High-energy Neutrino Spectrum Research Articles

Loaded layer-cake model for cosmic ray interaction around exploding super-giant stars making black holes

The experiment AMS on the International Space-Station has produced accurate cosmic ray spectra for many chemical elements, both primaries like He, C, O, Fe, other cosmic ray (CR) primaries like Ne, Mg, and Si, secondaries like Li, Be, B, and of mixed provenance, like N, Na, and Al. The AMS spectra demonstrate that interaction is seriously diminishing fluxes up to a rigidity of about 100 GV, and so the existing models for CR interaction have to be re-examined. Based on earlier well-established ideas a model is proposed here that focusses on the cosmic ray interaction first in the wind shock shell of super giant stars, when the supernova driven shock races through, and second in the OB-Superbubble surrounding the SN: These stars include both red super-giant stars and blue super-giant stars; both produce black holes in their explosion, and drive winds and jets with electric currents. Variability of these winds or jets gives rise to temporary electric fields, as has recently been demonstrated, and discharge (so lightning) acceleration gives steep spectra, with synchrotron losses to p−5 in momentum p; these spectra are typically observed in both Galactic and some extragalactic radio filaments. Analogous hadron spectra p−4 excite a flat spectrum of magnetic irregularities in the bubble zone, which in turn yields a steep dependence of residence time versus energy, with power −5/3. This spectrum is indicated by the AMS data and appears to be required to explain the CR spectra below 100 GV. The emphasis in this paper is to work out the interaction of the freshly accelerated cosmic ray particles. In the model presented here the interaction is derived as a function of time, and then integrated, or developed to long times. The model gives a rigidity dependence of the secondary/primary ratio of slope −1/3 as well as the strong reduction of the primary fluxes below a rigidity of about 100 GV, relative to a power-law injection spectrum, with slope +2. The two key aspects based on blue super-giant stars and a magnetic irregularity spectrum in the bubble zone given by lightning are (i) a much larger column of interaction, allowed because of heavy element enrichment of the interaction zone, and (ii) even He, C, and O may have a small secondary contribution, as the difference to the Fe spectrum suggests; this small secondary component is visible in the 3He/4He ratio. The model may also explain the spectrum of CR anti-protons, the gamma-ray spectra of the Galaxy and the high energy neutrino spectrum of our Galaxy, including also red super-giant stars as sources. ISM-SNe, i.e. SN Ia and neutron-star SNe, contribute to CR protons and CR He nuclei.

Simulating neutrino echoes induced by secret neutrino interactions

New neutrino interactions beyond the Standard Model (BSM) have been of much interest in not only particle physics but also cosmology and astroparticle physics. We numerically investigate the time delay distribution of astrophysical neutrinos that interact with the cosmic neutrino background. Using the Monte Carlo method, we develop a framework that enables us to simulate the time-dependent energy spectra of high-energy neutrinos that experience even multiple scatterings en route and to handle the sharp increase in the cross section at the resonance energy. As an example, we focus on the case of secret neutrino interactions with a scalar mediator. While we find the excellent agreement between analytical and simulation results for small optical depths, our simulations enable us to study optically thick cases that are not described by the simplest analytic estimates. Our simulations are used to understand effects of cosmological redshifts, neutrino spectra and flavors. The developments will be useful for probing BSM neutrino interactions with not only current neutrino detectors such as IceCube and Super-Kamiokande but also future neutrino detectors such as IceCube-Gen2 and Hyper-Kamiokande.

Signatures of secondary acceleration in neutrino flares

High-energy neutrino flares are interesting prospective counterparts to photon flares since their detection would guarantee the presence of accelerated hadrons within a source, in addition to providing precious information about cosmic-ray acceleration and interactions, thus impacting the subsequent modeling of non-thermal emissions in explosive transients. In these sources, photomeson production can be efficient, producing a large amount of secondary particles, such as charged pions and muons, that decay and produce high-energy neutrinos. Before their decay, secondary particles can experience energy losses and acceleration, which can impact high-energy neutrino spectra and thus affect their detectability. In this work, we focus on the impact of secondary acceleration. We consider a one zone model, characterized mainly by a variability timescaletvar, luminosityLbol, and bulk Lorentz factor Γ. The mean magnetic fieldBis deduced from these parameters. The photon field is modeled by a broken power-law. This generic model allows us to systematically evaluate the maximum energy of high-energy neutrinos in the parameter space of explosive transients and shows that it could be strongly affected by secondary acceleration for a large number of source categories. In order to determine the impact of secondary acceleration on the high-energy neutrino spectrum and, in particular, on its peak energy and flux, we complement these estimates with several case studies. We show that secondary acceleration can increase the maximum neutrino flux and produce a secondary peak at the maximum energy in the case of efficient acceleration. Secondary acceleration could, therefore, enhance the detectability of very-high-energy neutrinos that would be the target of next generation neutrino detectors, such as KM3NeT, IceCube-Gen2, POEMMA, or GRAND.

