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The Case of the Disappearing Neutrinos

Following up on yesterday’s intriguing antimatter results at Fermilab, a neutrino study called the Main Injector Neutrino Oscillation Search (MINOS) is providing independent confirmation of a critical idea: neutrinos have mass. This is significant news because it helps to illuminate earlier experiments that suggested neutrinos oscillate between three different types, something that could occur only if they do have mass, and an effect that, given the sheer abundance of neutrinos in the universe, may provide clues to why antimatter has disappeared and how galaxies originally formed.

Neutrinos are odd things indeed; they can pass through the entire Earth without interacting with matter. MINOS studies them by producing neutrinos at Fermilab using protons accelerated in a 4000 foot tunnel pointing toward a second detector some 450 miles away in Soudan, Minnesota. The neutrinos are measured first with a detector below the Fermilab site, with a second measurement being taken at a 6000-ton particle detector at Soudan. Researchers are examining how many muon neutrinos have disappeared along the way, presumably by turning into another type of neutrino and thus confirming that neutrinos have mass.

The result, based on only the first months of data: a signficant number of muon neutrinos are disappearing in ways consistent with the idea that neutrinos regularly transform themselves into different types. The mass difference between two of the types of neutrino is now found to be 0.056 eV, just 0.00001% of the mass of the electron. Further MINOS work should confirm whether actual neutrino oscillation is occurring, or whether we are observing some form of neutrino decay or, a more exotic possibility, the influence of extra dimensions.

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  • ljk January 23, 2008, 10:06

    Developments in Nanosecond Pulse Detection Methods and Technology

    Authors: R. A. McFadden, N. D. R. Bhat, R. D. Ekers, C. W. James, D. Jones, S. J. Tingay, P. P. Roberts, C. J. Phillips, R. J. Protheroe

    (Submitted on 22 Jan 2008)

    Abstract: A promising method for the detection of UHE neutrinos is the Lunar Cherenkov technique, which utilises Earth-based radio telescopes to detect the coherent Cherenkov radiation emitted when a UHE neutrino interacts in the outer layers of the Moon. The LUNASKA project aims to overcome the technological limitations of past experiments to utilise the next generation of radio telescopes in the search for these elusive particles. To take advantage of broad-bandwidth data from potentially thousands of antennas requires advances in signal processing technology.

    Here we describe recent developments in this field and their application in the search for UHE neutrinos, from a preliminary experiment using the first stage of an upgrade to the Australia Telescope Compact Array, to possibilities for fully utilising the completed Square Kilometre Array. We also explore a new real time technique for characterising ionospheric pulse dispersion which specifically measures ionospheric electron content that is line of sight to the moon.

    Comments: 4 pages, 1 figure, Proceedings from 30th ICRC, Merida, Mexico, 2007

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0801.3304v1 [astro-ph]

    Submission history

    From: Rebecca McFadden [view email]

    [v1] Tue, 22 Jan 2008 04:24:19 GMT (26kb)


  • ljk January 30, 2008, 13:42

    Muons and Neutrinos 2007

    Authors: Thomas K. Gaisser

    (Submitted on 29 Jan 2008)

    Abstract: This paper is the written version of the rapporteur talk on Section HE-2, muons and neutrinos, presented at the 30th International Cosmic Ray Conference, Merida, Yucatan, July 11, 2007. Topics include atmospheric muons and neutrinos, solar neutrinos and astrophysical neutrinos as well as calculations and instrumentation related to these topics.

    Comments: 16 pages, 10 figures. Rapporteur report on sessions HE2, Muons and Neutrinos, at the 30th International Cosmic Ray Conference, Merida, Yucatan, July, 2007

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0801.4542v1 [astro-ph]

    Submission history

    From: Thomas K. Gaisser [view email]

    [v1] Tue, 29 Jan 2008 18:52:50 GMT (683kb)


  • ljk February 5, 2008, 10:45

    Cosmic Neutrinos

    Authors: Chris Quigg

    (Submitted on 31 Jan 2008)

    Abstract: I recall the place of neutrinos in the electroweak theory and summarize what we know about neutrino mass and flavor change. I next review the essential characteristics expected for relic neutrinos and survey what we can say about the neutrino contribution to the dark matter of the Universe. Then I discuss the standard-model interactions of ultrahigh-energy neutrinos, paying attention to the consequences of neutrino oscillations, and illustrate a few topics of interest to neutrino observatories. I conclude with short comments on the remote possibility of detecting relic neutrinos through annihilations of ultrahigh-energy neutrinos at the $Z$ resonance.

    Comments: 27 pages, 16 figures, uses RevTeX, lecture at 2007 SLAC Summer Institute

    Subjects: High Energy Physics – Phenomenology (hep-ph); Astrophysics (astro-ph)

    Report number: FERMILAB-CONF-07-417/T

    Cite as: arXiv:0802.0013v1 [hep-ph]

    Submission history

    From: Chris Quigg [view email]

    [v1] Thu, 31 Jan 2008 21:37:49 GMT (421kb)


  • ljk March 14, 2008, 15:09

    Neutrino Flavor Goniometry by High Energy Astrophysical Beams

    Authors: Sandip Pakvasa

    (Submitted on 12 Mar 2008)

    Abstract: It is shown how high energy neutrino beams from very distant sources can be utilized to learn about many properties of neutrinos such as lifetimes, mass hierarchy, mixing, minuscule pseudo-Dirac mass splittings; in addition, the production mechanism of neutrinos in astrophysical sources can also be elucidated.

    Comments: 22 pages. Presented at the COSPA 2007, Taipei, November 2007; to be published in the proceedings

    Subjects: High Energy Physics – Phenomenology (hep-ph); Astrophysics (astro-ph); High Energy Physics – Experiment (hep-ex)

    Report number: UH-511-1124-2008

    Cite as: arXiv:0803.1701v1 [hep-ph]

    Submission history

    From: Sandip Pakvasa [view email]

    [v1] Wed, 12 Mar 2008 03:35:56 GMT (16kb)


  • James M. Essig March 15, 2008, 2:19

    Hi ljk;

    It would be intersting to study hot dark matter particles of other species also, such as some of the proposed super-symmetric matter particles, to see if simmilar studies can elucidate analogous properties of these other particles. Now all we need to do is to figure out how to detect and measure these other hot dark matter particles.

    I will read the paper at the link you provided in the above posting later this morning after I catch some Zzzz. The paper looked very interesting upon my quick glance at it.

    Thanks for providing the above link.


  • ljk November 3, 2008, 10:24

    A ghost muon – is it new physics?