![]() ![]() 2. CRITICAL DISCUSSION OF THE SINGLE-POWER-LAW MODEL A brief summary is contained in Section 5. In Section 4 we illustrate the predictions of our model for existing and future neutrino telescopes and the implications for gamma astronomy at the highest energy. In that section, we also quantify the relative intensity and discuss the spectra. In Section 3 we motivate and present the new hypothesis that includes two components: one due to extragalactic neutrinos and the other one due to galactic neutrinos. In Section 2 we examine the single-component hypothesis for high-energy neutrinos, stressing its shortcoming. The structure of this paper is as follows. Thus the free parameters for the fit are again two, the normalizations of the fluxes. Moreover, in the simplest version of our model, which we adopt, the spectrum has two components with fixed slopes: one of them behaves as, the other one as. ![]() However, in view of the fact that, to date, we lack a firm theoretical bases for the interpretation of IceCube observations, we should not exaggerate the heuristic power of mathematical criteria. The "single power law" hypothesis has two free parameters, the normalization and the slope, adding only one parameter to the previously adopted hypothesis (the normalization of the assumed flux). (2) Also, the issue of minimality requires additional discussion. Our aims are to illustrate the reasoning behind another hypothesis capable of interpreting the IceCube data, illustrating its advantages and its physical interest, deriving its implications, and showing that it can be tested with future data. This is still viable at present, if one adopts very conservative criteria (i.e., one discards some data set or information and/or if one accepts various discrepancies). (1) The aim of the present paper is not to prove wrong the assumption of a single power law E − α, isotropically distributed, which is most commonly adopted for analyses of IceCube data. Moreover, as we will discuss below, there are a lot of interesting consequences for the astronomy of high-energy neutrinos.īefore proceeding, two important clarifications are in order: If the alternative hypothesis is correct, it is premature to dismiss the position just described above. In this work, pluses and the minuses of this position are summarized, motivating an alternative and more satisfactory hypothesis to account for the observations of IceCube and to forecast future findings. The minimal modification consists of using a single power law E − α, isotropic and with α ∼ 2.5, a value obtained by fitting the observations of IceCube. A particular very well-known implementation was the one developed in Waxman & Bahcall ( 1999).Īfter IceCube, this hypothesis has been minimally modified in order to take into account that the observed spectrum does not agree well with. ![]() Before IceCube, the most popular expectations regarding ultra-high-energy neutrinos, typically adopted in sensitivity studies, were that (1) most of them have an extragalactic origin, as motivated by the existence of many extreme astrophysical objects and of extragalactic cosmic rays, and (2) their spectrum is distributed as, as motivated by the expectations for cosmic rays at the sources and by Fermi's acceleration mechanism. ![]()
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