The Russian-American experiment SAGE began to measure the solar neutrino capture rate with a target of gallium metal in December 1989. Measurements have continued with only a few brief interruptions since that time. In this article we present the experimental improvements in SAGE since its last published data summary in December 2001. Assuming the solar neutrino production rate was constant during the period of data collection, combined analysis of 168 extractions through December 2007 gives a capture rate of solar neutrinos with energy more than 233 keV of $65.{4}_{\ensuremath{-}3.0}^{+3.1}$ (stat) ${}_{\ensuremath{-}2.8}^{+2.6}$ (syst) SNU. The weighted average of the results of all three Ga solar neutrino experiments, SAGE, Gallex, and GNO, is now $66.1\ifmmode\pm\else\textpm\fi{}3.1$ SNU, where statistical and systematic uncertainties have been combined in quadrature. During the recent period of data collection a new test of SAGE was made with a reactor-produced $^{37}\mathrm{Ar}$ neutrino source. The ratio of observed to calculated rates in this experiment, combined with the measured rates in the three prior $^{51}\mathrm{Cr}$ neutrino-source experiments with Ga, is $0.87\ifmmode\pm\else\textpm\fi{}0.05$. A probable explanation for this low result is that the cross section for neutrino capture by the two lowest-lying excited states in $^{71}\mathrm{Ge}$ has been overestimated. If we assume these cross sections are zero, then the standard solar model including neutrino oscillations predicts a total capture rate in Ga in the range of 63 SNU to 66 SNU with an uncertainty of about 4%, in good agreement with experiment. We derive the current value of the neutrino flux produced in the Sun by the proton-proton fusion reaction to be ${\ensuremath{\phi}}_{\mathit{pp}}^{\ensuremath{\bigodot}}=(6.0\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{10}/({\mathrm{cm}}^{2} \mathrm{s})$, which agrees well with the $\mathit{pp}$ flux predicted by the standard solar model. Finally, we make several tests and show that the data are consistent with the assumption that the solar neutrino production rate is constant in time.

Measurement of the solar neutrino capture rate with gallium metal. III: Results for the 2002--2007 data-taking period

Neutrinoless double-beta decay, which is a very old and yet elusive process, is reviewed. Its observation will signal that the lepton number is not conserved and that the neutrinos are Majorana particles. More importantly it is our best hope for determining the absolute neutrino-mass scale at the level of a few tens of meV. To achieve the last goal certain hurdles must be overcome involving particle, nuclear and experimental physics. Nuclear physics is important for extracting useful information from the data. One must accurately evaluate the relevant nuclear matrix elements--a formidable task. To this end, we review the sophisticated nuclear structure approaches which have recently been developed, and which give confidence that the required nuclear matrix elements can be reliably calculated employing different methods: (a) the various versions of the quasiparticle random phase approximations, (b) the interacting boson model, (c) the energy density functional method and (d) the large basis interacting shell model. It is encouraging that, for the light neutrino-mass term at least, these vastly different approaches now give comparable results. From an experimental point of view it is challenging, since the life times are long and one has to fight against formidable backgrounds. One needs large isotopically enriched sources and detectors with high-energy resolution, low thresholds and very low background. If a signal is found, it will be a tremendous accomplishment. The real task then, of course, will be the extraction of the neutrino mass from the observations. This is not trivial, since current particle models predict the presence of many mechanisms other than the neutrino mass, which may contribute to or even dominate this process. In particular, we will consider the following processes: The neutrino induced, but neutrino-mass independent contribution. Heavy left and/or right-handed neutrino-mass contributions. Intermediate scalars (doubly charged, etc). Supersymmetric (SUSY) contributions. We will show that it is possible to disentangle the various mechanisms and unambiguously extract the important neutrino-mass scale, if all the signatures of the reaction are searched for in a sufficient number of nuclear isotopes.

/pdf/theory-of-neutrinoless-double-beta-decay-2c6bzk0uf6.pdf

Theory of neutrinoless double-beta decay.

Fluid transport that is driven by gradients of pressure, gravity, or electro-magnetic potential is well-known and studied in many fields. A subtler type of transport, called diffusiophoresis, occurs in a gradient of chemical concentration, either electrolyte or non-electrolyte. Diffusiophoresis works by driving a slip velocity at the fluid–solid interface. Although the mechanism is well-known, the diffusiophoresis mechanism is often considered to be an esoteric laboratory phenomenon. However, in this article we show that concentration gradients can develop in a surprisingly wide variety of physical phenomena – imposed gradients, asymmetric reactions, dissolution, crystallization, evaporation, mixing, sedimentation, and others – so that diffusiophoresis is in fact a very common transport mechanism, in both natural and artificial systems. We anticipate that in georeservoir extractions, physiological systems, drying operations, laboratory and industrial separations, crystallization operations, membrane processes, and many other situations, diffusiophoresis is already occurring – often without being recognized – and that opportunities exist for designing this transport to great advantage.

Origins of concentration gradients for diffusiophoresis

Neutrino–nuclear responses for astro-neutrinos, single beta decays and double beta decays

Energy levels of light nuclei A = 12

420MeVでの( 3 He,t)反応を通した弱い遷移強度導出

Differential cross sections for transitions of known weak strength were measured with the (He-3, t) reaction at 420 MeV on targets of C-12, C-13, O-18, Mg-26, Ni-58, Ni-60, Zr-90, Sn-118, Sn-120, and Pb-208. Using these data, it is shown that the proportionalities between strengths and cross sections for this probe follow simple trends as a function of mass number. These trends can be used to confidently determine Gamow-Teller strength distributions in nuclei for which the proportionality cannot be calibrated via beta-decay strengths. Although theoretical calculations in the distorted-wave Born approximation overestimate the data, they allow one to understand the main experimental features and to predict deviations from the simple trends observed in some of the transitions.

Extraction of weak transition strengths via the (He-3, t) reaction at 420 MeV

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420MeVでの( 3 He,t)反応を通した弱い遷移強度導出

Extraction of weak transition strengths via the (He-3, t) reaction at 420 MeV