Non-standard interactions in the propagation of neutrinos in matter can lead to significant deviations from expectations within the standard neutrino oscillation framework and atmospheric neutrino detectors have been considered to set constraints. However, most previous works have focused on relatively low-energy atmospheric neutrino data. Here, we consider the one-year high-energy through-going muon data in IceCube, which has been already used to search for light sterile neutrinos, to constrain new interactions in the $μτ$-sector. In our analysis we include several systematic uncertainties on both, the atmospheric neutrino flux and on the detector properties, which are accounted for via nuisance parameters. After considering different primary cosmic-ray spectra and hadronic interaction models, we obtain the most stringent bound on the off-diagonal $\varepsilon_{μτ}$ parameter to date, with the 90\% credible interval given by $-6.0 \times 10^{-3} < \varepsilon_{μτ} < 5.4 \times 10^{-3}$. In addition, we also estimate the expected sensitivity after 10~years of collected data in IceCube and study the precision at which non-standard parameters could be determined for the case of $\varepsilon_{μτ}$ near its current bound.
We demonstrate that atmospheric neutrino data accumulated with the AMANDA and the partially deployed IceCube experiments constrain the allowed parameter space for a hypothesized fourth sterile neutrino beyond the reach of a combined analysis of all other experiments. We also illustrate the sensitivity of the completed IceCube detector, that is now taking data, to the parameter space of 3+1 model.
We test the hypothesis of non-radiative neutrinos decay using the latest IceCube data. Namely, we calculate the track-to-shower ratio expected in IceCube for the normal and inverted neutrino mass hierarchy taking into account the uncertainties in neutrino oscillation parameters. We show that the subset of data with energy above 60 TeV actually excludes the possibility of a neutrinos decay at the 1 sigma level of significance for both neutrino mass hierarchies.
Astrophysical high-energy neutrinos observed by IceCube are sensitive to small effects in a vacuum such as those motivated from quantum gravity theories. Here, we discuss the potential sensitivity of Lorentz violation from the diffuse astrophysical neutrino data in IceCube. The estimated sensitivity reaches the Planck scale physics motivated region, providing IceCube with real discovery potential of Lorentz violation.
We investigate the prompt neutrino background at IceCube, as determined from forward charm. We consider the role of intrinsic charm and of a recombination model and show that the contribution of these mechanisms is at most a factor two.
The MiniBooNe collaboration has recently reported evidence for a light sterile neutrino with large mixing angles thus corroborating the measurement by LSND twenty years ago. Such a state would be directly in conflict with Planck measurement of BBN $N_{eff}$ unless there is self-interaction in the sterile sector. Our objective is to investigate if such interactions could result in resonant absorption in the cosmogenic neutrino spectrum and its consequences for the IceCube experiment. We show that it is possible to give independent bounds on sterile neutrino parameter space from IceCube observat…
The non-observation of neutrinos by the IceCube at the Glashow resonance energy of 6.3 PeV has been a long standing unresolved issue. In this paper we propose a t-channel neutrino absorption by the C$ν$B, which causes a cutoff at 4.5 PeV neutrino energy, to explain the IceCube observations. We present a neutrinophilic 2HDM where the neutrino masses are generated by a low scale seesaw mechanism. A $\mathcal{O}$(10) MeV scalar mediates the interactions between left and right handed neutrinos and generates the t-channel diagram used for explaining the absence of Glashow resonance. The same scalar…
We explore the possibility of distinguishing neutrino mass hierarchies through the neutrino signal from dark matter annihilation at neutrino telescopes. We consider a simple extension of the standard model where the neutrino masses and mixing angles are obtained via the type-II seesaw mechanism as an explicit example. We show that future extensions of IceCube neutrino telescope may detect the neutrino signal from DM annihilation at the Galactic Center and inside the Sun, and differentiate between the normal and inverted mass hierarchies, in this model.
