Now that PeV neutrinos have been discovered by IceCube, we optimistically entertain the possibility that neutrinos with energy above 100 PeV exist. We evaluate the dependence of event rates of such neutrinos on the neutrino-nucleon cross section at observatories that detect particles, atmospheric fluorescence, or Cherenkov radiation, initiated by neutrino interactions. We consider how (i) a simple scaling of the total standard model neutrino-nucleon cross section, (ii) a new elastic neutral current interaction, and (iii) a new completely inelastic interaction, individually impact event rates.
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 $pγ$ collisions as the dominant production mechanism for UHE neutrinos and antineutrinos in t…
A theoretical analysis of possible influence of neutrino magnetic moments on the propagation of ultrahigh-energy cosmic neutrinos in the interstellar space is carried out under the assumption of two-neutrino mixing. The exact solution of the effective equation for neutrino evolution in the presence of a magnetic field and matter is obtained, which accounts for four neutrino species corresponding to two different flavor states with positive and negative helicities. Using most stringent astrophysical bounds on the putative neutrino magnetic moment, probabilities of neutrino flavor and spin oscil…
The observation of ultra-high-energy EeV-energy cosmogenic neutrinos provides a direct path to identifying the sources of the highest energy cosmic rays; searches have so far resulted in only upper limits on their flux. However, with the realization of cubic-kilometer detectors such as IceCube and, in the near future, KM3NeT, GVD-Baikal, and similar instruments, we anticipate the observation of PeV-energy cosmic neutrinos with high statistics. In this context, we draw attention to the opportunity to identify EeV tau neutrinos at PeV energy using Earth-traversing tau neutrinos. We show that Che…
The IceCube collaboration has recently announced the discovery of ultra-high energy neutrino events. These neutrinos can be used to probe their production source, as well as leptonic mixing parameters. In this work, we have used the first IceCube data to constrain the leptonic CP violating phase $δ_{cp}$. For this, we have analyzed the data in the form of flux ratios. We find that the fit to $δ_{cp}$ depends on the assumptions made on the production mechanism of these astrophyscial neutrinos. Consequently, we also use this data to impose constraints on the sources of the neutrinos.
The ultrahigh energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviors for its magnitude for ultrahigh energies. In this contribution is presented a summary of current predictions based on the non-linear QCD evolution equations, the so-called perturbative saturation physics. In particular, predictions are shown based on the parton saturation approaches and the consequences of geometric scaling property at high energies are discussed. The scaling propert…
The number of ultrahigh energy events at IceCube is estimated, for the first time, taking into account non-linear QCD effects in the neutrino - hadron cross section. We assume that the extragalactic neutrino flux is given by $Φ_ν(E_ν)=Φ_{0}E^{-2}_ν$ and estimate the neutrino - hadron cross section using the dipole approach and a phenomenological model for the dipole - hadron cross section based on non-linear QCD dynamics. We demonstrate that the non-linear prediction is able to describe the current IceCube data and that the magnitude of the non-linear effects is larger than 20 % for visible en…
The high energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviours for its magnitude for ultrahigh energies. In this paper we present a comparison between the predictions based on linear DGLAP dynamics, non-linear QCD and in the imposition of a Froissart-like behaviour at high energies. In particular, we update the predictions based on the Color Glass Condensate, presenting for the first time the results for $σ_{νN}$ using the solution of the running co…
The discovery of ultra-high-energy neutrinos, with energies above 100 PeV, may soon be within reach of upcoming neutrino telescopes. We present a robust framework to compute the statistical significance of point-source discovery via the detection of neutrino multiplets. We apply it to the radio array component of IceCube-Gen2. To identify a source with $3σ$ significance, IceCube-Gen2 will need to detect a triplet, at best, and an octuplet, at worst, depending on whether the source is steady-state or transient, and on its position in the sky. The discovery, or absence, of sources significantly …
Neutrino interactions with protons and neutrons probe their deep structure and may reveal new physics. The higher the neutrino energy, the sharper the probe. So far, the neutrino-nucleon ($νN$) cross section is known across neutrino energies from a few hundred MeV to a few PeV. Soon, ultra-high-energy (UHE) cosmic neutrinos, with energies above 100 PeV, could take us farther. So far, they have evaded discovery, but upcoming UHE neutrino telescopes endeavor to find them. We present the first detailed measurement forecasts of the UHE $νN$ cross section, geared to IceCube-Gen2, one of the leading…
The opacity of the Earth to incident ultra high energy neutrinos is directly connected with the behaviour of the neutrino - nucleon ($σ^{νN}$) cross sections in a kinematic range utterly unexplored. In this work we investigate how the uncertainties in $σ^{νN}$ due the different QCD dynamic models modify the neutrino absorption while they travel across the Earth. In particular, we compare the predictions of two extreme scenarios for the high energy behaviour of the cross section, which are consistent with the current experimental data. The first scenario considered is based on the solution of t…
Gamma-ray bursts (GRBs) are expected to provide a source of ultra high energy cosmic rays, accompanied with potentially detectable neutrinos at neutrino telescopes. Recently, IceCube has set an upper bound on this neutrino flux well below theoretical expectation. We investigate whether this mismatch between expectation and observation can be due to neutrino decay. We demosntrate the phenomenological consistency and theoretical plausibility of the neutrino decay hypothesis. A potential implication is the observability of majoron-emitting neutrinoless double beta decay.
