A combined astrophysical and dark matter interpretation of the IceCube HESE and throughgoing muon events

Abstract

We perform a combined likelihood analysis for the IceCube 6-year high-energy starting events (HESE) above 60 TeV and 8-year throughgoing muon events above 10 TeV using a two-component neutrino flux model. The two-component flux can be motivated either from purely astrophysical sources or due to a beyond Standard Model contribution, such as decaying heavy dark matter. As for the astrophysical neutrinos, we consider two different source flavor compositions corresponding to the standard pion decay and muon-damped pion decay sources. We find that the latter is slightly preferred over the former as the high-energy component, while the low-energy component does not show any such preference. We also take into account the multi-messenger gamma-ray constraints and find that our two-component fit is compatible with these constraints, whereas the single-component power-law bestfit to the HESE data is ruled out. The astrophysical plus dark matter interpretation of the twocomponent flux is found to be mildly preferred by the current data and the gamma-ray constraints over the purely astrophysical explanation.

Decaying dark matter at IceCube and its signature on High Energy gamma experiments

“…Finally, we test whether the Dark Matter hypothesis could be further scrutinised by using forthcoming high energy gamma rays experiments. * m.chianese@uva.nl † dfgfiorillo@na.infn.it ‡ miele@na.infn.it § smorisi@na.infn.t ¶ a hard isotropic extragalactic neutrino flux and an additional softer one with a potential galactic origin [27][28][29][30][31][32][33]. This two-component hypothesis is at the same time supported by the first combined analysis of IceCube and ANTARES data [34].…”

“…It turns out that both IceCube and ANTARES telescopes have measured in the same energy range (about 40-200 TeV) a slight excess with respect to an astrophysical power-law flux deduced by TG data (γ ≤ 2.2), after the background subtraction [34][35][36][37].An alternative source for this diffuse UHE neutrino flux is decaying Dark Matter (DM) . While another available source might be identified with annihilating DM [33,35,39,[63][64][65][66][67], the unitarity limit leads in general to small neutrinos fluxes which are therefore not detectable. Bounds are available in previous studies both for decaying [68,69] and annihilating DM [70,71].…”

On the relevance of prompt neutrinos for the interpretation of the IceCube signals

“…In [7,8,32] the spectral difference between the HESE and the through-going muons spectra is labelled as an anomaly, and it has been already addressed in [33,34]. In fact, if we compare the astrophysical neutrino fits to the cascade and starting track samples, which together constitute the HESE dataset, from [31] to that from the through-going muons analysis [2] there is an evident difference, as can be appreciated from 2.13 ± 0.13 Table 3.…”

Zee-Burst: A New Probe of Neutrino Nonstandard Interactions at IceCube

“…One candidate Glashow event was identified in a partiallycontained PeV event (PEPE) search with deposited energy of 5.9 ± 0.18 PeV [5,13], but has not been included in the event spectrum yet [6]. The non-observation of Glashow events might be still consistent with the SM expectations within the error bars, given the uncertainty in the source type (pp versus pγ), as well as (ν e , ν µ , ν τ ) flavor composition (1:2:0 vs 0:1:0) [14][15][16][17][18]. On the other hand, the possibility of observing a Z-boson resonance (Z-burst) at IceCube due to UHE anti-neutrinos interacting with non-relativistic relic neutrinos [19] is bleak, as the required incoming neutrino energy in this case turns out to be E ν = m 2 Z /2m ν 10 23 eV, well beyond the GZK cut-off energy of 5 × 10 19 eV for the UHE cosmic rays [20,21]-the most likely progenitors of the UHE neutrinos (for related discussion, see Ref.…”