Explanation of IceCube spectrum with \u03bd \u2192 3\u03bd neutrino splitting in a \u03bd2HDM model

A single power law flux spectrum of high energy neutrinos does not adequately explain the entire 60 TeV to 10 PeV event spectrum observed at IceCube, specially the excess of PeV events and the lack of Glashow resonance events expected at 6.3 PeV cannot be simultaneously explained by a single power law source neutrino flux. Here we consider a model of neutrino splitting ν → 3ν over cosmological distances. Starting from a single power-law spectrum expected from the astrophysical sources, we show that by adjusting the decay length and spectral index one can give a better fit to the observed IceCube events over the entire 1 TeV-6 PeV, compared to that from a single power spectrum. For ν → 3ν neutrino splitting, the flavor ratios of the daughter neutrinos are different from the standard oscillation or invisible decay cases and can be used as a test of this scenario. We propose a ν2HDM where a light Higgs (∼0.1 eV) mediates neutrino splitting via a one-loop box diagram. The split in the masses of the scalars in the doublet gives a large contribution to the oblique T parameter which is severely constrained. This constraint from the S,T,U oblique parameters can be evaded by the introduction of an extra vector lepton doublet and with mass ∼ 200 GeV.

Calculation of atmospheric high-energy neutrino spectra and the measurement data of IceCube and ANTARES experiments

Presented are results of calculation of the atmospheric neutrino spectra in the energy range from 100 GeV to 10 PeV using the QGSJET-II and SIBYLL 2.1 models of hadron–nuclear interactions and two experimentally based Zatsepin–Sokol’skaya and Hillas–Gaisser models of the cosmic ray spectrum. It is shown that rare decays of short-lived neutral kaons produce about one third of the flux of electron neutrinos and up to 10% of muon neutrinos at energies above 100 TeV. The calculated spectra agree satisfactorily with the IceCube and ANTARES measurement data. The measurement errors leave open the possibility of a contribution from decays of charmed particles to fluxes of muon neutrinos with energies above 500 TeV and electron neutrinos with energies above 30 TeV.

Lepton flavor violating Z′ explanation of the muon anomalous magnetic moment

We discuss a minimal solution to the long-standing $(g-2)_\mu$ anomaly in a simple extension of the Standard Model with an extra $Z'$ vector boson that has only flavor off-diagonal couplings to the second and third generation of leptons, i.e. $\mu, \tau, \nu_\mu, \nu_\tau$ and their antiparticles. A simplified model realization, as well as various collider and low-energy constraints on this model, are discussed. We find that the $(g-2)_\mu$-favored region for a $Z'$ lighter than the tau lepton is totally excluded, while a heavier $Z'$ solution is still allowed. Some testable implications of this scenario in future experiments, such as lepton-flavor universality-violating tau decays at Belle 2, and a new four-lepton signature involving same-sign di-muons and di-taus at HL-LHC and FCC-ee, are pointed out. A characteristic resonant absorption feature in the high-energy neutrino spectrum might also be observed by neutrino telescopes like IceCube and KM3NeT.

Neutrino self-interactions

We propose a theory that equips the active neutrinos with interactions among themselves that are at least 3 orders of magnitude stronger than the weak interaction. We introduce an Abelian gauge group $U(1{)}_{X}$ with vacuum expectation value ${v}_{x}\ensuremath{\lesssim}\mathcal{O}(100\text{ }\text{ }\mathrm{MeV})$. An asymmetric mass matrix implements the active neutrinos as massless mass eigenstates carrying ``effective'' charges. To stabilize ${v}_{x}$, supersymmetry breaking is mediated via loops to the additional sector with the only exception of xHiggs terms. No Standard Model interaction eigenstate carries $U(1{)}_{X}$ charge. Thus, the dark photon's kinetic mixing is two-loop suppressed. With only simple and generic values of dimensionless parameters, our theory might explain the high-energy neutrino spectrum observed by IceCube including the PeV neutrinos. We comment on the imposing opportunity to incorporate a self-interacting dark matter candidate.