We discuss the possibility of utilizing the ultra-high energy neutrino beam (about 1000 TeV) to detect and destroy the nuclear bombs wherever they are and whoever possess them.
The width of the neutrino decay into the electron and $W$ boson in a strong external magnetic field is obtained from the imaginary part of the neutrino self-energy. This result corrects the formulae existing in the literature. The mean free path of an ultra-high energy neutrino in a strong magnetic field is calculated. An energy cutoff for neutrinos propagating in a strong field is defined.
Observation of ultra-high energy astrophysical neutrinos and identification of their flavors have been proposed for future neutrino telescopes. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. The flavor transition mechanisms are well-classified with our model-independent parametrization. We find a new parameter R=ϕ_e/(ϕ_μ + ϕ_τ) can probe directly the flavor transition in the framework of our model-independent parametrization, without the assumpti…
A growing class of ultra-high energy neutrino (UHE-nu) observatories based on the Askaryan effect and Antarctic ice is able to search for Lorentz invariance violation (LIV). The ARA, ARIANNA, ANITA and EVA collaborations have the power to constrain the Standard Model Extension (SME) by measuring the flux and energy distribution of neutrinos created through the GZK process. The future expansion of ARA, at the South Pole, pushes the discovery potential further.
Interest in light dark matter candidates has recently increased in the literature; some of these works consider the role of additional neutrinos, either active or sterile. Furthermore, extragalactic neutrinos have been detected with energies higher than have ever been reported before. This opens a new window of opportunities to the study of neutrino properties that were unreachable up to now. We investigate how an interaction potential between neutrinos and dark matter might induce a resonant enhancement in the oscillation probability, an effect that may be tested with future neutrino data.
Newborn, strongly magnetized neutron stars (so-called magnetars) surrounded by their stellar or merger ejecta are expected to be sources of ultrahigh-energy neutrinos via decay of mesons produced in hadronic interactions of protons which are accelerated to ultrahigh energies by magnetic dissipation of the spindown energy. We show that not only pions and kaons but also charm hadrons, which are typically neglected due to their small production cross sections, can represent dominant contributions to neutrino fluence at ultrahigh energies, because of their short lifetimes, while the ultrahigh-ener…
The next generation of radio telescopes will be sensitive to low-scale quantum gravity by measuring ultra-high-energy neutrinos. In this letter, we demonstrate for the first time that neutrino-nucleon soft interactions induced by TeV-scale gravity would significantly increase the number of events detected by the IceCube-Gen2 radio array in the EeV regime. However, we show that these experiments cannot measure the total cross section using only the angular and energy information of the neutrino flux, unless assumptions on the underlying inelasticity distribution of neutral interactions are made…
The number of events observed in neutrino telescopes depends on the neutrino fluxes in the Earth, their absorption while crossing the Earth and their interaction in the detector. In this paper, we investigate the impact of the QCD dynamics at high energies on the energy dependence of the average inelasticity and angular dependence of the absorption probability during the neutrino propagation through the Earth, as well in the determination of the properties of the incident astrophysical neutrino flux. Moreover, the number of events at the IceCube and IceCube - Gen2 are estimated considering dif…
We deduce the cosmogenic neutrino flux by jointly analysing ultra high energy cosmic ray data from HiRes-I and II, AGASA and the Pierre Auger Observatory. We make two determinations of the neutrino flux by using a model-dependent method and a model-independent method. The former is well-known, and involves the use of a power-law injection spectrum. The latter is a regularized unfolding procedure. We then use neutrino flux bounds obtained by the RICE experiment to constrain the neutrino-nucleon inelastic cross section at energies inaccessible at colliders. The cross section bounds obtained usin…
Future detection of ultrahigh-energy neutrinos will open a new window on physics at center-of-mass energy 10^5 GeV and higher. In particular, observations of neutrino-initiated showers will help test the Standard Model predictions for the neutrino-nucleon cross section.
