308 research outputs found
Ultra High Energy Neutrino-Relic Neutrino Interactions In Dark Halos to Solve Infrared-Tev And GZK Cut-Off
Ultra High Energy Neutrino scattering on Relic Light Neutrinos in Dark
Galactic or Local Group lead to Z and WW,ZZ showering: the nucleon component of
the shower may overcome the GZK cut-off while the electro-magnetic tail at TeVs
up to EeVs energy may solve the Infrared-TeV cut-off in a natural way.
Different Gamma TeV puzzles may find a solution within this scenario: new
predictions on UHECR spectra in future data are derived.Comment: 4 pages, 3 figures, 2 tables ICRC 2001 HE 3.6 Dark Matter - German
Upward Tau Air Showers from Earth
We estimate the rate of observable Horizontal and Upward Tau Air-Showers
(HORTAUs, UPTAUS) considering both the Earth opacity and the finite size of the
terrestrial atmosphere. We calculate the effective target volumes and masses
for Tau air-showers emerging from the Earth. The resulting model-independent
masses for satellite experiments such as EUSO may encompass at E_nu_tau = 10^19
eV a very large volume, V= 1020 km^3. Adopting simple power law neutrino
fluxes, E^-2 and E^-1, calibrated to GZK-like and Z-Burst-like models, we
estimate that at E= 10^19 eV nearly half a dozen horizontal shower events
should be detected by EUSO in three years of data collection by the
"guaranteed" GZK neutrino flux. We also find that the equivalent mass for an
Earth outer layer made of rock is dominant compared to the water, contrary to
simplified all-rock/all-water Earth models and previous Montecarlo simulations.
Therefore we expect an enhancement of neutrino detection along continental
shelves nearby the highest mountain chains, also given the better geometrical
acceptance for Earth skimming neutrinos. The Auger experiment might reveal such
a signature at E_nu= 10^{18} eV (with 26 events in 3 yr) towards the Andes, if
the angular resolution at the horizon (both in azimuth and zenith) would reach
an accuracy of nearly one degree needed to disentangle tau air showers from
common UHECR. The number of events increases at lower energies; therefore we
suggest an extension of the EUSO and Auger sensitivity down to (or even below)
E_nu = 10^19 eV and E_nu = 10^18 eV respectively.Comment: New version resubmitted to ApJ on the 6th April 2004; 55 Pages,20
figures, major changes following referee reques
Shadows of Relic Neutrino Masses and Spectra on Highest Energy GZK Cosmic Rays
The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos
in galactic and local halos offers an unique way to overcome GZK cut-off. The
UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel
on cosmic distances hitting local light relic neutrinos clustered in dark
halos. The Z resonant production and the competitive W^+W^-, ZZ pair production
define a characteristic imprint on hadronic consequent UHECR spectra. This
imprint keeps memory both of the primary UHE nu spectra as well as of the
possible relic neutrino masses values, energy spectra and relic densities. Such
an hadronic showering imprint should reflect into spectra morphology of cosmic
rays near and above GZK 10^{19}-10^{21}eV cut-off energies. A possible neutrino
degenerate masses at eVs or a more complex and significant neutrino mass split
below or near Super-Kamiokande \triangle m_{\nu_{SK}}= 0.1 eV masses might be
reflected after each corresponding Z peak showering, into new twin unexpected
UHECR flux modulation behind GZK energies: E_{p} sim 3(frac{triangle
m_{\nu_{SK}}}/m_{\nu}10^{21}),eV.
Other shadowsof lightest, nearly massless, neutrinos m_{nu_{2K} simeq 0.001eV
simeq kT_{\nu}, their lowest relic temperatures, energies and densities might
be also reflected at even higher energies edges near Grand Unification: E_{p}
\sim 2.2(m_{\nu_{2K}/E_{\nu}})10^{23}, eV .Comment: 14 pages, 6 Figures,Invited Talk Heidelberg DARK 200
Splitting neutrino masses and showering into Sky
Neutrino masses might be as light as a few time the atmospheric neutrino mass
splitting. High Energy ZeV cosmic neutrinos (in Z-Showering model) might hit
relic ones at each mass in different resonance energies in our nearby Universe.