We find the constraints on various non-standard interactions (NSI) of neutrinos from monojet+MET searches at the Large Hadron Collider (LHC). Also, we show that the measurement of neutrino-nucleon cross-section from the observation of high energy astrophysical neutrino events at IceCube facilitates strong constraints on NSI as well. To this end, we pursue a comparative study of the prospects of LHC and IceCube in detecting NSI, also mentioning the role of low-energy experiments. We discuss the case of NSI with a new vector boson $Z'$ and it is found that for some range of $m_{Z'}$ LHC puts mor…
The mixing parameters of sterile neutrino(s) preferred by the MiniBooNE and LNSD experiments are in strong tension with the exclusion limit from the IceCube experiment. Recently it has been claimed that by considering the non-standard neutrino interactions (NSI) in addition to the sterile neutrino, the IceCube's limit can be relaxed and the tension can be reconciled; a baroque scenario as it has been called. We will show that this claim is just an artifact originating from the energy cuts of the chosen datasets. Contrary to the claim, by turning on the NSI and fixing the NSI parameters to the …
The recent results of IceCube Neutrino Observatory include an excess of PeV neutrino events which appear to follow a broken power law different from the other lower energy neutrinos detected by IceCube. The possible astrophysical source of these neutrinos is still unknown. One possible source of such neutrinos could be the decay of non-thermal, long-living heavy mass Dark Matter, whose mass should be $> 10^{6} \rm {GeV}$ and could have produced at the very early Universe. They can undergo cascading decay via both hadronic and leptonic channels to finally produce such high energy neutrinos. Thi…
High-energy atmospheric neutrinos observed by the IceCube Neutrino Observatory are extremely sensitive probes of Lorentz violation (LV). Here we report the result of analyzing two years of IceCube data in the search for LV. This analysis places some of the strongest constraints on LV when considering high-dimensional operators.
We show that the excess of high energy neutrinos observed by the IceCube collaboration at energies above 100 TeV might originate from baryon number violating decays of heavy shadow baryons from mirror sector, which in turn constitute Dark Matter. Due to tiny mixing between mirror and ordinary neutrinos, it is possible to explain the specific features of the IceCube events spectrum.
Considering that the ultrahigh energy (UHE) upgoing muon neutrino events around the PeV energy region observed by the IceCube are due to the decay of super heavy dark matter to neutrinos, we constrain the mass of the decaying dark matter and its decay lifetime using the IceCube analysis of these neutrinos in the PeV region. The theoretical fluxes are computed by adpoting the procedure given in the reference [1,2], where the DGLAP numerical evolutions of QCD cascades as well as electroweak corrections are included for evolving the decay process of the super heavy dark matter. Our results indica…
We elucidate the mechanism of enhancement of the $\barν_μ \to \barν_{s}$ transitions at small mixing angles of Earth-core-crossing neutrinos, which is at the basis of the recent result of the IceCube experiment on atmospheric muon anti-neutrino oscillations into sterile anti-neutrino.
Introducing a leptonic U(1) gauge symmetry, we try to reproduce the gap in the cosmic neutrino spectrum reported by the IceCube collaboration, and at the same time, make an additional contribution to the muon anomalous magnetic moment, which fills the gap between the standard model prediction and the experimental observation.
Anomalies in short baseline experiments have been interpreted as evidence for additional neutrino mass states with large mass splittings from the known, active flavors. This explanation mandates a corresponding signature in the muon neutrino disappearance channel, which has yet to be observed. Searches for muon neutrino disappearance at the IceCube neutrino telescope presently provide the strongest limits in the space of mixing angles for eV-scale sterile neutrinos. This proceeding for the Very Large Volume Neutrino Telescopes (VLVnT) Workshop summarizes the IceCube analyses that have searched…
The predictions for the atmospheric neutrino flux at high energies strongly depend on the contribution of prompt neutrinos, which are determined by the production of charmed meson in the atmosphere at very forward rapidities. In this paper we estimate the related cross sections taking into account the presence of an intrinsic charm (IC) component in the proton wave function and the QCD dynamics modified by the onset of saturation effects. The impact on the predictions for the prompt neutrino flux is investigated assuming different values for the probability to find the IC in the nucleon. Compa…
The excess of high energy neutrinos observed by the IceCube collaboration might originate from baryon number violating decays of heavy shadow baryons from dark mirror sector which produce shadow neutrinos. These sterile neutrino species then oscillate into ordinary neutrinos transferring to them specific features of their spectrum. In particular, this scenario can explain the end of the spectrum above 2 PeV and the presence of the energy gap between 400 TeV and 1 PeV.
