49 research outputs found
Antimatter Bounds by Anti-Asteroids annihilations on Planets and Sun
The existence of antimatter stars in the Galaxy as possible signature for
inflationary models with non-homogeneous baryo-synthesis may leave the trace by
antimatter cosmic rays as well as by their secondaries (anti-planets and
anti-meteorites) diffused bodies in our galactic halo. The anti-meteorite flux
may leave its explosive gamma signature by colliding on lunar soil as well as
on terrestrial, jovian and solar atmospheres. However the propagation in galaxy
and the consequent evaporation in galactic matter gas suppress the lightest (m
< 10^(-2)g) anti-meteorites. Anisotropic annihilation of larger anti-meteorites
within a narrow mass window, maybe rarely deflected, bounced by the galactic
gas disk, escaping detection in our solar system. Nevertheless heaviest
anti-meteorites (m > 10^(-1)g up to 10^(6)g) are unable to be deflected by the
thin galactic gas surface annihilation; they might hit the Sun (or rarely
Jupiter) leading to an explosive gamma event and a spectacular track with a
bouncing and even a propelling annihilation on cromosphere and photosphere.
Their anti-nuclei annihilation in pions and their final hard gammas showering
may be observabe as a "solar flare" at a rate nearly comparable to the observed
ones. From their absence we may infer bounds on antimatter-matter ratio near or
below 10^(-9) limit: already recorded data in BATSE catalog might be applied.Comment: 6 pages, more accurate estimate and minor correction
Galactic Gamma Halo by Heavy Neutrino annihilations?
The diffused gamma halo around our Galaxy recently discovered by EGRET could
be produced by annihilations of relic neutrinos N (of fourth generation), whose
mass is within a narrow range (Mz /2 < M < Mz). Neutrino annihilations in the
halo may lead to either ultrarelativistic electron pairs whose inverse Compton
Scattering on infrared or optical galactic photons could be the source of the
observed GeV gamma rays, or to prompt 100 MeV- 1 GeV photons (due to neutral
pion secondaries) born by N - anti N --> Z--> quark pairs reactions. The
consequent gamma flux (10 ^(-7)- 10^(-6) cm ^(-2) s^(-1) sr^(-1)) is well
comparable to the EGRET observed one and it is also compatible with the narrow
window of neutrino mass : 45 GeV < M < 50 GeV recently required to explain the
underground DAMA signals. The presence of heavy neutrinos of fourth generation
do not contribute much to solve the dark matter problem of the Universe, but it
may be easily detectable by outcoming LEP II data.Comment: 16 pages, Latex text,in press in Astroparticle Physics 199
Signature of relic heavy stable neutrinos in underground experiments
Considering heavy stable neutrinos of 4th generation we calculate the relic
density of such neutrinos in the Universe. Taking into account the condensation
of heavy neutrinos in the Galaxy and applying the results of calculations to
experimental data from underground experiments on search for WIMPs in elastic
neutral current scattering on nuclei we found an exclusion region of neutrino
mass 60 GeV < m < 290 GeV. The bounds obtained from present underground
experiments while confirming the previous bounds derived from analysis of
cosmic ray spectra are more relible ones. We discuss also the first indication
of elastic scattering induced by WIMP in DAMA experiment finding a very narrow
window of neutrino mass 45 GeV < m < 50 GeV compatible with the possible signal
rate in the detector.Comment: 12 pages, 3 figure
Possible Effects of the Existence of the 4th Generation Neutrino
The 4th generation of fermions predicted by the phenomenology of heterotic
string models can possess new strictly conserved charge, which leads, in
particular, to the hypothesis of the existence of the 4th generation massive
stable neutrino. The compatibility of this hypothesis with the results of
underground experiment DAMA searching for weakly interactive particles of dark
matter and with the EGRET measurements of galactic gamma--background at
energies above 1 GeV fixes the possible mass of the 4th neutrino at the value
about 50 GeV. The possibility to test the hypothesis in accelerator experiments
is considered. Positron signal from the annihilation of relic massive neutrinos
in the galactic halo is calculated and is shown to be accessible for planned
cosmic ray experiments.Comment: 10 pages, 4 PostScript figure, Latex2