2,517 research outputs found
Dark Matter and the Baryon Asymmetry
We present a mechanism to generate the baryon asymmetry of the Universe which
preserves the net baryon number created in the Big Bang. If dark matter
particles carry baryon number , and , the 's freeze out at a higher temperature
and have a larger relic density than 's. If m_X \lsi 4.5 B_X GeV and the
annihilation cross sections differ by (10%) or more, this type of
scenario naturally explains the observed . Two
concrete examples are given, one of which can be excluded on observational
grounds
Vibration effects on heat transfer in cryogenic systems Quarterly progress report no. 1, Jun. 1 - Aug. 31, 1966
Vibration effects on natural convection and fluid transport properties in cryogenic system
Mass distributions for nuclear disintegration from fission to evaporation
By a proper choice of the excitation energy per nucleon we analyze the mass
distributions of the nuclear fragmentation at various excitation energies.
Starting from low energies (between 0.1 and 1 MeV/nucleon) up to higher
energies about 12 MeV/n, we classified the mass yield characteristics for heavy
nuclei (A>200) on the basis of Statistical Multifragmentation Model. The
evaluation of fragment distribution with the excitation energy show that the
present results exhibit the same trend as the experimental ones.Comment: 5 pages, 3 figure
LIGHT PHOTINOS AS DARK MATTER
There are good reasons to consider models of low-energy supersymmetry with
very light photinos and gluinos. In a wide class of models the lightest
-odd, color-singlet state containing a gluino, the , has a mass in the
1-2 GeV range and the slightly lighter photino, \pho, would survive as the
relic -odd species. For the light photino masses considered here, previous
calculations resulted in an unacceptable photino relic abundance. But we point
out that processes other than photino self-annihilation determine the relic
abundance when the photino and are close in mass. Including
\r0\longleftrightarrow\pho processes, we find that the photino relic
abundance is most sensitive to the -to-\pho mass ratio, and within model
uncertainties, a critical density in photinos may be obtained for an
-to-\pho mass ratio in the range 1.2 to 2.2. We propose photinos in the
mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a
strategy to test the hypothesis.Comment: uuencoded compressed tar file containing 32 page LaTeX file and eight
postscript figure
Possible manifestation of heavy stable colored particles in cosmology and cosmic rays
We discuss the cosmological implications as well as possible observability of
massive, stable, colored particles which often appear in the discussion of
physics beyond the standard model. We argue that if their masses are more than
a few hundred GeV and if they saturate the halo density and/or occur with
closure density of the universe, they are ruled out by the present WIMP search
experiments as well as the searches for anomalous heavy isotopes of ordinary
nuclei. We then comment on the possibility that these particles as well as the
monopoles could be responsible for the ultra high energy cosmic rays with
energy eV and point out that their low inelasticity argues
against this.Comment: 9 pages; UMD-PP-98-1
Experiments to Find or Exclude a Long-Lived, Light Gluino
Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter
gluinos are allowed, except for certain ranges of lifetime. Only small parts of
the mass-lifetime parameter space are excluded for larger masses unless the
lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and
lifetime estimates for R-hadrons are given, present direct and indirect
experimental constraints are reviewed, and experiments to find or definitively
exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies
discussion of some points and corresponds to version for Phys. Rev.
Probing small-x parton densities in proton- proton (-nucleus) collisions in the very forward direction
We present calculations of several pp scattering cross sections with
potential applications at the LHC. Significantly large rates for momentum
fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of
quark and gluon densities in the proton and nuclei down to these small x values
provided a detector with good acceptance at maximal rapidities is used.Comment: 14 pages, LaTeX, 12 figures, uses revtex.st
The pediatric asthma yardstick: Practical recommendations for a sustained step-up in asthma therapy for children with inadequately controlled asthma
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