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I Has anyone ever determined at what rate quarks move?

  1. Feb 16, 2017 #1
    I am wondering if anyone has determined by experiment or calculation at what rate or even better what frequency the quarks move around at inside a neutron and proton? Do neutrons or protons vibrate at a specific frequency.
     
  2. jcsd
  3. Feb 16, 2017 #2

    mfb

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    Quarks do not have well-defined speeds. The closest thing they have is their momentum distribution, described with parton distribution functions. Those are measured at every major collider experiment.
    No. They do not vibrate at all.
     
  4. Feb 23, 2017 #3
    Thanks for the links. They were very informative. So most everything we know about quarks comes from high energy collisions? In these collisions do quarks ever completely come out of the neutron and proton? According to what I read partons can not be observed as free particles. If so what happens to them? Do they change into other particles if a high energy collision destroys a proton? If so what do they change into? I would like to know more about these interesting objects called quarks. Its hard to imagine whether they are moving or not by thinking of their location changes as being defined as a probability density. This quantum mechanics is most confusing.
     
  5. Feb 23, 2017 #4

    mfb

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    Those are the only processes where we can study them in (sort of) isolation. Otherwise we only see hadrons.
    High-energetic collisions between hadrons (like protons or neutrons) can be summarized like that: 2*(bound state made out of 2-3 quarks) -> big mess -> n*(bound state made out of 2-3 quarks). In the big mess, quarks can be created and destroyed.

    If you start learning quantum mechanics, start with easier objects, like electrons in atoms.
     
  6. Feb 23, 2017 #5

    TeethWhitener

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    Just to horn in on the conversation: This was surprising to me. I know that nuclei have vibrational structure (as well as rotational structure if they're non-spherical), so I just assumed individual hadrons, being composite particles, would have vibrational structure as well. Why exactly don't they? (This can be split off into another thread if need be.)
     
  7. Feb 23, 2017 #6

    mfb

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    Nuclei: yes. For nucleons, excited states are called different particles, but they don't correspond to anything that could be called vibrations. There is simply no such state.
     
  8. Feb 23, 2017 #7
    Do you mean nucleons are different particles in excited states?
     
  9. Feb 23, 2017 #8
    https://en.wikipedia.org/wiki/Hadronization
     
  10. Feb 23, 2017 #9

    mfb

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    An excited state of a proton gets a different name, e.g. "N(1440)". This is just a naming convention.
     
  11. Feb 24, 2017 #10
    Yes, I will definitely do that. I am really interested in the details of the electrons as well.
    I am doing my best to dig through the QM mind field so that I can better visualize what is happening but I keep running into this problem. When using QM it becomes impossible to say anything with complete precision, unless that thing is so abstracted from the real physical world as to not represent any real thing.
    So thus far it seems as if the quarks do not have real trajectories or velocities or positions (except for when we look at them) they just seem to show up in different places when we force collisions into protons and neutrons. These manifestations of quarks are represented by a probability distribution only. We get different results in the rubble of the collisions depending on what type of particles we collide with the proton and neutron and how high the energy we use. If we really destroy a proton the quarks come out of the nucleon and become something else that is not a quark once they are no longer inside the neutron or proton. Hopefully I have got that part right.

    How exactly do we know that we are not just simply modifying the quarks into appearing as other types of particles by virtue of high energy collisions? In other words maybe all we are doing is creating these non-fundamental particles in colliders during these high energy collisions which are really nothing more than two particles or specific geometries crushed together for a short period of time and then they simply decay back into stable fundamental particles. It seems to me that the high energy collision process is a high invasive technique in regards to the neutron and the proton and we are creating particles that are not really a part of the normal nucleon process. Simply put maybe there is nothing more in protons and neutrons than the 3 quarks that were discovered early on using lower energy probes. Has anyone ever considered this possibility?
     
  12. Feb 24, 2017 #11

    mfb

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    We have a model that is simple and works great and can describe hundreds of of measurements with incredible precision. This includes modeling the internal structure of neutrons and protons (and several other particles) to predict their masses. The same model that leads to the correct masses (and spin, lifetime, and various other properties) also leads to the correct predictions for collisions.
    We don't have a model where there are some "conversions" ongoing that would remotely match any observations.
     
  13. Mar 2, 2017 #12
    MFB thanks for the info. You certainly seem to know a lot about the world of sub-atomic particles. I am curious about something. Is there ever a time at a certain energy level where the neutron or the proton is destroyed and the particles that come out are either two positrons and an electron or two electrons and a positron?
     
  14. Mar 2, 2017 #13

    mfb

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    I'm working with that.

    Such a process is not possible (at least not in the Standard Model), it violates baryon number conservation and lepton number conservation.
     
