Fast neutrino decay and solar neutrino detectors

The neutrino decay solution of the solar neutrino problem is revisited in the context of majoron models. It is shown that for a definite range of parameters this scenario reconciles both the Homestake and the Kamiokande data. The prediction for Gallium detectors is also given. Attention is devoted to the analysis of the signal, which is the crucial prediction of this scenario. It is shown that the sensitivity of Borexino is sufficient to observe this signal and to distinguish it from the alternative signal provided by hybrid models of neutrino oscillation and magnetic moment transitions. Other sources of solar production are also reviewed (matter induced decay, MSW catalized decay or the decay of solar 17 keV neutrinos).     

Experimental techniques for low energy neutrino experiments

During the past years it has become always more and more important to study solar neutrinos at low energies (below 1 MeV) in order to solve the solar neutrino problem.Measuring low energy solar neutrinos is not an easy task because of the rapidly increasing background in the sub-MeV region. Thus new experimental methods have been developed to accomplish the challenging aim.     

Liquid argon neutrino detectors

The Liquid Argon imaging technique, as proposed for the ICARUS detector, offers the possibility to perform complementary and simultaneous measurements of neutrinos, as those of CERN to Gran Sasso beam (CNGS) and those from cosmic ray events. For the currently allowed values of the Super—Kamiokande results, the combination of both CNGS and atmospheric data will provide a precise determination of the oscillation parameters. Since one can observe and unambiguously identify ν_e, ν_μ and ν_τ components, this technology allows to explore the full (3 x 3) mixing matrix. The same class of detector can be proposed for high precision measurements at a neutrino factory.     

40 MCi tritium source for experiments with low energy neutrino

The artificial tritium source of 40 MCi activity was developed for the scattering experiment to measure the electron antineutrino magnetic moment. We present R&D results which specify source design and physical parameters, its experimental effectiveness and guarantee safety during its life-cycle. Relevant technological issues are featured.     

High-energy neutrino astronomy with ?small? underground detectors

Summary High-energy (E _ν>(10÷30) GeV) neutrino sources which can be detected by underground detectors with areaS∼100 m² are discussed in this paper. It is shown that the horizon of these detectors is limited to our Galaxy. The main process to detect neutrino sources,i.e. production of high-energy muons in ν_μ N → μX scattering is studied in detail. Single sources (young supernova shells and supergiants fed by an active pulsar) and binary sources (young pulsar and giant, supernova explosion in a binary system, etc. …) are found to be able to produce a detectable neutrino flux. Special attention is given to Cyg X-3. Finally, it is shown that the possibility to detect neutrinos from solar flares on the opposite side of the Sun can be ruled out on the grounds of γ-rays observations.

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Riassunto Si discutono in questo lavoro le sorgenti di neutrini di alta energia (E _ν>(10÷30) GeV) che possono essere rivelate con rivelatori sotterranei di areaS∼100 m². Si mostra come l'orizzonte di questi rivelatori sia limitato alla nostra Galassia. Il processo principale di rivelazione di sorgenti cosmiche di neutrini, cioè la produzione di muoni di alta energia attraverso lo scattering ν_μ N → μX, è discusso in dettaglio. Si ottiene che sorgenti singole (gusci di suprenovae giovani e supergiganti con una pulsar attiva al loro interno) e sorgenti binarie (pulsar giovane e stella gigante, esplosione supernova in un sistema binario, ecc.…) sono in grado di produrre un flusso di neutrini rivelabili a Terra con rivelatori di piccole dimensioni. Si discute in particolare il sistema Cyg X-3. Infine, si dimostra che la possibilità di rivelare neutrini da flares solari sulla superficie del Sole opposta alla Terra deve essere scartata sulla base delle osservazioni di raggi γ.

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Резюме В этой статье обсуждаются источники нейтрино высоких энергий (E _ν>(10÷30) ГэВ), которые могут быть зарегистрированы с помощью подземных детекторов с площадьюS∼100 м². Показывается, что горизонт этих детекторов ограничен нашей Галактикой. Подробно исследуется основной процесс детектирования нейтринных источников, т.е. образование высокоэнергетичных мюонов при рассеянии ν_μ N → μX. Получено, что изолированные источники (оболочки молодых сверхновых и супергиганты с активным пульсаром внутри) и бинарные источники (молодой пульсар и гигант, взрыв сверхновой в бинарной системе и т.д.) могут генерировать детектируемые потоки нейтрино. Особое внимание уделяется источнику Лебедь X-3. В заключение, показывается, что возможность детектирования нейтрино от солнечных вспышек на противоположной Солнца должна быть исключена на основе наблюдений γ-лучей.

     

Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam

This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.).     

Low-energy neutrino and dark matter physics with sub-keV germanium detectors

The TEXONO-CDEX Collaboration (Taiwan experiment on neutrino?CChina dark matter experiment) explores high-purity germanium (HPGe) detection technology to develop a sub-keV threshold detector for pursuing studies on low mass weakly interacting massive particles (WIMPs), properties of neutrino and the possibilities of neutrino-nucleus coherent scattering observation. This article will introduce the facilities of newly established China Jing-Ping Underground Laboratory (CJPL), preliminary result of cosmic ray background studies at CJPL, the dark matter studies pursued at Kuo-Sheng Neutrino Laboratory (KSNL) and research efforts to accomplish our physics goals.     