The high parton density present at high energies and large nuclei is expected to modify the lepton - hadron cross section and the associated observables. In this paper we analyse the impact of the high density effects in the average inelasticity and the neutrino - nucleus cross section at ultra high energies. We compare the predictions associated to the linear DGLAP dynamics with those from the Color Glass Condensate formalism, which includes non-linear effects. Our results demonstrated that the non-linear effects reduce the average inelasticity and that the predictions of the distinct approac…
The unparticle is proposed by Georgi as a conceptual new physics beyond the standard model to describe the low energy sector of a nontrivial scale invariant sector of an effective theory. We consider the neutrino decay in unparticle scenario and investigate the effect of such decay for the case of ultra high energy neutrinos from GRB. The effect on the detection yield of these neutrinos are also probed for a kilometer scale ice-Cerenkov detector.
We present an updated version of the {\it SimProp} Monte Carlo code to study the propagation of ultra high energy cosmic rays in astrophysical backgrounds computing the cosmogenic neutrino fluxes expected on earth. The study of secondary neutrinos provides a powerful tool to constrain the source models of these extremely energetic particles. We will show how the newly detected IceCube neutrino events at PeV energies together with the the latest experimental results of the Pierre Auger Observatory and Telescope Array experiment are almost at the level of excluding several hypothesis on the astr…
We propose a simple but useful parametrization of the flavor composition of ultrahigh-energy neutrino fluxes produced from distant astrophysical sources: $ϕ^{}_e : ϕ^{}_μ: ϕ^{}_τ= \sin^2 ξ\cos^2 ζ: \cos^2 ξ\cos^2 ζ: \sin^2 ζ$. We show that it is possible to determine or constrain $ξ$ and $ζ$ by observing two independent neutrino flux ratios at the second-generation neutrino telescopes, provided three neutrino mixing angles and the Dirac CP-violating phase have been well measured in neutrino oscillations. Any deviation of $ζ$ from zero will signify the existence of cosmic $ν^{}_τ$ and $\barν^{}…
Several cosmologically distant astrophysical sources may produce ultra-high energy cosmic neutrinos (E > 10^6 GeV) of all flavors above the atmospheric neutrino background. I study the effects of vacuum neutrino flavor mixing on this cosmic neutrino flux. Prospects for observations of these ultra-high energy cosmic neutrinos in large underwater/ice neutrino telescopes are also briefly discussed.
We consider the effects of active-sterile secret neutrino interactions, mediated by a new pseudoscalar particle, on high- and ultra high-energy neutrino fluxes. In particular, we focus on the case of 3 active and 1 sterile neutrino coupled by a flavor dependent interaction, extending the case of 1 active and 1 sterile neutrino we have recently examined. We find that, depending on the kind of interaction of sterile neutrino with the active sector, new regions of the parameter space for secret interactions are now allowed leading to interesting phenomenological implications on two benchmark flux…
We have explored the question of whether the renormalization group running of the neutrino mixing parameters in the Minimal Supersymmetric Standard Model is detectable with ultra-high energy neutrinos from active galactic nuclei (AGN). We use as observables the ratios of neutrino fluxes produced at the AGN, focusing on four different neutrino production models: $(Φ_{ν_e+\barν_e}^0 : Φ_{ν_μ+\barν_μ}^0 : Φ_{ν_τ+\barν_τ}^0)$ = (1:2:0), (0:1:0), (1:0:0), and (1:1:0). The prospects for observing deviations experimentally are taken into consideration, and we find out that it is necessary to impose a…
Assuming that a single-flavor diffuse neutrino flux dN_nu/dE_nu is equal to k*E_nu^(-2) in the energy range 10^(17) eV - 2.5*10^(19) eV, an upper bound on k is calculated in the ADD model as a function of the number of extra dimensions n and gravity scale M_D. An expected number of neutrino induced events at the Surface Detector array of the Pierre Auger Observatory is estimated.
