Showing papers on "Neutrino detector published in 2011"

The T2K Experiment

Abstract: The T2K experiment is a long-baseline neutrino oscillation experiment Its main goal is to measure the last unknown lepton sector mixing angle {\theta}_{13} by observing { u}_e appearance in a { u}_{\mu} beam It also aims to make a precision measurement of the known oscillation parameters, {\Delta}m^{2}_{23} and sin^{2} 2{\theta}_{23}, via { u}_{\mu} disappearance studies Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem

Where we are on θ13: addendum to 'Global neutrino data and recent reactor fluxes: status of three-flavor oscillation parameters' (vol 13, 109401, 2011)

Abstract: In this addendum to Schwetz et al (2011 New J. Phys.13 063004), we consider the recent results from long-baseline νμ → νe searches at the Tokai to Kamioka (T2K) and Main Injector Neutrino Oscillation Search (MINOS) experiments and investigate their implications for the mixing angle θ13 and the leptonic Dirac CP phase δ. By combining the 2.5σ indication for a nonzero value of θ13 coming from the T2K data with global neutrino oscillation data, we obtain a significance for θ13 > 0 of about 3σ with best fit points sin2 θ13 = 0.013 (0.016) for normal (inverted) neutrino mass ordering. These results depend somewhat on assumptions concerning the analysis of reactor neutrino data.

Measurement of the atmospheric neutrino energy spectrum from 100 GeV to 400 TeV with IceCube

Abstract: A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18 000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject misreconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than 1%. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric nu(mu) + (nu) over bar (mu) flux.

IceCube sensitivity for low-energy neutrinos from nearby supernovae

Abstract: This paper describes the response of the IceCube neutrino telescope located at the geographic south pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of similar to 1 km(3) in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to detect the neutronization burst, a short outbreak of nu(e)'s released by electron capture on protons soon after collapse. Tantalizing signatures, such as the formation of a quark star or a black hole as well as the characteristics of shock waves, are investigated to illustrate IceCube's capability for supernova detection.

Time-integrated Searches for Point-like Sources of Neutrinos with the 40-string IceCube Detector

Abstract: We present the results of time-integrated searches for astrophysical neutrino sources in both the northern and southern skies. Data were collected using the partially completed IceCube detector in the 40-string configuration recorded between 2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum likelihood ratio method is used to search for astrophysical signals. The data sample contains 36,900 events: 14,121 from the northern sky, mostly muons induced by atmospheric neutrinos, and 22,779 from the southern sky, mostly high-energy atmospheric muons. The analysis includes searches for individual point sources and stacked searches for sources in a common class, sometimes including a spatial extent. While this analysis is sensitive to TeV-PeV energy neutrinos in the northern sky, it is primarily sensitive to neutrinos with energy greater than about 1 PeV in the southern sky. No evidence for a signal is found in any of the searches. Limits are set for neutrino fluxes from astrophysical sources over the entire sky and compared to predictions. The sensitivity is at least a factor of two better than previous searches (depending on declination), with 90% confidence level muon neutrino flux upper limits being between E(2)d Phi/dE similar to 2-200 x 10(-12) TeV cm(-2) s(-1) in the northern sky and between 3-700 x 10(-12) TeV cm(-2) s(-1) in the southern sky. The stacked source searches provide the best limits to specific source classes. The full IceCube detector is expected to improve the sensitivity to d Phi/dE proportional to E-2 sources by another factor of two in the first year of operation.

Limits on Neutrino Emission from Gamma-Ray Bursts with the 40 String IceCube Detector

Abstract: IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from p gamma interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.

Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube

Abstract: Between 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.

The 2010 Interim Report of the Long-Baseline Neutrino Experiment Collaboration Physics Working Groups

Abstract: In early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a study to investigate the physics potential of the experiment with a broad set of different beam, near- and far-detector configurations. Nine initial topics were identified as scientific areas that motivate construction of a long-baseline neutrino experiment with a very large far detector. We summarize the scientific justification for each topic and the estimated performance for a set of far detector reference configurations. We report also on a study of optimized beam parameters and the physics capability of proposed Near Detector configurations. This document was presented to the collaboration in fall 2010 and updated with minor modifications in early 2011.

Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 40-string detector

Abstract: The IceCube Neutrino Observatory is a 1 km(3) detector currently taking data at the South Pole. One of the main strategies used to look for astrophysical neutrinos with IceCube is the search for a diffuse flux of high-energy neutrinos from unresolved sources. A hard energy spectrum of neutrinos from isotropically distributed astrophysical sources could manifest itself as a detectable signal that may be differentiated from the atmospheric neutrino background by spectral measurement. This analysis uses data from the IceCube detector collected in its half completed configuration which operated between April 2008 and May 2009 to search for a diffuse flux of astrophysical muon neutrinos. A total of 12 877 upward-going candidate neutrino events have been selected for this analysis. No evidence for a diffuse flux of astrophysical muon neutrinos was found in the data set leading to a 90% C. L. upper limit on the normalization of an E-2 astrophysical nu(mu) flux of 8.9 x 10(-9) GeV cm(-2) s(-1) sr(-1). The analysis is sensitive in the energy range between 35 TeV and 7 PeV. The 12 877 candidate neutrino events are consistent with atmospheric muon neutrinos measured from 332 GeV to 84 TeV and no evidence for a prompt component to the atmospheric neutrino spectrum is found.

Search for dark matter from the Galactic halo with the IceCube Neutrino Telescope

Abstract: Self-annihilating or decaying dark matter in the Galactic halo might produce high energy neutrinos detectable with neutrino telescopes. We have conducted a search for such a signal using 276 days of data from the IceCube 22-string configuration detector acquired during 2007 and 2008. The effect of halo model choice in the extracted limit is reduced by performing a search that considers the outer halo region and not the Galactic Center. We constrain any large-scale neutrino anisotropy and are able to set a limit on the dark matter self-annihilation cross section of h similar or equal to 10(-22) cm(3) s(-1) for weakly interacting massive particle masses above 1 TeV, assuming a monochromatic neutrino line spectrum.

Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube

Abstract: Between May 2009 and May 2010, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mille anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of 5 weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at right ascension 122.4 degrees and declination -47.4 degrees, extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.

Constraints on the Extremely-high Energy Cosmic Neutrino Flux with the IceCube 2008-2009 Data

Abstract: We report on a search for extremely-high energy neutrinos with energies greater than 10(6) GeV using the data taken with the IceCube detector at the South Pole. The data was collected between April 2008 and May 2009 with the half-completed IceCube array. The absence of signal candidate events in the sample of 333.5 days of live time significantly improves model-independent limits from previous searches and allows to place a limit on the diffuse flux of cosmic neutrinos with an E-2 spectrum in the energy range 2.0 x 10(6) - 6.3 x 10(9) GeV to a level of E-2 phi <= 3.6 x 10(-8) GeV cm(-2) sec(-1) sr(-1).

A new water-based liquid scintillator and potential applications

Abstract: In this paper we describe a new type of scintillating liquid based on water. We describe the concept, preparation, and properties of this liquid, and how it could be used for a very large, but economical detector. The applications of such a detector range from fundamental physics such as nucleon decay and neutrino physics to physics with broader application such as neutron detection. We briefly describe the scientific requirements of these applications, and how they can be satisfied by the new material.

First operation of a double phase LAr Large Electron Multiplier Time Projection Chamber with a 2D projective readout anode

Abstract: We have previously reported on the construction and successful operation of the novel double phase Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC). This detector concept provides a 3D-tracking and calorimetric device capable of adjustable charge amplification, a promising readout technology for next generation neutrino detectors and direct Dark Matter searches. In this paper, we report on the first operation of a LAr LEM-TPC prototype equipped with a single 1 mm thick LEM amplifying stage and a 2D projective readout anode. The active area of the detector is 10×10 cm2 and the drift length is 21 cm. Cosmic muon events were collected, fully reconstructed and used to characterize the performance of the chamber. The obtained signals provide images of very high quality and the energy loss distributions of minimum ionizing tracks give a direct estimate of the amplification. We find that a stable gain of ∼ 30 can be achieved with this detector configuration corresponding to a signal-over-noise ratio larger than 200 for minimum ionizing tracks. The decoupling of the amplification stage and the use of the 2D readout anode offer several advantages which are described in the text.

Proposed search for a fourth neutrino with a PBq antineutrino source.

Abstract: Several observed anomalies in neutrino oscillation data can be explained by a hypothetical fourth neutrino separated from the three standard neutrinos by a squared mass difference of a few ${\mathrm{eV}}^{2}$. We show that this hypothesis can be tested with a PBq (ten kilocurie scale) $^{144}\mathrm{Ce}$ or $^{106}\mathrm{Ru}$ antineutrino beta source deployed at the center of a large low background liquid scintillator detector. In particular, the compact size of such a source could yield an energy-dependent oscillating pattern in event spatial distribution that would unambiguously determine neutrino mass differences and mixing angles.

