Ultra-high Energy Neutrinos Research Articles

Performance and science reach of the Probe of Extreme Multimessenger Astrophysics for ultrahigh-energy particles

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a potential NASA Astrophysics Probe-class mission designed to observe ultra-high energy cosmic rays (UHECRs) and cosmic neutrinos from space. POEMMA will monitor colossal volumes of the Earth's atmosphere to detect extensive air showers (EASs) produced by extremely energetic cosmic messengers: UHECRs above 20 EeV over the full sky and cosmic neutrinos above 20 PeV. We focus most of this study on the impact of POEMMA for UHECR science by simulating the detector response and mission performance for EAS from UHECRs. We show that POEMMA will provide a significant increase in the statistics of observed UHECRs at the highest energies over the entire sky. POEMMA will be the first UHECR fluorescence detector deployed in space that will provide high-quality stereoscopic observations of the longitudinal development of air showers. Therefore, it will be able to provide event-by-event estimates of the calorimetric energy and nuclear mass of UHECRs. The particle physics in the interactions limits the interpretation of the shower maximum on an event by event basis. In contrast, the calorimetric energy measurement is significantly less sensitive to the different possible final states in the early interactions. We study the prospects to discover the origin and nature of UHECRs using expectations for measurements of the energy spectrum, the distribution of arrival direction, and the atmospheric column depth at which the EAS longitudinal development reaches maximum. We also explore supplementary science capabilities of POEMMA through its sensitivity to particle interactions at extreme energies and its ability to detect ultra-high energy neutrinos and photons produced by top-down models including cosmic strings and super-heavy dark matter particle decay in the halo of the Milky Way.

Ultrahigh-energy cosmic-ray nuclei and neutrinos from engine-driven supernovae

Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahigh-energy cosmic rays (UHECRs). We investigate acceleration and survival of UHECR nuclei in the external reverse shock scenario. With composition models used in Zhang et al. (2018), we calculate spectra of escaping cosmic rays and secondary neutrinos. If their local rate is $\sim1$% of the core-collapse supernova rate, the observed UHECR spectrum and composition can be explained with the total cosmic-ray energy ${\mathcal E}_{\rm cr}\sim10^{51}$ erg. The maximum energy of UHECR nuclei can reach $\sim 10^{20}-{10}^{21}\rm~eV$. The diffuse flux of source neutrinos is predicted to be $\sim 10^{-11} - 10^{-10}~{\rm GeV}~{\rm cm}^{-2}~{\rm s}^{-1}~{\rm sr}^{-1}$ in the 0.1-1 EeV range, satisfying nucleus-survival bounds. The associated cosmogenic neutrino flux is calculated, and shown to be comparable or even higher than the source neutrino flux. These ultrahigh-energy neutrinos can be detected by ultimate detectors such as the Giant Radio Askaryan Neutrino Detector and Probe Of Extreme Multi-Messenger Astrophysics.

Neutrino vertex reconstruction with in-ice radio detectors using surface reflections and implications for the neutrino energy resolution

Ultra high energy neutrinos (Eν > 1016.5eV) are efficiently measured via radio signals following a neutrino interaction in ice. An antenna placed1\U0001d4aa(15 m) below the ice surface will measure two signals for the vast majority of events (90% at Eν=1018 eV): a direct pulse and a second delayed pulse from a reflection off the ice surface. This allows for a unique identification of neutrinos against backgrounds arriving from above. Furthermore, the time delay between the direct and reflected signal (D'n'R) correlates with the distance to the neutrino interaction vertex, a crucial quantity to determine the neutrino energy. In a simulation study, we derive the relation between time delay and distance and study the corresponding experimental uncertainties in estimating neutrino energies. We find that the resulting contribution to the energy resolution is well below the natural limit set by the unknown inelasticity in the initial neutrino interaction. We present an in-situ measurement that proves the experimental feasibility of this technique. Continuous monitoring of the local snow accumulation in the vicinity of the transmit and receive antennas using this technique provide a precision of \U0001d4aa(1 mm) in surface elevation, which is much better than that needed to apply the D'n'R technique to neutrinos.

