Neutrino oscillations in the sun and the205Tl solar neutrino experiment

Neutrino induced transition rates from²⁰⁵Tl to excited states in²⁰⁵Pb were calculated for neutrino fluxes from the different hydrogen burning reactions in the sun. Suppression factors for electron neutrinos due to flavor oscillations in the sun were obtained. The influence of neutrino oscillations on the neutrino capture rate of²⁰⁵Tl in dependence of the mixing angle and neutrino mass difference is discussed.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

208Pb(p, α)205Tl reaction at 16.475 MeV

The (p, α) reaction was studied on a²⁰⁸Pb target at 16.475 MeV. Nineteen states were observed in²⁰⁵Tl, up to 3.6 MeV in excitation. Angular distributions were obtained for five strong proton-hole transitions, and DWBA fits made to determinelj values. Results are compared with previous²⁰⁶Pb(t, α)²⁰⁵Tl,²⁰⁶Pb(d,³He)²⁰⁵Tl,²⁰⁵Tl(p, p′), and²⁰⁵Tl(n, n′) work.     

Salt neutrino detector for ultrahigh-energy neutrinos

Rock salt and limestone are studied to determine their suitability for use as a radio-wave transmission medium in an ultrahigh energy (UHE) cosmic neutrino detector. A sensible radio wave would be emitted by the coherent Cherenkov radiation from negative excess charges inside an electromagnetic shower upon interaction of a UHE neutrino in a high-density medium (Askar’yan effect). If the attenuation length for the radio wave in the material is large, a relatively small number of radio-wave sensors could detect the interaction occurring in the massive material. We measured the complex permittivity of the rock salt and limestone by the perturbed cavity resonator method at 9.4 and 1 GHz to good precision. We obtained new results of measurements at the frequency at 1.0 GHz. The measured value of the radio-wave attenuation length of synthetic rock salt samples is 1080 m. The samples from the Hockley salt mine in the United States show attenuation length of 180 m at 1 GHz, and then we estimate it by extrapolation to be as long as 900 m at 200 MHz. The results show that there is a possibility of utilizing natural massive deposits of rock salt for a UHE neutrino detector. A salt neutrino detector with a size of 2×2×2 km would detect 10 UHE neutrino/yr generated through the GZK process.     

High spin states in205Pb and a precision test of the nuclear shell model for three nucleons

Using the²⁰⁴Hg(α, 3n) reaction withα-particles of about 40 MeV, we have proved by applying nowadays conventionalγ-ray spectroscopy in-beam technique, that there are two isomeric states in²⁰⁵Pb at the excitation energies 5,161.3 and 3,195.5 keV having the half-lives 71±3 and 217±5 ns, respectively. These isomeric states have spins and parities 33/2⁺ and 25/2^? and are mainly due to thei ₁₃ ^2/?3 andi ₁₃ ^2/?2 p ₁ ^2/?1 configurations, respectively. This conclusion is supported by the experimentalg-factors of these states being ?0.159±0.008 and ?0.0676±0.0011, respectively. It is furthermore shown that theE2 effective neutron charge is the same forE2 transitions from the 33/2⁺ state in²⁰⁵Pb and from the 12⁺ state in²⁰⁶Pb as required by the assumption that the²⁰⁸Pb core is responsible for the totalE2 strength of the neutron holes, and that these states are due to thei ₁₃ ^2/?3 andi ₁₃ ^2/?2 configurations. The calculatedB(E3) values ofE3 transitions from isomeric states in²⁰⁵Pb and²⁰⁶Pb agree reasonably well with the experimental values as expected from the assumption that theE3-strength should come from particle coupling to the octupole states of the²⁰⁸Pb core. The energies of the six most well established excited states in²⁰⁵Pb with angular momenta in the region 19/2–33/2 were calculated using empirical single-particle energies, empirical two-particle interactions and angular momentum algebra. The average deviation between experimental and calculated energies is ?3 keV and the root mean square deviation 6 keV as compared to the uncertainty ± 5 keV in the nuclear masses used in the calculation. For the orbits concerned the shell model is thus valid with an extremely high precision. The contribution of effective three-particle interaction in these orbits must consequently be less than about 5 keV.     

