to manifest in the form of multiples of 1/2 integer spins?

Originally posted by mormonator_rm
The total energy within the baryon should remain fairly constant as long as it does not decay. Basically, the quark-antiquark "sea" and the potential will trade off, but always add up to the total energy that we see as the baryon's rest mass.

But isn't the mass of the proton and neutron attributed solely to the masses of the three quarks plus a little bit of binding energy (not even enough extra mass for one more quark)? Or do I have that totally wrong?

Originally posted by mormonator_rm
Mesons are in effect bosons. They have integer spin just like the Gauge Bosons do.

But they are fermionic, are they not (isn't their wavefunction overall antisymmetric)? The s shell electron pair in ground state He is also like a boson in the same respect, right? But the electrons are still fermions, and they only interact with other He electrons by mediating true bosons (and Pauli exclusion?), right?