HIGH-ENERGY NEUTRINOS FROM EXTRAGALACTIC JETS

In this paper I calculate the diffuse background of high-energy neutri nos from extragalactic jets emerging from active galactic nuclei (AGN) . I assume that radio-quiet AGN have jets that are disrupted by turbul ence in the vicinity of an accretion disk surrounding a central black hole and remain invisible in the radio band. In contrast, radio-loud A GN have high Mach number jets which dissipate in a strong shock far aw ay from the AGN, It is assumed that protons are accelerated to ultra-h igh energies in jets. Photo-production of pions induces neutrino emiss ion and electromagnetic cascades. The cascade spectra are in agreement with the most recent X- and gamma-ray observations of AGN; in particu lar with the lack of gamma-ray emission from radio-quiet AGN and the p owerful gamma-ray emission from flat-spectrum radio-loud AGN. A high e nergy neutrino background from radio-quiets is predicted assuming that they produce the cosmic diffuse X-ray background. However, the flux l imits from the Frejus proton decay experiment are violated by this pre diction. On the other hand, recent gamma-ray observations make it very plausible that the diffuse gamma-ray background at least above 100 Me V is due to radio-loud AGN. A striking similarity exists between the e nergy fluxes of diffuse gamma-rays above 100 MeV and cosmic ray proton s above the ankle. This is an independent argument for proton accelera tion in radio jets consistent with the explanation of the individual g amma-ray spectra by hadronically induced cascades. The corresponding p rediction of a neutrino flux at ultra-high energies therefore rests on a firm basis.