Supernova neutrino detection by terrestrial nuclear detectors

We present and discuss differential cross sections for the ^128,130Te isotopes, contents of the COBRA double beta decay detector. The response of these isotopes to energy spectra of supernova neutrinos is explored by convoluting the original results, calculated in the context of the quasi-particle random phase approximation (QRPA) using realistic two-body forces, with a two-parameter Fermi-Dirac (FD) and a Power-Law (PL) neutrino energy distributions.     

Search for T-violation in neutrino oscillation with the use of muon polarization at a neutrino factory

A possibility to search for T violation in neutrino oscillation with the use of muon polarization is studied. The sensitivity to T violation is examined with various magnitudes of muon polarization as a function of muon energy and long-baseline distances.     

Corrections to the fluxes of a neutrino factory

To reach their physical goals, future neutrino factories using muon decay aim at an overall flux precision of or better. We analytically study the QED radiative corrections to the neutrino differential distributions from muon decay. Kinematic uncertainties due to the divergence of the muon beam are considered as well. The resulting corrections to the neutrino flux turn out to be of order , safely below the required precision. Received: 10 September 2002 / Revised version: 4 April 2003 / Published online: 2 June 2003 RID="a" ID="a" e-mail: alicia@delta.ft.uam.es RID="b" ID="b" e-mail: mena@delta.ft.uam.es     

Measurement of neutrino oscillations with the MINOS detectors in the NuMI beam

This Letter reports new results from the MINOS experiment based on a two-year exposure to muon neutrinos from the Fermilab NuMI beam. Our data are consistent with quantum-mechanical oscillations of neutrino flavor with mass splitting |Deltam2| = (2.43+/-0.13) x 10(-3) eV2 (68% C.L.) and mixing angle sin2(2theta) > 0.90 (90% C.L.). Our data disfavor two alternative explanations for the disappearance of neutrinos in flight: namely, neutrino decays into lighter particles and quantum decoherence of neutrinos, at the 3.7 and 5.7 standard-deviation levels, respectively.     

On the possibility of measuring the mass of the neutrino with a low energy electron beam

The neutrino mass sensitivity of the cross section just above threshold in the reaction \(_Z^A X(\bar e,v_e )_{Z - 1}^A X\) is investigated. By general arguments we find the ₃₄ ⁷⁷ Se and ₅₁ ¹²¹ Sb as the most appropriate candidates for and eventual experiment.     

Searching for new physics in future neutrino factory experiments

An extension of the new standard model, by introducing a mixing of the low mass “active” neutrinos with heavy ones, or by any model with lepton flavor violation, is considered. This leads to non-orthogonal neutrino production and detection states and to modifications of neutrino oscillations in both vacuum and matter. The possibility of the discovery of such effects in current and future neutrino oscillation experiments is discussed. First order approximation formulas for the flavor transition probabilities in constant density matter, for all experimentally available channels, are given. Numerical calculations of flavor transition probabilities for two sets of new physics parameters describing a single “effective” heavy neutrino state, both satisfying present experimental constraints, have been performed. Two energy ranges and several baselines, assuming both the current (±2σ) and the expected future errors (±3%) of the neutrino oscillation parameters are considered, keeping their present central values. It appears that the biggest potential of the discovery of the possible presence of any new physics is pronounced in oscillation channels in which ν_e and ν_ē are not involved at all, especially for two baselines, L=3000 km and L=7500 km, which for other reasons are also called “magic” for future Neutrino Factory experiments. PACS 13.15.+g; 14.60.Pq; 14.60.St     

Prototype thermal detectors for a Re neutrino mass experiment

We report on a new method to measure the electron antineutrino mass, consisting of the end-point study of ¹⁸⁷Re β-spectrum (Q-value=2.6 keV) collected calorimetrically (source=detector approach) with high energy resolution and statistics. The proposed detector is a micro-bolometer, single or in an array structure, containing a total rhenium mass of 1 mg, operated at a temperature of a few tens of mK and able to reach 10 eV energy resolution. As phonon sensors, we are developing silicon thermistors doped by implantation; some tests are performed also with neutron transmutation doped germanium thermistors. We have obtained up to now promising energy resolutions down to 11 eV with tin absorbers (as test devices) and 70 eV with rhenium absorbers.     

The 2+2 and 3+1 four-family neutrino mixing at the neutrino factory

We upgrade the study of the physical reach of a neutrino factory in the four-family neutrino mixing scenario, taking into account the latest LSND results, which point out how the 3+1 scheme cannot be completely ruled out within the present experimental data (although the 2+2 scheme is still the preferred choice when four neutrinos are considered). A detailed comparison of the physical reach of the factory in the two schemes is given, with similar results for the sensitivity to the mixing angles. Huge CP-violating effects can be observed in both schemes with a near, O(10) km, detector of O(10) kton size in the channel. A smaller detector of 1 kton size can still observe very large effects in this channel. Received: 18 July 2001 / Published online: 21 September 2001     

Dark energy and neutrino CPT-violation

In this paper we study dynamical CPT-violation in the neutrino sector as induced by the dark energy of the universe. Specifically we consider a dark energy model where the dark energy scalar derivatively interacts with the right-handed neutrinos. This type of derivative coupling leads to cosmological CPT-violation during the evolution of the background field of the dark energy. We calculate the induced CPT-violation of left-handed neutrinos and find that the CPT-violation produced in this way is consistent with the present experimental limit and sensitive to future neutrino oscillation experiments such as the neutrino factory. PACS 95.36.+x; 14.60.St