Ultra-high energy neutrino searches and GW follow-up with the Pierre Auger Observatory

The surface detector array (SD) of the Pierre Auger Observatory is sensitive to neutrinos at energies in the 100 PeV to 100 EeV range. This sensitivity, together with its large acceptance, makes it a complementary detector to other neutrino telescopes, which have their peak sensitivities at lower energies. The neutrino-induced air showers that the SD of the Pierre Auger Observatory is sensitive to can be divided into those induced by interactions of neutrinos of any flavor deep in the atmosphere, and those induced by charged-current interactions of tau neutrinos in the Earth's crust. Both of these types can be efficiently distinguished from cosmic ray-induced air showers, provided that their zenith angles are larger than 60∘. As no neutrino candidates were found in the performed searches, we present limits on the diffuse all-flavor neutrino flux. Using these limits, we obtained constraints on cosmic-ray and neutrino production models. In the light of the recent observations of gravitational waves (GW), we also present the follow-up of LIGO/Virgo GW events. These include binary black hole merger events and also GW170817, the only binary neutron star merger ever observed directly.

Superheavy dark matter and ANITA’s anomalous events

The ANITA experiment, which is designed to detect ultra-high energy neutrinos, has reported the observation of two anomalous events, directed at angles of $27^{\circ}$ and $35^{\circ}$ with respect to the horizontal. At these angles, the Earth is expected to efficiently absorb ultra-high energy neutrinos, making the origin of these events unclear and motivating explanations involving physics beyond the Standard Model. In this study, we consider the possibility that ANITA's anomalous events are the result of Askaryan emission produced by exotic weakly interacting particles scattering elastically with nuclei in the Antarctic ice sheet. Such particles could be produced by superheavy ($\sim 10^{10}-10^{13}$ GeV) dark matter particles decaying in the halo of the Milky Way. Such scenarios can be constrained by existing measurements of the high-latitude gamma-ray background and the ultra-high energy cosmic ray spectrum, along with searches for ultra-high energy neutrinos by IceCube and other neutrino telescopes.

The Giant Radio Array for Neutrino Detection (GRAND): Science and design

The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 108 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km2. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.

The simulation of the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to Askaryan radiation from cosmogenic neutrinos interacting in the Antarctic Ice

A Monte Carlo simulation program for the radio detection of Ultra High Energy (UHE) neutrino interactions in the Antarctic ice as viewed by the Antarctic Impulsive Transient Antenna (ANITA) is described in this article. The program, icemc, provides an input spectrum of UHE neutrinos, the parametrization of the Askaryan radiation generated by their interaction in the ice, and the propagation of the radiation through ice and air to a simulated model of the third and fourth ANITA flights. This paper provides an overview of the icemc simulation, descriptions of the physics models used and of the ANITA electronics processing chain, data/simulation comparisons to validate the predicted performance, and a summary of the impact of published results.

Collision of ultra-relativistic proton with strong magnetic field: Production of ultra-high energy photons and neutrinos

Proton-proton interaction and photo-hadronic interaction in cosmic accelerators are the two main channels for the production of cosmic ultra-high energy photons and neutrinos (TeV-PeV). In this Letter, we use FWW approach to obtain the production of cosmic ultra-high energy photons and neutrinos from the collision between UHE proton with magnetic field which could be considered as the virtual photon in the rest frame of UHE proton. We name this as pB process. The threshold for the occurrence of the pB process is that the combination of the Lorentz factor of proton and the strength of the magnetic field is about γpB≃5×1018 Gauss. Beyond this threshold, the rate of energy loss of proton due to the pB process is about three orders higher than that due to the synchrotron radiation of proton in the same magnetic field. The pB process might potentially happen in the atmosphere of white dwarfs, neutron stars or even that of stellar massive black holes.

Targeting ultra-high energy neutrinos with the ARIANNA experiment

The measurement of ultra-high energy (UHE) neutrinos (E > 1016 eV) opens a new field of astronomy with the potential to reveal the sources of ultra-high energy cosmic rays especially if combined with observations in the electromagnetic spectrum and gravitational waves. The ARIANNA pilot detector explores the detection of UHE neutrinos with a surface array of independent radio detector stations in Antarctica which allows for a cost-effective instrumentation of large volumes. Twelve stations are currently operating successfully at the Moore’s Bay site (Ross Ice Shelf) in Antarctica and at the South Pole. We will review the current state of ARIANNA and its main results. We report on a newly developed wind generator that successfully operates in the harsh Antarctic conditions and powers the station for a substantial time during the dark winter months. The robust ARIANNA surface architecture, combined with environmentally friendly solar and wind power generators, can be installed at any deep ice location on the planet and operated autonomously. We report on the detector capabilities to determine the neutrino direction by reconstructing the signal arrival direction of a 800 m deep calibration pulser, and the reconstruction of the signal polarization using the more abundant cosmic-ray air showers. Finally, we describe a large-scale design – ARIA – that capitalizes on the successful experience of the ARIANNA operation and is designed sensitive enough to discover the first UHE neutrino.

