Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mit-eddie!ll-xn!ames!pasteur!agate!garnet!weemba From: weemba@garnet.berkeley.edu (Obnoxious Math Grad Student) Newsgroups: sci.misc Subject: Re: Neutrino Tomography Message-ID: <7949@agate.BERKELEY.EDU> Date: 24 Mar 88 03:03:43 GMT References: <73600013@uiucdcsp> <7831@agate.BERKELEY.EDU> <240@unisv.UUCP> <53@avsd.UUCP> Sender: usenet@agate.BERKELEY.EDU Reply-To: weemba@garnet.berkeley.edu (Obnoxious Math Grad Student) Organization: Brahms Gang Posting Central Lines: 72 In-reply-to: govett@avsd.UUCP (David Govett) In article <53@avsd.UUCP>, govett@avsd (David Govett) writes: >> >(1) De Rujula, Weinstein, and others have proposed Whoops, it's not Weinstein, it's not Weinberg, it's Glashow. >What would you use to detect neutrinos? Would you believe they plan to hear them? >Also, what kind of image would you obtain if there were no interaction >between the earth and the stream of neutrinos? A totally blank picture. Obviously, this is not part of their proposal. ----------------------------------------------------------------------- OK, enough people have e-mailed to me that I'm writing this article on the subject. The reference is A De Rujula, S L Glashow, R R Wilson, G Charpak, "Neutrino Exploration of the Earth", PHYSICS REPORTS, v99, #6 (1983), pp 341-396. While normally that journal is too arcane for all but the professionals, this article is a delightful exception. Anyone who knows elementary physics can read the whole thing, while those who get by on SCIENTIFIC AMERICAN or even ANALOG could read about 1/3 of the article, which consists of general descriptions of their idea. (Un- like the popular literature, they do not take the time to explain basic notions. But if you're interested in the stuff already, you probably won't need them. Indeed, this is why I don't like the popular science literature much anymore--seeing "neutrino" or "prime number" defined for the zillionth time bores me.) One thing that needs to be kept in mind is that the properties of neu- trino that you've been told about before--their ability to penetrate millions of light years of matter without interacting--needs qualifi- cation. The cross section (== interaction probability) of neutrinos increases with energy. Thus, by the time they reach Tev-Pev energies, the earth is only semi-transparent, and significant rates of neutrino interaction will occur. They propose three applications: Projects GENIUS, GEMINI, GEOSCAN. Project GENIUS (Geological Exploration by Neutrino-Induced Underground Sound) is meant to aid searches for deposits of oil and gas. They plan to detect neutrinos by *listening* for them. They estimate that the neu- trino impact will create a small noise about .1% of the background. The rough idea is that careful analysis of this signal as they vary the beam energy will reveal the speed of sound underground, plus give a rough map. Project GEMINI (Geological Exploraton with Muons Induced by Neutrino In- teractions) is meant to detect high-Z ore (= heavy metals), since the rate of muon formation near the surface will be sensitive to atomic number. The detectors for this are special muon trucks. Project GEOSCAN is meant to determine the vertical density profile of the earth, especially the core, as a form of Whole Earth Tomography. They estimate that an appropriate accelerator would cost 1-3 gigadollars. While primarily meant as a research instrument in high-energy physics, by planning ahead they hope to get much more out of it. They view the whole thing as technically feasible but financially impossible; note that this was the pre-SSC view of the matter. I suspect they also plan to get nice tans out it. You see, to maximize the ease of aiming this accelerator, they suggest floating it out at sea. They propose somewhere isolated bay, with calm seas, a coral reef for an- choring the device, etc. They didn't name any islands in particular, but it wasn't hard to guess general locations. ------------------------------------------------------------------------ I should point out things like the above are one of the reasons that so much science fiction leaves me unimpressed. REAL science is so much more mind-blowing. WOW! That theory goes STRAIGHT UP into the CLOUDS! AMAZING!! ucbvax!garnet!weemba Matthew P Wiener/Brahms Gang/Berkeley CA 94720