The MAGIC telescopes, located at the Roque de los Muchachos Observatory (2200 a.s.l.) in the Canary Island of La Palma, are placed on the top of a mountain, from where a window of visibility of about 5 deg in zenith and 80 deg in azimuth is open in the direction of the surrounding ocean. This permits to search for a signature of particle showers induced by earth-skimming cosmic tau neutrinos in the PeV to EeV energy range arising from the ocean. We have studied the response of MAGIC to such events, employing Monte Carlo simulations of upward-going tau neutrino showers. The analysis of the shower images shows that air showers induced by tau neutrinos can be discriminated from the hadronic background coming from a similar direction. We have calculated the point source acceptance and the expected event rates, assuming an incoming tau neutrino flux consistent with IceCube measurements, and for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about 30 hours of data taken toward the sea leads to a point source sensitivity for tau neutrinos at the level of the down-going point source analysis of the Pierre Auger Observatory.
We report the first observational search for tau neutrinos from gamma ray bursts (GRBs) using one of the Ashra light collectors. The earth-skimming tau-neutrino technique of imaging Cherenkov tau showers was applied as a detection method. We set stringent upper limits on the tau-neutrino fluence in PeV-EeV region for 3780 s (between 2.83 and 1.78 hours before) and another 3780 s (between 21.2 and 22.2 hours after) surrounding GRB081203A triggered by the Swift satellite. This first search for PeV-EeV tau neutrino complements other experiments in energy range and methodology, and suggests the pr…
The MAGIC telescopes, located at the Roque de los Muchachos Observatory (2200 a.s.l.) in the Canary Island of La Palma, are placed on the top of a mountain, from where a window of visibility of about 5 deg in zenith and 80 deg in azimuth is open in the direction of the surrounding ocean. This permits to search for a signature of particle showers induced by earth-skimming cosmic tau neutrinos in the PeV to EeV energy range arising from the ocean. We have studied the response of MAGIC to such events, employing Monte Carlo simulations of upward-going tau neutrino showers. The analysis of the show…
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…
We describe a method of observation for PeV--EeV tau neutrinos using Cherenkov light from the air showers of decayed taus produced by tau neutrino interactions in the Earth. Aiming for the realization of neutrino astronomy utilizing the Earth-skimming tau neutrino detection technique, highly precise determination of arrival direction is key due to the following issues: (1) Clear identification of neutrinos by identifying those vertices originating within the Earth's surface; (2) Identification of very high energy neutrino sources. The Ashra detector uses newly developed light collectors which …
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located on the Canary Island of La Palma and dedicated to the study of very high energy gamma rays above 30 GeV. MAGIC has recently demonstrated its capability as a neutrino detector, by exploiting the Earth-skimming technique. The neutrino-event selection has been studied by pointing the telescopes towards the sea a few degrees below the horizon, with no pre-defined source direction. An upper limit to the $ν_τ$ flux was set. In this work, a follow-up strategy of given source directions is presented. This new approach is charact…
Since 2013 IceCube cascade showers sudden overabundance have shown a fast flavor change above 30-60 TeV up to PeV energy. This flavor change from dominant muon tracks at TeVs to shower events at higher energies, has been indebted to a new injection of a neutrino astronomy. However the recent published 54 neutrino HESE, high energy starting events, as well as the 38 external muon tracks made by trough going muon formed around the IceCube, none of them are pointing to any expected X-gamma or radio sources: no one in connection to GRB, no toward active BL Lac, neither to AGN source in Fermi catal…
Tau neutrinos are expected to comprise roughly one third of both the astrophysical and cosmogenic neutrino flux, but currently the flavor ratio is poorly constrained and the expected flux at energies above $10^{17}$ eV is low. We present a detector concept aimed at measuring the diffuse flux of tau neutrinos in this energy range via a high-elevation mountaintop detector using the radio technique. The detector searches for radio signals from upgoing air showers generated by Earth-skimming tau neutrinos. Signals from several antennas in a compact array are coherently summed at the trigger level,…
The IceCube neutrino discovery was punctuated by three showers with $E_ν$ ~ 1-2 PeV. Interest is intense in possible fluxes at higher energies, though a marked deficit of $E_ν$ ~ 6 PeV Glashow resonance events implies a spectrum that is soft and/or cutoff below ~few PeV. However, IceCube recently reported a through-going track event depositing 2.6 $\pm$ 0.3 PeV. A muon depositing so much energy can imply $E_{ν_μ} \gtrsim$ 10 PeV. We show that extending the soft $E_ν^{-2.6}$ spectral fit from TeV-PeV data is unlikely to yield such an event. Alternatively, a tau can deposit this much energy, tho…