Coherent propagation of PeV neutrinos and the dip in the neutrino spectrum at IceCube

The energy spectrum of high-energy neutrinos reported by the IceCube collaboration shows a dip between 400 TeV and 1 PeV. One intriguing explanation is that high-energy neutrinos scatter with the cosmic neutrino background through a $\sim$ MeV mediator. Taking the density matrix approach, we develop a formalism to study the propagation of PeV neutrinos in the presence of the new neutrino interaction. If the interaction is flavored such as the gauged $L_\mu-L_\tau$ model we consider, the resonant collision may not suppress the PeV neutrino flux completely. The new force mediator may also contribute to the number of effectively massless degrees of freedom in the early universe and change the diffusion time of neutrinos from the supernova core. Astrophysical observations such as Big Bang Nucleosynthesis and supernova cooling provide an interesting test for the explanation.

Cosmic rays, γ-rays, and neutrinos in the starburst nuclei of Arp 220

The cores of Arp 220, the closest ultra-luminous infrared starburst galaxy, provide an opportunity to study interactions of cosmic rays under extreme conditions. In this paper, we model the populations of cosmic rays produced by supernovae in the central molecular zones of both starburst nuclei. We find that ~65 - 100% of cosmic rays are absorbed in these regions due to their huge molecular gas contents, and thus, the nuclei of Arp 220 nearly complete proton calorimeters. As the cosmic ray protons collide with the interstellar medium, they produce secondary electrons that are also contained within the system and radiate synchrotron emission. Using results from chi-squared tests between the model and the observed radio spectral energy distribution, we predict the emergent gamma-ray and high-energy neutrino spectra and find the magnetic field to be at milligauss levels. Because of the extremely intense far-infrared radiation fields, the gamma-ray spectrum steepens significantly at TeV energies due to gamma-gamma absorption.

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN) jets: their baryonic and leptonic contents, and particle production efficiency. Testing two standard neutrino production models for local source Cen A (Koers & Tinyakov and Becker & Biermann), we calculate the high-energy neutrino spectra of single AGN sources and derive the flux of high-energy neutrinos expected for the current epoch. Assuming that accretion determines both X-rays and particle creation, our parametric scaling relations predict neutrino yield in various AGN classes. We derive redshift-dependent number densities of each class, from Chandra and Swift/BAT X-ray luminosity functions (Silverman et al. and Ajello et al.). We integrate the neutrino spectrum expected from the cumulative history of AGN (correcting for cosmological and source effects, e.g. jet orientation and beaming). Both emission scenarios yield neutrino fluxes well above limits set by IceCube(by ∼4–10 6 × at 1 PeV, depending on the assumed jet models for neutrino production). This implies that: (i) Cen A might not be a typical neutrino source as commonly assumed; (ii) both neutrino production models overestimate the efficiency; (iii) neutrino luminosity scales with accretion power differently among AGN classes and hence does not follow X-ray luminosity universally; (iv) some AGN are neutrino-quiet (e.g. below a power threshold for neutrino production); (v) neutrino and X-ray emission have different duty cycles (e.g. jets alternate between baryonic and leptonic flows); or (vi) some combination of the above.

Prediction of the diffuse neutrino flux from cosmic ray interactions near supernova remnants

In this paper, we present high-energy neutrino spectra from 21 Galactic supernova remnants (SNRs), derived from gamma-ray measurements in the GeV–TeV range. We find that only the strongest sources, i.e. G40.5-0.5 in the north and Vela Junior in the south could be detected as single point sources by IceCube or KM3NeT, respectively. For the first time, it is also possible to derive a diffuse signal by applying the observed correlation between gamma-ray emission and radio signal. Radio data from 234 supernova remnants listed in Green’s catalog are used to show that the total diffuse neutrino flux is approximately a factor of 2.5 higher compared to the sources that are resolved so far. We show that the signal at above 10TeV energies can actually become comparable to the diffuse neutrino flux component from interactions in the interstellar medium. Recently, the IceCube collaboration announced the detection of a first diffuse signal of astrophysical high-energy neutrinos. Directional information cannot unambiguously reveal the nature of the sources at this point due to low statistics. A number of events come from close to the Galactic center and one of the main questions is whether at least a part of the signal can be of Galactic nature. In this paper, we show that the diffuse flux from well-resolved SNRs is at least a factor of 20 below the observed flux.