The distribution of205Tl proton hole states and estimation of the root mean square radii of206Pb and208Pb from their charge distributions

The fragmentations of the 3s _1/2, 2d _3/2, 2d _5/2 and 1.h _11/2 proton states were deduced using the hole-core coupling model calculation and compared with recent²⁰⁶Pb ( \(\vec d\) ,³He) reaction data. The energies of the proton fragments carrying the main shell-model strengths were used to deduce the radial wave functions of²⁰⁵T1 and²⁰⁷Tl that give rise to charge distributions of these nuclei. From their respective charge distributions, root mean square radii of²⁰⁶Pb and²⁰⁸Pb were extracted.     

Theory of the effects of nuclear structure on internal conversion in Tl203

The Fermi-liquid method is applied to consider the effects of the strong interaction on the penetration matrix element for the conversion transition in Tl²⁰³. The theoretical value agrees well with experiment.We are indebted to M. A. Listengarten for discussions.     

Search for neutrino radiative decay with a prototype Borexino detector

Results of background measurements with a prototype of the Borexino detector were used to obtain bounds on the lifetime of radiative neutrino decay ν_H→ν_L+γ. The new lower limit for the lifetime of pp and ⁷Be neutrinos is τ_c.m.(ν_H→ν_L+γ) /mν≥4.2×10³ s eV^?1(α)= 0). It is more than an order of magnitude stronger than the value obtained in previous experiments using nuclear reactors and accelerators.     

The NE detector for a long baseline neutrino oscillation experiment

The project of a large underground experiment, N^OE (Neutrino Oscillation Experiment), composed by modules of scintillating fiber calorimeter interleaved with TRD modules, total weight 6.7 ktons, is presented. This apparatus has been optimized for long baseline neutrino oscillation studies, in particular to be sensitive in the region of sin² 2θ and Δm² suggested by the atmospheric neutrino anomaly (fig. 3).     

Search for neutrino radiation from collapsing stars with the Artyomovsk scintillation detector

The current status of an experiment designed to search for neutrino radiation from collapsing stars using the Artyomovsk Liquid Scintillation Detector is described. Observations were conducted from November 1977 to July 2012. The upper limit for the mean rate at which neutrino bursts occur in the Galaxy is found to be f _col < 0.0658 events per year at a 90% confidence level. In 35 years of observations, no supernovae were detected in the Galaxy.     

DANSSino: a pilot version of the DANSS neutrino detector

DANSSino is a reduced pilot version of a solid-state detector of reactor antineutrinos (to be created within the DANSS project and installed under the industrial 3 GW_th reactor of the Kalinin Nuclear Power Plant—KNPP). Numerous tests performed at a distance of 11 m from the reactor core demonstrate operability of the chosen design and reveal the main sources of the background. In spite of its small size (20 × 20 × 100 cm³), the pilot detector turned out to be quite sensitive to reactor antineutrinos, detecting about 70 IBD events per day with the signal-to-background ratio about unity.     

Search for neutrino oscillations at the palo verde nuclear reactors

We report on the initial results from a measurement of the antineutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a segmented gadolinium-loaded scintillation detector. We find that the antineutrino flux agrees with that predicted in the absence of oscillations excluding at 90% C.L. nu;(e)-nu;(x) oscillations with Deltam(2)>1.12x10(-3) eV(2) for maximal mixing and sin (2)2straight theta>0.21 for large Deltam(2). Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve nu(e).     

205Tl NMR observation of vortex lattice formation in the high temperature superconductor Tl2Ba2CuO6

We report on the asymmetric field distribution of the triangular vortex lattice in the superconductor Tl₂Ba₂CuO₆ as observed by²⁰⁵Tl NMR atB _a =4.26 T. A penetration depth of =1700±100 Å is obtained.     

