294 research outputs found
Plasmas and Controlled Nuclear Fusion
Contains reports on two research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070
Strangelets: Who is Looking, and How?
It has been over 30 years since the first suggestion that the true ground
state of cold hadronic matter might be not nuclear matter but rather strange
quark matter (SQM). Ever since, searches for stable SQM have been proceeding in
various forms and have observed a handful of interesting events but have
neither been able to find compelling evidence for stable strangelets nor to
rule out their existence. I will survey the current status and near future of
such searches with particular emphasis on the idea of SQM from strange star
collisions as part of the cosmic ray flux.Comment: Talk given at International Conference on Strangeness in Quark
Matter, 2006. 8 pages. 1 figur
Plasmas and Controlled Nuclear Fusion
Contains reports on three research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980
Plasmas and Controlled Nuclear Fusion
Contains reports on three research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070
Indirect Detection of a Light Higgsino Motivated by Collider Data
Kane and Wells recently argued that collider data point to a Higgsino-like
lightest supersymmetric partner which would explain the dark matter in our
Galactic halo. They discuss direct detection of such dark-matter particles in
laboratory detectors. Here, we argue that such a particle, if it is indeed the
dark matter, might alternatively be accessible in experiments which search for
energetic neutrinos from dark-matter annihilation in the Sun. We provide
accurate analytic estimates for the rates which take into account all relevant
physical effects. Currently, the predicted signal falls roughly one to three
orders of magnitude below experimental bounds, depending on the mass and
coupling of the particle; however, detectors such as MACRO, super-Kamiokande,
and AMANDA will continue to take data and should be able to rule out or confirm
an interesting portion of the possible mass range for such a dark-matter
particle within the next five years.Comment: 10 pages, RevTe
The Energy Spectra and Relative Abundances of Electrons and Positrons in the Galactic Cosmic Radiation
Observations of cosmic-ray electrons and positrons have been made with a new
balloon-borne detector, HEAT (the "High-Energy Antimatter Telescope"), first
flown in 1994 May from Fort Sumner, NM. We describe the instrumental approach
and the data analysis procedures, and we present results from this flight. The
measurement has provided a new determination of the individual energy spectra
of electrons and positrons from 5 GeV to about 50 GeV, and of the combined
"all-electron" intensity (e+ + e-) up to about 100 GeV. The single power-law
spectral indices for electrons and positrons are alpha = 3.09 +/- 0.08 and 3.3
+/- 0.2, respectively. We find that a contribution from primary sources to the
positron intensity in this energy region, if it exists, must be quite small.Comment: latex2e file, 30 pages, 15 figures, aas2pp4.sty and epsf.tex needed.
To appear in May 10, 1998 issue of Ap.
Plasmas and Controlled Nuclear Fusion
Contains research objectives, summary of research and reports on six research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070
Plasmas and Controlled Nuclear Fusion
Contains reports on five research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980
Optical Properties of Deep Ice at the South Pole - Absorption
We discuss recent measurements of the wavelength-dependent absorption
coefficients in deep South Pole ice. The method uses transit time distributions
of pulses from a variable-frequency laser sent between emitters and receivers
embedded in the ice. At depths of 800 to 1000 m scattering is dominated by
residual air bubbles, whereas absorption occurs both in ice itself and in
insoluble impurities. The absorption coefficient increases approximately
exponentially with wavelength in the measured interval 410 to 610 nm. At the
shortest wavelength our value is about a factor 20 below previous values
obtained for laboratory ice and lake ice; with increasing wavelength the
discrepancy with previous measurements decreases. At around 415 to 500 nm the
experimental uncertainties are small enough for us to resolve an extrinsic
contribution to absorption in ice: submicron dust particles contribute by an
amount that increases with depth and corresponds well with the expected
increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The
laser pulse method allows remote mapping of gross structure in dust
concentration as a function of depth in glacial ice.Comment: 26 pages, LaTex, Accepted for publication in Applied Optics. 9
figures, not included, available on request from [email protected]
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