Scalar ultra-light dark matter (ULDM) interacting with neutrinos can induce, under certain conditions, time-dependent modifications to neutrino oscillation probabilities. The limit in which the ULDM perturbation can be treated as constant throughout the neutrino propagation time has been addressed by several previous works. We complement these by systematically analyzing the opposite limit -- accounting for the temporal-variations of the ULDM potential by solving time-dependent Schrödinger equations. In particular, we study a novel two-generations-like CP violating (CPV) signature unique to ra…
Neutrino Oscillations in the presence of strong gravitational fields are studied specifically for Majorana neutrinos. We look at ultra high energy neutrinos $(\sim 1$ PeV) emanating from Active Galactic Nuclei (AGN). Fluxes of different flavor neutrinos are estimated and probabilities for different neutrino transitions calculated.
A study of the ultra high energy neutrino detection performances of a km^3 Neutrino Telescope sitting at the three proposed sites for "ANTARES", "NEMO" and "NESTOR" in the Mediterranean sea is here performed. The detected charged leptons energy spectra, entangled with their arrival directions, provide an unique tool to both determine the neutrino flux and the neutrino-nucleon cross section.
The search for ultra-high energy downward-going and Earth-skimming cosmic neutrinos by the Surface Detector array of the Pierre Auger Observatory (PAO) is analyzed in the ADD model with n extra flat spatial dimensions. We assumed that the diffuse neutrino flux dN_nu/dE_nu$ is equal to k E_nu^(-20) in the energy range 10^(17) eV - 2.5 10^(19) eV. Taking into account that no neutrino events where found by the PAO, we have estimated an upper bound on a value of k. It is shown that this bound can be stronger than the upper bound on k recently obtained by the Pierre Auger Collaboration, depending o…
Neutrino Physics is now entering precision era and neutrino-nucleon cross sections are an im- portant ingredient in all neutrino oscillation experiments. Specially, precise knowledge of neutrino- nucleon cross sections in Ultra High Energy (UHE) regime (TeV-PeV) is becoming more important now, as several experiments worldwide are going to observe processes involving such UHE neutrinos. In this work, we present new results on neutrino-nucleon cross-sections in this UHE regime, using QCD.
We study ultrahigh energy astrophysical neutrinos and the contribution of tau neutrinos from neutrino oscillations, relative to the contribution of the other flavors. We show the effect of tau neutrino regeneration and tau energy loss as they propagate through the Earth. We consider a variety of neutrino fluxes, such as cosmogenic neutrinos and neutrinos that originate in Active Galactic Nuclei. We discuss signals of tau neutrinos in detectors such as IceCube, RICE and ANITA.
The IceCube collaboration has recently identified events due to ultrahigh-energy neutrino interactions. Predictions of the neutrino-nucleon cross section at ultrahigh energies require a huge extrapolation of the cross sections experimentally measured at laboratory energies. Upon relating neutrino scattering to deep inelastic electron scattering, we show that the empirically verified color dipole picture is well suited for such an extrapolation. The dominant contribution to the total neutrino-nucleon cross section, even at ultrahigh energies, is due to the kinematic range where color transparen…
We predict the neutrino-nucleon cross section at ultrahigh energies relevant in connection with the search for high-energy cosmic neutrinos. Our investigation, employing the color-dipole picture, among other things allows us to quantitatively determine which fraction of the ultrahigh-energy neutrino-nucleon cross section stems from the saturation versus the color-transparency region. We disagree with various results in the literature that predict a strong suppression of the neutrino-nucleon cross section at neutrino energies above $E \cong 10^9 GeV$. Suppression in the sense of a diminished in…
We report results from 120 hours of livetime with the Goldstone Lunar Ultra-high energy neutrino Experiment (GLUE). The experiment searches for <10 ns microwave pulses from the lunar regolith, appearing in coincidence at two large radio telescopes separated by 22 km and linked by optical fiber. Such pulses would arise from subsurface electromagnetic cascades induced by interactions of >= 100 EeV neutrinos in the lunar regolith. No candidates are yet seen, and the implied limits constrain several current models for ultra-high energy neutrino fluxes.
IceCube detects more than 100,000 neutrinos per year in the GeV- to PeV-energy range. Among those, we have isolated a flux of high-energy cosmic neutrinos. I will discuss the instrument, the analysis of the data, the significance of the discovery of cosmic neutrinos, and the recent multi-messenger observation of a flaring TeV blazar in coincidence with the IceCube neutrino alert IC170922.
