856 research outputs found
A parameterisation of single and multiple muons in the deep water or ice
A new parameterisation of atmospheric muons deep underwater (or ice) is
presented. It takes into account the simultaneous arrival of muons in bundle
giving the multiplicity of the events and the muon energy spectrum as a
function of their lateral distribution in a shower.Comment: 3 pages, 2 figures, talk given at TAUP 2005, Zaragoza (Spain) (to
appear in the proceedings of TAUP 2005
Cosmic Rays and Stochastic Magnetic Reconnection in the Heliotail
Galactic cosmic rays are believed to be generated by diffusive shock
acceleration processes in Supernova Remnants, and the arrival direction is
likely determined by the distribution of their sources throughout the Galaxy,
in particular by the nearest and youngest ones. Transport to Earth through the
interstellar medium is expected to affect the cosmic ray properties as well.
However, the observed anisotropy of TeV cosmic rays and its energy dependence
cannot be explained with diffusion models of particle propagation in the
Galaxy. Within a distance of a few parsec, diffusion regime is not valid and
particles with energy below about 100 TeV must be influenced by the heliosphere
and its elongated tail. The observation of a highly significant localized
excess region of cosmic rays from the apparent direction of the downstream
interstellar flow at 1-10 TeV energies might provide the first experimental
evidence that the heliotail can affect the transport of energetic particles. In
particular, TeV cosmic rays propagating through the heliotail interact with the
100-300 AU wide magnetic field polarity domains generated by the 11 year
cycles. Since the strength of non-linear convective processes is expected to be
larger than viscous damping, the plasma in the heliotail is turbulent. Where
magnetic field domains converge on each other due to solar wind gradient,
stochastic magnetic reconnection likely occurs. Such processes may be efficient
enough to re-accelerate a fraction of TeV particles as long as scattering
processes are not strong. Therefore the fractional excess of TeV cosmic rays
from the narrow region toward the heliotail direction traces sightlines with
the lowest smearing scattering effects, that can also explain the observation
of a harder than average energy spectrum.Comment: 14 pages, 7 figures. Accepted for publication by Nonlinear Processes
in Geophysic
Cosmic Ray Small Scale Anisotropies and Local Turbulent Magnetic Fields
Cosmic ray anisotropy has been observed in a wide energy range and at
different angular scales by a variety of experiments over the past decade.
However, no comprehensive or satisfactory explanation has been put forth to
date. The arrival distribution of cosmic rays at Earth is the convolution of
the distribution of their sources and of the effects of geometry and properties
of the magnetic field through which particles propagate. It is generally
believed that the anisotropy topology at the largest angular scale is
adiabatically shaped by diffusion in the structured interstellar magnetic
field. On the contrary, the medium- and small-scale angular structure could be
an effect of non-diffusive propagation of cosmic rays in perturbed magnetic
fields. In particular, a possible explanation of the observed small-scale
anisotropy observed at TeV energy scale, may come from the effect of particle
scattering in turbulent magnetized plasmas. We perform numerical integration of
test particle trajectories in low- compressible magnetohydrodynamic
turbulence to study how the cosmic rays arrival direction distribution is
perturbed when they stream along the local turbulent magnetic field. We utilize
Liouville's theorem for obtaining the anisotropy at Earth and provide the
theoretical framework for the application of the theorem in the specific case
of cosmic ray arrival distribution. In this work, we discuss the effects on the
anisotropy arising from propagation in this inhomogeneous and turbulent
interstellar magnetic field.Comment: 14 pages, 7 figures. Accepted for publication in Ap
Magnetic reconnection as the cause of cosmic ray excess from the heliospheric tail
The observation of a broad excess of sub-TeV cosmic rays compatible with the
direction of the heliospheric tail (Nagashima et al. 1998) and the discovery of
two significant localized excess regions of multi-TeV cosmic rays by the
MILAGRO collaboration (Abdo et al. 2008), also from the same region of the sky,
have raised questions on their origin. In particular, the coincidence of the
most significant localized region with the direction of the heliospheric tail
and the small angular scale of the observed anisotropy (~ 10deg) is suggestive
a local origin and of a possible connection to the low energy broad excess.
Cosmic ray acceleration from magnetic reconnection in the magnetotail is
proposed as a possible source of the energetic particles.Comment: 10 pages, 5 figures, accepted for publication in Ap
Light tracking through ice and water -- Scattering and absorption in heterogeneous media with Photonics
In the field of neutrino astronomy, large volumes of optically transparent
matter like glacial ice, lake water, or deep ocean water are used as detector
media. Elementary particle interactions are studied using in situ detectors
recording time distributions and fluxes of the faint photon fields of Cherenkov
radiation generated by ultra-relativistic charged particles, typically muons or
electrons.
