834 research outputs found
Ultra high energy cosmic rays: clustering, GUT scale and neutrino masses
The clustering of ultra high energy (above 5\cdot 10^{19} eV) cosmic rays
(UHECR) suggests that they might be emitted by compact sources. We present a
statistical analysis on the source density based on the multiplicities. The
propagation of UHECR protons is studied in detail. The UHECR spectrum is
consistent with the decay of GUT scale particles and/or with the Z-burst. The
predicted GUT mass is m_X=10^b GeV, where b=14.6_{-1.7}^{+1.6}. Our neutrino
mass prediction depends on the origin of the power part of the spectrum:
m_\nu=2.75^{+1.28}_{-0.97} eV for halo and 0.26^{+0.20}_{-0.14} eV for
extragalactic (EG) origin.Comment: 4 pages, 5 figures. Talk given at TAUP 2001, September 8-12, 2001 in
Gran Sass
BL Lacertae are probable sources of the observed ultra-high energy cosmic rays
We calculate angular correlation function between ultra-high energy cosmic
rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL
Lacertae objects. We find significant correlations which correspond to the
probability of statistical fluctuation less than , including penatly
for selecting the subset of brightest BL Lacs. We conclude that some of BL Lacs
are sources of the observed UHECR and present a list of most probable
candidates.Comment: Replaced with the version accepted for publication in JETP Let
Source position reconstruction and constraints on the galactic magnetic field from ultra-high energy cosmic rays
We study the possibility to reconstruct the position of ultra-high energy
cosmic ray sources and some properties of the magnetic field along the line of
sight towards them in the case that several events from the same source are
detected. By considering an illustrative model for the galactic magnetic field,
including both a regular and a turbulent component, we estimate the accuracy
that can be achieved in the reconstruction. We analyse the effect of the
experimental energy and angular resolutions on these results. We show that if
about ten events with energies above 30 EeV are detected coming from the same
source, it should be possible to reconstruct the source position with an
accuracy of 0.5 and the integral of the orthogonal component of the
magnetic field along the line of sight with an accuracy of 0.6 G kpc
Z (with Z the electric charge of the particles).Comment: Added references and referee comments, accepted for publicatio
Cluster Analysis of Extremely High Energy Cosmic Rays in the Northern Sky
The arrival directions of extremely high energy cosmic rays (EHECR) above
eV, observed by four surface array experiments in the northern
hemisphere,are examined for coincidences from similar directions in the sky.
The total number of cosmic rays is 92.A significant number of double
coincidences (doublet) and triple coincidences (triplet) are observed on the
supergalactic plane within the experimental angular resolution. The chance
probability of such multiplets from a uniform distribution is less than 1 % if
we consider a restricted region within of the supergalactic
plane. Though there is still a possibility of chance coincidence, the present
results on small angle clustering along the supergalactic plane may be
important in interpreting EHECR enigma. An independent set of data is required
to check our claims.Comment: 9 pages, 6 tables, 8 figures. submitted to Astroparticle Physic
The Small Scale Anisotropies, the Spectrum and the Sources of Ultra High Energy Cosmic Rays
We calculate the number density and luminosity of the sources of ultra high
energy cosmic rays (UHECRs), using the information about the small scale
anisotropies and the observed spectra. We find that the number of doublets and
triplets observed by AGASA can be best reproduced for a source density of , with large uncertainties. The spectrum of UHECRs implies an
energy input of above eV
and an injection spectrum . A flatter injection spectrum,
, can be adopted if the sources have luminosity evolution . The combination of these two pieces of information suggests that the
single sources should on average have a cosmic ray luminosity above
eV of , weakly dependent upon the
injection spectrum. Unfortunately, with the limited statistics of events
available at present, there are approximately one-two orders of magnitude
uncertainty in the source density provided above. We make predictions on the
expected performances of the Auger and EUSO experiments, with particular
attention for the expected improvements in our understanding of the nature of
the sources of UHECRs. We find that a critical experimental exposure
exists, such that experiments with exposure larger than can detect
at least one event from each source at energies above eV. This
represents a unique opportunity to directly count and identify the sources of
UHECRs.Comment: Submitted to Astropart. Phy
Development of the analog ASIC for multi-channel readout X-ray CCD camera
We report on the performance of an analog application-specific integrated
circuit (ASIC) developed aiming for the front-end electronics of the X-ray
CCDcamera system onboard the next X-ray astronomical satellite, ASTRO-H. It has
four identical channels that simultaneously process the CCD signals.
Distinctive capability of analog-to-digital conversion enables us to construct
a CCD camera body that outputs only digital signals. As the result of the
front-end electronics test, it works properly with low input noise of =<30 uV
at the pixel rate below 100 kHz. The power consumption is sufficiently low of
about 150 mW/chip. The input signal range of 720 mV covers the effective energy
range of the typical X-ray photon counting CCD (up to 20 keV). The integrated
non-linearity is 0.2% that is similar as those of the conventional CCDs in
orbit. We also performed a radiation tolerance test against the total ionizing
dose (TID) effect and the single event effect. The irradiation test using 60Co
and proton beam showed that the ASIC has the sufficient tolerance against TID
up to 200 krad, which absolutely exceeds the expected amount of dose during the
period of operating in a low-inclination low-earth orbit. The irradiation of Fe
ions with the fluence of 5.2x10^8 Ion/cm2 resulted in no single event latchup
(SEL), although there were some possible single event upsets. The threshold
against SEL is higher than 1.68 MeV cm^2/mg, which is sufficiently high enough
that the SEL event should not be one of major causes of instrument downtime in
orbit.Comment: 16 pages, 6 figure
Halo Dark Matter and Ultra-High Energy Cosmic Rays
The decay of very heavy metastable relics of the Early Universe can produce
ultra-high energy cosmic rays (UHECRs) in the halo of our own Galaxy. On
distance scales of the order of the halo size, energy losses are
negligible---no Greisen-Zatsepin-Kuzmin cutoff is expected. In this letter we
show that, as a consequence of the hierarchical build up of the halo, this
scenario predicts the existence of small scale anisotropies in the arrival
directions of UHECRs. We also suggest some consequences of this scenario which
will be testable with upcoming experiments, as Auger.Comment: 9 pages, 2 figures. Accepted for Publication in Phys. Lett.
Statistics of clustering of ultra-high energy cosmic rays and the number of their sources
Observation of clustering of ultra-high energy cosmic rays (UHECR) suggests
that they are emitted by compact sources. Assuming small deflection of UHECR
during the propagation, the statistical analysis of clustering allows to
estimate the spatial density of the sources, h, including those which have not
yet been observed directly. When applied to astrophysical models involving
extra-galactic sources, the estimate based on 14 events with energy E>10^{20}
eV gives h ~ 6 X 10^{-3} Mps^{-3}. With increasing statistics, this estimate
may lead to exclusion of the models which associate the production of UHECR
with exceptional galaxies such as AGN, powerful radio-galaxies, dead quasars,
and models based on gamma ray bursts.Comment: The version accepted for publication in Phys. Rev. Lett. Notations
changed to conventional ones. The estimate of the effective GZK radius
replaced by the result of numerical simulatio
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