We propose the construction of LEGEND-1000, the ton-scale Large Enriched Germanium Experiment for Neutrinoless \(\beta \beta\) Decay. This international experiment is designed to answer one of the ...highest priority questions in fundamental physics. It consists of 1000 kg of Ge detectors enriched to more than 90% in the \(^{76}\)Ge isotope operated in a liquid argon active shield at a deep underground laboratory. By combining the lowest background levels with the best energy resolution in the field, LEGEND-1000 will perform a quasi-background-free search and can make an unambiguous discovery of neutrinoless double-beta decay with just a handful of counts at the decay \(Q\) value. The experiment is designed to probe this decay with a 99.7%-CL discovery sensitivity in the \(^{76}\)Ge half-life of \(1.3\times10^{28}\) years, corresponding to an effective Majorana mass upper limit in the range of 9-21 meV, to cover the inverted-ordering neutrino mass scale with 10 yr of live time.
The Majorana Demonstrator is a neutrinoless double-beta decay search consisting of a low-background modular array of high-purity germanium detectors, \(\sim2/3\) of which are enriched to 88\% in ...\(^{76}\)Ge. The experiment is also searching for double-beta decay of \(^{76}\)Ge to excited states (e.s.) in \(^{76}\)Se. \(^{76}\)Ge can decay into three daughter states of \(^{76}\)Se, with clear event signatures consisting of a \(\beta\beta\)-decay followed by the prompt emission of one or two \(\gamma\)-rays. This results with high probability in multi-detector coincidences. The granularity of the Demonstrator detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9~kg-y of isotopic exposure, the Demonstrator has set world leading limits for each e.s.\ decay of \(^{76}\)Ge, with 90\% CL lower half-life limits in the range of \((0.75-4.0)\times10^{24}\)~y. In particular, for the \(2\nu\) transition to the first \(0^+\) e.s.\ of \(^{76}\)Se, a lower half-life limit of \(7.5\times10^{23}\)~y at 90\% CL was achieved.
We report measurements of the mechanical properties by nanoindentation at room temperature on coherently strained superlattices of InxGa1-xAs grown on InP. Elastic deformation and then plastic ...deformation are obtained. The yield pressure decreases with increasing strain modulation in the superlattice and, at the highest strains of 0.8%, the yield pressure is halved. In the plastic regime the behaviour again depends on the strain modulation. These results demonstrate the potential of tailoring coherency strain between layers in thin films to control their mechanical properties.
Genetic Data and the African Origin of Humans Pritchard, Jonathan K.; Feldman, Marcus W.; Risch, Neil ...
Science (American Association for the Advancement of Science),
1996-Nov-29, Volume:
274, Issue:
5292
Journal Article
Peer reviewed
The research of Tishkoff et al on human genetic variation at the CD4 locus is discussed. Tishkoff et al respond.
The MAJORANA DEMONSTRATOR is searching for double-beta decay of \(^{76}\)Ge to excited states (E.S.) in \(^{76}\)Se using a modular array of high purity Germanium detectors. \(^{76}\)Ge can decay ...into three E.S.s of \(^{76}\)Se. The E.S. decays have a clear event signature consisting of a \(\beta\beta\)-decay with the prompt emission of one or two \(\gamma\)-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of \((0.56-2.1)\cdot10^{24}\) y. In particular, for the \(2\nu\) transition to the first \(0^+\) E.S. of \(^{76}\)Se, a lower half-life limit of \(0.68\cdot10^{24}\) at 90% CL was achieved.
The \MJ\ Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-beta decay in \(^{76}\)Ge. The \MJ\ \DEM\ comprises 44.1~kg of Ge detectors (29.7 kg ...enriched in \(^{76}\)Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at \qval\ and a very low background with no observed candidate events in 10 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of \(1.9\times10^{25}\) yr (90\% CL). This result constrains the effective Majorana neutrino mass to below 240 to 520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is \(4.0_{-2.5}^{+3.1}\) counts/(FWHM t yr).
The pseudoautosomal boundary is defined by an Alu repeat element on the Y chromosome. The Alu element is found on all Y chromosomes and on no X chromosomes, establishing it as part of Y-specific ...sequences. Distal to the Alu element, sequences from the X and Y are strictly homologous, suggesting that the boundary is formed by an abrupt break in sequence homology. Further investigation of the function of the boundary has been undertaken by examining the population structure of an MspI restriction-site polymorphism (XY274), which is located 274 bp distal to the Alu insertion site. Southern blot and polymerase chain reaction analysis demonstrate fixation of the high allele (noncutting or AT base pair) of XY274 on the Y chromosome in most populations, while a full range of high allele frequencies is found on the X chromosomes of different populations. Two exceptions to fixation on the Y chromosome were found in African populations. The level of linkage disequilibrium suggests that the first few hundred base pairs of the pseudoautosomal region on the Y chromosome share a single common origin more recent than the origin of the species.
Phys.Rev.Lett.84:4276-4279,2000 The average mass composition of cosmic rays with primary energies between
$10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting
of the High ...Resolution Fly's Eye (HiRes) prototype and the MIA muon array.
Measurements have been made of the change in the depth of shower maximum,
$X_{max}$, and in the change in the muon density at a fixed core location,
$\rho_\mu(600m)$, as a function of energy. The composition has also been
evaluated in terms of the combination of $X_{max}$ and $\rho_\mu(600m)$. The
results show that the composition is changing from a heavy to lighter mix as
the energy increases.
The D20S6 locus has been sublocalized by in situ hybridization using the pD3H12 probe to human chromosome band 20p12 and the D20S4 locus using the pMS1-27 probe to 20q13.2. A rare new restriction ...fragment length polymorphism detected in MspI-digested DNA by the pMSI-27 probe is reported. Linkage studies in nine families have shown that the D20S6 locus is linked to D20S5 (formerly mapped to 20p12 by in situ hybridization) with a maximum likelihood estimate of 0.07 for the recombination frequency (lod score = 9.07) and a confidence interval of 0.02 to 0.14. Estimated recombination frequencies were similar in males and females. Using both two- and multipoint analyses, linkage of D20S4 with the D20S5 and D20S6 loci was excluded and the suggested order for the three loci on chromosome 20 is D20S5-D20S6-centromere-D20S4. D20S5 and D20S6 are very useful markers for linkage studies because of their close proximity and reasonably good polymorphic information content values.