Mass hierarchy determination using neutrinos from multiple reactors

We report the results of Monte Carlo simulations of a medium baseline reactor neutrino experiment. The difference in baselines resulting from the 1 km separations of Daya Bay and Ling Ao reactors reduces the amplitudes of 1-3 oscillations at low energies, decreasing the sensitivity to the neutrino mass hierarchy. A perpendicular detector location eliminates this effect. We simulate experiments under several mountains perpendicular to the Daya Bay/Ling Ao reactors, considering in particular the background from the TaiShan and YangJiang reactor complexes. In general the hierarchy can be determined most reliably underneath the 1000 meter mountain BaiYunZhang, which is 44.5 km from Daya Bay. If some planned reactors are not built then nearby 700 meter mountains at 47-51 km baselines gain a small advantage. Neglecting their low overhead burdens, hills near BaiMianShi or DongKeng would be the optimal locations. We use a weighted Fourier transform to avoid a spurious dependence on the high energy neutrino spectrum and find that a neural network can extract quantities which determine the hierarchy marginally better than the traditional RL + PV.

High energy neutrinos from dissipative photospheric models of gamma ray bursts

We calculate the high energy neutrino spectrum from gamma-raybursts where the emission arises in a dissipative jet photosphere determined byeither baryonically or magnetically dominated dynamics, and compare theseneutrino spectra to those obtained in conventional internal shock models. Wealso calculate the diffuse neutrino spectra based on these models, which appearcompatible with the current IceCube 40+59 constraints. While a re-analysisbased on the models discussed here and the data from the full array would beneeded, it appears that only those models with the most extreme parameters areclose to being constrained at present. A multi-year operation of the fullIceCube and perhaps a next generation of large volume neutrino detectors may berequired in order to distinguish between the various models discussed.

Multi-waveband photons and high energy neutrinos from the Crab nebula

We study multi-waveband photon emission properties and possible high-energy neutrino emission from the Crab nebula produced by pulsar’s accelerated heavy nuclei. Heavy nuclei are accelerated in the outer magnetosphere of the Crab pulsar, and then suffer partial photo-disintegration in the non-thermal radiation fields of the pulsar’s outer magnetosphere. The products (protons and neutrons) of the photo-disintegration and surviving heavier nuclei are injected into the expanding supernova remnant in which the surviving heavier nuclei are further accelerated in the pulsar wind zone. In such a case, relativistic hadrons and leptons are produced; the hadrons consist of direct protons and the protons produced through neutron decay in nuclei disintegration process, the leptons consist of positrons accelerated in a realistic magneto-sonic lepton-heavy iron plasma shock, electrons from the neutron decay, direct electrons, and secondary electron/positron pairs in a proton-proton interaction. We calculate the photo-disintegration rate for a nucleus of atomic number A releasing i nucleons and the hadronic and leptonic spectra in the Crab nebula. We then calculate the multi-waveband nonthermal photon spectrum and possible high-energy neutrino spectrum of the Crab nebula. Our results indicate that the photon spectrum up to ∼10 TeV has a leptonic origin, but it is difficult to distinguish leptonic and hadronic origins of the spectrum with energy greater than 10 TeV.

High-energy cosmic-ray nuclei from high- and low-luminosity gamma-ray bursts and implications for multimessenger astronomy

Gamma-ray bursts (GRBs) are one of the candidates of ultrahigh-energy ($\ensuremath{\gtrsim}{10}^{18.5}\text{ }\text{ }\mathrm{eV}$) cosmic-ray (UHECR) sources. We investigate high-energy cosmic-ray acceleration including heavy nuclei in GRBs by using Geant 4, and discuss its various implications, taking both high-luminosity (HL) and low-luminosity (LL) GRBs into account. This is because LL GRBs may also make a significant contribution to the observed UHECR flux if they form a distinct population. We show that not only protons, but also heavier nuclei can be accelerated up to ultrahigh energies in the internal, (external) reverse, and forward shock models. We also show that the condition for ultrahigh-energy heavy nuclei such as iron to survive is almost the same as that for $\ensuremath{\sim}\mathrm{TeV}$ gamma rays to escape from the source and for high-energy neutrinos not to be much produced. The multimessenger astronomy by neutrino and GeV-TeV gamma-ray telescopes such as IceCube and KM3Net, GLAST and MAGIC will be important to see whether GRBs can be accelerators of ultrahigh-energy heavy nuclei. We also demonstrate expected spectra of high-energy neutrinos and gamma rays, and discuss their detectabilities. In addition, we discuss implications of the GRB-UHECR hypothesis. We point out, since the number densities of HL GRBs and LL GRBs are quite different, its determination by UHECR observations is also important.

