Search

Low fluxes of astrophysical neutrinos at TeV energies, and the overwhelming background of atmospheric neutrinos below that, render the current paradigm of neutrino astronomy a severely statistics-limited one. While many hints have emerged, all the evidence gathered by IceCube and ANTARES, over the course of almost a decade and a half of operation, has fallen short of providing any conclusive answer to the puzzle of the origin of high-energy cosmic rays and neutrinos. The advancement of the field is thus closely associated with not only the neutrino observatories coming online in the next few years, but also on the coordinated efforts of the EM, GW and cosmic ray communities to develop dedicated channels and infrastructure that allow for the swift and comprehensive multi-messenger follow-up of relevant events detected in any of these sectors. This paper highlights the strides that have been already taken in that direction and the fruits that they have borne, as well as the challenges that lie ahead. [ABSTRACT FROM AUTHOR]

The Cygnus region, which contains massive molecular and atomic clouds and young stars, is a promising Galactic neutrino source candidate. Cosmic-ray transport in the region can produce neutrinos and γ -rays. Recently, the Large High Altitude Air Shower Observatory (LHAASO) detected an ultrahigh-energy γ -ray bubble (Cygnus Bubble) in this region. Using publicly available track events detected by the IceCube Neutrino Observatory in 7 yr of full detector operation, we conduct searches for correlated neutrino signals from the Cygnus Bubble with neutrino emission templates based on LHAASO γ -ray observations. No significant signals were found for any employed templates. With the 7 TeV γ -ray flux template, we set a flux upper limit of 90% confidence level for the neutrino emission from the Cygnus Bubble to be 5.7 × 10−13 TeV−1 cm−2 s−1 at 5 TeV. [ABSTRACT FROM AUTHOR]

The observation of supernova neutrinos from SN1987A by Kamiokande was an epoch-making event for both neutrino astronomy and supernova physics. Basic points in the standard pictures of stellar evolution and core-collapse supernovae were verified and research on them entered new advanced stages. In this article we give an overview of the supernova neutrinos emitted from core-collapse supernova explosions as well as the significance of their observations. [ABSTRACT FROM AUTHOR]

Active galaxies, especially blazars, are among the most promising extragalactic candidates for high-energy neutrino sources. To date, ANTARES searches included these objects and used GeV–TeV γ -ray flux to select blazars. Here, a statistically complete blazar sample selected by their bright radio emission is used as the target for searches of origins of neutrinos collected by the ANTARES neutrino telescope over 13 yr of operation. The hypothesis of a neutrino–blazar directional correlation is tested by pair counting and a complementary likelihood-based approach. The resulting posttrial p -value is 3.0% (2.2 σ in the two-sided convention). Additionally, a time-dependent analysis is performed to search for temporal clustering of neutrino candidates as a means of detecting neutrino flares in blazars. None of the investigated sources alone reaches a significant flare detection level. However, the presence of 18 sources with a pretrial significance above 3 σ indicates a p = 1.4% (2.5 σ in the two-sided convention) detection of a time-variable neutrino flux. An a posteriori investigation reveals an intriguing temporal coincidence of neutrino, radio, and γ -ray flares of the J0242+1101 blazar at a p = 0.5% (2.9 σ in the two-sided convention) level. Altogether, the results presented here suggest a possible connection of neutrino candidates detected by the ANTARES telescope with radio-bright blazars. [ABSTRACT FROM AUTHOR]

The origin of high-energy cosmic rays, and their behavior in astrophysical sources, remains an open question. Recently, new ways to address this question have been made possible by the observation of a new astrophysical messenger, namely neutrinos. The IceCube telescope has detected a diffuse flux of astrophysical neutrinos in the TeV-PeV energy range, likely produced in astrophysical sources accelerating cosmic rays, and more recently it has reported on a few candidate individual neutrino sources. Future experiments will be able to improve on these measurements quantitatively, by the detection of more events, and qualitatively, by extending the measurement into the EeV energy range. In this paper, we review the main features of the neutrino emission and sources observed by IceCube, as well as the main candidate sources that could contribute to the diffuse neutrino flux. As a parallel question, we review the status of high-energy neutrinos as a probe of Beyond the Standard Model physics coupling to the neutrino sector. [ABSTRACT FROM AUTHOR]

