High-energy Cosmic Neutrino Flux Research Articles

Bump hunting in the diffuse flux of high-energy cosmic neutrinos

The origin of the bulk of the high-energy astrophysical neutrinos seen by IceCube, with TeV--PeV energies, is unknown. If they are made in photohadronic, i.e., proton-photon, interactions in astrophysical sources, this may manifest as a bump-like feature in their diffuse flux, centered around a characteristic energy. We search for evidence of this feature, allowing for variety in its shape and size, in 7.5 years of High-Energy Starting Events (HESE) collected by the IceCube neutrino telescope, and make forecasts using larger data samples from upcoming neutrino telescopes. Present-day data reveals no evidence of bump-like features, which allows us to constrain candidate populations of photohadronic neutrino sources. Near-future forecasts show promising potential for stringent constraints or decisive discovery of bump-like features. Our results provide new insight into the origins of high-energy astrophysical neutrinos, complementing those from point-source searches.

Candidate Tidal Disruption Event AT2019fdr Coincident with a High-Energy Neutrino.

The origins of the high-energy cosmic neutrino flux remain largely unknown. Recently, one high-energy neutrino was associated with a tidal disruption event (TDE). Here we present AT2019fdr, an exceptionally luminous TDE candidate, coincident with another high-energy neutrino. Our observations, including a bright dust echo and soft late-time x-ray emission, further support a TDE origin of this flare. The probability of finding two such bright events by chance is just 0.034%. We evaluate several models for neutrino production and show that AT2019fdr is capable of producing the observed high-energy neutrino, reinforcing the case for TDEs as neutrino sources.

Identifying Galactic sources of high-energy neutrinos

High-energy neutrinos present the ultimate signature for a cosmic ray accelerator. Galactic sources responsible for acceleration of cosmic ray up to the knee in cosmic ray spectrum will provide a guaranteed, albeit subdominant, contribution to the high-energy cosmic neutrino flux. In this review, we discuss the the prospects for identification of high-energy neutrinos from sources of the very high energy gamma ray emission in the Milky Way. We present the status of the search for point-like and extended emission from these sources, and describe how the results of these studies indicate that neutrino telescopes are closing in on identifying Galactic sources of high-energy neutrinos.

IceCube Search for Galactic Neutrino Sources based on Very High Energy γ-ray Observations

Galactic cosmic rays reach energies of at least several PeV, and their interactions should generate γ-rays and neutrinos from decay of secondary pions. Therefore, Galactic sources have a guaranteed contribution to the total high-energy cosmic neutrino flux observed by IceCube. Assuming that the highest energy γ-rays are pionic, promising neutrino source candidates have been identified based on their spectra, and observing them is likely over the lifetime of the IceCube experiment. Here, we present the search for Galactic sources of high-energy cosmic neutrinos by focusing on sources identified by HAWC’s very high energy γ-ray survey.

Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A.

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.

Modeling the radar scatter off of high-energy neutrino-induced particle cascades in ice

We discuss the radar detection method as a probe for high-energy neutrino induced particle cascades in ice. In a previous work we showed that the radar detection techniqe is a promising method to probe the high-energy cosmic neutrino flux above PeV energies. This was done by considering a simplified cascade geometry and scattering model. In this article we discuss the scattering in more detail. We provide a model for the radar cross-section based on the induced plasma properties, and discuss the angular dependence of the scatter.

Charm contribution to the atmospheric neutrino flux

We revisit the estimate of the charm particle contribution to the atmospheric neutrino flux that is expected to dominate at high energies because long-lived high-energy pions and kaons interact in the atmosphere before decaying into neutrinos. We focus on the production of forward charm particles which carry a large fraction of the momentum of the incident proton. In the case of strange particles, such a component is familiar from the abundant production of $K^{+} \Lambda$ pairs. These forward charm particles can dominate the high-energy atmospheric neutrino flux in underground experiments. Modern collider experiments have no coverage in the very large rapidity region where charm forward pair production dominates. Using archival accelerator data as well as IceCube measurements of atmospheric electron and muon neutrino fluxes, we obtain an upper limit on forward $\bar{D}^0 \Lambda_c$ pair production and on the associated flux of high-energy atmospheric neutrinos. We conclude that the prompt flux may dominate the much-studied central component and represent a significant contribution to the TeV atmospheric neutrino flux. Importantly, it cannot accommodate the PeV flux of high-energy cosmic neutrinos, nor the excess of events observed by IceCube in the 30--200 TeV energy range indicating either structure in the flux of cosmic accelerators, or a presence of more than one component in the cosmic flux observed.

Neutrino astrophysics with the ANTARES Cherenkov Detector

The ANTARES neutrino telescope is currently the largest water Cherenkov detector in operation in the Northern Hemisphere. The detector is a lattice of 885 Optical Modules distributed over 12 lines, located 40 km off the Southern French coast at a depth of about 2500 m. Its main scientific goal is the detection of high energy cosmic neutrinos from galactic and extra galactic sources using the Cherenkov photons emitted along the pattern of neutrino-induced charged leptons. The detector has been taking data regularly since 2006 in a partial configuration and has been completed in Spring 2008. The status of the experiment is reported and a selection of the latest results is discussed. In particular, this paper presents the up to date upper limits for diffuse high-energy cosmic neutrino flux, the searches for point sources, the multi-messenger analyses and the measurement of the neutrino oscillations.

Status and recent results of the ANTARES deep-sea neutrino telescope

ANTARES is currently the largest operating neutrino telescope located in the Northern Hemisphere. The main goal of ANTARES is to detect high energy neutrinos that are expected from cosmic ray acceleration sites. The construction of ANTARES was completed in 2008. It consists of 12 lines deployed at 2475m depth offshore from Toulon. Data are continuously taken by 885 photo-multipliers that detect the Cherenkov light induced by relativistic charge particles reaching the detector. The status of the experiment will be discussed, together with the latest results including searches for a diffuse high-energy cosmic neutrino flux and for neutrinos from point-like sources.

Long-lived staus at neutrino telescopes

We perform an exhaustive study of the role neutrino telescopes could play in the discoveryand exploration of supersymmetric extensions of the Standard Model with a long-lived staunext-to-lightest superparticle. These staus are produced in pairs by cosmic neutrinointeractions in the Earth matter. We show that the background of stau events to thestandard muon signal is negligible and plays no role in the determination of thecosmic neutrino flux. On the other hand, one can expect up to 50 pair events peryear in a cubic kilometre detector such as IceCube, if the superpartner massspectrum and the high-energy cosmic neutrino flux are close to experimental bounds.

Effects of neutrino mixing on high-energy cosmic neutrino flux

Several cosmologically distant astrophysical sources may produce high-energy cosmic neutrinos $(Eg~{10}^{6}$ GeV) of all flavors above the atmospheric neutrino background. We study the effects of vacuum neutrino mixing in the three flavor framework on this cosmic neutrino flux. We also consider the effects of possible mixing between the three active neutrinos and the (fourth) sterile neutrino with or without big-bang nucleosynthesis constraints and estimate the resulting final high-energy cosmic neutrino flux ratios on Earth compatible with currently existing different neutrino oscillation hints in a model independent way. Further, we discuss the case where the intrinsic cosmic neutrino flux does not have the standard ratio.