TY - JOUR
T1 - Ultra high energy neutrinos
T2 - Absorption, thermal effects and signatures
AU - Lunardini, Cecilia
AU - Sabancilar, Eray
AU - Yang, Lili
PY - 2013/8
Y1 - 2013/8
N2 - We study absorption of ultra high energy neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel. For a hierarchical neutrino mass spectrum (with at least one neutrino with mass below ∼ 10-2 eV), thermal effects are important for ultra high energy neutrino sources at z≳16. The neutrino transmission probability shows no more than two separate suppression dips since the two lightest mass eigenstates contribute as a single species when thermal effects are included. Results are applied to a number of models of ultra high energy neutrino emission. Suppression effects are strong for sources that extend beyond z ∼ 10, which can be realized for certain top down scenarios, such as superheavy dark matter decays, cosmic strings and cosmic necklaces. For these, a broad suppression valley should affect the neutrino spectrum at least in the energy interval 1012-10 13 GeV - which therefore is disfavored for ultra high energy neutrino searches - with only a mild dependence on the neutrino mass spectrum and hierarchy. The observation of absorption effects would indicate a population of sources beyond z ∼ 10, and favor top-down mechanisms; it would also be an interesting probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10-100.
AB - We study absorption of ultra high energy neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel. For a hierarchical neutrino mass spectrum (with at least one neutrino with mass below ∼ 10-2 eV), thermal effects are important for ultra high energy neutrino sources at z≳16. The neutrino transmission probability shows no more than two separate suppression dips since the two lightest mass eigenstates contribute as a single species when thermal effects are included. Results are applied to a number of models of ultra high energy neutrino emission. Suppression effects are strong for sources that extend beyond z ∼ 10, which can be realized for certain top down scenarios, such as superheavy dark matter decays, cosmic strings and cosmic necklaces. For these, a broad suppression valley should affect the neutrino spectrum at least in the energy interval 1012-10 13 GeV - which therefore is disfavored for ultra high energy neutrino searches - with only a mild dependence on the neutrino mass spectrum and hierarchy. The observation of absorption effects would indicate a population of sources beyond z ∼ 10, and favor top-down mechanisms; it would also be an interesting probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10-100.
KW - cosmic ray theory
KW - cosmological neutrinos
KW - ultra high energy cosmic rays
KW - ultra high energy photons and neutrinos
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U2 - 10.1088/1475-7516/2013/08/014
DO - 10.1088/1475-7516/2013/08/014
M3 - Article
AN - SCOPUS:84883607184
SN - 1475-7516
VL - 2013
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 8
M1 - 014
ER -