Following the breakthrough discoveries of very-high-energy neutrinos of astrophysical origin by IceCube, a new field of research, neutrino astronomy, was established in the previous decade. Even though two extragalactic point sources of such neutrinos have been identified by now, TXS 0506+056 and NGC 1068, the origin and processes of the creation of astrophysical neutrinos are still mostly unexplored. To advance quickly in this new field, more neutrino telescopes are needed. This article describes the current status and plans for the development of the Pacific Ocean Neutrino Experiment (P-ONE), which is under construction in the Pacific Ocean near Vancouver Island. The deployment of P-ONE is expected to start in 2025, exploiting the already available deep-sea infrastructure provided by Ocean Networks Canada. P-ONE will complement the existing IceCube, Baikal-GVD, and KM3NeT neutrino telescopes not only with its large detection volume, but also by providing insight into the southern celestial hemisphere, where the central region of the Galactic Plane is located. [ABSTRACT FROM AUTHOR]

The Cherenkov Telescope Array and the KM3NeT neutrino telescopes are major upcoming facilities in the fields of γ -ray and neutrino astronomy, respectively. Possible simultaneous production of γ rays and neutrinos in astrophysical accelerators of cosmic-ray nuclei motivates a combination of their data. We assess the potential of a combined analysis of CTA and KM3NeT data to determine the contribution of hadronic emission processes in known Galactic γ -ray emitters, comparing this result to the cases of two separate analyses. In doing so, we demonstrate the capability of Gammapy, an open-source software package for the analysis of γ -ray data, to also process data from neutrino telescopes. For a selection of prototypical γ -ray sources within our Galaxy, we obtain models for primary proton and electron spectra in the hadronic and leptonic emission scenario, respectively, by fitting published γ -ray spectra. Using these models and instrument response functions for both detectors, we employ the Gammapy package to generate pseudo data sets, where we assume 200 h of CTA observations and 10 years of KM3NeT detector operation. We then apply a three-dimensional binned likelihood analysis to these data sets, separately for each instrument and jointly for both. We find that the largest benefit of the combined analysis lies in the possibility of a consistent modelling of the γ -ray and neutrino emission. Assuming a purely leptonic scenario as input, we obtain, for the most favourable source, an average expected 68% credible interval that constrains the contribution of hadronic processes to the observed γ -ray emission to below 15%. [ABSTRACT FROM AUTHOR]

The existence of high-energy astrophysical neutrinos has been unambiguously demonstrated, but their sources remain elusive. IceCube reported an association of a 290-TeV neutrino with a gamma-ray flare of TXS 0506 + 056, an active galactic nucleus with a compact radio jet pointing to us. Later, radio-bright blazars were shown to be associated with IceCube neutrino events with high statistical significance. These associations remained unconfirmed with the data of independent experiments. Here, we report on the detection of a rare neutrino event with the estimated energy of 224 ± 75 TeV from the direction of TXS 0506 + 056 by the new Baikal Gigaton Volume Detector (Baikal-GVD) in April 2021. This event is the highest energy cascade detected so far by the Baikal-GVD neutrino telescope from a direction below horizon. The result supports previous suggestions that radio blazars in general, and TXS 0506 + 056 in particular, are the sources of high-energy neutrinos, and opens up the cascade channel for the neutrino astronomy. [ABSTRACT FROM AUTHOR]

Some Seyfert galaxies are detected in high-energy gamma rays, but the mechanism and site of gamma-ray emission are unknown. Also, the origins of the cosmic high-energy neutrino and MeV gamma-ray backgrounds have been veiled in mystery since their discoveries. We propose emission from stellar-mass BHs (sBHs) embedded in disks of active galactic nuclei as their possible sources. These sBHs are predicted to launch jets due to the Blandford–Znajek mechanism, which can produce intense electromagnetic, neutrino, and cosmic-ray emissions. We investigate whether these emissions can be the sources of cosmic high-energy particles. We find that emission from internal shocks in the jets can explain gamma rays from nearby radio-quiet Seyfert galaxies including NGC 1068, if the Lorentz factor of the jets (Γj) is high. On the other hand, for moderate Γj, the emission can significantly contribute to the background gamma-ray and neutrino intensities in the ~MeV and ≲PeV bands, respectively. Furthermore, for moderate Γj with efficient amplification of the magnetic field and cosmic-ray acceleration, the neutrino emission from NGC 1068 and the ultrahigh-energy cosmic rays can be explained. These results suggest that the neutrino flux from NGC 1068 as well as the background intensities of MeV gamma rays, neutrinos, and the ultrahigh-energy cosmic rays can be explained by a unified model. Future MeV gamma-ray satellites will test our scenario for neutrino emission. [ABSTRACT FROM AUTHOR]

