quark mass and proton mass
- Thread starter devire
- Start date
Th extra mass comes from energy stored between the quarks from the strong-force bonds, since E=mc^2 this energy resaults in an increase of mass for the proton.
Can't talk about what this energy is in detail though, because im not too familliar with QCD
-Andrew
that's what i thought, but it seems like a lot, since it is far more than the binding energy of any atom per nucleon.
(Don't think I am being sarcastic but...) YES!
And you have just noticed something that so many who ask these questions don't!!!
Congratulations!!!
Now, why would the force that bonds the quarks together ``weigh'' more than the force that binds the atoms together?
Think about it, and if you have trouble I will help you.
you know i meant nuclear binding energy not chemical binding energy, right?
i know that one can find the nuclear binding energy in an atom by taking the mass of the atom minus the mass of the protons and nuetrons and multiplying that by the speed of light squared, but what does that have to do with quarks having more binding energy than nucleons?
Ahh yes, but the point remains the same.
Because they are two different forces! Sorry if you already knew that, but people don't realize that there are two forces---the strong force which governs the interractions of quarks and the weak force that governs the interractions of the nuclei, and the electromagnetic force which governs the interractions of the atoms.
The strong force has more energy stored in the bonds because it is (as per its name!) stronger. There is more energy stored in the bond, and this manifests itself as mass.
wow, i am almost positive that i was taught that the strong force governed the interactions of the nucleus in high school physics. and all this time i wondered what the weak force was for. lol. thanks.
Here's my weak (pun!) understanding.
Nucleons are bound together by the strong nuclear force and repelled by the weak nuclear force.
The strong force that binds is actually a residual of the force that binds quarks together into nucleons - ie two nucleons are bound together by the strong force acting between quarks in adjacent nucleons.
The strong force drops off with distance faster than the weak (and electromagnetic) forces, so as atoms get larger they aren't as strongly bound.
I think that this is the main reason that light atoms release energy when they fuse, heavy atoms release energy when they split, and why very heavy atoms are unstable (yes, I said my understanding was weak
).
Nucleons are bound together by the strong nuclear force and repelled by the weak nuclear force.
The strong force that binds is actually a residual of the force that binds quarks together into nucleons - ie two nucleons are bound together by the strong force acting between quarks in adjacent nucleons.
The strong force drops off with distance faster than the weak (and electromagnetic) forces, so as atoms get larger they aren't as strongly bound.
I think that this is the main reason that light atoms release energy when they fuse, heavy atoms release energy when they split, and why very heavy atoms are unstable (yes, I said my understanding was weak
).Here's my weak (pun!) understanding.
Nucleons are bound together by the strong nuclear force and repelled by the weak nuclear force.
The strong force that binds is actually a residual of the force that binds quarks together into nucleons - ie two nucleons are bound together by the strong force acting between quarks in adjacent nucleons.
The strong force drops off with distance faster than the weak (and electromagnetic) forces, so as atoms get larger they aren't as strongly bound.
I think that this is the main reason that light atoms release energy when they fuse, heavy atoms release energy when they split, and why very heavy atoms are unstable (yes, I said my understanding was weak
i think the lighter atoms release energy when they fuse because they weigh more than the atom they fuse into. while the heavier atoms weigh more than the atoms and the other particles that are released after fission takes place.
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A bit of browsing indicates that the Weak force doesn't do much energy-wise. It is very weak (1 million times weaker than the strong force), and acts over an extremely short range (1000 times shorter than the strong force). It is important in other ways. It allows quarks to change color, and is thus responsible for beta decay. It mediates all interactions with neutrinos.
But, according to what i can find, it doesn't bind nucleons together. It doesn't have the strength or the range to do that. Hyperphysics says that nucleons are bound together by the residual strong force - the attractive force between quarks in adjacent nucleons. Actually, I'm not sure that nucleons are distinct within a nucleus... some things I've read seem to indicate that a nucleus is a ball of quarks, rather than a ball of protons and neutrons. But I could be misinterpreting.
I think of it the other way around - it seems to me that the mass difference is because of the energy released or absorbed.
And in turn, the energy differences are due to the potential energies of the strong and electromagnetic forces:
When two nucleii fuse, the electromagnetic potential energy between them increases, and the strong potential energy between them decreases.
Now, for small nucleii fusing, the difference in strong potential energy is more than the difference in electromagnetic potential energy, so the total energy decreases. Since mass and energy are equivalent, the total mass decreases.
For large nucleii fusing, the difference in strong potential energy is less than the difference in electromagnetic potential energy, so the opposite happens.
But I'm no expert. I don't have a solid understanding of this stuff, and my vague understanding could be flat out wrong.
Better check it out for yourself
But, according to what i can find, it doesn't bind nucleons together. It doesn't have the strength or the range to do that. Hyperphysics says that nucleons are bound together by the residual strong force - the attractive force between quarks in adjacent nucleons. Actually, I'm not sure that nucleons are distinct within a nucleus... some things I've read seem to indicate that a nucleus is a ball of quarks, rather than a ball of protons and neutrons. But I could be misinterpreting.
