Kilometer-scale Neutrino Telescope Research Articles

Baikal-GVD: cascades

Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently under construction in Lake Baikal. GVD is formed by multi-megaton subarrays (clusters) and is designed for the detection of astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. The design of Baikal-GVD allows one to search for astrophysical neutrinos with flux values measured by IceCube already at early phases of the array construction. We present here preliminary results of the search for high-energy neutrinos via the cascade mode obtained in 2015 and 2016.

Spatial positioning of underwater components for Baikal- GVD

Baikal-GVD is a cubic kilometer-scale neutrino telescope currently under construction in Lake Baikal. The detector’s components are mobile and may drift from their initial coordinates or change their spatial orientation. This introduces a reconstruction error, particularly a timing error for PMT hits. This problem is mitigated by a combination of a hydroacoustic positioning system and per-component acceleration and orientation sensors. Under regular conditions, the average positioning accuracy for a GVD component is estimated to be less than 13 cm.

Baikal-GVD: status and prospects

Baikal-GVD is a next generation, kilometer-scale neutrino telescope under construction in Lake Baikal. It is designed to detect astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. GVD is formed by multi-megaton subarrays (clusters). The array construction started in 2015 by deployment of a reduced-size demonstration cluster named "Dubna" . The first cluster in it’s baseline configuration was deployed in 2016, the second in 2017 and the third in 2018. The full-scale GVD will be an array of ~10.000 light sensors with an instrumented volume about of 2 cubic km. The first phase (GVD-1) is planned to be completed by 2020-2021. It will comprise 8 clusters with 2304 light sensors in total. We describe the design of Baikal-GVD and present selected results obtained in 2015 - 2017.

Composition from highpTmuons in IceCube

Cosmic rays with energies up to 1011 GeV enter the atmosphere and produce showers of secondary particles. Inside these showers muons with high transverse momentum (p T ≳ 2 GeV ) are produced from the decay of heavy hadrons, or from high p T pions and kaons very early in the shower development. These isolated muons can have large transverse separations from the shower core up to several hundred meters, together with the muon bundle forming a double or triple track signature in IceCube. The separation from the core is a measure of the transverse momentum of the muon's parent particle. Assuming the validity of perturbative quantum chromodynamics (pQCD) the muon lateral distribution depends on the composition of the incident nuclei, thus the composition of high energy cosmic rays can be determined from muon separation measurements. Vice versa these muons can help to understand uncertainties due to phenomenological models as well as test pQCD predictions of high energy interactions involving heavy nuclei. After introducing the physics scenario of high p T muons in kilometer-scale neutrino telescopes we will review results from IceCube in its 59-string configuration as a starting point and discuss recent studies on composition using laterally separated muons in the final detector configuration.

Extending the IceCube DAQ System by Integration of the Generic High-Speed Sorter Module TESS

In the extreme environment of Antarctica at the South Pole, the IceCube experiment, the world's first kilometer-scale neutrino telescope, collects cosmic ray events. IceCube consists of over 5000 digital optical sensor modules (DOMs) deployed on 86 instrumentation lines each extending 2.5 km deep in the antarctic ice. The array of optical modules monitors the Cherenkov light emitted by passing radiation, which, when digitized and timestamped to nanosecond precision, is used as input to sophisticated reconstruction algorithms that determine the direction, energy, and type of the incident cosmic ray event. In order to achieve this goal, the IceCube data acquisition system merges the digital data streams from each photodetector into a single time-ordered list which is presented to online triggers that determine, in realtime, whether or not a given pattern of hits is noise or signal. At the present time, the data provided to the triggers is limited by the performance of sorting and merging algorithms: the 500 Hz raw data rate from each sensor (2.5 MHz array aggregate rate) is beyond the capability of the central sort and merge. The current solution adopted by the IceCube detector is to impose a hardware-based pretrigger coincidence on hits emanating from the DOMs which reduces the rate by a factor of 20. While this pretrigger coincidence has negligible impact on the detector sensitivity for the principal goal of high-energy neutrinos from galactic or extragalactic sources, other low-energy physics searches are affected. This presentation details work done to develop and implement a system, TESS, which is capable of merging the full raw data stream being produced by the IceCube DOMs. TESS is designed as a pipelined architecture with three major modules: server, selector and the client glued together by circular buffers. The three modules runs in only three threads and since the architecture is self synchronizing and uses no data copying maximum performance can be achieved for global sorting of payloads. The TESS sorting architecture was originally designed to provide a globally sorted data stream for triggers targeting low-energy events from annihilation of hypothesized dark-matter particles, however its utility is generalizable to any IceCube trigger which requires inspection of the full data stream. The IceCube online supernova detection system is a notable example. Moreover, the algorithm is generic to any system involving multiple, independently sorted data streams which must be merged into a single sorted data stream.

