Search results for "COSMIC"
showing 10 items of 656 documents
Atmospheric neutrino oscillations and tau neutrinos in ice
2010
The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show here that cascade measurements in the Ice Cube Deep Core Array can provide strong evidence for tau neutrino appearance in atmospheric neutrino oscillations. Controlling systematic uncertainties will be the limiting factor in the analysis. A careful study of these tau neutrinos is crucial, since they constitute an irreducible background for astrophysical neutrino detection.
Higher-order coupled quintessence
2010
We study a coupled quintessence model in which the interaction with the dark-matter sector is a function of the quintessence potential. Such a coupling can arise from a field dependent mass term for the dark-matter field. The dynamical analysis of a standard quintessence potential coupled with the interaction explored here shows that the system possesses a late-time accelerated attractor. In light of these results, we perform a fit to the most recent Supernovae Ia, Cosmic Microwave Background, and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments are also discussed.
Secondary gravitational anisotropies in open universes
1998
The applicability of the potential approximation in the case of open universes is tested. Great Attractor-like structures are considered in the test. Previous estimates of the Cosmic Microwave background anisotropies produced by these structures are analyzed and interpreted. The anisotropies corresponding to inhomogeneous ellipsoidal models are also computed. It is proved that, whatever the spatial symmetry may be, Great Attractor-like objects with extended cores (radius $\sim 10h^{-1}$),located at redshift $z=5.9$ in an open universe with density parameter $\Omega_{0}=0.2$, produce secondary gravitational anisotropies of the order of $10^{-5}$ on angular scales of a few degrees. This aniso…
Deconvolving the Beam in Small Angular Scale CMB Experiments
2000
This paper is concerned with experiments which measure CMB anisotropies on small angular scales. A certain coverage, a beam structure and a level of uncorrelated noise define each experiment. We focus our atention on the reversion of the beam average. In each experiment, we look for the best pixelization for reversion, namely, for the pixelization that -after reversion- leads to good maps containing right spectra for the most wide range of angular scales. Squared pixels having different sizes "smaller" than the beam radius are considered. For a given size, the following question arises: How well can we assign a temperature to each pixel? Various mathematical methods are used to show that, i…
Large‐Scale Vector Modes and the First CMB Temperature Multipoles
2008
Recent observations have pointed out various anomalies in some multipoles (small $\ell $) of the cosmic microwave background (CMB). In this paper, it is proved that some of these anomalies could be explained in the framework of a modified concordance model, in which, there is an appropriate distribution of vector perturbations with very large spatial scales. Vector modes are associated with divergenceless (vortical) velocity fields. Here, the generation of these modes is not studied in detail (it can be done "a posteriori"); on the contrary, we directly look for the distributions of these vector modes which lead to both alignments of the second and third multipoles and a planar octopole. A …
Studying neutrinos at the LHC: FASER and its impact to the cosmic-ray physics
2021
Studies of high energy proton interactions have been basic inputs to understand the cosmic-ray spectra observed on the earth. Yet, the experimental knowledge with controlled beams has been limited. In fact, uncertainties of the forward hadron production are very large due to the lack of experimental data. The FASER experiment is proposed to measure particles, such as neutrinos and hypothetical dark-sector particles, at the forward location of the 14 TeV proton-proton collisions at the LHC. As it corresponds to 100-PeV proton interactions in fixed target mode, a precise measurement by FASER would provide information relevant for PeV-scale cosmic rays. By studying three flavor neutrinos with …
Probing the effects of hadronic acceleration at the SN 1006 shock front
2014
AbstractSupernova remnant shocks are strong candidates for being the source of energetic cosmic rays and hadron acceleration is expected to increase the shock compression ratio, providing higher post-shock densities. We exploited the deep observations of the XMM-Newton Large Program on SN 1006 to verify this prediction. Spatially resolved spectral analysis led us to detect X-ray emission from the shocked ambient medium in SN 1006 and to find that its density significantly increases in regions where particle acceleration is efficient. Our results provide evidence for the effects of acceleration of cosmic ray hadrons on the post-shock plasma in supernova remnants.
Actinides and the sources of cosmic rays
2004
Abstract The abundances of the actinide elements in the cosmic rays can provide critical constraints on the major sites of their acceleration. Using recent calculations of the r-process yields in core-collapse supernovae (SNe), we have determined the actinide abundances averaged over various assumed time intervals for their supernovae generation and their cosmic-ray acceleration. Using standard Galactic chemical evolution models, we have also determined the expected actinide abundances in the present interstellar medium. From these two components, we have calculated the U/Th and other actinide abundances expected in the SN-active cores of superbubbles, as a function of their ages and mean m…
Ultra–High‐Energy Cosmic Rays from Hypothetical Quark Novae
2005
We explore acceleration of ions in the Quark Nova (QN) scenario, where a neutron star experiences an explosive phase transition into a quark star (born in the propeller regime). In this picture, two cosmic ray components are isolated: one related to the randomized pulsar wind and the other to the propelled wind, both boosted by the ultra-relativistic Quark Nova shock. The latter component acquires energies $10^{15} {\rm eV} 10^{18.6}$ eV. The composition is dominated by ions present in the pulsar wind in the energy range above $10^{18.6}$ eV, while at energies below $10^{18}$ eV the propelled ejecta, consisting of the fall-back neutron star crust material from the explosion, is the dominant…
Antideuterons as an indirect dark matter signature: Si(Li) detector development and a GAPS balloon mission
2010
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