This non-degenerated density and energy must split UHE Z-boson secondaries (in
Z-Burst model) leading to multi injection of UHECR nucleons within future
extreme AUGER energy. Secondaries of Z-Burst as neutral gamma, below a few tens
EeV are better surviving local GZK cut-off and they might explain recent Hires
BL-Lac UHECR correlations at small angles. A different high energy resonance
must lead to Glashow's anti-neutrino showers while hitting electrons in matter.
In air, Glashow's anti-neutrino showers lead to collimated and directional
air-showers offering a new Neutrino Astronomy. At greater energy around PeV,
Tau escaping mountains and Earth and decaying in flight are effectively
showering in air sky. These Horizontal showering is splitting by geomagnetic
field in forked shapes. Such air-showers secondaries release amplified and
beamed gamma bursts (like observed TGF), made also by muon and electron pair
bundles, with their accompanying rich Cherenkov flashes. Also planet' s largest
(Saturn, Jupiter) atmosphere limbs offer an ideal screen for UHE GZK and
Z-burst tau neutrino, because their largest sizes. Titan thick atmosphere and
small radius are optimal for discovering up-going resonant Glashow resonant
showers. Earth detection of Neutrino showering by twin Magic Telescopes on top
mountains, or by balloons and satellites arrays facing the limbs are the
simplest and cheapest way toward UHE Neutrino Astronomy .Comment: 4 pages, 7 figures; an author's name correction and Journal Referenc
A novel TOF-PET MRI detector for diagnosis and follow up of the prostate cancer
Prostate cancer is the most common disease in men and the second leading
cause of death from cancer. Generic large imaging instruments used in cancer
diagnosis have sensitivity, spatial resolution, and contrast inadequate for the
task of imaging details of a small organ such as the prostate. In addition,
multimodality imaging can play a significant role merging anatomical and
functional details coming from simultaneous PET and MRI. Indeed,
multi-parametric PET/MRI was demonstrated to improve diagnosis, but it suffers
from too many false positives. In order to address the above limits of the
current techniques, we have proposed, built and tested, thanks to the TOPEM
project funded by Italian National Institute of Nuclear Phisics a prototype of
an endorectal PET-TOF/MRI probe. In the applied magnification PET geometry,
performance is dominated by a high-resolution detector placed closer to the
source. The expected spatial resolution in the selected geometry is about 1.5
mm FWHM and efficiency a factor of 2 with respect to what obtained with the
conventional PET scanner. In our experimental studies, we have obtained timing
resolution of ~ 320 ps FWHM and at the same time Depth of Interaction (DOI)
resolution of under 1 mm. Tests also showed that mutual adverse PET-MR effects
are minimal. In addition, the matching endorectal RF coil was designed, built
and tested. In the next planned studies, we expect that benefiting from the
further progress in scintillator crystal surface treatment, in SiPM technology
and associated electronics would allow us to significantly improve TOF
resolutio
The Potential-Density Phase Shift Method for Determining the Corotation Radii in Spiral and Barred Galaxies
We have developed a new method for determining the corotation radii of
density waves in disk galaxies, which makes use of the radial distribution of
an azimuthal phase shift between the potential and density wave patterns. The
approach originated from improved theoretical understandings of the relation
between the morphology and kinematics of galaxies, and on the dynamical
interaction between density waves and the basic-state disk stars which results
in the secular evolution of disk galaxies. In this paper, we present the
rationales behind the method, and the first application of it to several
representative barred and grand-design spiral galaxies, using near-infrared
images to trace the mass distributions, as well as to calculate the potential
distributions used in the phase shift calculations. We compare our results with
those from other existing methods for locating the corotations, and show that
the new method both confirms the previously-established trends of bar-length
dependence on galaxy morphological types, as well as provides new insights into
the possible extent of bars in disk galaxies. Application of the method to a
larger sample and the preliminary analysis of which show that the phase shift
method is likely to be a generally-applicable, accurate, and essentially
model-independent method for determining the pattern speeds and corotation
radii of single or nested density wave patterns in galaxies. Other implications
of this work are: most of the nearby bright disk galaxies appear to possess
quasi-stationary spiral modes; that these density wave modes and the associated
basic state of the galactic disk slowly transform over time; and that
self-consistent N-particle systems contain physics not revealed by the passive
orbit analysis approaches.Comment: 48 pages, 16 figures. Accepted for publication in the Astronomical
Journa
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