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Science

The Search For The 'Body' Of The Neutrino 30

Posted by timothy from the one-hundred-and-seventy-million-dollars dept.
An anonymous reader writes: "CNN has an interesting story about the scientists who are searching for proof that neutrinos have mass a half mile below Minnesota. Not alot of scientific theory but a good overall perspective on what is taking place. One of the more interesting quotes: "We're going to take a sawed-off shotgun and blast a bunch of neutrinos toward Minnesota and measure what sticks," said Marvin Marshak, a physics professor at the University of Minnesota."
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The Search For The 'Body' Of The Neutrino More

The Search For The 'Body' Of The Neutrino

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  • Neutrino research (Score:4, Informative)

    by ktulu1115 ( 567549 ) on Monday July 08, 2002 @02:09PM (#3843950)
    There's been a lot of research going on about neutrinos in the recent years. I still recall the big recent newsbreak when they discovered that they can spontaneously change to another form. The Ultimate Neutrino Page [cupp.oulu.fi] and Neutrino History [in2p3.fr] have some good news.

    The thing I've been thinking is... what they really need is another somewhat-close supernova to occur. That should give scientists even more data to digest.

    • Re:Neutrino research (Score:3, Informative)

      by Anonymous Coward
      The thing I've been thinking is... what they really need is another somewhat-close supernova to occur. That should give scientists even more data to digest.

      That's not actually enormously useful (although supernovae are free, so ....) Apart from the fact that you can expect to wait about 100 years for the next supernova anywhere close, like our old friend SN1987A, you don't actually learn a great deal about neutrinos from a supernova - there's too much that we don't really understand about the supernova itself.

      On the other hand, if we figure out what's going on with neutrinos, they'll give an extra handle to learn about supernovae.
      • You're right that you'd probably learn more about SNs than about neutrinos, but you can learn about neutrinos from a SN. For instance, when you look at the ratios of the different flavors of neutrinos that come out, you can figure out some of their properties, such as their relative masses. (And it's about three local SN per century, rather than one, which means that there's a reasonable chance of seeing one during a research career.)

    • Re:Neutrino research (Score:4, Interesting)

      by bcrowell ( 177657 ) on Monday July 08, 2002 @02:53PM (#3844281) Homepage
      I still recall the big recent newsbreak when they discovered that they can spontaneously change to another form
      Yeah, and that proved that neutrinos have mass, so both the CNN article and the Slashdot blurb are inaccurate. I'm sure there is something new that this experiment is going to be able to find out, something different than the solar neutrino experiments. But determining whether neutrinos have mass isn't it.

      The MINOS site [fnal.gov] has a bunch of information, but I didn't have much luck finding any specifics on how it really differs from the solar neutrino approach. A bunch of it is PowerPoint files of people's talks, which I can't read, and a bunch of it is password-protected.

  • Canada does not want your neutrino byproducts (Score:1, Funny)

    by Anonymous Coward
    send 'em to oklahoma or the middle east instead.

  • (GASP)! War with Canada! :-) (Score:5, Funny)

    by Dr.Dubious DDQ ( 11968 ) on Monday July 08, 2002 @02:37PM (#3844149) Homepage

    Ha! The article gives it all away! This isn't about some sort of scientific research! This is just the first field-test of the latest insidious high-tech military hardware...on the innocent people of Canada!

    It's plain to me that the US has developed a highly sophisticated Neutrino Ray Cannon(tm) that can be fired THROUGH THE EARTH and still hit targets in other countries! The article plainly describes that the beam will be fired through the earth, past the detectors, and INTO CANADA. Naturally, the US has chosen a nearby country to test it on, so that the results can be assessed quickly.

    I'm willing to bet it'll be a successful test, too. Being a Neutrino-based Ray Gun(tm), we'll know it works if the characteristic effects of Neutrino Bombardment (that is to say, "Nothing") are seen among the Canadian populace after the test! Previous tests were less successful, though they are rumored to have caused speech alterations described as a very mild form of Tourette's Syndrome, wherein the victims add an extra syllable (described as "Eh") to their sentences...though one heavily affected region is rumored to have had their language altered so severely that they now speak FRENCH instead of Canadian! [Probably just a rumor, I don't believe it myself. Nor do I believe the rumors that the US Government experimented on its own citizens similarly, resulting in the "y'know" at the end of victim's sentences, and inability to spell "lose" with less than 2 "O's" in it.]

    In the interests of World Peace(tm), I feel compelled to warn the People of Canada now - PROTECT YOURSELF WITH ALUMINUM FOIL DEFLECTOR BEANIES NOW! [zapatopi.net] Before it's TOO LATE!

    • The article plainly describes that the beam will be fired through the earth, past the detectors, and INTO CANADA

      Can't you see that this is a retaliatory attack. The people of the United States have lived in fear of the looming Canadian invasion forces [standonguard.com] for the nearly two centuries since Canadian troups burned down their presidential mansion [whitehouse.com]. It's only right that the US should be able to defend itself against the Canadian menace.

  • huh? (Score:4, Funny)

    by Mt._Honkey ( 514673 ) on Monday July 08, 2002 @02:46PM (#3844227)
    To brighten up the often dreary working conditions, Minneapolis artist Joseph Giannetti painted a 25- by 60-foot mural in the laboratory. It depicts his interpretation of the project with a blazing sun at the epicenter with rings of scientific symbols and physicists expanding outward.

    What kind of sick bastard makes a mural of physicists being blasted out of a sun and then expanding in the vacuum of space? That's disgusting.
    • What kind of sick bastard makes a mural of physicists being blasted out of a sun and then expanding in the vacuum of space? That's disgusting.

      I guess the lab was out of lawyers that day.

  • So does it look like neutrinos will lend themselves to a better communication medium then what we generally use now?