Dark matter particles can be gravitationally trapped by celestial bodies, motivating searches for localized annihilation or decay. If neutrinos are among the decay products, then IceCube and other neutrino observatories could detect them. We investigate this scenario for dark matter particles above $m_χ \gtrsim$ PeV producing tau neutrino signals, using updated modeling of dark matter capture and thermalization. At these energies, tau neutrino regeneration is an important effect during propagation through Earth, allowing detection at distances far longer than one interaction length. We show ho…
IceCube collaboration has seen an unexpected population of high energy neutrinos compatible with an astrophysical origin. We consider two categories of events that can help to diagnose cosmic neutrinos: double pulse, that may allow us to clearly discriminate the cosmic component of tau neutrinos; cascades with deposited energy above 2 PeV, including events produced by electron antineutrinos at the Glashow resonance, that can be used to investigate the neutrino production mechanisms. We show that one half of the double pulse signal is due to the neutrinos spectral region already probed by IceCu…
We interpret the PeV shower events observed by the IceCube collaboration as an s-channel enhancement of neutrino-quark scattering by a leptoquark that couples to the tau-flavor and light quarks. With a leptoquark mass of ~ 0.6 TeV and a steep 1/E^{2.3} neutrino flux, charged-current scattering gives shower events at ~ 1 PeV and neutral-current scattering gives shower events at ~ 0.5 PeV. This mechanism is also consistent with the paucity of muon-track events above 100 TeV.
High-energy astrophysical neutrinos, recently discovered by IceCube up to energies of several PeV, opened a new window to the high-energy Universe. Yet much remains to be known. IceCube has excellent muon flavor identification, but tau flavor identification is challenging. This limits its ability to probe neutrino physics and astrophysics. To address this limitation, we present a concept for a large-scale observatory of astrophysical tau neutrinos in the 1-100 PeV range, where a flux is guaranteed to exist. Its detection would allow us to characterize the neutrino sources observed by IceCube, …
Multi-messenger observations of transient astrophysical sources have the potential to characterize the highest energy accelerators and the most extreme environments in the Universe. Detection of neutrinos, in particular tau neutrinos generated by neutrino oscillations in transit from their sources to Earth, is possible for neutrino energies above 10 PeV using optical Cherenkov detectors imaging upward-moving extensive air showers (EAS). These EAS are produced from Earth interacting tau neutrinos leading to tau leptons that subsequently decay in the atmosphere. We compare neutrino detection sen…
Tau neutrinos with energies in the PeV-EeV range produce up-going extensive air showers (UEAS) if they interact underground close enough to the surface of the Earth. This work studies detectability of the UEAS with a system of fluorescence telescopes overlooking dark, low reflectivity, area on the ground up to the distances 20-30 km from mountain top(s). Such system could provide sensitivity sufficient for accumulation of the astrophysical neutrino signal statistics at the rate ten(s) events per year in the energy range beyond 10 PeV, thus allowing to extend the energy frontier of neutrino ast…
MAGIC is an instrument composed of a pair of telescopes for gamma- ray and cosmic-ray astrophysics in the TeV range. It is operating for more than a decade now, and is one of the current best performing instruments in this field, specifically at low energies, where it achieves the largest sensitivity. MAGIC pursues a strong program in galactic and extragalactic gamma-ray science. Its catalog of blazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae, pulsar wind nebulae, pulsars and binary systems has now increased to several tens of detected targets. In addition, …
We propose an interpretation of the two neutrino initiated cascade events with PeV energies observed by IceCube: Ultra-high energy cosmic ray protons (or Fe nuclei) scatter on CMB photons through the Delta-resonance (the Berezinsky-Zatsepin process) yielding charged pions and neutrons. The neutron decays give electron-antineutrinos which undergo neutrino oscillations to populate all antineutrino flavors, but the electron-antineutrino flux remains dominant. At 6.3 PeV electron-antineutrino energy their annihilation on electrons in the IceCube detector is enhanced by the Glashow resonance (the W…