IceCube collaboration has published two papers on ultrahigh energy neutrinos observation, recently. They have used the data collected in two years in their first publication, which reveals observation of two PeV energy neutrino events. The second publication of the collaboration including more data has also confirmed main features of the former paper. In literature, various interpretations of the IceCube data have been proposed. In this study, it is shown that PeV energy neutrino events observed by the IceCube collaboration can be interpreted as resonance production of color octet neutrinos wi…
IceCube has detected many TeV--PeV neutrinos, but their astrophysical origins remain largely unknown. Motivated by the observed late-time X-ray/optical bumps in some gamma-ray bursts (GRBs), we examine the correlation between IceCube neutrinos and GRBs allowing delayed neutrinos $\sim$days after the prompt gamma rays. Although we have not found any definitive correlation, up to $\sim$10\% of the events observed so far at IceCube may have been neutrinos produced by the late-time GRB activities at $\sim$1 day. Assuming a connection between some IceCube events and the late GRB bumps, we show in a…
A search for extremely high energy cosmic neutrinos has been carried out with the IceCube Neutrino Observatory. The main signals in the search are neutrino-induced energetic charged leptons and their rate depends on the neutrino-nucleon cross section. The upper-limit on the neutrino flux has implications for possible new physics beyond the standard model such as the extra space-time dimension scenarios which lead to a cross section much higher than the standard particle physics prediction. In this study we constrain the neutrino-nucleon cross section at energies beyond $10^9$ GeV with the IceC…
We study the phenomenology of neutrino decay together with neutrino oscillations in the context of eV-scale sterile neutrinos. We review the formalism of visible neutrino decay in which one of the decay products is a neutrino that potentially can be observed. We apply the formalism developed for decay to the recent sterile neutrino search performed by IceCube with TeV neutrinos. We show that for $ν_4$ lifetime $τ_4/m_4 \lesssim 10^{-16} {\rm eV^{-1}s}$, the interpretation of the high-energy IceCube analysis can be significantly changed.
The observed spectrum of ultrahigh energy neutrinos at IceCube might be indicative of absorption of such neutrinos in ultralight dark matter halos. We point out that various features of this spectrum can be explained by such absorptions. For a light $Z^\prime$-mediated $t$-channel interaction between dark matter and neutrinos, we propose a novel mechanism of absorption of these neutrinos at particular energies. This can save the models of AGN predicting large neutrino flux at energies more than a PeV.
The recent high-statistics high-energy atmospheric neutrino data collected by IceCube open a new window to probe new physics scenarios that are suppressed in lower energy neutrino experiments. In this paper we analyze the IceCube atmospheric neutrino data to constrain the Violation of Equivalence Principle (VEP) in the framework of three neutrinos with non-universal gravitational couplings. In this scenario the effect of VEP on neutrino oscillation probabilities can be parametrized by two parameters $Δγ_{21}\equiv γ_2-γ_1$ and $Δγ_{31}\equiv γ_3-γ_1$, where $γ_i$'s denote the coupling of neutr…
We present a flavor and energy inference analysis for each high-energy neutrino event observed by the IceCube observatory during six years of data taking. Our goal is to obtain, for the first time, an estimate of the posterior probability distribution for the most relevant properties, such as the neutrino energy and flavor, of the neutrino-nucleon interactions producing shower and track events in the IceCube detector. For each event the main observables in the IceCube detector are the deposited energy and the event topology (showers or tracks) produced by the Cherenkov light by the transit thr…
A signal of high-energy extraterrestrial neutrinos from unknown source(s) was recently discovered by the IceCube experiment. Neutrinos are always produced together with gamma-rays, but the gamma-ray flux from extragalactic sources is suppressed due to attenuation in the intergalactic medium. We report the discovery of a gamma-ray excess at high Galactic latitudes starting at energies 300 GeV in the data of the Fermi telescope. We show that the multi-TeV gamma-ray diffuse emission has spectral characteristics at both low and high Galactic latitudes compatible with those of the IceCube high neut…
If light sterile neutrinos exist and mix with the active neutrino flavors, this mixing will affect the propagation of high-energy neutrinos from dark matter annihilation in the Sun. In particular, new Mikheyev-Smirnov-Wolfenstein resonances can occur, leading to almost complete conversion of some active neutrino flavors into sterile states. We demonstrate how this can weaken IceCube limits on neutrino capture and annihilation in the Sun and how potential future conflicts between IceCube constraints and direct detection or collider data might be resolved by invoking sterile neutrinos. We also p…