    Seems like the ability to beam communication through the earth could have a big impact. Not to mention, seems like they would slip through water as easily as well. I assume size of the neutrion gun is the biggest hinderance?

    -malakai
    • If the technology could get data to the other side of the planet faster than trans-oceanic fiber, then the size (or cost) of the device wouldn't matter a whit.

      The trick is catching the things. Communication isn't just about throwing, you've got to be able to know what has been thrown. Don't expect neutrino-based communication anytime soon.
    • There are a few problems with using neutrinos for communications. First, they are only produced in subatomic interactions involving the weak force, or basically any event in which a lepton decays or one quark turns into another (beta decay and the like). I believe that right now we can only do this in nuclear reactions and high energy particle collisions. You can't aim them in nuclear reactions, and I believe that it takes a pretty big particle accelerator.

      Second, neutrinos can pass through anything you throw at them (except for black holes, I would guess). Nearly all neutrinos that enter the earth exit the other side without interacting with a single particle. That means that even if you manage to transmit a neutrino signal, you won't be able to receive it, because they will go right through the receiver. "But how does MINOS detect them?" I think that it just take a whole shitload of steel, puts it in the way of the beam, and once out of a great while, a single neutrino might interact and cause high energy muons (or maybe other particles) to fly out, emitting cherenkov radiation (a flash of light, the light equivalent to a sonic boom).

      particle physics rocks.
  • If you shoot neutrinos, which travel in straight lines at nearly the speed of light, from Chicago to Minnesota, they will not pass through Canada! They will, in fact, pass well above Canada, since the Earth is not flat and the ground will fall away under the poor neutrinos as they travel away from Soudan, MN. Since Soudan is so far North, though, maybe some of them will fly through Canadian airspace -- I hope they get clearance from ATC.
  • This has been bothering me for a while. Science articles for layman always seem to gloss over it. Regardless of whether or not a neutrino has rest mass, wouldn't it still contribute to "dark matter"? Einstein told us that the curvature of the universe is determined by the mass and energy density in a given region. A neutrino, just like a photon, contributes to the overall "mass" of the universe.

    This article is a bit better than others. Most other "neutrino mass" articles simply say that if a neutrino has mass (assume rest mass), it's path will be deflected by the gravitational pull of the earth. Granted, if a particle has rest mass it will be deflected orders of magnitude more than a photon (rest-massless), but a photon will still be deflected. This article says "if they do have mass, they'll be altered on the voyage from Chicago to Minnesota by a process that can only act on particles that respond to gravity." I don't know of any "process" other than gravity that "can only act on particles that respond to gravity."

    My point is that something is being left out of all of these articles, or maybe I am always missing something. If anyone can help me out, I would greatly appreciate it.

    • Short answer: neutrinos do contribute to dark matter, but not all that much. Long answer: There's two types of dark matter. Ordinary, or "baryonic" dark matter, is made of hydrogen, helium, and other types of matter we encounter every day. The second is "exotic" dark matter that is made of everything else: neutrinos and perhaps yet undiscovered neutral particles like axions or neutralinos. Scientists know how much ordinary matter there is in the universe from various measurements (abundances of elements, features in the cosmic background radiation). About 5% of the "stuff" in the universe is ordinary matter -- and about 90% of that is dark. However, those observations also show that there's considerably more mass than ordinary matter; an additional 30% of the "stuff" in the universe is "exotic." Neutrinos fall into that category, but unfortunately, they don't account for all that much because too many of them would mess up the formation of stars and galaxies. They're "hot" matter because they move so quickly, while models greatly prefer "cold" dark matter. The best candidate is a light supersymmetric particle that hasn't been discovered yet.

    • Oh... and mass (Score:2, Insightful)

      by Peter T Ermit ( 577444 )
      You're right that even massless things are deflected by curved spacetime, so it's a bad definition of mass. Neutrino mass is just like the mass of an electron -- or the mass of a brick. You can think of it as the resistance to acceleration by an outside force. The difference is that neutrino masses are inferred without seeing the neutrino accelerate. The process in question is neutrino oscillation; basically, the neutrino changes flavors from, say, a muon neutrino to a tau neutrino. This oscillation phenomenon comes from a weird mismatch between how the neutrino behaves under different conditions -- and one of those conditions requires mass. So seeing neutrino oscillations implies that neutrinos have mass.
      • Thank you.

        Why can't they just add that into the article? It seems to me that these articles are just out there to introduce the new buzzwords that the author just learned.

        BTW, wasn't it found from the "closing of the solar neutrino problem" [aip.org] that neutrinos do undergo flavor fluctuations? Didn't that make this experiment pointless?

        • They didn't put it in the article because most science reporters don't understand physics, unfortunately.

          And your confusion about whether MINOS is a repeat of SNO is quite understandable -- and also due to shoddy journalism. In the obsession over neutrino mass, almost nobody got the real news from SNO, which has to do with neutrino "mixing angles." (See #3848535 [slashdot.org] which I posted anonymously this morning -- couldn't be arsed to log in. :) )

          MINOS, along with a few other experiments, like K2K, are pinning down those mixing angles. (Plus they get an extra-clean signal b/c they control the source of neutrinos as well as the target.)

          This is very cool science, but it's way too technical for most journalists to understand. And sadly, even if they *did* understand, they would have a tough time getting the space to explain it to the readers.

  • IIRC, neutrinos have 0 radius and therefore 0 volume (please correct me if I'm wrong), so wouldn't neutrinos having mass mean that they have infinite density?
    • As far as the standard model goes, all elementary particles are point particles. There are several problems with that. You pointed out one. Another is simultaneity of interactions for different observers.

      String theory demands a minimum non-zero size for all of it's constituents (except for 0-branes, which are point particles and are part of M-theory).

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