Core-collapse astrophysics with a five-megaton neutrino detector

Abstract: The legacy of solar neutrinos suggests that large neutrino detectors should be sited underground. However, to instead go underwater bypasses the need to move mountains, allowing much larger water Cerenkov detectors. We show that reaching a detector mass scale of ~5 Megatons, the size of the proposed Deep-TITAND, would permit observations of neutrino “mini-bursts” from supernovae in nearby galaxies on a roughly yearly basis, and we develop the immediate qualitative and quantitative consequences. Importantly, these mini-bursts would be detected over backgrounds without the need for optical evidence of the supernova, guaranteeing the beginning of time-domain MeV neutrino astronomy. The ability to identify, to the second, every core collapse in the local Universe would allow a continuous “death watch” of all stars within ~5 Mpc, making practical many previously-impossible tasks in probing rare outcomes and refining coordination of multiwavelength/multiparticle observations and analysis. These include the abilities to promptly detect otherwise-invisible prompt black hole formation, provide advance warning for supernova shock-breakout searches, define tight time windows for gravitational-wave searches, and identify “supernova impostors” by the nondetection of neutrinos. Observations of many supernovae, even with low numbers of detected neutrinos, will help answer questions about supernovae that cannot be resolved with a single high-statistics event in the Milky Way.

First search for point sources of high-energy cosmic neutrinos with the antares neutrino telescope*

Abstract: Results are presented of a search for cosmic sources of high energy neutrinos with the ANTARES neutrino telescope. The data were collected during 2007 and 2008 using detector configurations containing between 5 and 12 detection lines. The integrated live time of the analyzed data is 304 days. Muon tracks are reconstructed using a likelihood-based algorithm. Studies of the detector timing indicate a median angular resolution of 0.5 +/- 0.1 degrees. The neutrino flux sensitivity is 7.5 x 10-8 ~ (E/GeV)^-2 GeV^-1 s^-1 cm^-2 for the part of the sky that is always visible (declination < -48 degrees), which is better than limits obtained by previous experiments. No cosmic neutrino sources have been observed.

Magnetic Field and Flavor Effects on the Gamma-Ray Burst Neutrino Flux

Abstract: We reanalyze the prompt muon neutrino flux from gamma-ray bursts (GRBs) in terms of the particle physics involved, as in the example of the often-used reference Waxman-Bahcall GRB flux. We first reproduce this reference flux explicitly treating synchrotron energy losses of the secondary pions. Then we include additional neutrino production modes, the neutrinos from muon decays, the magnetic field effects on all secondary species, and flavor mixing with the current parameter uncertainties. We demonstrate that the combination of these effects modifies the shape of the original Waxman-Bahcall GRB flux significantly and changes the normalization by a factor of 3 to 4. As a consequence, the gamma-ray burst search strategy of neutrino telescopes may be based on the wrong flux shape, and the constraints derived for the GRB neutrino flux, such as the baryonic loading, may in fact be much stronger than anticipated.

AMADEUS—The acoustic neutrino detection test system of the ANTARES deep-sea neutrino telescope

Abstract: The AMADEUS system described in this article is integrated into the ANTARES neutrino telescope in the Mediterranean Sea and aims at the investigation of techniques for acoustic detection of neutrinos in the deep sea. Installed at water depths between 2000 and 2400m, its acoustic sensors employ piezo-electric elements for the broad-band recording of signals with frequencies ranging up to 125 kHz with typical sensitivities around −145 dB re. 1V/μPa (including preamplifier). Completed in May 2008, AMADEUS consists of six "acoustic clusters", each comprising six acoustic sensors that are arranged at distances of roughly 1m from each other. Three acoustic clusters each are installed along two vertical mechanical structures (so-called lines) of the ANTARES detector at a horizontal distance of 240m. Vertical spacings within a line range from 15m to 125m. Each cluster contains custom-designed electronics boards to amplify and digitise the acoustic data from the sensors. The data transmission to shore is done via optical fibres, using the TCP/IP protocol. An on-shore computer cluster, currently consisting of four dedicated servers, is used to process, filter and store the selected data. The daily volume of recorded data is about 10 - 20 GByte. The system is operating continuously and automatically, requiring only little human intervention. AMADEUS allows for extensive studies of both transient signals and ambient noise in the deep sea as well as signal correlations on several length scales and localisation of acoustic point sources. Thus the system is excellently suited to assess the background conditions that affect the measurement of bipolar pulses expected to originate from neutrino interactions. This in turn allows for feasibility studies of a future large-scale acoustic neutrino telescope in the Mediterranean Sea.