Lorentz invariance is a fundamental symmetry of spacetime underpinning the Standard Model (SM) and our understanding of high-energy phenomena in particle physics. However, beyond the quantum gravity scale, we expect the SM to be replaced with a more fundamental, covariant theory giving a quantum description of gravity. The effective theory arising from this theory can break Lorentz invariance and thus predicts observables that exhibit low-energy manifestations of Lorentz violation. In particular, these observables could be a subleading contribution to neutrino oscillations and could therefore …
The IceCube Collaboration has observed 37 neutrino events in the energy range $30\, TeV\leq E_ν \leq 2$ PeV and the sources of these neutrinos are unknown. Here we have shown that positions of 12 high energy blazars and the position of the FR-I galaxy Centaurus A, coincide within the error circles of ten IceCube events, the later being in the error circle of the highest energy event so far observed by IceCube. Two of the above blazars are simultaneously within the error circles of the Telescope Array hotspot and one IceCube event. We found that the blazar H2356-309 is within the error circles …
New physics in neutrino sector can reveal itself via non-standard neutrino interactions which can result in modification of the standard picture of neutrino propagation in matter. Experiments with atmospheric neutrinos has been used to probe this scenario. Using publicly available three-year low energy data in IceCube DeepCore we place bounds on the parameters $ε_{αβ}$ of non-standard neutrino interactions in propagation. We obtain restrictive constraints not only for $μτ$ sector but also for flavor changing interactions involving electron neutrinos.
Self-interaction in the active neutrinos is studied in the literature to alleviate the $H_0$ tension. Similar self-interaction can also explain the observed dips in the flux of the neutrinos coming from the distant astro-physical sources in IceCube detectors. In contrast to the flavour universal neutrino interaction considered for solving the $H_0$ tension, which is ruled out from particle physics experiments, we consider flavour specific neutrino interactions. We show that the values of self-interaction coupling constant and mediator mass required for explaining the IceCube dips are inconsist…
The recent study on the the 6-year up-going muon neutrinos by the IceCube Collaboration support the hypothesis of a two-component scenario explaining the diffuse TeV-PeV neutrino flux. Once a hard astrophysical power-law is considered, an excess in the IceCube data is shown in the energy range 10-100 TeV (low-energy excess}). By means of a statistical analysis on the neutrino energy spectrum and on the angular distribution of neutrino arrival directions, we characterize a two-component neutrino flux where decaying/annihilating Dark Matter particles provide a contribution to the IceCube observa…
Astrophysical neutrinos travel long distances from their sources to the Earth traversing dark matter halos of clusters of galaxies and that of our own Milky Way. The interaction of neutrinos with dark matter may affect the flux of neutrinos. The recent multi-messenger observation of a high energy neutrino, IceCube-170922A, can give a robust upper bound $σ/M_{dm} \lesssim 5.1\times 10^{-23} {\rm cm}^2 /$GeV on the interaction between neutrino and dark matter at a neutrino energy of 290 TeV allowing 90\% suppression. Combining the constraints from CMB and LSS at different neutrino energies, we c…
We study oscillations of the high energy atmospheric neutrinos in the Earth into sterile neutrinos with the eV-scale mass. The MSW resonance and parametric enhancement of the $\barν_μ\to\barν_s$ oscillations lead to distortion of the zenith angle distribution of the muon-track events which can be observed by IceCube. Due to matter effect, the IceCube signal depends not only on the mixing element $U_{μ4}$ relevant for LSND and MiniBooNE but also on $U_{τ4}$ and the CP-violating phase $δ_{24}$. We show that the case with $U_{τ4} = δ_{24} = 0$ leads to the weakest IceCube signal and therefore sho…
In ten years of observations, the IceCube neutrino observatory has revealed a neutrino sky in tension with previous expectations for neutrino point source emissions. Astrophysical objects associated with hadronic processes might act as production sites for neutrinos, observed as point sources at Earth. Instead, a nearly isotropic flux of astrophysical neutrinos is observed up to PeV energies, prompting a reassessment of the assumed transport and production physics. This work applies a new physical explanation for neutrino production from populations of active galactic nuclei (AGN) and starburs…
Motivated by the discovery of the first high-energy astrophysical neutrino source, the blazar TXS 0506+056, we revisit the IceCube flavor ratio analysis. Assuming large statistics from identified blazars, collected in the forthcoming years by the IceCube detector and its successor IceCube-Gen2, we demonstrate that the constraints on several new physics scenarios in which the baseline dependent terms in neutrino oscillation probabilities are not averaged, can be improved. As a representative case, we consider pseudo-Dirac neutrinos while neutrino decay is also discussed.
