AMANDA Neutrino Telescope Research Articles

Observation of TeV–PeV cosmic ray anisotropy with IceCube, IceTop and AMANDA

The study of cosmic ray anisotropy in the TeV–PeV energy range could provide clues about the origin and propagation of cosmic rays in our galactic neighborhood. Since the observed anisotropy is very small, below the per mille level, large event volumes are needed in order to characterize it in sufficient detail. The IceCube Observatory has already collected more than 150 billion cosmic ray induced muon events. This large data sample made it possible to detect anisotropies in the southern hemisphere, down to the 10−5 level, at primary energies in excess of 10TeV. The observed anisotropy is not a simple dipole, but it can be described as composed of multipole components of the spherical harmonic expansion, down to about 10°. A change in topological structure of the cosmic ray arrival distribution is observed above 100TeV. Data collected with the air shower array IceTop above 300TeV confirm the observations up to the PeV energy scale. Moreover, the addition of data collected with the AMANDA neutrino telescope, which operated between 2000 and 2007, has enabled us to search for time variability in the observed TeV anisotropy.

Search for neutrino-induced cascades with five years of AMANDA data

We report on the search for electromagnetic and hadronic showers (“cascades”) produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000–2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of ν e : ν μ : ν τ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Φ ∝ E −2 is less than 5.0 × 10 −7 GeV s −1 sr −1 cm −2 at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.

Status and prospects of the IceCube neutrino telescope

The IceCube neutrino observatory, under construction at the South Pole, consists of three sub-detectors: a km-scale array of digital optical modules deployed deep in the ice, the AMANDA neutrino telescope and the surface array IceTop. We summarize results from searches for cosmic neutrinos with the AMANDA telescope and review expected sensitivities for IceCube at various installation phases. Reliability and robustness of installation at the South Pole has been demonstrated during the past four successful construction seasons. The 40 installed IceCube strings are working well. We are developing detailed plans for the final construction of IceCube, including extensions optimized for low and high energy. We describe the IceCube Deep Core project which will extend the low energy response of IceCube.

High energy and prompt neutrino production in the atmosphere

The AMANDA neutrino telescope has measured the spectrum of atmospheric neutrinos up to 100 TeV and IceCube, which has about 100 times higher acceptance, is expected to collect unprecedented statistics at even higher energies in the near future. IceCube, with 22 strings, has measured about 1.4 kHz of muon rate at trigger level and about 20 neutrino events per day at cut levels suitable for reducing the atmospheric muon content at the level of less than 10%. At energies of about 100 TeV we expect about 1 event per day for atmospheric muons with zenith angle larger than 70 degrees. With these numbers an amount of interesting physics items can be covered, such as investigations of hadronic models in region not covered by colliders, with particular attention to kaon and charm meson and barion physics. In the poster we have shown some of the MC tests we have been performing. As a summary here we show 2 preliminary plots: the one on the left shows what we obtain for CORSIKA using two different hadronic models (SIBYLL and 2 versions of QGSJET) as the fraction of pions and kaons contributing to the production of muons and neutrinos as a function of energy (integrated over all angles); the other shows how these models compare to the muon charge ratio measured by MINOS (P. Adamson et al., Phys. Rev D 76 (2007) 052003) and L3 COSMIC (M. Aglietta et al., Phys. Rev. D 58 (1998) 092005). Other results concerning the introduction of DPMJET with charm production in CORSIKA have been published in Berghaus et al., JCAP06 (2008) 003.

Astroparticle physics with the AMANDA neutrino telescope

The AMANDA neutrino telescope at the South Pole has been taking data successfully since 1997. This detector opened a new window on a wide range of physics including atmospheric neutrinos, indirect searches for WIMP dark matter and possible astrophysical sources of high energy neutrinos such as Gamma Ray Bursts and Active galactic Nuclei. With the detection of several thousand atmospheric neutrinos it has proved the feasibility of using the South Pole icecap as a Cherenkov medium for the detection of high energy neutrinos, and provided much useful technical information for its successor experiment IceCube of which it is now the low energy extension. We present here a selection of the various searches performed and the increasingly stringent limits obtained over many years of operation.