Cosmic neutrinos above a PeV are produced either within astrophysical sources or when ultra-high energy cosmic rays interact in transit through the cosmic background radiation. Detection of these neutrinos will be essential for understanding cosmic ray acceleration, composition and source evolution. By using the Earth as a tau neutrino converter for upward-going extensive air showers from tau decays, balloon-borne and space-based instruments can take advantage of a large volume and mass of the terrestrial neutrino target. The theoretical inputs and uncertainties in determining the tau lepton e…
We discuss a simple non-supersymmetric model based on the electroweak gauge group $SU(2)_L\times SU(2)^\prime\times U(1)_{B-L}$ where the lightest of the right-handed neutrinos, which are part of the leptonic doublet of $SU(2)^\prime$, play the role of a long-lived unstable dark matter with mass in the multi-PeV range. We use a resonant $s$-channel annihilation to obtain the correct thermal relic density and relax the unitarity bound on dark matter mass. In this model, there exists a 3-body dark matter decay mode producing tau leptons and neutrinos, which could be the source for the PeV cascad…
Earth-skimming neutrinos are those which travel through the Earth's crust at a shallow angle. For Ultra-High-Energy (E > 1 PeV; UHE) earth-skimming tau neutrinos, there is a high-probability that the tau lepton created by a neutrino-Earth interaction will emerge from the ground before it decays. When this happens, the decaying tau particle initiates an air shower of relativistic sub-atomic particles which emit Cherenkov radiation. To observe this Cherenkov radiation, we propose the Trinity Observatory. Using a novel optical structure design, pointing at the horizon, Trinity will observe the Ch…
A search for tau neutrino induced showers with the MAGIC telescopes is presented. The MAGIC telescopes located at an altitude of 2200 m a.s.l. in the Canary Island of La Palma, can point towards the horizon or a few degrees below across an azimuthal range of about 80 degrees. This provides a possibility to search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In this paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking…
Cherenkov telescopes could have the capability of detecting high energy tau neutrinos by searching for very inclined showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth crust, it will decay and initiate an air shower which can be detected by a fluorescence/Cherenkov telescope. Here we present a detailed Monte Carlo simulation of event rates induced by tau neutrinos in the energy range from 1 PeV to 1 EeV. Topographic conditions are taken into account for a set of example locations. As expected, we find a neutrino sensitivity which depends on the shape of the energy spe…
The detection of the radio emission following a neutrino interaction in ice is a promising technique to obtain significant sensitivities to neutrinos with energies above PeV. The detectable radio emission stems from particle showers in the ice. So far, detector simulations have considered only the radio emission from the primary interaction of the neutrino. For this study, existing simulation tools have been extended to cover secondary interactions from muons and taus. We find that secondary interactions of both leptons add up to 25\% to the effective volume of neutrino detectors. Also, muon a…
Earliest 2007 UHECR anisotropy findings and ICRC AUGER updated maps and clustering confirms our understanding of CenA as the main nearby UHECR source. Those events are mostly lightest nuclei, as He. The events are spread by galactic fields. We argue that the main UHECR event bending, along CenA, is spreading vertically (respect to horizontal spiral galactic fields) by random (and a final coherent) Lorentz force. The He-nuclei dominance is also well probed by detailed AUGER composition data. The Lightest nuclei are still compatible with most recent Hires composition results. Such lightest UHECR…
The Sun albedo of cosmic rays at GeVs energy has been discovered recently by FERMI satellite. They are traces of atmospheric CR hitting solar atmosphere and reflecting skimming gamma photons. Even if relevant for astrophysics, as being trace of atmospheric solar Cosmic Ray noises they cannot offer any signal of neutrino astronomy. On the contrary the Moon, with no atmosphere, may become soon a novel filtering calorimeter and an amplifier of energetic muon astronomical neutrinos (at TeV up to hundred TeV energy); these lepton tracks leave an imprint in their beta decay while in flight to Earth.…
We perform a new, detailed calculation of the flux and energy spectrum of Earth-emerging $τ$-leptons generated from the interactions of tau neutrinos and antineutrinos in the Earth. A layered model of the Earth is used to describe the variable density profile of the Earth. Different assumptions regarding the neutrino charged- and neutral-current cross sections as well as the $τ$-lepton energy loss models are used to quantify the systematic uncertainty from these on the results. A baseline simulation is then used to generate the optical Cherenkov signal from upward-moving extensive air showers …
