75,227 research outputs found
Neutrino Mass and Dark Matter
Despite direct observations favoring a low mass density, a critical density
universe with a neutrino component of dark matter provides the best existing
model to explain the observed structure of the universe over more than three
orders of magnitude in distance scale. In principle this hot dark matter could
consist of one, two, or three species of active neutrinos. If all present
indications for neutrino mass are correct, however, only the two-species (muon
neutrino and tau neutrino) possibility works. This requires the existence of at
least one light sterile neutrino to explain the solar electron neutrino deficit
via nu(e)->nu(s), leaving nu(mu)->nu(tau) as the explanation for the anomalous
nu(mu)/nu(e) ratio produced by atmospheric neutrinos, and having the LSND
experiment demonstrating via anti-nu(mu)-> anti-nu(e) the mass difference
between the light nu(e)-nu(s) pair and the heavier nu(mu)-nu(tau) pair required
for dark matter. Other experiments do not conflict with the LSND results when
all the experiments are analyzed in the same way, and when analyzed
conservatively the LSND data is quite compatible with the mass difference
needed for dark matter. Further support for this mass pattern is provided by
the need for a sterile neutrino to rescue heavy-element nucleosynthesis in
supernovae, and it could even aid the concordance in light element abundances
from the early universe.Comment: 13 pages, 3 figures, IDM 98 conferenc
A Sterile Neutrino Needed for Heavy-Element Nucleosynthesis
A neutrino mass-mixing scheme which successfully avoids the "alpha effect,"
allowing r-process nucleosynthesis in the neutrino-heated ejecta of supernovae,
quite independently requires the same parameters as the scheme which best fits
all current indications for neutrino mass. The significance for particle
physics is this independent evidence for (1) at least one light sterile
neutrino, nu_s; (2) a near maximally-mixed nu_mu-nu_tau doublet split from a
lower mass nu_mu-nu_s doublet; (3) nu_mu-nu_e mixing >~ 10^-4; and (4) a
splitting between the doublets (measured by the nu_mu-nu_e mass difference) >~
1 eV^2, favoring the upper part of the LSND range. If correct, it is
tantalizing that neutrinos with tiny masses which mix with sterile species have
profound effects on massive objects and the creation of the heaviest elements.Comment: 7 pages, 1 figure, PASCOS '99 conference tal
“Pushing Their Necks Out”: Ultra, The Black Watch, and Command Relations, May-sur-Orne, Normandy, 5 August 1944
In 1974 Group Captain Frederick Winterbotham shocked the world when he revealed in his semiautobiographical work, The Ultra Secret, that the Allies had been breaking high-grade German ciphers throughout the greater portion of the Second World War in an effort commonly referred to as ULTRA.1 His disclosure sparked a tempest as historians anticipated that his admission would lead to a major revision of Second World War historiography. At first, what promised to be a new vista for historical research soon turned into a quagmire. When the British Government selectively released files pertaining to ULTRA, only messages sent to commands in the field were originally released whereas the supporting documents necessary to properly assess and interpret the impact of ULTRA in general, and on Army Group, Army and Corps commanders and their subordinates in the field in particular, were retained. As a result, the reassessment of this aspect of military history met a similar fate to that of British armour at the foot of Verrières-Bourgébus ridge during Operation Goodwood—very good initial progress followed by confusion and lack of consolidation resulting in the perception that ULTRA was nothing more than a highly overrated white elephant. Two decades later, Government Communication Headquarters (GCHQ) in the UK wisely reviewed their policy and began a protracted release of millions of pages of material to coincide with the 50th anniversary of the end of the Second World War. Included were materials that shed new light on the production and dissemination of ULTRA (at Bletchley Park) and its employment by the consumer, Allied High Command, in the field.2 The releases have thus far included everything from security regulations for the handling of messages, to classified inhouse accounts of the impact of ULTRA on commands, to high-level policy papers and distribution lists to name but a few. In addition to the ULTRA material, formerly classified Intelligence summaries (produced at each level of command from Eisenhower’s Supreme Headquarters down to brigade level) were also declassified during this period providing the historian with two mutually supporting sources to layer upon the existing corpus of material.3 As a result, new insight and further understanding can be achieved concerning intentions, orders, decisions and operations that may have been regarded, at that time or since, as peculiar, questionable or ill-conceived. The impact of these new releases on the historiography of Canada’s role in the Second World War can be witnessed in part by re-examining the costly and seemingly questionable advance by the Black Watch (Royal Highland Regiment) of Canada on May-sur-Orne during the afternoon of 5 August 1944
On the use of Satellite Television in High Energy Physics
This paper assesses the feasibility of exploiting commercial satellite
television technologies to broadcast video signals and data from major High
Energy Physics facilities to collaborating institutes throughout the world.Comment: Invited talk at CHEP'98, Chicago, USA, August 31 - September 4, 199
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