Gamow-teller strengths of the inverse beta transition 176Yb-->176Lu for spectroscopy of proton-proton and other sub-MeV solar neutrinos

Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos.     

Experience on using titanium as a structural material for a solar neutrino lithium detector

Data obtained by the radiotracer method on a specially designed test bench show that a lithium oxide film serves as a trap for beryllium extracted from lithium. No tangible chemisorption of beryllium on the titanium surface is observed. These finding are used to design and fabricate a lithium detector for solar neutrinos. They will also find application in designing power nuclear facilities with liquid-metal heat carriers.     

The MSW mechanism for three neutrino generations and the solar neutrino puzzle

We analyse the ³⁷Cl experiment for three neutrino generations with arbitrary mixing angles in the adiabatic approximation and present the resulting ⁸B-neutrino energy spectrum.     

pep neutrino detection by a lithium detector as a direct way to seek oscillations of solar neutrinos

The high sensitivity of a lithium detector to pep and ⁷Be neutrinos renders a radiochemical lithium detector a powerful tool for seeking solar-neutrino oscillations. The first phase of the lithium experiment with an apparatus involving 10 t of metallic lithium will allow collecting data within 1 yr of measurements to provide very definite information about a MSW SMA solution. The second phase with ten modules 10 t each will measure the semiannual variations of the signal, whereby the contributions of pep and ⁷Be lines will be weighted, which will give “smoking-gun” evidence for the “just-so” solution for large mixing angles and Δm ² about 10^?10–10^?9 eV². If both regions are not confirmed, the results of the lithium detector can be interpreted in favor of the MSW LMA solution.     

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.     

Measurement of B(t --> Wb)/B(t--> Wq) at the collider detector at fermilab

We present a measurement of the ratio of top-quark branching fractions R = B(t --> Wb)/B(t --> Wq), where q can be a b, s, or a d quark, using lepton-plus-jets and dilepton data sets with an integrated luminosity of approximately 162 pb(-1) collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of tt events with different multiplicity of identified secondary vertices. We set a lower limit of R > 0.61 at 95% confidence level.     

Measurement of the response of a Ga solar neutrino experiment to 37Ar source

An intense ³⁷Ar source was produced by the (n, α) reaction on ⁴⁰Ca by irradiating 330 kg of calcium oxide in the fast neutron breeder reactor at Zarechny, Russia. The ³⁷Ar was released from the solid target by dissolution in acid, collected from this solution, purified, sealed into a small source, and brought to the Baksan Neutrino Observatory, where it was used to irradiate 13 t of gallium metal in the Russian—American solar neutrino experiment SAGE. Ten exposures of the gallium to the source, whose initial strength was ∼ 409 ± 2kCi, were carried out during the period from April to September 2004. The ⁷¹Ge produced by the reaction ⁷¹Ga(ν _e, e ⁻)⁷¹Ge was extracted, purified, and counted. The measured production rate was 11.0 _−0.9 ^+1.0 (stat.) ±0.6 (syst.) atoms of ⁷¹Ge/d, which is 0.79 _−0.10 ^+0.09 of the theoretically calculated production rate. The text was submitted by the authors in English.     

Detector lens as a new tool for solar neutrino spectroscopy

The LENS detector is a ν _e-flavor real-time detector for measurement of low-energy solar neutrino flux and spectral shape, specifying the pp and ⁷Be neutrinos individually. It will complement future low-energy neutrino experiments (BOREXINO, HELLAZ, GENIUS), all of which are scattering experiments. The main goal of the LENS collaboration is to develop final formulation of Yb-and In-loaded liquid scintillators and to build a prototype of suitable volume to study the backgrounds and detector performance.