Coincidence analysis in ANTARES: Potassium-40 and muons

The ANTARES neutrino detector, located deep underwater in Mediterranean sea, is currently almost complete and taking physics data. The amount of data collected so far allows for several kinds of neutrino studies. Yet, presently the principal task of the collaboration is to achieve thorough and precise understanding of the detector. Therefore, detector calibration and atmospheric muon studies are currently given high priorities. A new calibration technique, based on the use of natural background light in seawater, was recently invented. The method relies on correlated coincidences produced in triplets of ANTARES optical modules by Cherenkov light of beta-particles originated from ⁴⁰K decays. Based on similar ideas of coincidence analysis, a simple but powerful approach to atmospheric muon flux studies is currently being developed. The two methods and their role in the ANTARES experiment are briefly presented.     

ANTARES—deep undersea neutrino observatory: Status report

The ANTARES project aims at the construction of an array of 900 optical modules to form a high-energy neutrino detector with an effective area of about 0.1 km² (ANTARES Collab., astro-ph/9907432; http://antares.in2p3.fr/). The detector will be built in the Mediterranean Sea, 40 km off the coast near Toulon (France) at a depth of 2400 m. The detector has the following main physics goals: measuring the high-energy neutrino flux in the TeV-PeV range with a good pointing resolution, studying atmospheric neutrino oscillations in the region of the parameter space favored by Super-Kamiokande, and searching for supersymmetric dark matter in a region of model parameters of interest in cosmology and particle physics.     

Study of atmospheric neutrino oscillations in ANTARES

The potential of the ANTARES 0.1 km² detector for the study of the atmospheric neutrino oscillations is discussed.     

IceCube Neutrinos: from Oscillations to PeV-Energy Events

With IceCube and its low-energy extension DeepCore, a neutrino detector with an energy reach from tens of gigaelectronvolt to exaelectronvolt has been commissioned. It measures the atmospheric neutrino spectrum from the lower energies where neutrinos oscillate to energies as large as 100 TeV with a statistic of more than 100,000 events per year. The initial results suggest that IceCube can measure the oscillation parameters in an energy range that exceeds existing observations by 1 order of magnitude, thus opening a new window on neutrino physics. We emphasize the search for sterile neutrinos particularly relevant to cosmology. We also discuss the first observation of (PEV) petaelectronvolt-Energy events that cannot be accommodated by the flux anticipated by extrapolation of the present atmospheric neutrino measurements.     

High energy neutrinos from galactic sources

Analytical expressions are derived which allow to calculate flux densities of energetic neutrinos from hypothetical galactic sources, consisting of a proton accelerator and a dilute gas beam dump. The same formalism is used to calculate atmospheric muon and μ-neutrino fluxes. From the results, rates of upward going muons, both from the atmosphere and galactic sources, are computed and detection limits for neutrino emitters in the sky are established. Finally, the background in a surface detector, caused by scattered muons and charm decays in the rock, is estimated for the case of a flat surrounding.     

ANTARES, Physics potential, progress and status

Observational neutrino astronomy can bring information - also on particle physics - that can not be obtained in other ways. In general this concerns processes at extreme energy and distance scales. Particularly of interest are cosmic accelerators, GUT phase transition remnants and dark matter annihilation. After four years of R&D the ANTARES Collaboration begins the actual construction of a neutrino telescope to be deployed at 2400 m depth near Toulon in the Mediterranean sea. The telescope will be particularly sensitive to high-energy upward-going neutrinos. The physics case, measurements, the structure of the detector and recent progress are discussed.     

Recent Results from the ANTARES Neutrino Telescope

The ANTARES detector, located 40 km off the French coast, is the largest deep-sea neutrino telescope in the world. It consists of an array of 885 photomultipliers detecting the Cherenkov light induced by charged leptons produced by neutrino interactions in and around the detector. The primary goal of ANTARES is to search for astrophysical neutrinos in the TeV–PeV range. This comprises generic searches for any diffuse cosmic neutrino flux as well as more specific searches for astrophysical sources such as active galactic nuclei or galactic sources. The search program also includes multi-messenger analyses based on time and/or space coincidences with other cosmic probes. The ANTARES observatory is sensitive to a wide range of other phenomena, from atmospheric neutrino oscillations to dark matter annihilation or potential exotics such as nuclearites and magnetic monopoles. The most recent results are reported.     

The Baikal Neutrino Telescope

We review the present status of the Baikal Neutrino Experiment and present results of a search for upward-going atmospheric neutrinos and magnetic monopoles obtained with the detector NT200. The results of a search for very high energy neutrinos are presented and an upper limit on the extraterrestrial diffuse neutrino flux is obtained. We describe the strategy of upgrading the NT200 to NT200+ and creating a detector on the Gigaton scale at Lake Baikal. The first results obtained with the new NT200+ detector as a basic cell of a future Gigaton detector are presented. The text was submitted by the authors in English.     

