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31.
Resonant photo-pion production with the cosmic microwave background predicts a suppression of extragalactic protons above the famous Greisen–Zatsepin–Kuzmin cutoff at about EGZK ≈ 5 × 1010 GeV. Current cosmic ray data measured by the AGASA and HiRes Collaborations do not unambiguously confirm the GZK cutoff and leave a window for speculations about the origin and chemical composition of the highest energy cosmic rays. In this work we analyze the possibility of strongly interacting neutrino primaries and derive model-independent quantitative requirements on the neutrino–nucleon inelastic cross section for a viable explanation of the cosmic ray data. Search results on weakly interacting cosmic particles from the AGASA and RICE experiments are taken into account simultaneously. Using a flexible parameterization of the inelastic neutrino–nucleon cross section we find that a combined fit of the data does not favor the Standard Model neutrino–nucleon inelastic cross section, but requires, at 90% confidence level, a steep increase within one energy decade around EGZK by four orders of magnitude. We illustrate such an enhancement within some extensions of the Standard Model. The impact of new cosmic ray data or cosmic neutrino search results on this scenario, notably from the Pierre Auger Observatory soon, can be immediately evaluated within our approach. 相似文献
32.
High energy neutrinos play a very important role for the understanding of the origin and propagation of ultra high energy cosmic rays (UHECR). They can be produced as a consequence of the hadronic interactions suffered by the cosmic rays in the acceleration regions, as by products of the propagation of the UHECR in the radiation background and as a main product of the decay of super heavy relic particles. A new era of very large exposure space observatories, of which the JEM-EUSO mission is a prime example, is on the horizon which opens the possibility of neutrino detection in the highest energy region of the spectrum. In the present work we use a combination of the PYTHIA interaction code with the CONEX shower simulation package in order to produce fast one-dimensional simulations of neutrino initiated showers in air. We make a detail study of the structure of the corresponding longitudinal profiles, but focus our physical analysis mainly on the development of showers at mid and high altitudes, where they can be an interesting target for space fluorescence observatories. 相似文献
33.
M. M. Reynoso † G. E. Romero ‡ H. R. Christiansen 《Monthly notices of the Royal Astronomical Society》2008,387(4):1745-1754
We study the spectral energy distribution of gamma rays and neutrinos in the precessing microquasar SS433 as a result of pp interactions within its dark jets. Gamma-ray absorption due to interactions with matter of the extended disc and of the star is found to be important, as well as absorption caused by the ultraviolet and mid-infrared radiation from the equatorial envelopment. We analyse the range of precessional phases for which this attenuation is at a minimum and the chances for detection of a gamma-ray signal are enhanced. The power of relativistic protons in the jets, a free parameter of the model, is constrained by HEGRA data. This imposes limits on the gamma-ray fluxes to be detected with instruments such as GLAST, VERITAS and MAGIC II. A future detection of high-energy neutrinos with cubic kilometre telescopes such as IceCube would also yield important information about acceleration mechanisms that may take place in the dark jets. Overall, the determination of the ratio of gamma-ray to neutrino flux will result in a key observational tool to clarify the physics of heavy jets. 相似文献
34.
Weakly interacting massive particles (WIMPs) are a viable candidate for the relic abundance of dark matter (DM) produced in the early universe. So far, WIMPs have eluded direct detection through interactions with baryonic matter. Neutrino emission from accumulated WIMP annihilations in the solar core has been proposed as a signature of DM, but has not yet been detected. These null results may be due to small-scale DM density fluctuations in the halo with the density of our local region being lower than the average (∼0.3 GeV cm−3 ) . However, the accumulated neutrino signal from WIMP annihilations in the Galactic stellar disc would be insensitive to local density variations. Inside the disc, DM can be captured by stars causing an enhanced annihilation rate and therefore a potentially higher neutrino flux than what would be observed from elsewhere in the halo. We estimate a neutrino flux from the WIMP annihilations in the stellar disc to be enhanced by more than an order of magnitude compared to the neutrino fluxes from the halo. We offer a conservative estimate for this enhanced flux, based on the WIMP–nucleon cross-sections obtained from direct-detection experiments by assuming a density of ∼0.3 GeV cm−3 for the local DM. We also compare the detectability of these fluxes with a signal of diffuse high-energy neutrinos produced in the Milky Way by the interaction of cosmic rays with the interstellar medium. These comparative signals should be observable by large neutrino detectors. 相似文献
35.
P. A. Sturrock 《Solar physics》2008,252(2):221-233
There has for some time been evidence of variability in radiochemical solar neutrino measurements, but this evidence has seemed
suspect since the Cerenkov experiments have not shown similar evidence of variability. The present reanalysis of Super-Kamiokande
data shows strong evidence of r-mode oscillations. The frequencies of these oscillations correspond to a region with a sidereal
rotation rate of 13.97 year−1. This estimate is incompatible with the rotation rate in the convection zone but is compatible with current estimates of
the rotation rate in the radiative zone. The excitation of r modes in the radiative zone may be due to a velocity field originating
in or related to the nuclear-burning core. 相似文献
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We show that, contrary to a recent suggestion, fluxes of 30 GeV-1 TeV neutrinos that may accompany-ray bursts are at least a few orders of magnitude too weak to be detected by the current or planned neutrino detectors. 相似文献
39.
Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a unique probe of the Earth interior. The characterization
of their fluxes is subject, however, to rather large and highly correlated uncertainties. The geochemical covariance of the
U, Th and K abundances in various Earth reservoirs induces positive correlations among the associated geo-neutrino fluxes,
and between these and the radiogenic heat. Mass-balance constraints in the Bulk Silicate Earth (BSE) tend instead to anti-correlate
the radiogenic element abundances in complementary reservoirs. Experimental geo-neutrino observables may be further (anti)correlated
by instrumental effects. In this context, we propose a systematic approach to covariance matrices, based on the fact that
all the relevant geo-neutrino observables and constraints can be expressed as linear functions of the U, Th and K abundances
in the Earth’s reservoirs (with relatively well-known coefficients). We briefly discuss here the construction of a tentative
“geo-neutrino source model” (GNSM) for the U, Th, and K abundances in the main Earth reservoirs, based on selected geophysical
and geochemical data and models (when available), on plausible hypotheses (when possible), and admittedly on arbitrary assumptions
(when unavoidable). We use then the GNSM to make predictions about several experiments (“forward approach”), and to show how
future data can constrain a posteriori the error matrix of the model itself (“backward approach”). The method may provide a useful statistical framework for evaluating
the impact and the global consistency of prospective geo-neutrino measurements and Earth models. 相似文献
40.
The Antarctic Ross Ice Shelf Antenna Neutrino Array (ARIANNA) is a high-energy neutrino detector designed to record the Askaryan electric field signature of cosmogenic neutrino interactions in ice. To understand the inherent radio-frequency (RF) neutrino signature, the time-domain response of the ARIANNA RF receiver must be measured. ARIANNA uses Create CLP5130-2N log-periodic dipole arrays (LPDAs). The associated effective height operator converts incident electric fields to voltage waveforms at the LDPA terminals. The effective height versus time and incident angle was measured, along with the associated response of the ARIANNA RF amplifier. The results are verified by correlating to field measurements in air and ice, using oscilloscopes. Finally, theoretical models for the Askaryan electric field are combined with the detector response to predict the neutrino signature. 相似文献