Results from the AMANDA Neutrino Telescope

High-energy neutrinos are very promising probes for Astrophysics. Neutrinos interact very weakly, so they are unique sources of information at high energies. However, since they interact very rarely, very large detectors are needed to observe them. The detection principle in a neutrino telescope is based on the observation of the Cherenkov light produced by the muons generated in the interactions of muon neutrinos. Other signatures, such as cascades from electrons produced by electron neutrinos, are also identifiable. AMANDA-II, with 677 optical sensors, has demonstrated the feasibility of such a detector in the Antarctic ice and provided important Physics results. In this presentation we will review this scientific output, which includes the first sky map using neutrinos from the Northern Hemisphere, the measure of the atmospheric neutrino spectrum, the study of astrophysical objects like gamma-ray bursts, active galactic nuclei, soft-gamma repeaters or supernovae and limits on the neutralino flux from the Sun and the Earth.

The IceCube neutrino observatory: latest results on the search for point sources and status of IceCube construction

AbstractThe AMANDA neutrino telescope, prototype instrument of the IceCube neutrino observatory at South Pole, has collected data since 2000 in its final configuration. A period of 1001 days of livetime between 2000 and 2004 has been analysed in order to find evidence of a neutrino signal coming from point-like sources such as microquasars, active galactic nuclei, supernovae remnants or gamma ray bursts. A sensitivity to fluxes of νμ + νμ + ντ + ντ of dΦ/dE =1.0 · 10−10 (E/TeV)−2 · TeV−1 cm−2 s−1 was reached in the energy range between 1.6 TeV and 1.6 PeV. No significant excess over the background has been found so far. Flux upper limits infered from this study can constrain certain neutrino emission models of X-ray binaries. IceCube will have a substantially higher sensitivity. Currently at 10% of its final extension, it will comprise 4800 optical sensors deployed along 80 strings by early 2011, instrumenting one cubic kilometre volume of ice and 1 km2 at the surface.

Optical properties of deep glacial ice at the South Pole

We have remotely mapped optical scattering and absorption in glacial ice at the South Pole for wavelengths between 313 and 560 nm and depths between 1100 and 2350 m. We used pulsed and continuous light sources embedded with the AMANDA neutrino telescope, an array of more than six hundred photomultiplier tubes buried deep in the ice. At depths greater than 1300 m, both the scattering coefficient and absorptivity follow vertical variations in concentration of dust impurities, which are seen in ice cores from other Antarctic sites and which track climatological changes. The scattering coefficient varies by a factor of seven, and absorptivity (for wavelengths less than ∼450 nm) varies by a factor of three in the depth range between 1300 and 2300 m, where four dust peaks due to stadials in the late Pleistocene have been identified. In our absorption data, we also identify a broad peak due to the Last Glacial Maximum around 1300 m. In the scattering data, this peak is partially masked by scattering on residual air bubbles, whose contribution dominates the scattering coefficient in shallower ice but vanishes at ∼1350 m where all bubbles have converted to nonscattering air hydrates. The wavelength dependence of scattering by dust is described by a power law with exponent −0.90 ± 0.03, independent of depth. The wavelength dependence of absorptivity in the studied wavelength range is described by the sum of two components: a power law due to absorption by dust, with exponent −1.08 ± 0.01 and a normalization proportional to dust concentration that varies with depth; and a rising exponential due to intrinsic ice absorption which dominates at wavelengths greater than ∼500 nm.

AMANDA: Selected physics results

Since the commissioning of the first 10 strings of the AMANDA neutrino telescope, more than nine years of data has been collected. The proof of principle of high-energy neutrino detection in ice is established. No positive signal of an extra-terrestrial high-energy neutrino flux have been found so far. However, the most stringent upper limits to the flux of cosmic neutrinos—respectively, diffuse, point like or associated with gamma-ray bursts—have been presented. A sample of 3329 up-going muon tracks, representing the largest statistics ever of high-energy neutrino induced events, has been collected between 2000 and 2003. A coincidence of neutrino with an anomalous high-energy gamma-ray flare has been observed from the direction of the Blazar 1ES1959+650—although the observation were not conclusive. Selected results of data taken with the AMANDA detector are here reported.

NEUTRINO ASTRONOMY AND COSMIC RAYS AT THE SOUTH POLE: LATEST RESULTS FROM AMANDA AND PERSPECTIVES FOR ICECUBE

The AMANDA neutrino telescope has been in operation at the South Pole since 1996. The present final array configuration, operational since 2000, consists of 677 photomultiplier tubes arranged in 19 strings, buried at depths between 1500 and 2000 m in the ice. The most recent results on a multi-year search for point sources of neutrinos will be shown. The study of events triggered in coincidence with the surface array SPASE and AMANDA provided a result on cosmic ray composition. Expected improvements from IceCube/IceTop will also be discussed.