The cross sections for neutrino interactions with nucleons have been measured directly in accelerator experiments and through the zenith-angle and energy dependence of neutrino events at the IceCube Neutrino Observatory. Fluxes of high-energy neutrinos are produced at the Large Hadron Collider and by cosmic rays in the atmosphere. High-energy neutrinos also come from astrophysical and cosmic sources. The theory of neutrino interactions is reviewed. Current cross-section measurements and prospects for the future are discussed. The focus here is on neutrino interactions for energies larger than 1 TeV. [ABSTRACT FROM AUTHOR]

The Pierre Auger Observatory (PAO) and Telescope Array (TA) collaborations report significant differences in the observed energy spectra of ultra-high-energy cosmic rays (UHECRs) above 30 EeV. In this work we present a joint fit of TA and PAO data using the rigidity-dependent maximum energy model, including a full marginalization over all relevant parameters. We test two possible scenarios to explain these differences. One is that they are due to complex energy-dependent experimental systematics; the other is the presence of a local astrophysical source in the Northern Hemisphere, which is only visible by the TA experiment. We show that the astrophysical and systematic scenarios improve the explanation of the data equally well, compared to the scenario where both experiments observe the same UHECR flux from a cosmological source distribution and have energy-independent systematics. We test different mass compositions emitted from the local source and conclude that the data are best described by a source lying at a distance below 26 Mpc that emits cosmic rays dominated by the silicon mass group. We also discuss possible source candidates and the possible role of the putative local UHECR source in the observed TA anisotropy and in the differences in TA spectral data from different decl. bands. [ABSTRACT FROM AUTHOR]

Neutrino astronomy has opened a new window to the extreme Universe, entering into a fruitful era built upon the success of neutrino telescopes, which have already given a new step forward in this novel and growing field by the first observation of steady point-like sources already achieved by IceCube. Neutrino telescopes equipped with Silicon PhotoMultipliers (SiPMs) will significantly increase in number, because of their excellent time resolution and the angular resolution, and will be in better condition to detect more steady sources as well as the unexpected. The use of SiPMs represents a challenge to the acquisition electronics because of the fast signals as well as the high levels of dark noise produced by SiPMs. The acquisition electronics need to include a noise rejection scheme by implementing a coincidence filter between channels. This work discusses the advantages and disadvantages of using SiPMs for the next generation of neutrino telescopes, focusing on the possible developments that could help for their adoption in the near future. [ABSTRACT FROM AUTHOR]

In this work, we study the parameter space of neutrino-emitting BL Lacs under the framework of the one-zone lepto-hadronic model. We show that constraints on the model come from various aspects of observations such as the variability timescale of blazar flares, gamma ray opacity and the spectral energy distribution of electromagnetic emission, as well as the inferred neutrino emissivity of the blazar. We apply our method to two potential neutrino sources, i.e., TXS 0506+056 and PKS 0735+178, which are BL Lacs. Then, we explore and summarize the allowed range of parameters such as the bulk Lorentz factor and the blob radius under different distributions of injected protons. We find that the parameter space that is available to explain the BL Lac–neutrino association is sensitive to the proton distribution, and usually, an injected proton luminosity significantly exceeding the Eddington luminosity is required for both sources. Our results suggest that the simple lepto-hadronic one-zone model may not be a reasonable interpretation for BL Lac–neutrino associations. [ABSTRACT FROM AUTHOR]

The origin of high-energy cosmic rays, and their behavior in astrophysical sources, remains an open question. Recently, new ways to address this question have been made possible by the observation of a new astrophysical messenger, namely neutrinos. The IceCube telescope has detected a diffuse flux of astrophysical neutrinos in the TeV-PeV energy range, likely produced in astrophysical sources accelerating cosmic rays, and more recently it has reported on a few candidate individual neutrino sources. Future experiments will be able to improve on these measurements quantitatively, by the detection of more events, and qualitatively, by extending the measurement into the EeV energy range. In this paper, we review the main features of the neutrino emission and sources observed by IceCube, as well as the main candidate sources that could contribute to the diffuse neutrino flux. As a parallel question, we review the status of high-energy neutrinos as a probe of Beyond the Standard Model physics coupling to the neutrino sector.

