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How would a photon or neutrino interact within a quantum system? Wh

  1. Dec 14, 2009 #1
    When you attempt to measure the motion a neutrino or a photon, one of the two subatomic particles being a massless particle and the other particle being a ghost particle, how would either of the two particles interact in a quantum state if both particles don't posses an inherent mass?

    I know when you attempt to measure the position of a subatomic particle, that measurement you make on the subatomic particle affects the position of the particle greatly .
     
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  3. Dec 14, 2009 #2

    bcrowell

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    Looking up "ghost particle" on wikipedia, I found the following:

    http://en.wikipedia.org/wiki/Faddeev–Popov_ghost

    Is this what you're referring to? At the end of the article they say there are other uses of the term. A Faddeev–Popov ghost is always virtual, not real, so I don't see how you can use it to measure anything about a neutrino or photon. It's also a mathematical trick, not a particle in the ordinary sense.

    Why is it relevant that the target particle is massless?
     
  4. Dec 14, 2009 #3
    Because how is the quantum system disturbed when attempting to make a measure of the motion of an elementary particle like a neutrino if the neutrino does not interact with anything?
     
  5. Dec 14, 2009 #4
    Why do you think neutrinos do not interact with anything? They interact, just very weakly. If they did not interact we would have a very difficult time detecting them.

    Notice that I did not state that it would be impossible to detect them. You just could not detect them directly. For particles that do not interact, you can look for missing energy in reactions in which you are (fairly) certain you measured everything else.
     
  6. Dec 14, 2009 #5
    The neutrinos interact with W and Z bosons. Photons interact with all electrically charged particles.
     
  7. Dec 14, 2009 #6

    bcrowell

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    Noblegas, there seem to be three different issues here:

    (1) ghost particles

    (2) massless particles

    (3) weakly interacting particles

    You haven't replied re #1, and your reply re #2 brings up #3 rather than explaining why you thought #2 was relevant.
     
  8. Dec 14, 2009 #7
    #1, neutrininos are ghost particles. #2, photons are mass less particles. #3 , both ghost and massless particles . Questions answered:) Obviously both particles would be detected but how would you affect the motion of a neutrino if its is massless and heisenberg uncertainty principle says that when you attempt to measure the motion of a particle, the measurement is meaningless seeing that when measuring the position of the particle , you change its position and subsequently its velocity. But how can you disturbed the motion of a particle like a neutrinon at the subatomic level if it can travel through solid matter? Sorry for the unintended redundancy.
     
  9. Dec 15, 2009 #8

    Vanadium 50

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    Neutrinos are not ghost particles. A ghost particle is a very specific thing with specific properties, and a neutrino is not one of them.

    A neutrino is a particle like any other. Yes, it interacts quite rarely, but this is a matter of degree, not character.
     
  10. Dec 15, 2009 #9
    That response is so vague and it still does not answer my question about why the uncertainty principle still applies to subatomic particles that travel through solid matter. "A neutrino is a particle like any other"? That statement doesn't really explain to me what a neutrino particle is . Apparently, using google, I found out that Issac Asimov coined the term for ghost particle and when he was speaking of a ghost particle , he was specificaly talking about the neutrino . Explain to me how the heisenberg uncertainity prinicple applies to the neutrino when it travels so easily through solid matter?
     
  11. Dec 15, 2009 #10

    Vanadium 50

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    The Heisenberg Uncertainty Principle applies to everything. Why would it not apply to neutrinos.
     
  12. Dec 15, 2009 #11
    That is fine that Asimov coined the word "ghost particle" to describe the neutrino, but when talking about "ghosts" in particle physics, there is a much different meaning. It usually applies to Faddeev-Popov ghosts which are used in the path-integral formulation of gauge field theories to solve an over-counting problem. There are also other uses of the word "ghost" in particle physics, but no one commonly uses the term "ghost" for a neutrino.

    What Vanadium was referring to when he said "A neutrino is a particle like any other" is that there is really nothing all that special about a neutrino compared to any other particle. Neutrinos carries quantum numbers just like other particles. They don't carry a strong or electromagnetic charge, so they do not interact easily. We now know they have a very small mass.

    If you want to know more about the qualities of a neutrino, I would suggest taking a look at http://theparticleadventure.org [Broken] and specifically at http://particleadventure.org/neutrinos.html
     
    Last edited by a moderator: May 4, 2017
  13. Dec 15, 2009 #12
    Yes, but as I stated, information on that site says that a neutrino passes right straight through the earth, without its properties being affected and said to interact with other matter very rarely . So when attempting to measure the motion of a neutrino, how would measuring the neutrino affect its velocity like measuring the motion of any other subatomic particles would affect that subatomic particle velocity , rarely interacts with matter , including the instrument we used to try measure the motion of the neutrino ?
     
    Last edited by a moderator: May 4, 2017
  14. Dec 15, 2009 #13
    You are misreading what the site says.

    So, no not every single neutrino passes through the earth before interacting. The vast majority do not interact, but some do. So, yes you can detect neutrinos.

    You might want to look up some of the neutrino detection experiments like IceCube (http://www.icecube.wisc.edu/info/explained.php [Broken]) and ANTARES (http://antares.in2p3.fr/Overview/index.html)
     
    Last edited by a moderator: May 4, 2017
  15. Dec 15, 2009 #14
    What you seem to be missing is that the only way we can measure anything about the neutrinos is if they interact. The neutrinos that don't interact with our measurement apparatus aren't affected by it and they aren't measured.
     
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