The IceCube Neutrino Observatory detects high energy astrophysical neutrinos in two event topologies: tracks and cascades. Since the flavor composition of each event topology differs, tracks and cascades can be used to test the neutrino properties and the mechanisms behind the neutrino production in astrophysical sources. Assuming a conventional model for the neutrino production, the IceCube data sets related to the two channels are in $>3σ$ tension with each other. Invisible neutrino decay with lifetime $τ/m=10^2$ s/eV solves this tension. Noticeably, it leads to an improvement over the stand…
We search for a spatial association between the CHIME FRBs and IceCube neutrinos detected in the TeV energy range, by counting the total number of neutrino-FRB pairs with angular separations of $< 3 $ degrees, as well as within the observed neutrino error circle. This number constitutes the total signal events, which is then compared to the total background, corresponding to the null hypothesis of no spatial association. The background was obtained from the total neutrino-FRB matches in off-source angular windows with the same solid angle as the signal window. We do not find any statistically …
At very-high energies (100 TeV - 1 PeV), the small value of Bjorken-x ($\le10^{-3}-10^{-7}$) at which the parton distribution functions are evaluated makes the calculation of charm quark production very difficult. The charm quark has mass ($\sim$1.5$\pm$0.2 GeV) significantly above the $Λ$$_{QCD}$ scale ($\sim$200 MeV), and therefore its production is perturbatively calculable. However, the uncertainty in the data and the calculations cannot exclude some smaller non-perturbative contribution. To evaluate the prompt neutrino flux, one needs to know the charm production cross-section in pN -> c$…
We determine constraints on parameters of a single eV-scale light neutrino using IceCube-59 data. Particular emphasis is put on the question whether such an analysis can rule out sterile neutrino hints. While important complementary information is provided, the different dependence on the various sterile neutrino mixing angles makes it currently not possible to fully exclude short baseline appearance results or sterile neutrinos in general.
Motivated by the recent IceCube result, we study high energy cosmic-ray neutrino flux from the decay of a long-lived particle. Because neutrinos are so transparent, high energy neutrinos produced in the past may also contribute to the present neutrino flux. We point out that the PeV neutrino events observed by IceCube may originate in the decay of a particle much heavier than PeV if its lifetime is shorter than the present cosmic time. It is shown that the mass of the particle responsible for the IceCube event can be as large as $\sim 10^{10}\ {\rm GeV}$. We also discuss several possibilities …
Neutrino decay modifies neutrino propagation in a unique way; not only is there flavor changing as there is in neutrino oscillations, there is also energy transport from initial to final neutrinos. The most sensitive direct probe of neutrino decay is currently IceCube which can measure the energy and flavor of neutrinos traveling over extragalactic distances. For the first time we calculate the flavor transition probability for the cases of visible and invisible neutrino decay, including the effects of the expansion of the universe, and consider the implications for IceCube. As an example, we …
The 4.8$σ$ anomaly in MiniBooNE data cannot be reconciled with MINOS+ and IceCube data within the vanilla framework of neutrino oscillations involving an eV-mass sterile neutrino. We show that an apparently consistent picture can be drawn if charged-current and neutral-current nonstandard neutrino interactions are at work in the 3+1 neutrino scheme. It appears that either the neutrino sector is more elaborate than usually envisioned, or one or more datasets needs revision.
