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There may be a high-energy cutoff of neutrino events in IceCube data. In particular, IceCube does not observe either continuum events above 2 PeV, or the Standard Model Glashow-resonance events expected at 6.3 PeV. There are also no higher energy neutrino signatures in the ANITA and Auger experiments. This absence of high-energy neutrino events motivates a fundamental restriction on neutrino energies above a few PeV. We postulate a simple scenario to terminate the neutrino spectrum that is Lorentz-invariance violating, but with a limiting neutrino velocity that is always smaller than the speed of light. If the limiting velocity of the neutrino applies also to its associated charged lepton, then a significant consequence is that the two-body decay modes of the charged pion are forbidden above two times the maximum neutrino energy, while the radiative decay modes are suppressed at higher energies. Such stabilized pions may serve as cosmic ray primaries.
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The solar neutrino spectrum measured by the Super-Kamiokande shows an excess in high energy bins, which may be explained by vacuum oscillation solution or $hep$ neutrino effect. Here we reconsider an uncertainty of the data caused by the tail of the energy resolution function. Events observed at energy higher than 13.5 MeV are induced by the tail of the resolution. At Super-Kamiokande precision level this uncertainty is no more than few percent within a Gaussian tail. But a power-law decay tail at 3 $sigma$ results considerable excesses in these bins, which may be another possible explanation of the anomaly in 708d(825d) data.
In this paper, we propose a hexagonal description for the flavor composition of ultrahigh-energy (UHE) neutrinos and antineutrinos, which will hopefully be determined at the future large neutrino telescopes. With such a geometrical description, we are able to clearly separate the individual flavor composition of neutrinos from that of antineutrinos in one single regular hexagon, which can be regarded as a natural generalization of the widely-used ternary plot. For illustration, we consider the $pp$ or $pgamma$ collisions as the dominant production mechanism for UHE neutrinos and antineutrinos in the cosmic accelerator, and investigate how neutrino oscillations in the standard picture and in the presence of Lindblad decoherence could change the flavor composition of neutrinos and antineutrinos at neutrino telescopes.
The flavor conversion of a neutrino usually occurs at densities $lesssim G_F^{-1} omega$, whether in the ordinary matter or the neutrino medium, and on time/distance scales of order $omega^{-1}$, where $G_F$ is the Fermi weak coupling constant and $omega$ is the vacuum oscillation frequency of the neutrino. In 2005 Sawyer and more recently both he and other groups have shown that neutrino flavor
Since the launch of LHC experiments it has been discovered that the high multiplicity trigger in pp, pA collisions finds events behaving differently from the typical (minimally biased) ones. In central pPb case it has been proven that those possess collective phenomena known as the radial, elliptic and triangular flows, similar to what is known in heavy ion (AA) collisions. In this paper we argue that at the ultra-high energies, E_lab ~ 10^{20} eV, of the observed cosmic rays this regime changes from a small-probability fluctuation to a dominant one. We estimate velocity of the transverse collective expansion for the light-light and heavy-light collisions, and find it comparable to what is observed at LHC for the central PbPb case. We argue that significant changes of spectra of various secondaries associated with this phenomenon should be important for the development of the cosmic ray cascades.
We forecast constraints on neutrino decay via capture of the Cosmic Neutrino Background on tritium, with emphasis on the PTOLEMY-type experiment. In particular, in the case of invisible neutrino decay into lighter neutrinos in the Standard Model and invisible particles, we can constrain not only the neutrino lifetime but also the masses of the invisible particles. For this purpose, we also formulate the energy spectra of the lighter neutrinos produced by 2-body and 3-body decays, and those of the electrons emitted in the process of the detection of the lighter neutrinos.
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