Detecting MeV gauge bosons with high-energy neutrino telescopes

If annihilating MeV-scale dark matter particles are responsible for the observed 511 keV emission from the Galactic bulge, then new light gauge bosons which mediate the dark matter annihilations may have other observable consequences. In particular, if such a gauge boson exists and has even very small couplings to standard model neutrinos, cosmic neutrinos with $\ensuremath{\sim}\mathrm{TeV}$ energies will scatter with the cosmic neutrino background through resonant exchange, resulting in a distinctive spectral absorption line in the high-energy neutrino spectrum. Such a feature could potentially be detected by future high-energy neutrino telescopes.

Neutrinos from the annihilation or decay of superheavy relic dark matter particles

In light of the mounting evidence that the highest energy cosmic rays are dominated by protons and not gamma-rays, we discuss the prospect that these cosmic rays are generated in the decay or annihilation of superheavy relic particles. We calculate the high energy neutrino spectrum which results and normalize our results to the ultra-high energy cosmic ray spectrum. We show that most scenerios are already constrained by present limits placed by the AMANDA experiment.

Measuring the spectra of high energy neutrinos with a kilometer-scale neutrino telescope

We investigate the potential of a future kilometer-scale neutrino telescope such as the proposed IceCube detector in the South Pole, to measure and disentangle the yet unknown components of the cosmic neutrino flux, the prompt atmospheric neutrinos coming from the decay of charmed particles and the extra-galactic neutrinos, in the 10 TeV to 1 EeV energy range. Assuming a power law type spectra, $d\phi_\nu/dE_\nu \sim \alpha E_\nu^\beta$, we quantify the discriminating power of the IceCube detector and discuss how well we can determine magnitude ($\alpha$) as well as slope ($\beta$) of these two components of the high energy neutrino spectrum, taking into account the background coming from the conventional atmospheric neutrinos.

BL Lac objects in the synchrotron proton blazar model

We calculate the spectral energy distribution (SED) of electromagnetic radiation and the spectrum of high-energy neutrinos from BL Lac objects in the context of the synchrotron proton blazar model. In this model, the high-energy hump of the SED is due to accelerated protons, while most of the low-energy hump is due to synchrotron radiation by co-accelerated electrons. To accelerate protons to sufficiently high energies to produce the high-energy hump, rather high magnetic fields are required. Assuming reasonable emission region volumes and Doppler factors, we then find that in low-frequency peaked BL Lacs (LBLs), which have higher luminosities than high-frequency peaked BL Lacs (HBLs), there is a significant contribution to the high-frequency hump of the SED from pion photoproduction and subsequent cascading, including synchrotron radiation by muons. In contrast, in HBLs we find that the high-frequency hump of the SED is dominated by proton synchrotron radiation. We are able to model the SED of typical LBLs and HBLs, and to model the famous 1997 flare of Markarian 501. We also calculate the expected neutrino output of typical BL Lac objects, and estimate the diffuse neutrino intensity due to all BL Lacs. Because pion photoproduction is inefficient in HBLs, as protons lose energy predominantly by synchrotron radiation, the contribution of LBLs dominates the diffuse neutrino intensity. We suggest that nearby LBLs may well be observable with future high-sensitivity TeV γ-ray telescopes.

Energy Spectra of High Energy Neutrinos and Cosmic Rays from Pulsars

~ 1016 e V may be generated during a few months after the birth of a pulsar, through the nuclear collisions of high energy particles generated at the pulsar with dense envelope matter. The permissible maximum flux of such neutrinos is estimated phenomenologically under a constraint that the flux of the particles ejected into the Galactic pool does not exceed the observed flux of the Galactic cosmic rays. For reason­ able choices of the parameters, the neutrino flux is too small to be detectable by the DUMAND project.