Showing papers by "Graciela B. Gelmini published in 2000"
TL;DR: This scenario is consistent with the neutrino mass reported by super-Kamiokande and requires no lepton asymmetry or clustering of the background neutrinos and predicts no directional correlation of the ultrahigh-energy cosmic rays with the galactic halo.
Abstract: Decays of superheavy relic particles may produce extremely energetic neutrinos. Their annihilations on the relic neutrinos can be the origin of the cosmic rays with energies beyond the Greisen-Zatsepin-Kuzmin cutoff. The redshift acts as a cosmological filter selecting the sources at some particular value ${z}_{e}\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta}z$, for which the present neutrino energy is close to the $Z$ pole of the annihilation cross section. We predict no directional correlation of the ultrahigh-energy cosmic rays with the galactic halo. At the same time, there can be some directional correlations in the data, reflecting the distribution of matter at redshift ${z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}z}_{e}\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta}z$. Both of these features are manifest in the existing data. Our scenario is consistent with the neutrino mass reported by super-Kamiokande and requires no lepton asymmetry or clustering of the background neutrinos.
62 citations
TL;DR: In this article, the spectral index of the atmospheric leptonic fluxes depends linearly on the slope of the gluon distribution function at very small partonic momentum fraction x. This suggests the possibility of obtaining some bounds on this slope in ''neutrino telescopes'' at values of x not reachable at colliders.
Abstract: We compute the next-to-leading order QCD predictions for the vertical flux of atmospheric muons and neutrinos from decays of charmed particles, for different PDF's (MRS-R1, MRS-R2, CTEQ-4M and MRST) and different extrapolations of these at a small partonic momentum fraction x. We find that the predicted fluxes vary up to almost two orders of magnitude at the largest energies studied, depending on the chosen extrapolation of the PDF's. We show that the spectral index of the atmospheric leptonic fluxes depends linearly on the slope of the gluon distribution function at very small x. This suggests the possibility of obtaining some bounds on this slope in ``neutrino telescopes,'' at values of x not reachable at colliders, provided the spectral index of atmospheric leptonic fluxes could be determined.
32 citations
TL;DR: In this paper, the leading and next-to-leading order QCD predictions for the flux of atmospheric muons and neutrinos from decays of charmed particles were compared.
Abstract: We compare the leading and next-to-leading order QCD predictions for the flux of atmospheric muons and neutrinos from decays of charmed particles. We find that the full NLO lepton fluxes can be approximated to within {approx}10% by the Born-level fluxes multiplied by an overall factor of 2.2-2.4, which depends slightly on the PDF. This supports the approach of Thunman, Ingelman and Gondolo. We also find that their very low lepton fluxes are due to the mild slope they used for the gluon distribution function at small momentum fractions, and that substantially larger lepton fluxes result when the slope of the gluon distribution function at small momentum fractions is larger. (c) 2000 The American Physical Society.
27 citations
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TL;DR: In this paper, it was shown that neutrinos with mass in the range indicated by Super-Kamiokande results are significantly contribute to the dark matter of the universe and that their existence might be revealed by the spectrum of ultra high energy cosmic rays.
Abstract: Relic neutrinos with mass in the range indicated by Super-Kamiokande results if neutrino masses are hierarchial (about 0.07 eV) are many times deemed too light to be cosmologically relevant. Here we remark that these neutrinos may significantly contribute to the dark matter of the Universe (with a large lepton asymmetry $L$) and that their existence might be revealed by the spectrum of ultra high energy cosmic rays (maybe even in the absence of a large $L$).
1 citations