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Do Neutrinos Have Mass?

Posted by michael on from the but-were-afraid-to-ask dept.

amyjigglypuff writes "MINOS, a joint project between Fermi National Accelerator Laboratory and the University of Minnesota, is going to attempt to uncover the mysteries of the neutrino. Scientists plan to study the mass of neutrinos, whether they are stable or oscillate, and their electromagnetic structure. If they are found to have mass, it could prove that neutrinos are responsible for the cosmic "dark matter" that has baffled scientists for decades. Here is a link for scientists and a summary for the general public."

6 of 50 comments (clear)

  1. Some may have mass, and others may not... by kenthorvath · · Score: 4, Informative

    I attended a seminar where one group was attempting to measure neutrino oscillations and found convincing evidence that this happens. In order for neutrinos to oscillate, however, they would have to have some mass. In the model that they proposed, some neutrinos may have mass and some may not. Also, if super symmetry comes into play, you could potentially have some very heavy neutrinos. For some cutting edge theories consult the archives.

  2. Re:Wha? -- Becomes Hruh? by barakn · · Score: 4, Informative

    The three neutrinos are each associated with a lepton (electron, tau, muon). The electron neutrino indeed has no charge. Electron neutrinos are typically emitted in beta+ decays or electron captues, both events involving a nucleus swallowing or spitting out an electron.

    --
    "I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
  3. Arrrgh! by jwriney · · Score: 4, Funny

    These Ask Slashdot questions are getting tough. I've got no friggin' idea!

    --riney

  4. Re:WIMPs win by Peter+T+Ermit · · Score: 4, Informative
    Neutrinos are weakly interacting and they've got mass, but they're not a real candidate for exotic dark matter. (There are two types of dark matter: baryonic, which is about 4% of the "stuff" in the universe and exotic, which is about 23% of the stuff. [The remainder is dark energy.])

    Because of oscillation measurements of neutrinos, of CMB fluctuations, and of galaxy clusters, scientists have concluded that neutrinos make up only about 0.5% of the stuff in the universe. This is as much matter as is in the visible stars and galaxies, but it's not enough to account for exotic dark matter.

    (MACHOs are thought to be baryonic dark matter.)

  5. What's really neat about neutrinos by Mt._Honkey · · Score: 4, Interesting

    is that they carry away a significant portion of the energy that stars emit. Something on the order of a few % of the Sun's power is radiated away through neutrinos. Neutron stars cool down because their energy is carried away by neutrinos. It really gets cool in supernovae, because as much as 40% of a supernova's energy is in the form of neutrinos. I believe that this can be detected in theory, but I don't remember if it ever has been.

    Another neat thing is that there may be a 4th neutrino that does not interact via the weak force. Imagine that! It has already been said that a neutino is as close to nothing you can get and still have something, but a neutino that does not weakly interact is virtualy undetectable!

    Cool stuff, if you like physics.


    PIFMA-GASP

    --

    Don't Bogart the fish sticks
  6. More on neutrino experiments... by apirkle · · Score: 4, Informative

    I've actually been working as an undergrad assistant in a lab at UT Austin that is very active in the MINOS consortium, so it's pretty cool to see the experiment getting some attention.

    There are some neat photos of the detector; the steel scintillator modules weigh about 5,000 tons (!), and you can see one as it is lifted into place. The detector uses something like 2000 16 channel photomultiplier tubes (I don't remember the exact number of tubes) to detect the showers of particles that are created as neutrinos interact with the steel scintillator plates, and the data from those tubes is processed to reconstruct events. Did I mention that the whole thing is in a cavern about 1/2 mile underground to reduce background noise from cosmic rays?

    The detector is supposed to come online and start collecting real data in 2004.

    Another very interesting neutrino experiment is SNO, the Sudbury Neutrino Observatory, which is in an underground mine in Canada. SNO resolved the solar neutrino problem; people previously couldn't explain why we weren't seeing the right number of neutrinos coming from the sun - it turns out that they "oscillate" and change into other types of neutrinos, and SNO verified this. The neutrino oscillations also imply that they have a non-zero mass (explanation beyond the scope of this comment ;)

    The point of MINOS is to observe neutrinos from a controlled high-energy accelerator beam, rather than whatever we get from the sun, to very accurately measure the oscillations.