Consistent Lorentz violation features from near-TeV IceCube neutrinos

A recent proposal to associate 60~TeV to 2~PeV IceCube neutrino events with gamma-ray bursts~(GRBs) indicates the Lorentz violation of cosmic neutrinos and leads further to the $CPT$ symmetry violation between neutrinos and antineutrinos. Here we find that another 12 northern hemisphere track events possibly correlated with GRBs from three-year IceCube data satisfy the same regularity at a lower energy scale around 1~TeV. The combined fitting indicates a Lorentz violation scale ${E}_{\rm LV}=(6.4\pm 1.5)\times10^{17}~{ \rm GeV}$ and an intrinsic time difference ${\Delta {t}_{\rm in}=(-2.8\pm 0.7)\times10^2~{\rm s}}$, from which we find an earlier emission of neutrinos than photons at the GRB source. We also suggest analyzing neutrino events detected a few minutes before the GRB trigger time to test the $CPT$ violation of ultrahigh-energy neutrinos.

Cosmogenic neutrinos through the GRAND lens unveil the nature of cosmic accelerators

The sources of cosmic rays with energies above 55 EeV are still mysterious. A guaranteed associated flux of ultra high energy neutrinos known as the cosmogenic neutrino flux will be measured by next generation radio facilities, such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using the orthogonal information provided by the cosmogenic neutrino flux, we here determine the prospects of GRAND to constrain the source redshift evolution and the chemical composition of the cosmic ray sources. If the redshift evolution is known, independently on GRAND's energy resolution, GRAND with 200,000 antennas will constrain the proton/iron fraction to the ∼5–10% level after one year of data taking; on the other hand, if hints on the average source composition are given, GRAND will measure the redshift evolution of the sources to a ∼ 10% uncertainty. However, the foreseen configuration of GRAND alone will not be able to break the degeneracy between redshift evolution of the sources and their composition. Our findings underline the discriminating potential of next generation radio array detectors and motivate further efforts in this direction.

Ultrahigh energy cosmic rays and neutrinos from light nuclei composition

The baryonic mass composition of ultrahigh energy ($\gtrsim 10^{18}$ eV) cosmic rays (UHECRs) at injection accompanied by their interactions on universal photon backgrounds during propagation directly governs the UHECR flux on the Earth. Secondary neutrinos and photons produced in these interactions serve as crucial astrophysical messengers of UHECR sources. A modeling of the latest data obtained by the Pierre Auger Observatory (PAO) suggests a mixed element composition of UHECRs with the sub-ankle spectrum being explained by a different class of sources than the super-ankle region ($> 10^{18.7}$ eV). In this work, we obtain two kinds of fit to the UHECR spectrum -- one with a single population of sources comprising of $^1$H and $^2$He, over an energy range commencing at $\approx 10^{18}$ eV -- another for a mixed composition of representative nuclei $^1$H, $^4$He, $^{14}$N and $^{28}$Si at injection, for which a fit is obtained from above $\approx 10^{18.7}$ eV. In both cases, we consider the source emissivity evolution to be a simple power-law in redshift. We test the credibility of H+He composition by varying the source properties over a wide range of values and compare the results to that obtained for H+He+N+Si composition, using the Monte Carlo simulation tool CRPropa 3. The secondary electrons and photons are propagated using the cosmic ray transport code DINT. We place limits on the source spectral index, source evolution index and cutoff rigidity of the source population in each case by fitting the UHECR spectrum. Cosmogenic neutrino fluxes can further constrain the abundance fraction and maximum source redshift in case of light nuclei injection model.

Direct Detection of Ultrahigh-energy WIMPs with a Satellite Detector Like JEM-EUSO

Abstract The possibility of directly detecting ultrahigh-energy (UHE) weakly interacting massive particles (WIMPs) are considered by the WIMPs’ interaction with the nuclei in the air. Because neutrinos dominate the events from the spherical crown near the Extreme Universe Space Observatory on board the Japanese Experiment Module (JEM-EUSO), all the events from this region are ignored in my work. Then the numbers of UHE WIMPs and neutrinos detected by JEM-EUSO are evaluated at different energies (1 PeV < E < 100 EeV) in 10 years, respectively. If the energy thresholds are taken to be 20 EeV, neutrino events can be almost rejected in the detection of UHE WIMPs. According to my evaluation, O(10–100) UHE WIMP events can be detected by JEM-EUSO at energies above 70 EeV in 10 years.