Interplay of valence-shell clusters and the vibrational field in205Pb and206Pb

The properties of²⁰⁵Pb and²⁰⁶pb are described in the cluster vibrational field coupling model. Excitation energies, strengths for one-particle transfers,E2 andM1 observables are compatible with the available experimental data. Other theoretical approaches for these nuclei are discussed and compared with the results of the present investigation.     

Calculation of double-beta-decay rates and the neutrino mass

Summary Predictions for 2ν and 0ν double-beta-decay rates are given for all nuclei withA≥70, for which double beta decay is energetically allowed. These predictions are based on detailed nuclear structure studies of the beta strength distribution and replace earlier estimates basing mostly on phase space considerations. New and more stringent limits on the Majorana neutrino mass are deduced from existing double-betadecay experiments. If is found that a proper treatment of the collective effects arising from spin-isospin as well as quadrupole-quadrupole forces leads to a strong reduction of the nuclear matrix elements for two-neutrino double beta decay, but has only minor influence on the matrix elementsM ^0ν for the neutrinoless decay mode. The smaller limits form _ν result, therefore, mainly from the fact that the widely used scaling procedure underestimates the 0ν matrix elements. It is further discussed to what extent interference between different neutrinos affects the obtained mass limits.

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Rissunto Si fanno previsioni per i tassi di doppio decadimento beta a 2v e 0v per tutti i nuclei conA≥70, per i quali il doppio decadimento beta è ammesso energeticamente. Queste previsioni sono basate su studi dettagliati della struttura nucleare della distribuzione della forza di beta e sostituiscono stime precedenti basate solo su considerazioni riguardanti lo spazio tempo. Si deducono limiti nuovi e piú rigorosi sulla massa del neutrino di Majorana da esperimenti di doppio decadimento beta usando i risultati di recenti studi sulla struttura nucleare. Si trova che un trattamento appropriato degli effetti collettivi che derivano da forze spin-isospin ed anche quadrupolo-qudrupolo porta ad una forte riduzione degli elementi della matrice nucleare per il doppio decadimento beta a due neutrini, ma ha solo una minore influenza sugli elementi matricialiM ^ov per il modo di decadimento senza neutrini. I limiti piú piccoli perm _v risultano, perciò, principalmente dal fatto che la procedura di scaling ampiamente usati sottostima gli elementi matriciali 0v. Si discute inoltre che in misura l'interferenza tra neutrini diversi influisce sui limiti di massa ottenuti.

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Резюме Из экспериментов по двойному бета-распады, выводятся новые и более строгие пределы для массы нетрино Майораны. Получено, что соответствующее рассмотрение коллективных эффектов, обусловленных спин-изоспиновыми, а также квадруполь-квадрупольными силами, приводит к существенному ядерных матричных элементов, для двух-нейтринного двойного бета-распада; однако влияние на матричные элементыM ^ov для безнейтринной моды распада оказывается минимальным. Таким образом, получаются более низкие пределы дляm _v из того факта, что широко используемая процедура скейлинга переоценивает величины матричных элементов 0v. Обсуждается влияние интерференции между различными видами нейтрино на вычисленные значения пределов для массы нейтрино.

     

The search for different neutrino flavors from collapsing stars using the LVD detector

The main goal of the Large Volume Detector (LVD) is to search for neutrino burst from gravitational stellar collapses in our Galaxy. The apparatus is shown to be able to register stellar collapse even if there is none of the antineutrino emission specific to the standard scenario. The data from more than nine years of detector operation have been processed, and no candidate events for neutrino bursts have been detected. This implies the existence of an experimental limit to the galactic stellar collapse rate in those cases where collapse is not accompanied by electron antineutrino emission: less than one event per 4.1 yr at the 90% confidence level.