The origin of the astrophysical neutrino flux reported by the IceCube Collaboration remains an open question. In this study, we use three years of publicly available IceCube data to search for evidence of neutrino emission from the blazars and non-blazar Active Galactic Nuclei (AGN) contained the Fermi 4LAC catalog. We find no evidence that these sources produce high-energy neutrinos, and conclude that blazars can produce no more than 15% of IceCube's observed flux. The constraint we derive on the contribution from non-blazar AGN, which are less luminous and more numerous than blazars, is sign…
The Precision IceCube Next Generation Upgrade (PINGU) is a proposed extension to the IceCube detector. The design of PINGU would augment the existing 86 strings with an additional 40 with the main goal of determining the neutrino mass ordering (NMO). Preliminary studies of the NMO can start with IceCube/DeepCore, a sub-array of more densely- packed strings in operation since 2011. This detector has a neutrino energy threshold of roughly 10 GeV and allows for high-statistics datasets of atmospheric neutrinos to be collected. This data provides a unique opportunity to better understand the syste…
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.
We discuss the possibility that a sterile neutrino of mass around 50 MeV slightly mixed with the muon flavor may be the origin of the MiniBooNE anomaly. We show that its production in the atmosphere in a fraction of kaon decays would imply an excess of contained showers at IceCube from down-going and near-horizontal directions.
This paper investigates the physics reach of the IceCube neutrino detector when it will have collected a data set of order one million atmospheric neutrinos with energies in the 0.1 \sim 10^4 TeV range. The paper consists of three parts. We first demonstrate how to simulate the detector performance using relatively simple analytic methods. Because of the high energies of the neutrinos, their oscillations, propagation in the Earth and regeneration due to τdecay must be treated in a coherent way. We set up the formalism to do this and discuss the implications. In a final section we apply the met…
We examine a framework with light new physics, which couples to the Standard Model only via neutrino mixing. Taking the hints from the short-baseline anomalies seriously and combining them with modern cosmological data and recent IceCube measurements, we obtain surprisingly effective constraints on the hidden force: keV $\lesssim M \lesssim0.3$ GeV for the mediator mass and $g_{h}>10^{-6}-10^{-3}$ for the coupling constant. Flavor equilibration between the hidden and active neutrinos can be delayed until temperatures of $\sim 1$ MeV, but not below $\sim 100$ keV. This scenario can be tested wi…
We present an argument that radio galaxies (active galaxies with mis-aligned jets) are likely to be the primary sources of the high-energy astrophysical neutrinos observed by IceCube. In particular, if the gamma-ray emission observed from radio galaxies is generated through the interactions of cosmic-ray protons with gas, these interactions can also produce a population of neutrinos with a flux and spectral shape similar to that measured by IceCube. We present a simple physical model in which high-energy cosmic rays are confined within the volumes of radio galaxies, where they interact with ga…
The IceCube Collaboration has recently reported the observation of a flux of high-energy astrophysical neutrinos. The angular distribution of events is consistent with an isotropic arrival direction of neutrinos which is expected for an extragalactic origin. We estimate the prospects of detecting individual neutrino sources from a quasi-diffuse superposition of many extragalactic sources at the level of the IceCube observation. Our analysis takes into account ensemble variations of the source distribution as well as the event statistics of individual sources. We show that IceCube in its presen…
We propose a new way to probe non-standard interactions (NSI) of neutrinos with matter using the ultra-high energy (UHE) neutrino data at current and future neutrino telescopes. We consider the Zee model of radiative neutrino mass generation as a prototype, which allows two charged scalars -- one $SU(2)_L$-doublet and one singlet, both being leptophilic, to be as light as 100 GeV, thereby inducing potentially observable NSI with electrons. We show that these light charged Zee-scalars could give rise to a Glashow-like resonance feature in the UHE neutrino event spectrum at the IceCube neutrino …
IceCube observed high-energy neutrino flux in the energy region from TeV to PeV. The decay of a massive long-lived particle in the early universe can be the origin of the IceCube neutrino events, which we call an "early decay scenario." In this paper, we construct a particle physics model that contains such a massive long-lived particle based on the Peccei-Quinn model. We calculate the present neutrino flux, taking account of realistic initial energy distributions of particles produced by the decay of the massive long-lived particle. We show that the early decay scenario naturally fits into th…
