Future Neutrino Detectors Research Articles

Self-calibration of neutrino detectors using characteristic backgrounds

We introduce the possibility to use natural neutrino backgrounds, such as Geo-neutrinos ( ν ¯ e ) or solar neutrinos ( ν e ), with known characteristic spectral shape for the energy calibration of future neutrino detectors, e.g. Large Liquid Scintillator Detectors. This “CalEffect” could be used without the need to apply any modifications to the experiment in all situations where one has a suitable background with sufficient statistics. After deriving the effect analytically using χ 2 statistics, we show that it is only tiny for reactor neutrino experiments, but can be applicable in other situations. As an example, we present its impact on the identification of the wiggles in the power spectrum of supernova neutrinos caused by Earth matter effects. The Self-Calibration Effect could be used for cross checking other calibration methods and to resolve systematical effects in the primary neutrino interaction processes, in particular in the energy dependence of low-energy cross-sections.

First results from the NEMO Test Site

The NEMO (NEutrino Mediterranean Observatory) Collaboration is constructing, 25 km E from Catania (Sicily) at 2000 m depth, an underwater test site to perform long-term tests of prototypes and new technologies for an underwater high energy neutrino detector in the Mediterranean Sea. In this framework the collaboration deployed and operated an experimental apparatus for on-line monitoring of deep-sea noise. The station is equipped with 4 hydrophones operational in the range 30 Hz - 40 kHz. This interval of frequencies matches the range suitable for acoustic detection of high energy neutrino-induced showers in water. Hydrophone signals are digitized underwater at 96 kHz sampling frequency and 24 bits resolution. A custom software was developed to record data on high resolution 4-channels PCM .le. Data are used to model underwater acoustic noise as a function of frequency and time, a mandatory parametre for future acoustic neutrino detectors. Results indicate that the average noise in the site is compatible with noise produced in condition of sea surface agitation (sea state.)

New Prospects for High-energy Neutrinos from gamma-ray Bursts

High-energy neutrinos from Gamma-Ray Bursts (GRBs) have been expected since the pre-Swift era. Such signals may be detected by future large neutrino detectors such as IceCube. Recently Swift has shown several novel phenomena. We suggest the new prospects for high-energy neutrino emission in the Swift era. Expected signals, if detected, are useful for revealing of the nature of GRBs.

A new readout of large area smart photomultipliers by Geiger-mode APDs

Future neutrino detectors require large, transparent detection volumes (water, ice, scintillator) and in turn a large number of large photomultipliers. We present a possible photon detector design based on the light amplification concept, e.g., a large, nearly spherical vacuum photon detector where the photoelectrons are accelerated onto a small scintillator. As secondary readout element Geiger-mode Avalanche photodiodes are used. Advantages and drawbacks of this readout will be discussed. Some results from initial studies will be presented.

Anti-neutrino imprint in solar neutrino flare**This paper is dedicated to the memory of the flaring life of Jonathan Evron, fallen at brightest age 20 on 2nd November 2005 for the Jewish State of Israel.

A future neutrino detector at megaton mass might enlarge the neutrino telescope thresholds revealing cosmic supernova background and largest solar flares (SFs) neutrinos. Indeed the solar energetic (Ep>100 MeV) flare particles (protons, α), while scattering among themselves on solar corona atmosphere must produce prompt charged pions, whose chain decays are source of a solar (electron–muon) neutrino ‘flare’ (at tens or hundreds MeV energy). These brief (minutes) neutrino ‘bursts’ at largest flare peak may overcome by three to five orders of magnitude the steady atmospheric neutrino noise on the Earth, possibly leading to their detection above detection thresholds (in a full mixed three flavour state). Moreover the birth of anti-neutrinos at a few tens of MeV very clearly flares above a null thermal ‘hep’ anti-neutrino solar background and also above a tiny supernova relic and atmospheric noise. The largest prompt solar anti-neutrino ‘burst’ may be well detected in future Super Kamikande (gadolinium implemented) anti-neutrino signatures mostly in inverse beta decay () and rarely in higher energy muon, or even rarest tau neutrino leptons reactions. Our estimate for the recent and exceptional October–November 2003 SFs and January 20th 2005 exceptional flare might lead to a few events above or near unity for existing Super-Kamiokande and above unity for megaton detectors. The ν spectra may reflect in a subtle way the neutrino flavour oscillations and mixing in flight. A comparison of the solar neutrino flare (at their birth place on the Sun and after oscillation on arrival on the Earth) with other neutrino foreground is estimated: it offers an independent track to disentangle the neutrino flavour puzzles and its most secret mixing angles. The sharpest noise-free anti-neutrino imprint maybe its first clean voice.