  15. Mar 2, 2017 #14
    What happens when two protons collide at the highest energy do they still remain protons or do they turn into a shower of other particles? I am unclear on what happens in the collider to protons and neutrons when they are bombarded by other particles especially at the highest energies. Is there a chart that exists that shows for instance at different energy levels of electron bombardment of protons what other particles are produced at each increasing energy levels? In each case does the proton remain intact? I would love to see that info all together in some sort of chart. Perhaps someone has written a program that simulates a particle collider using just the standard model and Quantum Mechanics. That would really be fun to play with and be a great learning tool. I want to understand where are all these new particles coming from?
     
  16. Mar 2, 2017 #15

    mfb

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    Both are possible options. It is random.
    The result is random. Often several pions are created, sometimes kaons, neutrons, protons, sometimes heavier particles. Typically lighter particles are more frequent than heavier particles, and hadrons are more frequent than anything else, but there are some exceptions. More and heavier collision products correspond to a smaller probability that the proton stays intact.

    There are many programs, and hundreds of theorists work on calculations for specific processes. It is challenging to get accurate predictions. The tools typically need hundreds to thousands of CPU hours and a lot of experience from the user to produce anything useful - to get interesting results you cannot just play around with them on your home computer. There are some public results from those calculations, ATLAS and CMS at CERN made some of them public for example. But playing around with that will still take at least a few days to get used to the basics of the frameworks.
    They are created in the collisions.
     
  17. Mar 3, 2017 #16

    ChrisVer

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    What would you learn from a chart?
    It's easier to learn the Standard Model itself than look at a table of several hundrends of possible outcomes...
     
  18. Mar 6, 2017 #17
    ChrisVer > I am a self taught person so using a chart allows me to examine the data directly so I can look for patterns. Its just how I learn best in this particular situation.
    There is something in this conversation that has caused me to pause. I see a paradox. Perhaps someone can help me resolve this paradox. I see references to the Standard Model and thanks to the powerful predictive power of Quantum Mechanics it can be used to predict the large scale statistical outcome of various particle collisions and their by products. The conflict in my mind occurs as it has been mentioned that the outcomes of these collisions are purely random. In this case I am assuming that what is random is the prediction of an individual event. On the other hand how can we have predictive capabilities when conducting particle collision experiments and claim that they are random? If we can predict the results of particle experiments when a large statistical sample is used then the results overall are not random. They are not random because a statistical pattern emerges. Something can only be random if it has no specific pattern. Can someone please help me clear up this conflict?
     
  19. Mar 6, 2017 #18

    mfb

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    Such a chart cannot exist. You can just go by the masses of the particles to see what is possible.

    We can predict probabilities for every event. For many events, the observed probabilities will approximate the predictions (if the predictions are right).

    This is similar to predicting what a die will do. You predict "every side has a probability of 1/6 each time". I predict "1 has 50% probability, the others have 10% probability". Then we roll it 10000 times and write down how often each side occurs. Then we see which prediction was better. Each roll is random, but with many rolls we can see that some theories fit and some do not.
     
  20. Mar 6, 2017 #19
    I noticed this technique of retrofitting equations to match the results of experiments when I was going to websites of physicists that were talking about the search for the Higgs particle. Each time the Higgs was not found at the energy level that the equations were predicting it appeared to me that the professor modified the equation to predict the discovery at the next energy level. Is this a common practice?

    I get what you are saying in your example concerning the die. Unfortunately I have detected a logical inconsistency in my mind that I can't seem to overcome. That logical inconsistency is how we can say that a series of singular random events when compiled form predictive patterns that are not random. How can something that is random when repeatedly performed turn into a pattern that is not random. Logically if the group of events is not random then the set of individual events which make up the predictable non-random group must also not be random. For example the double slit experiment when done with firing single electrons or photons through the double slit. Each singular detection appears to be random but when we compare a sample of several thousand events we see the striped pattern. This in my mind can only happen because there is an interaction going on between the particle in motion and the physical geometrical structure of the test apparatus and this interaction is determining the path of each and every particle. This logically must be interpreted that while singular events are not predictable by any math or model we possess they give the impression of being random but in reality they are not. Is there something wrong with my logic? I can't seem to find a logical way out of this knotted logic. Perhaps the world is so chaotic it just appears to be random. This question I have sounds like it might be a question to be dealt with as the start of a new thread concerning the proper interpretation of the double slit experiment. If an admin thinks it is worthy of discussion and wants to move it that is fine with me.

    Thank you MFB for your help I have enjoyed the conversation. I have many more questions about particles and so I will start a new thread to ask other questions later on.
     
  21. Mar 6, 2017 #20

    Vanadium 50

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    That is untrue.

    That is one of the problems of being self-taught. Your teacher doesn't know any more than you do.
     
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