The ultrahigh energy neutrino cross section is well understood in the standard model for neutrino energies up to 10$^{12}$ GeV. Test of neutrino oscillations ($ν_μ\leftrightarrowν_τ$) from extragalactic sources of neutrinos are possible with large underground detectors. Measurments of horizontal air shower event rates at neutrino energies above 10$^{10}$ GeV will be able to constrain nonstandard model contributions to the neutrino-nucleon cross section, e.g., from mini-black hole production.
Ultra-high-energy (UHE) neutrinos, with EeV-scale energies, carry with them unique insight into fundamental open questions in astrophysics and particle physics. For fifty years, they have evaded discovery, but maybe not for much longer, thanks to new UHE neutrino telescopes, presently under development. We capitalize on this upcoming opportunity by producing state-of-the-art forecasts of the discovery of a diffuse flux of UHE neutrinos in the next 10-20 years. By design, our forecasts are anchored in often-overlooked nuance from theory and experiment; we gear them to the radio array of the pla…
We use an updated version of {\it SimProp}, a Monte Carlo simulation scheme for the propagation of ultra-high energy cosmic rays, to compute cosmogenic neutrino fluxes expected on Earth in various scenarios. These fluxes are compared with the newly detected IceCube events at PeV energies and with recent experimental limits at EeV energies of the Pierre Auger Observatory. This comparison allows us to draw some interesting conclusions about the source models for ultra-high energy cosmic rays. We will show how the available experimental observations are almost at the level of constraining such mo…
A bilinear R-Parity breaking SUSY model for neutrino mass and mixing predicts the lightest superparticle to decay mainly into a pair of tau leptons or b quarks along with a neutrino for relatively light SUSY spectra. This leads to a distinctive triple bang signature of SUSY events at ultrahigh energy neutrino telescopes like IceCube or Antares. While the expected signal size is only marginal at IceCube, it will be promising for a future multi-km^3 size neutrino telescope.
The source of Ultra High Energy Cosmic Rays (UHECR) is still an unresolved mystery. Up until recently, sources of Gamma Ray Bursts (GRBs) had been considered as a suitable source for UHECR. Within the fireball model, the UHECR produced at GRBs should be accompanied with a neutrino flux detectable at the neutrino telescope such as IceCube. Recently, IceCube has set an upper bound on the neutrino flux accompanied by GRBs about 3.7 times below the prediction. We investigate whether this deficit can be explained by the oscillation of the active neutrinos to sterile neutrinos en route from the sour…
We discuss prospects for probing Z-prime and non-standard neutrino interactions using neutrino-nucleus coherent scattering with ultra-low energy (~ 10 eV) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC s…
We review the phenomenology of ultra-high energy (UHE) neutrino detection. The motivations for looking for such neutrinos stemming from observational evidence and the potential for new physics discoveries are enumerated, and their expected sources and fluxes are given. Cross-sections with nucleons all the way upto neutrino energies of 10^20 eV, and the attenuation of the fluxes in the earth are discussed. Finally, sample event-rates for existing and future Water/Ice Cerenkov detectors are provided.
We apply new upper limits on neutrino fluxes and the diffuse extragalactic component of the GeV gamma-ray flux to various scenarios for ultra high energy cosmic rays and neutrinos. As a result we find that extra-galactic top-down sources can not contribute significantly to the observed flux of highest energy cosmic rays. The Z-burst mechanism where ultra-high energy neutrinos produce cosmic rays via interactions with relic neutrinos is practically ruled out if cosmological limits on neutrino mass and clustering apply.
If high-energy neutrinos propagate in a background of ultralight scalar field particles of dark matter ($m_φ\sim 10^{-23}$eV), neutrino-dark matter interactions can play a role and affect the neutrino flux. In this work we analyse this effect using transport equations that account for the neutrino regeneration as well as absorption, and we consider the neutrino flux propagation in the extragalactic medium and also through the galactic halo of dark matter. We show the results for the final flux to arrive on Earth for different cases of point and diffuse neutrino fluxes. {We conclude that this t…
We discuss W and Z production through the deep inelastic neutrino-nucleon scattering in the context of the standard model SU(3)x SU(2)x U(1) of the strong and electroweak interactions. We find the cross section rates for the process neutrino + nucleon --> lepton(-) + W(+) + X for the case of ultrahigh-energy neutrinos colliding on a target nucleon.