Time Calibration of the KM3NeT Neutrino Telescope

Abstract KM3NeT is a future deep-sea Research Infrastructure hosting a cubic kilometer-scale neutrino telescope and facilities for marine and earth sciences in the Mediterranean Sea. The consortium is made up of 40 institutes from 10 European countries, and includes all the groups that have developed the pilot projects, ANTARES, NEMO and NESTOR. The KM3NeT telescope will consist of a three-dimensional array of optical modules arranged on vertical detection units (DUs), anchored to the sea floor and held in tension by submerged buoys. The time resolution of this detector has to be known with great accuracy since the angular resolution of the track reconstruction depends on the accurate measurement of the relative arrival times of Cherenkov photons reaching the photon sensors. The intrinsic, unavoidable limitation in time resolution (chromatic dispersion and PMT transit time spread) imply that the calibration system of a water-based neutrino telescope must provide a precision at the nanosecond level. The experience with the ANTARES deep sea neutrino telescope has shown that a distributed system of external light sources illuminating the photon detectors with short (∼ 5 ns FWHM) time-referenced light flashes is very useful to ensure the time calibration of the detector and to measure water optical properties. Whilst the basic timing calibration concept applied in ANTARES will be retained, the larger spacing between photo-detectors required in a cubic-kilometer-scale detector results in modified requirements for the KM3NeT system. A three-dimensional system of optical emitters has been studied: several LED models have been tested, and four models preselected as suitable for use in KM3NeT were incorporated into ANTARES for in-situ testing. Based on the resulting data, several LED beacons will be integrated in the forthcoming deployment of a pre-production KM3NeT detection unit planned for autumn 2011. The design, optimization and construction of the KM3NeT optical time calibration devices are described.

A prototype for the acoustic triangulation system of the KM3NeT deep sea neutrino telescope

The KM3NeT consortium is designing a research facility with a cubic kilometer-scale neutrino telescope in the Mediterranean Sea. The neutrino telescope will consist of an array of optical modules which detect Cherenkov light from muon tracks. The optical modules are subject to motion in the presence of deep sea currents, and an acoustic triangulation system is needed to determine their positions to provide the required tracking precision and angular resolution for astronomical neutrino source searches. In this paper we will describe one of the solutions proposed for the acoustic system for KM3NeT and the work done in order to develop a prototype. The system consists of an array of affordable transducers that can operate as transceivers in the 20–40 kHz region and withstand the high pressures (up to 500 bar). Versatile associated low-power electronics has been developed, implementing the all-data-to-shore approach. Besides accomplishing the control of signal transmission and reception, it allows for transducer configuration from shore to benefit from varied on-shore signal processing techniques.

A novel tau signature in neutrino telescopes

Kilometer-scale neutrino telescopes will detect muon and electron neutrinos from astrophysical sources at the TeV scale and above. Tau neutrinos are also expected from these sources due to neutrino oscillations over astrophysical baselines. Identification of tau neutrinos is expected to be possible above the PeV energy range through the "double bang" and "lollipop" signatures. We discuss another signature of tau in the PeV-EeV range, arising from the decay of tau leptons inside the detector to much brighter muons.

Neutrino Astrophysics Experiments Beneath the Sea and Ice

Neutrino astronomy beyond the Sun was first imagined in the late 1950s. A neutrino detector at the bottom of Lake Baikal, the deployment of detectors in the Mediterranean Sea, and the construction of a kilometer-scale neutrino telescope at the South Pole exemplify current efforts to realize this dream.

Prospects for detecting dark matter with neutrino telescopes in light of recent results from direct detection experiments

Direct detection dark matter experiments, lead by the CDMS collaboration, have placed increasingly stronger constraints on the cross sections for elastic scattering of WIMPs on nucleons. These results impact the prospects for the indirect detection of dark matter using neutrino telescopes. With this in mind, we revisit the prospects for detecting neutrinos produced by the annihilation of WIMPs in the Sun. We find that the latest bounds do not seriously limit the models most accessible to next generation kilometer-scale neutrino telescopes such as IceCube. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes still have the opportunity to play an important as well as complementary role in the search for particle dark matter.

STATUS OF THE ICECUBE NEUTRINO TELESCOPE

IceCube is a kilometer-scale deep-ice neutrino telescope, to be constructed at the South Pole beginning in January 2005. The concept and design of IceCube, its science goals, present status, and expected performance will be discussed.

Probing the LSND mass scale and four neutrino scenarios with a neutrino telescope

We show in this Letter that the observation of the angular distribution of upward-going muons and cascade events induced by atmospheric neutrinos at the TeV energy scale, which can be performed by a kilometer-scale neutrino telescope, such as the IceCube detector, can be used to probe a large neutrino mass splitting, |Δm2|∼(0.5–2.0) eV2, implied by the LSND experiment and discriminate among four neutrino mass schemes. This is due to the fact that such a large mass scale can promote non-negligible νμ→νe,ντ/ν̄μ→ν̄e,ν̄τ conversions at these energies by the MSW effect as well as vacuum oscillation, unlike what is expected if all the neutrino mass splittings are small.