Cosmic multimessenger backgrounds include relic diffuse components created in the early universe and contributions from individual sources. Here, we study both type Ia supernovae (SNe Ia) and core-collapse supernovae (CCSNe) contributions to the diffuse neutrino and gamma-ray backgrounds in the MeV regime referred to as DSNB and DSGB respectively. We show that the diffuse SN Ia background is 106 times lower (for ν ¯ e ) than the CCSN background making it negligible. Our predicted DSNB ν ¯ e flux at earth in the 19.3–32 MeV regime is 0.36 ν cm−2 s−1. We also find that the DSNB flux in the energy range from 11.3 to 32 MeV varies by +29% with a change in the SFRD model from Madau & Fragos which yielded a minimum predicted flux, to the extragalactic background light reconstruction model (maximum predicted flux). The diffuse SN Ia gamma-ray background and its dependence on the progenitor supernova delay time distribution are also evaluated. Furthermore, we address the origin of the CGB (Cosmic Gamma-ray Background) in the 0.1–7 MeV regime by adding contributions from sources such as SNe Ia, CCSNe, radio-quiet Active Galactic Nuclei, Flat spectrum radio quasars (FSRQs) and Neutron star—neutron star mergers. We find that our modeled background (including uncertainties) matches the observed CGB above 1.0 MeV, but is a factor ≈2 lower than the observed flux in the 0.1–1.0 MeV range, highlighting the need for future MeV missions to establish the CGB spectrum more reliably, and to possibly identify additional sources or even source classes in the underexplored MeV band. [ABSTRACT FROM AUTHOR]

In the standard picture of Galactic cosmic rays, a diffuse flux of high-energy gamma rays and neutrinos is produced from inelastic collisions of cosmic-ray nuclei with the interstellar gas. The neutrino flux is a guaranteed signal for high-energy neutrino observatories such as IceCube but has not been found yet. Experimental searches for this flux constitute an important test of the standard picture of Galactic cosmic rays. Both observation and nonobservation would allow important implications for the physics of cosmic-ray acceleration and transport. We present CRINGE, a new model of Galactic diffuse high-energy gamma rays and neutrinos, fitted to recent cosmic-ray data from AMS-02, DAMPE, IceTop, as well as KASCADE. We quantify the uncertainties for the predicted emission from the cosmic-ray model but also from the choice of source distribution, gas maps, and cross sections. We consider the possibility of a contribution from unresolved sources. Our model predictions exhibit significant deviations from older models. Our fiducial model is available at https://doi.org/10.5281/zenodo.7859442. [ABSTRACT FROM AUTHOR]

This is an editorial on low energy nuclear astrophysics and sterile neutrinos as dark matter. First, the symmetric cosmic microwave background radiation and the the symmetric evolution of the Universe are editorialized. Then, low energy astrophysics with the evolution of the Sun, supernovae, and the Galaxy's rotation are editorialized. In the final section, sterile neutrinos as dark matter is editorialized. [ABSTRACT FROM AUTHOR]

A neutrino outburst between September 2014 and March 2015 was discovered from the blazar TXS 0506+056 by an investigation of 9.5 years of IceCube data, while the blazar was in a quiescent state during the outburst with a gamma-ray flux of only about one-fifth of the neutrino flux. In this work, we give a possible interpretation of the abnormal feature by proposing that the neutrino outburst originated from the interaction between a relativistic jet and a dense gas cloud formed via the tidally disrupted envelope of a red giant being blown apart by the impact of the jet. Gamma-ray photons and electron/positron pairs produced through the hadronuclear interactions, correspondingly, will induce electromagnetic cascades and then make the cloud ionized and thermalized. The EM radiation from jet cloud–star interaction is mainly contributed by the relatively low-energy relativistic protons which propagate in the diffusion regime inside the cloud due to magnetic deflections, whereas the observed high-energy neutrinos (≳100 TeV) are produced by the relatively high-energy protons which can continue to beam owing to the weak magnetic deflections, inducing a much higher flux of neutrinos than electromagnetic radiation. The observed low-energy electromagnetic radiations during the neutrino outburst period are almost the same as that in the quiescent state of the source, so it may arise mainly as the same state as the generally quiescent. As a result, due to the intrusion of a dense cloud, the neutrino outburst can be expected, and, in the meantime, the accompanying electromagnetic radiations from hadronic processes will not cause any enhancement in the blazar's electromagnetic flux. [ABSTRACT FROM AUTHOR]

In cosmic ray physics and high-energy neutrino astronomy, muons are ubiquitous. Due to their slow energy loss and consequently large range at high energies, the correct simulation of their transport through matter is especially important for underground experiments. The dominant energy loss processes are ionization and at higher energies pair production, bremsstrahlung and inelastic interaction with nuclei. A muon energy loss process, which has hitherto been neglected in such simulations, is the diffractive scattering of virtual photons on nuclei. As the elastic channel of this process has the same final state as the bremsstrahlung process (μ + A → μ + A + γ) , an interference term arises, whose sign depends on the charge of the lepton. It is found that the contribution of this process was overestimated in earlier works and is significantly affected by shadowing. [ABSTRACT FROM AUTHOR]