From AMANDA to IceCube

The first string of the neoteric high-energy neutrino telescope IceCube successfully began operating in January 2005. It is anticipated that, upon completion, the new detector will vastly increase the sensitivity and extend the reach of AMANDA to higher energies. A discussion of the IceCube’s discovery potential for extraterrestrial neutrinos, together with the prospects of new physics derived from the ongoing AMANDA research, will be the focus of this paper. Preliminary results of the first antarctic high-energy neutrino telescope AMANDA searching in the muon-neutrino channel for localized and diffuse excess of extraterrestrial neutrinos will be reviewed using data collected between 2000 and 2003. Neutrino flux limits obtained with the all-flavor dedicated ultrahigh energy and cascade analyses will be described. A first neutrino spectrum above 1 TeV in agreement with atmospheric neutrino flux expectations and no extraterrestrial contribution will be presented, followed by a discussion of a limit for neutralino cold dark matter candidates annihilating in the center of the Sun. on behalf of the IceCube Collaboration The text was submitted by the author in English.     

Can FSRQs produce the Ice Cube detected diffuse neutrino emission?

Ice Cube has reported the detection of a diffuse Te V-Pe V neutrino emission, for which the flat spectrum radio quasars(FSRQs) have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by Ice Cube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the Ice Cube point source search has predicted neutrino flux above the Ice Cube upper limit; and for the sample of stacking search for neutrinos by Ice Cube, the predicted stacked flux is even larger than the upper limit of stacked flux by orders of magnitude. Therefore the Ice Cube limit from stacking searches, combined with the Fermi-LAT observations, already rejects FSRQs as the main sources of Ice Cube-detected diffuse neutrinos: FSRQs can only account for 10%( 4%) of the Ice Cube-detected diffuse neutrino flux, according to the stacking searches from the whole(northern) sky. The derived small neutrino/gamma-ray flux ratio also implies that the gamma-ray emission from FSRQs cannot be produced by the secondary leptons and photons from the pion production processes. The caveat in the assumptions is discussed.     

Atmospheric Neutrinos as a Tool for Exploring the Earth’s Inner Parts

Investigation of the Earth’s inner parts requires developing new methods. It is well known that atmospheric neutrinos traverse the Earth, undergoing virtually no interaction. The change in the neutrino flux is due exclusively to neutrino oscillations, which are enhanced by the effect of Earth’s matter. At the present time, there are two projects outside Russia (PINGU and ORCA) that are aimed at detecting atmospheric neutrinos that traversed the Earth, which are supposed to be used for purposes of Earth’s tomography. The creation of a large neutrino detector on the basis of a liquid scintillator is planned at the BaksanNeutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) in the North Caucasus. After testing this detector, there will arise the possibility of employing it as part of the worldwide network of neutrino detectors for studying the Earth’s inner parts.     

The LVD experiment at Gran Sasso

Summary The Large-Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator (at present 562 tons are in data taking) interleaved with limited-streamer tubes. Several physical problems are investigated with LVD, the major being the search for neutrino bursts from gravitational stellar collapses in our Galaxy. In this paper we discuss some results on cosmic neutrinos and cosmic-ray muons obtained with the first of the five towers of LVD (operational since June 1992) and part of the second tower (operational since June 1994). The results of the search for supernovae neutrinos show that LVD is a neutrino observatory able to detect neutrinos of different flavours from gravitational stellar collapses in all our Galaxy, over a wide range of burst durations. Indeed, the carbon-based liquid-scintillator target gives a unique possibility to directly detect neutral- and charged-currents neutrino interactions with a very good signature. This characteristic of LVD allows us to make an indirect estimate of the neutrino rest mass and of neutrino oscillations from supernovae in our Galaxy. No evidence for burst candidates has been found in the data recorded from June 1992 to March 1995, for a total live time of 682 days and a total exposure of 613 tons per year. We present the results of a time coincidence analysis between low-energy signals, eventually due to neutrinos of different flavours, and γ-ray bursts (GRBs) detected by the BATSE experiment. This search covers the period from June 1993 to March 1995, during which 41 GRBs have been selected from the BATSE data. Since no excess of events in LVD has been found, upper limits on the neutrino fluxes are reported for (ν_e, p), and for neutral- and charged-currents neutrino interactions of different flavours with the C-nuclei of the scintillator. The muon intensity as a function of slant depth is presented. These measurements, obtained during a live time period of 11.556 hours, cover a slant depths range from about 3000 to about 20 000 hg/cm² of standard rock and extend over five decades of intensity. An interesting result is that the muon flux is independent of slant depth beyond a depth of about 14 000 hg/cm² of standard rock, and corresponds to near horizontal muons. This is direct evidence that this flux is due to atmospheric neutrinos interacting in the rock surrounding LVD.     