Hi devire,devire said:
I think of it the other way around - it seems to me that the mass difference is because of the energy released or absorbed.
And in turn, the energy differences are due to the potential energies of the strong and electromagnetic forces:
When two nucleii fuse, the electromagnetic potential energy between them increases, and the strong potential energy between them decreases.
Now, for small nucleii fusing, the difference in strong potential energy is more than the difference in electromagnetic potential energy, so the total energy decreases. Since mass and energy are equivalent, the total mass decreases.
For large nucleii fusing, the difference in strong potential energy is less than the difference in electromagnetic potential energy, so the opposite happens.
But I'm no expert. I don't have a solid understanding of this stuff, and my vague understanding could be flat out wrong.
Better check it out for yourself
Scrap that. Definitely misinterpreting.
the nucleons themselves r like bags of quarks, that can stretch out to an infinite length, correct?
I am a bit embarassed about this. Sigh. Pete is right. It's the exchange of something called pions that keeps nucleons together. I hope I haven't confused anyone terribly---I didn't think before I posted.
This isn't correct. The idea of ``confinement'' is that the quarks are bound together in protons, neutrons, pions, and whatnot. The strong force is a bit weird because it increases in strength as you pull two quarks apart. This idea is called asymptotic freedom, for which Gross, Politzer and Wilczek won the Nobel prize in 2005.
Let's look at a pion to make things easier.
In a pion, there are two quarks, say up and anti-up (called up-bar). Now, if one were to physically grab each of the quarks and pull them apart (nevermind how you would do this!), it would be like taking a strip of rubber and stretching it...literally.
The further you pull the quarks apart, the stronger their attraction is, until eventually there is enough energy in the bond to create another quark-anti-quark pair. So you started with one pion and made two! This is exactly like a rubber strip breaking---the quarks live at the ends of the rubber strip.
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Pete this isn't quite correct. The strong force changes color, the weak force changes flavor.
For example, there are six flavors of quarks, arranged in three generations: up down, charm strange, and top bottom. The weak force would change, say, an up quark into a down quark. This would cause a proton (made of up-up-down) to turn into a neutron (made of up-down-down). Because charge must also be conserved, a positron is created in the process, and we see beta radiation.
Pete and BenTheMan:
The nucleus of a larger atom [e.g. Fe] appears to be arranged in a 'shell' structure, similar in concept to the electron orbitals being in quantized shells of discrete energy levels.
We see transistions from a more-energetic shell to a less-energetic shell by way of a discrete gamma [high-E photon, typically in the 100s of KeV range] emission unique to that particular nucleus, and which can be used to identify the nucelus [its A and Z].
The protons and neutrons are not uniformly 'mixed', but rather their quark-constituents are arranged heirarchically in a manner that is not yet fully elucidated. Nucleii are not necessarily 'spherical', but can have 'pointed-ends', allowing for some unusual decay modes.
A more stable form of a nucleus has been hypothesized to be able to exist, consisting not only of up and down quarks [as in normal nuclear matter], but an equal number of strange quarks as well. This theoretical nucleus was aptly named a "strangelet", and you can learn more about nuclear forms by googling on that term.
The nucleus of a larger atom [e.g. Fe] appears to be arranged in a 'shell' structure, similar in concept to the electron orbitals being in quantized shells of discrete energy levels.
We see transistions from a more-energetic shell to a less-energetic shell by way of a discrete gamma [high-E photon, typically in the 100s of KeV range] emission unique to that particular nucleus, and which can be used to identify the nucelus [its A and Z].
The protons and neutrons are not uniformly 'mixed', but rather their quark-constituents are arranged heirarchically in a manner that is not yet fully elucidated. Nucleii are not necessarily 'spherical', but can have 'pointed-ends', allowing for some unusual decay modes.
A more stable form of a nucleus has been hypothesized to be able to exist, consisting not only of up and down quarks [as in normal nuclear matter], but an equal number of strange quarks as well. This theoretical nucleus was aptly named a "strangelet", and you can learn more about nuclear forms by googling on that term.
Walter---
I am beginning to recall some of my nuclear physics now. The nuclear shell model predicts (as I recall) that Element 118 (it would be the next ``noble gas'') would have a half life on the order of years. the most stable nuclei are those that have complete ``shells''.
Is this correcT?
I am beginning to recall some of my nuclear physics now. The nuclear shell model predicts (as I recall) that Element 118 (it would be the next ``noble gas'') would have a half life on the order of years. the most stable nuclei are those that have complete ``shells''.
Is this correcT?
Three atoms of Element 118 have been created, according to an October 2006 publication in Physics Review C. Researchers at the Joint Institute For Nuclear Physics in Russia published the experiment. An earlier claim (2002) by researchers at Lawerence Livermore National Labs was discredited and the lead researcher fired when it was discovered some of the data was falsified. In both cases, however, element 118 decayed into element 116 in a half-life of less than a millisecond. Element 116 then decays into element 114, etc.
http://www.aip.org/pnu/2006/split/797-1.html