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Neutrinos vs. gamma rays.

  1. Nov 17, 2006 #1

    taylaron

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    neutrinos are like electrons but not charged. its partner in the subatomic universe. no charge and subsiquently no mass.
    http://www.ps.uci.edu/~superk/neutrino.html
    part of the electromagnetic spectrum??

    gamma rays are also electrons, no charge and no significant mass.
    part of the electromagnetic spectrum

    if we are able to detect gamma rays through devices such as a geiger counter, than why is it so darn diffucult to detect neutrinos.
    i am however familiar with the process of discovering neutrinos with the massive chamber of heavy water, and another with chlorine. etc....... 3 kinds , yadi yadi yada.
    detecting neutrinos in a MASSIVE tank of chlorine after ~3 weeks only about 7 atoms interacted with the neutrinos (because of no charge) which were i think it was argon, or xeon gas. something like that.
    if it is so diffucult to detect with this kind of space and since takes so long to detetct neutrinos in this kind of space, how is it possible to detect gamma rays? which it too, has no electrical charge.
    if these 2 particles are so alike, and we are able to detect the gamma ray particles with devices such as a type of geiger counter?



    my point im trying to get to her guys is, if the neutrino and the gamma particle both have 0 mass and 0 charge. can both pass through almost anything without attraction of another particle due to charge, than how are we able to detect gamma rays so easily and neutrinos not?
    neutrinos are everywhere. billions of trillions per seccond through your finger.
    if gamma rays are so dangerous because they have the potiential to pass through cells, than why arent neutrinos so dangerous??? they pass through us just as easily as neutrinos if not more. right???:surprised


    pardon my spelling and grammar mistakes.
     
  2. jcsd
  3. Nov 18, 2006 #2
    Neither neutrinos nor gamma rays are electrons, nor are they particularly similar.

    Gamma rays are photons of above a certain energy. This means that they have no charge or mass, have spin-1, and interact directly with all charged particles.

    Neutrinos are, themselves, a type of fundamental particle. They have no electrical charge but do have (very small) masses and (like electrons) have spin-1/2. Neutrinos can interact with other spin-1/2 particles by exchanging either a W or a Z boson - both of which are very massive (and thus hard to exchange).
     
  4. Nov 18, 2006 #3

    ZapperZ

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    I think you are a bit behind in your knowledge here. Neutrinos do have mass. That is what the big brouhaha from many years ago coming out out of Super Kamiokande when they discovered neutrino oscillations.

    Please do a search on neutrinos for the latest development.

    http://neutrinooscillation.org/
    http://arxiv.org/abs/hep-ph/0305245

    Zz.
     
    Last edited: Nov 18, 2006
  5. Nov 18, 2006 #4

    jtbell

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    From the bottom of the very page that you cite:

    The page appears to be part of a site written by a participant in the Super-K collaboration, specifically to present their results on neutrino oscillations and neutrino mass to a general audience. It apparently hasn't been updated since 1998, and since then (eight years!) there has been a lot of work by other people confirming their results and expanding on them.
     
  6. Nov 18, 2006 #5

    CarlB

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    That neutrinos have mass has nothing to do with their ability to move through matter without interacting. The reason that gamma rays are easy to detect and neutrinos are not is that gamma rays interact electromagnetically, neutrinos interact through the weak force.

    While the weak and electromagnetic forces are approximately equal, the weak force is mediated by a very massive particle which reduces the range of the interaction. The electromagnetic force is intermediated by a massless particle, the photon, and has a very long range.

    Another difference between neutrinos and gamma rays is that neutrinos are elementary fermions while gamma rays are gauge bosons.
     
  7. Nov 19, 2006 #6
    IMHO, the experimental result of that dectector (that neutrinos have rest mass) is one of the most important experimental finding in modern era of physics .
    Next interesting question and experimental challenge is to answer :[tex]m_o=?[/tex] for neutrino!
     
    Last edited: Nov 19, 2006
  8. Nov 19, 2006 #7

    taylaron

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    thanks guys.
     
  9. Nov 20, 2006 #8
    I'd add a little to the other good posts so far. Neutrinos are often referred to as 'WIMPs' (weakly interacting massive particles). This is not because they are MASSIVE particles, but because they DO have a mass (which was not always thought of as to be the case).

    The Super-K detector can only detect electron neutrinos and muon neutrinos and only detects a few per year do to neutrinos' notoriously weak interactions with matter. If you want to detect Tau neutrinos you need to use the SNO (Sudbury Neutrino Observatory) which lies 2km underground. SNO can detect all 3 types of neutrinos.
     
  10. Nov 20, 2006 #9

    taylaron

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    right, SNO was how they discovered how many neutrinos are coming from the sun.
     
  11. Nov 21, 2006 #10
    The reason that gammas are more dangerous and neutrinos are in no way dangerous to cells is due to the dose rate for each of these. As people have mentioned, the neutrino weakly interacts with matter. Because of this, it has a huge mean free path (about a light year of lead per collision), whereas the gamma (depending on its energy) is much less (seevral mm to several cm). Since the neutrinos do not interact with matter (other than in dense neutron stars from what I hear), you get hit with one much less often than you get hit with gammas (especially if you're referring to a radioactive source). Even though the neutrino has energy on the order of GeV (I think, don't quote me on that one) , it is so much less massive than an electron that it won't impart a large portion of its energy in a collision, the same way a ping pong ball won't impart a large portion of its energy to a bowling ball. This deposition of energy in matter is what actually damages tissue. So the linear energy transfer (LET) of gammas is 1, whereas the LET of a neutrino is almost 0.
     
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