Detection of magnetic monopoles with the ANTARES detector

The ANTARES Collaboration is constructing a neutrino telescope on the bottom of the Mediterranean Sea. The main goal of ANTARES is to detect high-energy cosmic neutrinos. The detection principle relies on the observation of Čerenkov light emitted by neutrino-induced muons. It is shown that this type of detector is also able to detect exotic particles such as magnetic monopoles. Above the Čerenkov limit, monopoles can be detected because of the emission of large amounts of direct Čerenkov light. Monopoles are also detectable below the Čerenkov limit through the production of δ rays, which in turn emit Čerenkov light. The development of a software trigger for ANTARES designed for monopole detection is presented. A simulation of the δ-ray-induced and direct Čerenkov light emission by monopoles has been made and used to study the trigger efficiency for the detection of monopoles. Techniques to suppress background at the trigger level are presented, and plans for the future are discussed. for the ANTARES Collaboration The text was submitted by the author in English.     

Millimetric flux densities as a test of atmospheric turbulence

In this paper it is shown how submillimetre and millimetre flux density measurements of sky fluctuations can be used to infer the characteristics of atmospheric turbulence.Two different approaches have been followed: first, by considering the observed process as due to the atmospheric turbulence, we used the r.m.s. sky fluctuations to derive some physical parametres characterizing the phenomenon; second, by investigating the power spectrum and the autocorrelation function, we derive an empirical model (the AR model) to try to deduce the physical process. In this case, the fitted power spectrum agrees strikingly with that predicted by the theory of a stationary turbulent flow for the atmosphere in the sampled frequency range. This kind of modeling can help to disentangle the atmospheric fluctuations from the extraterrestrial signal in ground-based astrophysical measurements.Measurements of the water vapour content and atmospheric transmission at the Italian Base in Antarctica, where the data have been taken, at the wavelengths of 350 μm, 1 and 2mm are also reported.     

Precise determination of the unperturbed 8B neutrino spectrum

A measurement of the final state distribution of the (8)B β decay, obtained by implanting a (8)B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jyv?skyl? [O. S. Kirsebom et al., Phys. Rev. C 83, 065802 (2011)]. It shows discrepancies with previously measured spectra, leading to differences in the derived neutrino spectrum. Thanks to a low detection threshold, the neutrino spectrum is for the first time directly extracted from the measured final state distribution, thus avoiding the uncertainties related to the extrapolation of R-matrix fits. Combined with the IGISOL data, this leads to an improvement of the overall errors and the extension of the neutrino spectrum at high energy. The new unperturbed neutrino spectrum represents a benchmark for future measurements of the solar neutrino flux as a function of energy.     

The measurement of upward going muons using the MACRO detector

The upward-going muon flux (E_μ > 1 GeV) has been measured with the underground detector MACRO at LNGS. The total number of measured events is compatible at the 8% c.l. with the expected one. Moreover, the zenith angular distribution of the measured flux does not match the expectation showing a deficit in the vertical direction where the apparatus performance is best known. Assuming an oscillation hypothesis with parameters in the range recently suggested to solve the atmospheric neutrino problem, the agreement increases, but not significantly. The results of an indirect dark matter search for a signal of WIMPs from the core of the Sun and of the Earth are given. Neutrino astronomy with MACRO is giving interesting results regarding possible high energy neutrino emission from pointlike sources and coincidences of neutrino events with γ-ray bursts.     

Neutrino hierarchy from CP-blind observables with high density magnetized detectors

High density magnetized detectors are well suited to exploit the outstanding purity and intensities of novel neutrino sources like neutrino factories and beta beams. They can also provide independent measurements of leptonic mixing parameters through the observation of atmospheric muon-neutrinos. In this paper, we discuss the combination of these observables from a multi-kT iron detector and a high energy beta beam; in particular, we demonstrate that even with moderate detector granularities the neutrino mass hierarchy can be determined for θ₁₃ values greater than 4°. PACS 14.60.Pq; 14.60.Lm     

Nonaccelerator neutrino physics

The subject of these lectures is experimental nonaccelerator neutrino physics. We discuss experiments on solar and atmospheric neutrino flux measurements, as well as experiments devoted to recording the antineutrino on nuclear reactors in the context of determining the parameters of neutrino oscillations. Neutrino geophysics, a new field of science, is overviewed.     

Physical substantiation of the lithium experiment

The lithium detector is highly efficient for measurement of CNO neutrino flux. The application of the equation of solar luminosity balance provides a possibility of determination of the total pp-neutrino flux with an uncertainty of approximately 1% if the neutrino flux from CNO cycle is measured with an uncertainty of 30%. This is possible if the measurement uncertainty of the total neutrino capture rate by lithium is 10%, which can be reached using a detector with a mass of 10 t during 5 years. As a rule, experiments with solar neutrinos are carried out for 10 years and longer.     

Search for sterile neutrinos in the neutrino-4 experiment

An experimental search for sterile neutrinos has been carried out at a neutrino facility based on the SM-3 nuclear reactor in Dimitrovgrad, Russia. The movable detector with passive shielding against the external radiation may be positioned at a distance varying between 6 and 12 m from the center of the reactor. The antineutrino flux has for the first time been measured using a movable detector placed close to the antineutrino source. The accuracy of the measurements is largely restricted by the cosmic background. The results of the measurements performed at small and large distances are analyzed in terms of the sterile-neutrino model parameters Δm ₁₄ ² and sin²2θ₁₄.