Coherent radio pulses from showers in different media: A unified parametrization

We study the frequency and angular dependences of Cherenkov radio pulses originated by the excess of electrons in electromagnetic showers in different dense media that are being given consideration as targets for ultra high energy neutrino detection such as ice, salt and the lunar regolith. By means of a simple model of shower development we rederive the scaling of the electric field spectrum with the properties of the media such as density, radiation length, Moli\`ere radius, critical energy and refraction index. We compare the predictions of the scaling relations to the numerical results obtained in our own developed GEANT4-based Monte Carlo simulation, and address in a quantitative manner the predictive power of the scaling relations. We also give a unified parametrization of the frequency spectrum and angular distribution of the electric field in ice, salt, and the lunar regolith, in terms of the relevant properties of the media to be used in practical applications. We establish the applicability of our parametrizations. Our formulas are useful for estimates of the acceptance of current and future neutrino detectors using the radio technique, and for many other practical applications.

Probing very high energy prompt muon and neutrino fluxes and the cosmic ray knee viaunderground muons

We calculate event rates and demonstrate the observational feasibility of veryhigh energy muons (1–1000 TeV) in a large-mass underground detector operatingas a pair-meter. This energy range corresponds to surface muon energies of∼(5–5000 TeV) and primary cosmicray energies of ∼(50 TeV–5 × 104 TeV). Such measurements would significantly assist in an improved understanding of the prompt contributionto νe,νμ and μ fluxes in present and future ultra high energy neutrino detectors. In addition, they wouldshed light on the origin of and possible compositional changes at and around the observed‘knee’ in the cosmic ray spectrum.

Constraints on neutrino masses from a galactic supernova neutrino signal at present and future detectors

We study the constraints on neutrino masses that could be derived from the observation of a galactic supernova neutrino signal with present and future neutrino detectors. Our analysis is based on a recently proposed method that uses the full statistics of neutrino events and does not depend on particular astrophysical assumptions. The statistical approach, originally justified mainly in terms of intuitive reasoning, is put on a more solid basis by means of Bayesian inference reasoning. Theoretical uncertainties in the neutrino signal time profiles are estimated by applying the method to two widely different supernova models. Present detectors can reach a sensitivity down to 1 eV. This is better than limits from tritium β-decay experiments, competitive with the most conservative results from neutrinoless double β-decay, less precise but less dependent from prior assumptions than cosmological bounds. Future megaton water Čerenkov detectors will allow for about a factor of two improvement. However, they will not be competitive with the next generation of laboratory experiments.

First results from a liquid argon time projection chamber in a magnetic field

A small liquid argon Time Projection Chamber (LAr TPC) was operated for the first time in a magnetic field of 0.55 T. The imaging properties of the detector were not affected by the magnetic field. In a test run with cosmic rays a sample of through going and stopping muons was collected. The chamber with the readout electronics and the experimental setup are described. A few selected events were reconstructed and analyzed and the results are presented. The magnetic bending of the charged particle tracks allows the determination of the electric charge and the momentum, even for particles not fully contained in the drift chamber. These features are e.g. required for future neutrino detectors at a neutrino factory.

Solar neutrino day-night effect and θ13

We consider the possibility of probing the leptonic mixing angle θ13 through day–night asymmetry measurements at future water Cherenkov solar neutrino detectors. It is shown that, depending on the measured value of the asymmetry, the current upper bound on θ13 may be improved, or even a lower bound on this mixing parameter may be obtained.

Measuring diffuse neutrino fluxes with IceCube

In this paper the sensitivity of a future kilometre-sized neutrino detector to detect andmeasure the diffuse flux of high energy neutrinos is evaluated. Event rates inestablished detection channels, such as muon events from charged currentνμ interactions orcascade events from νe and ντ interaction, are calculated using a detailed Monte Carlo simulation. Neutrino fluxesas expected from prompt charm decay in the atmosphere or from astrophysicalsources such as Active Galactic Nuclei are modelled assuming power laws. Theability to measure the normalization and slope of these spectra is then analysed.It is found that the cascade channel generally has a high sensitivity for the detection andcharacterization of the diffuse flux, when compared to what is expected for the upgoing- anddowngoing-muon channels. A flux at the level of the Waxman–Bahcall upper bound shouldbe detectable in all channels separately while a combination of the information of thedifferent channels will allow detection of a flux more than one order of magnitudelower. Neutrinos from the prompt decay of charmed mesons in the atmosphereshould be detectable in future measurements for all but the lowest predictions.

A simple analytic three-flavour description of the day-night effect in the solar neutrino flux

In the 3-flavour framework we derive a simple approximate analytic expression for the day-night difference of the flux of solar $\nu_e$ at terrestrial detectors which is valid for an arbitrary Earth density profile. Our formula has the accuracy of a few per cent and reproduces all the known analytic expressions for the Earth matter effects on the solar neutrino oscillations obtained under simplifying assumptions about the Earth's density profile (matter of constant density, 3 layers of constant densities, and adiabatic approximation). It can also be used for studying the Earth matter effects on the oscillations of supernova neutrinos. We also discuss the possibility of probing the leptonic mixing angle $\theta_{13}$ through day--night asymmetry measurements at future water Cherenkov solar neutrino detectors. We show that, depending on the measured value of the asymmetry, the current upper bound on $\theta_{13}$ may be improved, or even a lower bound on this mixing parameter may be obtained.