Enhanced neutrino signals from dark matter annihilation in the Sun via metastable mediators

Abstract: We calculate the neutrino signal resulting from annihilation of secluded dark matter in the Sun. In this class of models, dark matter annihilates first into metastable mediators, which subsequently decay into Standard Model particles. If the mediators are long lived, they will propagate out from the dense solar core before decaying. High energy neutrinos undergo absorption in the Sun. In the standard scenario in which neutrinos are produced directly in the centre of the Sun, absorption is relevant for E100 GeV, resulting in a significant suppression of the neutrino spectrum beyond E ~ 1 TeV. In the secluded dark matter scenario, the neutrino signal is greatly enhanced because neutrinos are injected away from the core, at lower density. Since the solar density falls exponentially with radius, metastable mediators have a significant effect on the neutrino flux, even for decay lengths which are small compared to the solar radius. Moreover, since neutrino detection cross sections grow with energy, this enhancement of the high energy region of the neutrino spectrum would have a large effect on overall event rates.

Detecting sterile neutrinos with KATRIN like experiments

Abstract: A sterile neutrino with mass in the eV range, mixing with e, is allowed and possibly even preferred by cosmology and oscillation experiments. If such eV-mass neutrinos exist they provide a much better target for direct detection in beta decay experiments than the active neutrinos which are expected to have sub-eV masses. Their relatively high mass would allow for an easy separation from the primary decay signal in experiments such as KATRIN.

Coherent Neutrino Scattering in Dark Matter Detectors

Abstract: Coherent elastic neutrino-nucleus and weakly interacting massive particle-nucleus interaction signatures are expected to be quite similar. This paper discusses how a next-generation ton-scale dark matter detector could discover neutrino-nucleus coherent scattering, a precisely-predicted standard model process. A high-intensity pion- and muon- decay-at-rest neutrino source recently proposed for oscillation physics at underground laboratories would provide the neutrinos for these measurements. In this paper, we calculate raw rates for various target materials commonly used in dark matter detectors and show that discovery of this interaction is possible with a $2\text{ }\text{ }\mathrm{ton}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{year}$ GEODM exposure in an optimistic energy threshold and efficiency scenario. We also study the effects of the neutrino source on weakly interacting massive particle sensitivity and discuss the modulated neutrino signal as a sensitivity/consistency check between different dark matter experiments at the Deep Underground Science and Engineering Laboratory. Furthermore, we consider the possibility of coherent neutrino physics with a GEODM module placed within tens of meters of the neutrino source.

Icecube-deepcore-pingu: fundamental neutrino and dark matter physics at the south pole

Abstract: The IceCube neutrino observatory at the South Pole uses 1 km3 of instrumented ice to detect both astrophysical and atmospheric neutrinos. Expanding the capabilities of the original design, the DeepCore sub-array is a low-energy extension to IceCube which will collect $\mathcal{O}(100, 000)$ atmospheric neutrinos a year. The high statistics sample will allow DeepCore to make neutrino oscillation measurements at higher energies and longer baselines than current experiments. The first successful observation of neutrino induced cascades in a neutrino telescope has recently been observed in DeepCore, which upon further cultivation should help refine atmospheric neutrino flux models. Besides the fundamental neutrino physics, the low-energy reach of DeepCore, down to as low as 10 GeV, and multi-megaton effective volume will enhance indirect searches for WIMP-like dark matter. A new proposal seeking to lower the energy reach down to $\mathcal{O}(1)$ GeV known as the Phased IceCube Next Generation Upgrade (or PING...

First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector

Abstract: We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16 TeV remained after event selections in the diffuse analysis, with an expected total background contribution of 8.3 +/- 3.6. At 90% confidence we set an upper limit of E-2 Phi(90%CL) < 3.6 x 10(-7) GeV.cm(-2).s(-1).sr(-1) on the diffuse flux of neutrinos of all flavors in the energy range between 24 TeV and 6.6 PeV assuming that Phi proportional to E-2 and the flavor composition of the nu(e):nu(mu):nu(tau) flux is 1:1:1 at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5 TeV. The observed number of events is consistent with the expected background, within the uncertainties.

Resolving the reactor neutrino anomaly with the KATRIN neutrino experiment

Abstract: Abstract The KArlsruhe TRItium Neutrino experiment (KATRIN) combines an ultra-luminous molecular tritium source with an integrating high-resolution spectrometer to gain sensitivity to the absolute mass scale of neutrinos. The projected sensitivity of the experiment on the electron neutrino mass is 200 meV at 90% C.L. With such unprecedented resolution, the experiment is also sensitive to physics beyond the Standard Model, particularly to the existence of additional sterile neutrinos at the eV mass scale. A recent analysis of available reactor data appears to favor the existence of such a sterile neutrino with a mass splitting of | Δ m sterile | 2 ⩾ 1.5 eV 2 and mixing strength of sin 2 2 θ sterile = 0.17 ± 0.08 at 95% C.L. Upcoming tritium beta decay experiments should be able to rule out or confirm the presence of the new phenomenon for a substantial fraction of the allowed parameter space.