Studies of an air-shower imaging system for the detection of ultrahigh-energy neutrinos

We discuss the acceptance and sensitivity of a small air-shower imaging system to detect earth-skimming ultrahigh-energy tau neutrinos. The instrument we study is located on top of a mountain and has an azimuthal field of view of $360^\circ$. We find that the acceptance and sensitivity of such a system is close to maximal if it is located about 2 km above ground, has a vertical field of view of $5^\circ$, allows the reconstruction of an at least $0.3^\circ$ long air-shower image, and features an effective light-collection area of $10$ m$^2$ in any direction. After three years of operation, an imaging system with these features achieves an all-flavor neutrino flux sensitivity of $5\times10^{-9}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ at $2\times10^8$ GeV.

Multi-Messenger Physics With the Pierre Auger Observatory

An overview about the multi-messenger capabilities of the Pierre Auger Observatory is presented. The techniques and performance of searching for Ultra-High Energy neutrinos, photons and neutrons are described. Some of the most relevant results are reviewed, such as stringent upper bounds that were placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on neutrinos emitted from compact binary mergers that were detected by LIGO and Virgo during their first and second observing runs, as well as searches for high energy photons and neutrons from the galactic center that constrain the properties of the putative galactic PeVatron, observed by the H.E.S.S. collaboration. The observation of directional correlations between ultra-high energy cosmic rays and either high energy astrophysical neutrinos or specific source populations weighted by their electromagnetic radiation are also discussed. They constitute additional multi-messenger approaches aimed at identifying the sources of high energy cosmic rays.

Detection of Ultra-High Energy neutrinos skimming the Earth due to decay of superheavy dark matter at JEM-EUSO

The possibility of detecting Ultra-high energy (UHE from now on) neutrinos due to superheavy dark matter are considered by the neutrinos interaction with the nuclei in the air in the present paper. To reject other standard model particles, UHE neutrinos, from superheavy dark matter and astrophysical sources, skimming the Earth are detected at JEM-EUSO. Then the numbers of UHE neutrinos detected by JEM-EUSO are evaluated at different energies (1 EeV < E < 1 ZeV) in 5 years. If the energy thresholds are taken to be 100 EeV, the astrophysical neutrino contamination could be negligible in this detection. It is possible that UHE neutrinos from the decay of superheavy dark matter are detected at JEM-EUSO when $O(10^{27})s < \tau_{\phi}< O(10^{31})s$. For example, O($10^4$) UHE neutrino events could be detected by JEM-EUSO at 30 EeV in 5 years when $\tau_{\phi}=O(10^{27})$s. If so, it may be confirmed that there may exist superheavy dark matter in the Universe.

Phenomenological implications of the Friedberg-Lee transformation in a neutrino mass model with \u03bc\u03c4-flavored CP symmetry

We propose a neutrino mass model with μτ-flavored CP symmetry, where the effective light neutrino Lagrangian enjoys an additional invariance under a Friedberg-Lee (FL) transformation on the left-handed flavor neutrino fields that leads to a highly predictive and testable scenario. While both types of the light neutrino mass ordering, i.e., Normal Ordering (NO) as well as the Inverted Ordering (IO) are allowed, the absolute scale of neutrino masses is fixed by the vanishing determinant of light Majorana neutrino mass matrix Mν. We show that for both types of mass ordering, whilst the atmospheric mixing angle θ23 is in general nonmaximal (θ23 ≠ π/4), the Dirac CP phase δ is exactly maximal (δ = π/2, 3π/2) for IO and nearly maximal for NO owing to cos δ ∝ sin θ13. For the NO, very tiny nonvanishing Majorana CP violation might appear through one of the Majorana phases β; otherwise the model predicts vanishing Majorana CP violation. Thus, despite the fact, that from the measurement of θ23, it is difficult to rule out the model, any large deviation of δ from its maximality, will surely falsify the scenario. For a comprehensive numerical analysis, beside fitting the neutrino oscillation global fit data, we also present a study on the νμ → νe oscillation which is expected to show up Dirac CP violation in different long baseline experiments. Finally, assuming purely astrophysical sources, we calculate the Ultra High Energy (UHE) neutrino flavor flux ratios at neutrino telescopes, such as IceCube, from which statements on the octant of θ23 could be made in our model.