We present a novel analysis method for the determination of the neutrino-nucleon Deep Inelastic Scattering (DIS) cross section in the TeV - PeV energy range utilizing neutrino absorption by the Earth. We analyze five years of data collected with the complete IceCube detector from May 2011 to May 2016. This analysis focuses on electromagnetic and hadronic showers (cascades) mainly induced by electron and tau neutrinos. The applied event selection features high background rejection (< 10% background contamination below 60 TeV, background free above 60 TeV) of atmospheric muons and high signal ef…
The Glashow resonant scattering, $i.e$. ${\overlineν^{}_{e} + e^{-} \rightarrow W^{-} \rightarrow \text{anything}}$, offers us a possibility of disentangling $\overlineν^{}_{e}$ from the total astrophysical neutrino fluxes. Meanwhile, a great number of high-energy neutrino telescopes, with various detection mechanisms, are advancing towards a better understanding of one of the most energetic frontiers of the Universe. In this work, we investigate a connection between through-going muons at IceCube and the Glashow resonance signal through the channel $W^{-} \rightarrow μ$. We find that for IceC…
High-energy (TeV-PeV) cosmic neutrinos are expected to be produced in extremely energetic astrophysical sources such as active galactic nuclei. The IceCube Neutrino Observatory at the South Pole has recently detected a diffuse astrophysical neutrino flux. While the flux is consistent with all flavors of neutrinos being present, identification of tau neutrinos within the flux is yet to occur. Although tau neutrino production is thought to be low at the source, an equal fraction of neutrinos are expected at Earth due to averaged neutrino oscillations over astronomical distances. Above a few hund…
UHECR may be either nucleons or nuclei; in the latter case the Lightest Nuclei, as He, Li, Be, explains at best the absence of Virgo signals and the crowding of events around Cen-A bent by galactic magnetic fields. This model fit the observed nuclear mass composition discovered in AUGER. However UHECR nucleons above GZK produce EeV neutrinos while Heavy Nuclei, as Fe UHECR do not produce much. UHECR He nuclei at few tens EeV suffer nuclear fragmentation (producing low energetic neutrino at tens PeVs) but it suffer anyway photo-pion GZK suppression (leading to EeV neutrinos) once above one-few …
The announcement by the IceCube Collaboration of the observation of 53 astrophysical neutrino candidates in the energy range 0.03 \alt E_ν/PeV \alt 2 has been greeted with a great deal of justified excitement. Herein we provide fits of single and a broken power-law energy-spectra to these high-energy starting events (HESEs). By comparing our statistical results from fits to (background-free) shower HESE data with the spectral shape of muon neutrinos recently reported by the IceCube Collaboration, we show that there is (3 σ) evidence for a break in the spectrum of astrophysical neutrinos. After…
Cherenkov telescopes have the capability of detecting high energy tau neutrinos in the energy range of 1--1000 PeV by searching for very inclined showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth or a mountain, it will decay and initiate a shower in the air which can be detected by an air shower fluorescence or Cherenkov telescope. In this paper, we present detailed Monte Carlo simulations of corresponding event rates for the VERITAS and two proposed Cherenkov Telescope Array sites: Meteor Crater and Yavapai Ranch, which use representative AGN neutrino flux models an…
Generation of TeV Photons by PeV Neutrinos in Dense Astrophysical Environments
The Hong Kong University of Science and Technology（香港科技大学）；Jockey Club Institute for Advanced Study, The Hong Kong University of Science and Technology（香港科技大学聚龙高等研究院）；School of Physics, Peking University（北京大学物理学院）；Center for Gravitational Wave Experiment, National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所微重力国家实验室引力波实验中心）；Department of Physics, Chongqing University（重庆大学物理学院）；School of Physics, Zhengzhou University（郑州大学物理学院）
The IceCube Neutrino Observatory has observed a diffuse flux of TeV-PeV astrophysical neutrinos at 5.7σ significance from an all-flavor search. The direct detection of tau neutrinos in this flux has yet to occur. Tau neutrinos become distinguishable from other flavors in IceCube at energies above a few hundred TeV, when the cascade from the tau neutrino charged current interaction becomes resolvable from the cascade from the tau lepton decay. This paper presents results from a dedicated search for tau neutrinos with energies between 214 TeV and 72 PeV. The analysis searches for IceCube optical…
We present a detailed modeling and computation methodology to determine the optical Cherenkov signals produced by upward-moving extensive air showers (EASs) induced by $τ$-leptons and muons, sourced from the interaction of high-energy astrophysical neutrinos interacting in the Earth. Following and extending the physics modeling and Cherenkov signal simulations performed in arxiv:1902.11287, this scheme encompasses a new, state-of-the-art computation of the muon neutrino propagation inside the Earth and the contribution to the $τ$-lepton muon decay channel. The modeling takes into account all p…
Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau neutrinos that carry a significant fraction of the primary neutrino energy. This effect, known as tau neutrino regeneration, has not been applied to its full potential in current generation neutrino experiments. In this work, we present an updated calculation of tau neutrino regeneration, and explore its implications for two scenarios: the recent anomalous ANITA events and the cosmogenic neutrino flux. Fo…
POLARIS: A Sparse Radial Neutrino Telescope Design for the Pacific Ocean
Institute of Physics, Academia Sinica（中央研究院物理研究所）；New York University（纽约大学）；National Central University（国立中央大学）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）
Long-term study of the gamma-ray emission of Cygnus X-3 with MAGIC and Fermi-LAT
Tokai University（东海大学）；Kyoto University（京都大学）；ETH Zürich（苏黎世联邦理工学院）；Università di Siena（锡耶纳大学）；INFN Pisa（意大利国家核物理研究所比萨分部）；Institut de Física d’Altes Energies (IFAE)（高能物理研究所）；The Barcelona Institute of Science and Technology (BIST)（巴塞罗那科学技术研究所）；Universitat de Barcelona（巴塞罗那大学）；Instituto de Astrofísica de Andalucía-CSIC（安达卢西亚天体物理学研究所-西班牙高等科学研究委员会）；Università di Padova（帕多瓦大学）；INFN（意大利国家核物理研究所）；National Institute for Astrophysics (INAF)（国家天体物理研究所）；Università di Udine（乌迪内大学）；INFN Trieste（意大利国家核物理研究所的里雅斯特分部）；International Center for Relativistic Astrophysics (ICRA)（相对论天体物理学国际中心）；Max-Planck-Institut für Physik（马克斯·普朗克物理研究所）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；Universidad de La Laguna（拉古纳大学）；University of Zagreb Faculty of Electrical Engineering（萨格勒布大学电气工程学院）
Despite not have been yet identified by the IceCube detector, events generated from $ν_τ$ deep inelastic neutrino scattering in ice with varied topologies, such as double cascades (often called \textit{double bangs}), \textit{lollipops} and \textit{sugardaddies}, constitute a potential laboratory for low-x parton studies. Here we investigate these events, analyzing the effect of next-to-next-to-leading order (NNLO) Parton Distribution Function (PDFs) in the total neutrino--nucleon cross section, as compared with the color dipole formalism, where saturation effects play a major role. Energy dep…
Cosmic-ray accelerators capable of reaching ultra-high energies are expected to also produce very-high energy neutrinos via hadronic interactions within the source or its surrounding environment. Many of the candidate astrophysical source classes are either transient in nature or exhibit flaring activity. Using the Earth as a neutrino converter, suborbital and space-based optical Cherenkov detectors, such as POEMMA and EUSO-SPB2, will be able to detect upward-moving extensive air showers induced by decaying tau-leptons generated from cosmic tau neutrinos with energies $\sim 10$ PeV and above. …
The study of the distintive signatures of the ultra high energy events recently seen by IceCube can allow to single the neutrino origin out. The detection of tau neutrinos would be a clear way to prove that they come from cosmic distances, but at the highest energies currently seen, about 1 PeV, an experimental characterization of tau events is difficult. The study of the fraction of the muon tracks seems more promising. In fact, for any initial composition, because of the occurrence of flavor oscillations and despite their uncertainties, the fraction of muon tracks in the cosmic neutrinos is …
The detection of very-high-energy (VHE) neutrinos ($E_ν\gtrsim 10$ PeV) is a challenge that future generations of experiments are being designed and constructed to address. One promising method relies on using the Earth as a neutrino target for indirect detection of skimming tau neutrinos interacting within the Earth and producing tau leptons that are able to escape and decay in the atmosphere. The tau decay produces upward-moving Extensive Air Showers (EASs). A space-based or suborbital instrument observing the ground near the Earth limb can search for the beamed Cherenkov signal produced by …
We explain the two upgoing ultra-high energy shower events observed by ANITA as arising from the decay in the Earth's interior of the quasi-stable dark matter candidate in the CPT symmetric universe. The dark matter particle is a 480 PeV right-handed neutrino that decays into a Higgs boson and a light Majorana neutrino. The latter interacts in the Earth's crust to produce a tau lepton that in turn initiates an atmospheric upgoing shower. The fact that both events emerge at the same angle from the Antarctic ice-cap suggests an atypical dark matter density distribution in the Earth.
Probing Neutrino Flavor Composition with the Glashow Resonance at Tau Air-Shower Neutrino Telescopes
University of Nevada Las Vegas（内华达大学拉斯维加斯分校）；Nevada Center for Astrophysics (NCfA), University of Nevada Las Vegas（内华达天体物理学中心，内华达大学拉斯维加斯分校）；Simon Fraser University（西蒙菲莎大学）；Arthur B. McDonald Canadian Astroparticle Physics Research Institute（亚瑟·B·麦克唐纳加拿大粒子物理研究所）