Neutral Beams from Blazar Jets

We treat the production of neutrons, photons, and neutrinos through photomeson interactions of relativistic protons with ambient photons in the compact inner jets of blazars. Internal synchrotron and external isotropic radiation due to scattered optical/UV accretion-disk radiation are considered as target photon fields. Protons are assumed to be accelerated to a maximum energy limited by the size scale and magnetic field of the jet, and by competing energy losses. We characterize the conditions when the photomeson interactions of ultrarelativistic protons become effective, and show that the presence of the external radiation field makes possible strong energy losses for protons with energies Ep 1015 eV. Without this component, effective energy losses of protons begin at Ep 1018 eV, and would rapidly disappear with expansion of the blob. We develop a model describing the production and escape of neutrons from a comoving spherical blob, which continue to interact with the ambient external radiation field on the parsec-scale broad-line region (BLR). Neutrons may carry ≈10% of the overall energy of the accelerated protons with Ep 1015 eV outside the BLR. Ultra-high-energy gamma rays produced by photomeson interaction of neutrons outside the blob can also escape the BLR. The escaping neutrons, gamma rays, and neutrinos form a collimated neutral beam with a characteristic opening angle θ ~ 1/Γ, where Γ is the bulk Lorentz factor of the inner jet. Energy and momentum is deposited in the extended jet from the decay of neutrons at distances ld(En) ≈ (En/1017 eV) kpc, and through pair-production attenuation of gamma rays with energies Eγ 1015 eV which propagate to ~10-100 kpc distances. In this scenario, neutral beams of ultra-high-energy gamma rays and neutrons can be the reason for straight extended jets, such as in Pictor A. Fluxes of neutrinos detectable with kilometer-scale neutrino telescopes are predicted from flat-spectrum radio quasars such as 3C 279.

Signatures of Hadronic Cosmic Rays in Starbursts? High-Energy Photons and Neutrinos from NGC 253

We show that it appears possible for starburst galaxies, like the nearby NGC 253, recently identified as a TeV source by the CANGAROO collaboration, to emit a significant amount of high-energy γ-rays and neutrinos through hadronic processes in their cores. We suggest that proton illumination of the inner winds of massive stars can be a viable mechanism for producing TeV γ-rays and neutrinos without a strong MeV-GeV counterpart. The rich stellar content of the starbursts, with millions of early-type stars concentrated in the central regions, where collective effects of the stellar winds and supernovae can produce a significant enhancement of the cosmic-ray density, provides an adequate scenario for TeV γ-ray generation. Close starbursts are also found to be potential sources for kilometer-scale neutrino telescopes, like IceCube, within reasonable integration times.

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.

Prompt TeV-PeV atmospheric neutrino window

We discuss the possible existence of an observational window, in the TeV-PeV energy range, for the detection of prompt neutrinos from the decay of charmed particles produced in cosmic-ray interactions with the atmosphere. The flux calculations for prompt muon and tau neutrinos are subject to large uncertainties, which we quantify. We investigate the interplay of the predicted fluxes with those produced by the flavor oscillation of conventional atmospheric neutrinos, and by anticipated cosmic sources. We calculate the event rates for the detection of prompt neutrinos and argue that they may be observable in a kilometer-scale neutrino telescope.

Measuring high energy neutrino-nucleon cross sections with future neutrino telescopes

Next generation kilometer-scale neutrino telescopes, such as ICECUBE, can test standard model predictions for neutrino-nucleon cross sections at energies well beyond the reach of collider experiments. At energies near a PeV and higher, the Earth becomes opaque to neutrinos. At these energies, the ratio of upgoing and downgoing events can be used to measure the total neutrino-nucleon cross section given the presence of an adequate high energy neutrino flux.

1020 eVcosmic-ray and particle physics with kilometer-scale neutrino telescopes

We show that a kilometer-scale neutrino observatory, though optimized for TeV to PeV energy, is sensitive to the neutrinos associated with super-EeV sources. These include super-heavy relics, neutrinos associated with the Greisen cutoff, and topological defects which are remnant cosmic structures associated with phase transitions in grand unified gauge theories. It is a misconception that new instruments optimized to EeV energy are required to do this important science, although this is not their primary goal. Because kilometer-scale neutrino telescopes can reject atmospheric backgrounds by establishing the very high energy of the signal events, they have sensitivity over the full solid angle, including the horizon where most of the signal is concentrated. This is important because up-going neutrino-induced muons, routinely considered in previous calculations, are absorbed by the Earth.

Prediction on the Ultrahigh Energy Neutrino-Nucleon Cross Section from New Structure Function Data at Smallx

New structure function data at small Bjorken $x$ from HERA are used along with next-to-leading order QCD evolution to predict a cross section for charged-current interactions of ultrahigh energy neutrinos with nucleons. This new result is over twice the size of previous estimates and has important implications for cosmic ray experiments now underway as well as for KM3 arrays (cubic kilometer-scale neutrino telescopes) now in the planning stages.

Prediction for the ultrahigh energy neutrino-nucleon cross section from new structure function data at small x.

New structure function data at small Bjorken $x$ from HERA are used along with next-to-leading order QCD evolution to predict a cross section for charged-current interactions of ultrahigh energy neutrinos with nucleons. This new result is over twice the size of previous estimates and has important implications for cosmic ray experiments now underway as well as for KM3 arrays (cubic kilometer-scale neutrino telescopes) now in the planning stages.