LAB4D: A low power, multi-GSa/s, transient digitizer with sampling timebase trimming capabilities

The LAB4D is a new application-specific integrated circuit (ASIC) of the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) family, for use in direct wideband radio frequency digitization such as is used in ultrahigh energy neutrino and cosmic ray astrophysics. The LAB4D is a single channel switched-capacitor array (SCA) 12-bit sampler with integrated analog-to-digital converters (ADC), developed in the TSMC 0.25µm process. The LAB4D, operating at 3.2GSa∕s, contains 4096 total samples arranged in 32 windows, for a total record length of 1280ns. The 3dB bandwidth is approximately 1.3GHz, with a directly-coupled 50Ω input. This represents a factor of 16 increase in the sample depth and an increase in analog bandwidth in comparison to the previous generation (LAB3) digitizer. Individually addressable windows allow for sampling and digitization to occur simultaneously, leading to nearly dead time-free kHz readout rates. All biases and current references are generated via internal digital-to-analog converters (DACs), resulting in a digitizer that requires minimal support circuitry. In addition, the LAB4D contains sample cell timebase trimming capabilities, reducing the intrinsic sample-to-sample time variance to less than 5ps, an improvement of about 80%. This feature allows the LAB4D to be used in precision timing applications and reduces post-hoc calibration requirements.

A study on a minimally broken residual TBM-Klein symmetry with its implications on flavoured leptogenesis and ultra high energy neutrino flux ratios

We present a systematic study on minimally perturbed neutrino mass matrices which at the leading order give rise to Tri-BiMaximal (TBM) mixing due to a residual ℤ2× ℤ2μτ Klein symmetry in the neutrino mass term of the low energy effective seesaw Lagrangian. Considering only the breaking of ℤ2μτ with two relevant breaking parameters (ϵ4,6′), after a comprehensive numerical analysis, we show that the phenomenologically viable case in this scenario is a special case of TM1 mixing. For this class of models, from the phenomenological perspective, one always needs large breaking (more than 45%) in one of the breaking parameters. However, to be consistent the maximal mixing of θ23, while more than 35% breaking is needed in the other, a range 49.4̂−53̂ and 38̂−40̂ could be probed allowing breaking up to 25% in the same parameter. Thus though this model cannot distinguish the octant of θ23, non-maximal mixing is preferred from the viewpoint of small breaking. The full ℤ2× ℤ2μτ symmetry leads to a degeneracy in the eigenvalues of right handed (RH) neutrino mass matrices (MR). Nevertheless, breaking of ℤ2μτ which is also necessary to generate nonzero θ13 in this model, lifts that degeneracy. Thus unlike the standard N1-leptogenesis scenario where only the decays and other interactions due to the lightest RH neutrino N1 are relevant, here all the RH neutrinos contribute to the process of baryogenesis via leptogenesis due to the small mass splitting controlled by the ℤ2μτ breaking parameters. Including flavour coupling effects (In general, which have been partially included in all the leptogenesis studies in perturbed TBM framework), we solve flavour dependent coupled Boltzmann equations for heavy neutrino as well as the light leptonic number densities to compute the final baryon asymmetry YB. Thus our analysis and results pertaining to a successful leptogenesis are more accurate than any other studies in existing literature that deal with perturbed TBM scenario. Finally, in the context of recent discovery of the ultra high energy (UHE) neutrino events at IceCube, assuming UHE neutrinos originate from purely astrophysical sources, we obtain prediction on the neutrino flux ratios at neutrino telescopes.

Searches for ultrahigh-energy neutrinos from gravitational wave events with the Pierre Auger Observatory

With the advent of the multi-messenger astronomy era, neutrinos open a unique window to the Universe allowing one to relate the most violent phenomena with the production and origin of the highest energy cosmic rays at distances beyond the GZK horizon. Neutrinos with E > 0.1 EeV of all flavors can be detected with the Surface Detector array of the Pierre Auger Observatory by means of their interaction in the atmosphere (downward-going ) or in the Earth crust (Earth-skimming ). The Pierre Auger Collaboration has searched for neutrino candidates in coincidence with gravitational wave events detected by LIGO/Virgo. Up to the present moment no neutrino candidates were found in any of these searches, which allows us to put competitive limits on the energy radiated in ultra-high energy neutrinos. The most stringent limits to the neutrino spectral fluence arise from the binary neutron star merger event GW170817 at a Ds ∼ 40 Mpc. The non-detection of neutrinos from this event is compatible with the predictions of a short GRB observed at a large off-axis angle.