In recent years, evidence has started piling up that some high-energy cosmic neutrinos can be associated with blazars in flaring states. On 2022 February 26, a new blazar-neutrino coincidence was reported: the track-like neutrino event IC220225A detected by IceCube is spatially coincident with the flat-spectrum radio quasar PKS 0215+015. Like previous associations, this source was found to be in a high optical and γ -ray state. Moreover, the source showed a bright radio outburst, which substantially increases the probability of a true physical association. We have performed six observations with the VLBA shortly after the neutrino event with a monthly cadence and are monitoring the source with the Effelsberg 100m-Telescope, and with the Australia Compact Telescope Array. Here, we present first results on the contemporary parsec-scale jet structure of PKS 0215+015 in total intensity and polarization to constrain possible physical processes leading to neutrino emission in blazars. [ABSTRACT FROM AUTHOR]

In this paper work, we study the nature of neutrino potential exchange with the Bessel function of lower order n = 0 and n = 1. To study the potential exchange author used theoretical method to develop the relation to study the nature of potential exchange. By developing the different equations, we study the exchange potential of neutrino by changing the masses of particles m(ve) ≤7ev,m(vμ) ≤ 0.27MeV, m(vr) ≤ 31eV respectively through the Bessel function. For the Bessel function (Jo) of neutrino potential exchange has greater value in the mass of m(v) ≤ 0.27MeV and Bessel function (J₁) is greater in m(vμ) ≤ 7eV andm(vr) ≤ 31eV respectively. But in equation (17) and (18), the Jo shows a minimum value of neutrino potential function with increasing the exchange distance. [ABSTRACT FROM AUTHOR]

Using idealized models of the accretion disk, we investigate the effects induced by the modified theories of gravity on the annihilation of the neutrino pair annihilation into electronâ€"positron pairs ( ν ν ÂŻ â†' e âˆ' e + ), occurring near the rotational axis. For the accretion disk, we have considered the models with temperature T = constant and T ∝ r âˆ'1. In both cases, we find that the modified theories of gravity lead to an enhancement, up to more than 1 order of magnitude with respect to general relativity, of the neutrino pair annihilation. [ABSTRACT FROM AUTHOR]

The diffuse flux of cosmic neutrinos has been measured by the IceCube Observatory from TeV to PeV energies. We show that an improved characterization of this flux at lower energies, TeV and sub-TeV, reveals important information on the nature of the astrophysical neutrino sources in a model-independent way. Most significantly, it could confirm the present indications that neutrinos originate in cosmic environments that are optically thick to GeVâ€"TeV Îł -rays. This conclusion will become inevitable if an uninterrupted or even steeper neutrino power law is observed in the TeV region. In such Îł -ray-obscured sources, the Îł -rays that inevitably accompany cosmic neutrinos will cascade down to MeVâ€"GeV energies. The requirement that the cascaded Îł -ray flux accompanying cosmic neutrinos should not exceed the observed diffuse Îł -ray background puts constraints on the peak energy and density of the radiation fields in the sources. Our calculations inspired by the existing data suggest that a fraction of the observed diffuse MeVâ€"GeV Îł -ray background may be contributed by neutrino sources with intense radiation fields that obscure the high-energy Îł -ray emission accompanying the neutrinos. [ABSTRACT FROM AUTHOR]

DUNE is a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual Phase (DP) is a 6 × 6 × 6 m 3 liquid argon time-projection-chamber (LArTPC) that recorded cosmic-muon data at the CERN Neutrino Platform in 2019–2020 as a prototype of the DUNE Far Detector. Charged particles propagating through the LArTPC produce ionization and scintillation light. The scintillation light signal in these detectors can provide the trigger for non-beam events. In addition, it adds precise timing capabilities and improves the calorimetry measurements. In ProtoDUNE-DP, scintillation and electroluminescence light produced by cosmic muons in the LArTPC is collected by photomultiplier tubes placed up to 7 m away from the ionizing track. In this paper, the ProtoDUNE-DP photon detection system performance is evaluated with a particular focus on the different wavelength shifters, such as PEN and TPB, and the use of Xe-doped LAr, considering its future use in giant LArTPCs. The scintillation light production and propagation processes are analyzed and a comparison of simulation to data is performed, improving understanding of the liquid argon properties. [ABSTRACT FROM AUTHOR]