The Photonics software package was developed to determine photon flux and
time distributions throughout a volume containing a light source through Monte
Carlo simulation. Photons are propagated and time distributions are recorded
throughout a cellular grid constituting the simulation volume, and Mie
scattering and absorption are realised using wavelength and position dependent
parameterisations. The photon tracking results are stored in binary tables for
transparent access through ANSI-C and C++ interfaces. For higher-level physics
applications, like simulation or reconstruction of particle events, it is then
possible to quickly acquire the light yield and time distributions for a
pre-specified set of light source and detector properties and geometries
without real-time photon propagation.
In this paper the Photonics light propagation routines and methodology are
presented and applied to the IceCube and Antares neutrino telescopes. The way
in which inhomogeneities of the Antarctic glacial ice distort the signatures of
elementary particle interactions, and how Photonics can be used to account for
these effects, is described.Comment: 22 pages, 8 Postscript figures, uses elsart.cl
Global Anisotropies in TeV Cosmic Rays Related to the Sun's Local Galactic Environment from IBEX
Observations with the Interstellar Boundary Explorer (IBEX) have shown enhanced energetic neutral atom (ENA) emission from a narrow, circular ribbon likely centered on the direction of the local interstellar medium (LISM) magnetic field. Here, we show that recent determinations of the local interstellar velocity, based on interstellar atom measurements with IBEX, are consistent with the interstellar modulation of high-energy (tera-electron volts, TeV) cosmic rays and diffusive propagation from supernova sources revealed in global anisotropy maps of ground-based high-energy cosmic-ray observatories (Milagro, Asg, and IceCube). Establishing a consistent local interstellar magnetic field direction using IBEX ENAs at hundreds to thousands of eV and galactic cosmic rays at tens of TeV has wide-ranging implications for the structure of our heliosphere and its interactions with the LISM, which is particularly important at the time when the Voyager spacecraft are leaving our heliosphere
IceCube Sensitivity for Low-Energy Neutrinos from Nearby Supernovae
This paper describes the response of the IceCube neutrino telescope located at the geographic South Pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of approx. 1 cu km in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to detect the neutronization burst, a short outbreak's released by electron capture on protons soon after collapse. Tantalizing signatures, such as the formation of a quark star or a black hole as well as the characteristics of shock waves, are investigated to illustrate IceCube's capability for supernova detection
Limits on diffuse fluxes of high energy extraterrestrial neutrinos with the AMANDA-B10 detector
Data from the AMANDA-B10 detector taken during the austral winter of 1997
have been searched for a diffuse flux of high energy extraterrestrial
muon-neutrinos, as predicted from, e.g., the sum of all active galaxies in the
universe. This search yielded no excess events above those expected from the
background atmospheric neutrinos, leading to upper limits on the
extraterrestrial neutrino flux. For an assumed E^-2 spectrum, a 90% classical
confidence level upper limit has been placed at a level E^2 Phi(E) = 8.4 x
10^-7 GeV cm^-2 s^-1 sr^-1 (for a predominant neutrino energy range 6-1000 TeV)
which is the most restrictive bound placed by any neutrino detector. When
specific predicted spectral forms are considered, it is found that some are
excluded.Comment: Submitted to Physical Review Letter
Search for Point Sources of High Energy Neutrinos with AMANDA
This paper describes the search for astronomical sources of high-energy
neutrinos using the AMANDA-B10 detector, an array of 302 photomultiplier tubes,
used for the detection of Cherenkov light from upward traveling
neutrino-induced muons, buried deep in ice at the South Pole. The absolute
pointing accuracy and angular resolution were studied by using coincident
events between the AMANDA detector and two independent telescopes on the
surface, the GASP air Cherenkov telescope and the SPASE extensive air shower
array. Using data collected from April to October of 1997 (130.1 days of
livetime), a general survey of the northern hemisphere revealed no
statistically significant excess of events from any direction. The sensitivity
for a flux of muon neutrinos is based on the effective detection area for
through-going muons. Averaged over the Northern sky, the effective detection
area exceeds 10,000 m^2 for E_{mu} ~ 10 TeV. Neutrinos generated in the
atmosphere by cosmic ray interactions were used to verify the predicted
performance of the detector. For a source with a differential energy spectrum
proportional to E_{nu}^{-2} and declination larger than +40 degrees, we obtain
E^2(dN_{nu}/dE) <= 10^{-6}GeVcm^{-2}s^{-1} for an energy threshold of 10 GeV.Comment: 46 pages, 22 figures, 4 tables, submitted to Ap.
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