High energy neutrinos from the TeV Blazar 1ES 1959 + 650

The AMANDA neutrino telescope has recently reported the detection of high-energy neutrinos spatially and temporally coincident with the flaring of the TeV blazar 1ES 1959 + 650. If high-energy neutrinos are in fact generated by this blazar, it would be the first strong evidence for the hadronic acceleration of cosmic rays. At present, the statistical significance of this observation cannot be reliably assessed, however. In this letter, we investigate whether circumstances exist where the source can produce the flux implied by the coincident events. We show that if the TeV gamma-ray emission observed from 1ES 1959 + 650 or other nearby TeV blazars is the result of accelerated protons interacting with nucleons, it is reasonable that AMANDA could detect several events during a flaring period. Such rates require that the spectral index of the source be rather high (for instance ∼2.8 for 1ES 1959 + 650) and that the Lorentz factor of the jet be fairly small ( Γ ∼ 1).

Results from the AMANDA neutrino telescope

Results from the AMANDA neutrino telescope

Results from the AMANDA neutrino telescope

We review recent results from AMANDA on the search for cosmic point sources of neutrinos, both in the diffuse and point-like channels. Assuming a E −2 spectral shape of the neutrino energy at the source, we derive limits on the diffuse ν μ flux as well as in the all-flavour diffuse flux from the cascade search. We report limits on selected point sources as well as on GRB searches. We present results on primary cosmic CR composition in the range ∼100 TeV-PeV obtained with the help of the SPASE air shower array run in coincidence with AMANDA.

Enhancement of the Sensitivity of Neutrino-Telescope Optical Modules to Cerenkov Light

The results of studies of thin-film wavelength shifters developed for optical modules of large-scale neutrino telescopes are presented. The effect of such wavelength shifters is an increase in the sensitivity of an optical module of the AMANDA neutrino telescope to Cerenkov light of 48%.

Search for supernova neutrino bursts with the AMANDA detector

The core collapse of a massive star in the Milky Way will produce a neutrino burst, intense enough to be detected by existing underground detectors. The AMANDA neutrino telescope located deep in the South Pole ice can detect MeV neutrinos by a collective rate increase in all photo-multipliers on top of dark noise. The main source of light comes from positrons produced in the CC reaction of anti-electron neutrinos on free protons ν ̄ e + p→ e ++ n . This paper describes the first supernova search performed on the full sets of data taken during 1997 and 1998 (215 days of live time) with 302 of the detector's optical modules. No candidate events resulted from this search. The performance of the detector is calculated, yielding a 70% coverage of the galaxy with one background fake per year with 90% efficiency for the detector configuration under study. An upper limit at the 90% c.l. on the rate of stellar collapses in the Milky Way is derived, yielding 4.3 events per year. A trigger algorithm is presented and its performance estimated. Possible improvements of the detector hardware are reviewed.

The AMANDA neutrino telescope: principle of operation and first results

AMANDA is a high-energy neutrino telescope presently under construction at the geographical South Pole. In the Antarctic summer 1995/96, an array of 80 optical modules (OMs) arranged on 4 strings (AMANDA-B4) was deployed at depths between 1.5 and 2 km. In this paper we describe the design and performance of the AMANDA-B4 prototype, based on data collected between February and November 1996. Monte Carlo simulations of the detector response to down-going atmospheric muon tracks show that the global behavior of the detector is understood. We describe the data analysis method and present first results on atmospheric muon reconstruction and separation of neutrino candidates. The AMANDA array was upgraded with 216 OMs on 6 new strings in 1996/97 (AMANDA-B10), and 122 additional OMs on 3 strings in 1997/98.

The AMANDA neutrino telescope and the indirect search for dark matter: AMANDA Colaboration

With an effective telescope area of order 10 4 m 2, a threshold of ∼50 GeV and a pointing accuracy of 2.5°, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe its performance, focussing on the capability to detect halo dark matter particles via their annihilation into neutrinos.

The AMANDA neutrino telescope: Science prospects and performance at first light

We update the science prospects for the recently completed AMANDA South Pole neutrino detector. With an effective telescope area of order 10 4 m 2 and a threshold of ∼50 GeV, it represents the first instrument of a new generation of high energy neutrino detectors, envisaged over 25 years ago. We describe the instrument and its performance, and map its expansion to a detector of kilometer dimension.