Neutrino cross-section measurement with neutrinos from muon decay

In this paper, we stress the idea that new, more precise neutrino cross-sections measurements at low energies will be necessary to improve the results of future big neutrino detectors, which will be dominated by the contribution of the systematic errors. The use of a muon beam instead of the traditional pion beams is proposed. This choice allows the simultaneous measurement of both, ν μ and ν e interactions and the two helicities, in a clean environment and with a precise knowledge of the beam flux. We show that with ∼10 15 μ 's/year and a moderate mass detector (∼100 tons) placed close to the muon storage ring, precisions of the order of 10% in σ ν/ E ν ( E ν bin size of 100 MeV ) can be reached for neutrino energies below 2 GeV .

Role ofν−inducedreactions on lead and iron in neutrino detectors

We have calculated cross sections and branching ratios for neutrino induced reactions on ^{208}Pb and ^{56}Fe for various supernova and accelerator-relevant neutrino spectra. This was motivated by the facts that lead and iron will be used on one hand as target materials in future neutrino detectors, on the other hand have been and are still used as shielding materials in accelerator-based experiments. In particular we study the inclusive ^{56}$Fe(\nu_e,e^-)$^{56}Co and ^{208}$Pb(\nu_e,e^-)$^{208}Bi cross sections and calculate the neutron energy spectra following the decay of the daughter nuclei. These reactions give a potential background signal in the KARMEN and LSND experiment and are discussed as a detection scheme for supernova neutrinos in the proposed OMNIS and LAND detectors. We also study the neutron-emission following the neutrino-induced neutral-current excitation of ^{56}Fe and ^{208}Pb.

Strongly Interacting Neutrinos and the Highest Energy Cosmic Rays

Cosmic rays of energies larger than the Greisen-Zatsepin-Kuzmin (GZK) cutoff may be neutrinos if they acquire strong interactions due to a ``precocious unification'' of forces. A scenario for this to happen is outlined. There is no contradiction with precision measurements carried out at LEP and SLAC. Observable consequences at LHC and future neutrino detectors are discussed.

Three flavour Majorana neutrinos with magnetic moments in a supernova

The resonant transition effects MSW and NSFP for three flavour Majorana neutrinos in a supernova are considered, where the transition magnetic moments are likely to play a relevant role in neutrino physics. In this scenario, the deformed thermal neutrino distributions are obtained for different choices of the electron-tau mixing angle. Detailed predictions for the future large neutrino detectors are also given in terms of the ratio between the spectra of recoil electrons for deformed and undeformed spectra.

Testing the vacuum oscillation and the MSW solutions of the solar neutrino problem

Solar model independent tests of the vacuum oscillation and MSW solutions of the solar neutrino problem are considered. Detailed predictions for time (seasonal) variations of the signals due to neutrino oscillations in vacuum are given for the future solar neutrino detectors (SNO, Super-Kamiokande, BOREXINO, HELLAZ). Results on the distortions of the spectra of 8B neutrinos, and of e − from the reaction ν + e − → ν + e − induced by 8B neutrinos, are presented in the cases of vacuum oscillations or MSW transitions for a large number of values of the relevant parameters. The possibilities to distinguish between the vacuum oscillation, the MSW adiabatic, and the MSW nonadiabatic transitions in the future solar neutrino experiments are discussed.

BOUNDS ON LEPTON FLAVOR CHANGING CURRENTS AND THE SOLAR NEUTRINO PUZZLE: Bounds on Lepton Flavor Changing Currents

We present a phenomenological analysis of a lepton flavor changing current, considering the case of interactions among leptons which change the neutrino flavor and are diagonal in the charged lepton sector. In the case of νe↔νµ transition, we derive a bound on the vector coupling constant GV≤0.16 GF from experimental data on νµ−e scattering. For a transition νe↔νx, from (anti) νe−e scattering experiments and from the analysis of advanced stellar evolutionary phases, we find GV≤0.55 GF. We discuss the compatibility of these data with a possible explanation of the solar neutrino puzzle. We also analyze how the present bounds can be improved in future long baseline neutrino experiments and atmospheric neutrino detectors.

A neutrino decay model, solar antineutrinos and atmospheric neutrinos

The neutrino decay solution to the solar neutrino problem calls for large mixing and a short lifetime for the decaying neutrino. We propose a model for neutrino masses which has these features and furthermore leads to decays into antineutrinos. The resulting fluxes of v e 's are detectable in future solar neutrino detectors. The large v e− v μ mixing can account for the atmospheric neutrino anomaly at the same time.