Taxonomic revision and phylogeny of the sharpshooter genus Dasmeusa Melichar, 1926, with a scanning electron microscopy study of D. pauperata (Fabricius, 1803) (Hemiptera: Cicadellidae: Cicadellini)

The genus Dasmeusa is distributed in Northern and Northeastern Brazil and the Guianas. Until the present study, six species were recognized within Dasmeusa. The species of this genus are very similar in terms of color and external morphology, being distinguished mainly by the male terminalia. Here, we review and redescribe Dasmeusa and its species, describe four new species, and present the first phylogenetic analysis of the genus, including 40 morphological characters and 15 terminal taxa. Dasmeusa flavescens Metcalf and Erythrogonia bicolor Metcalf are considered junior synonyms of the type-species, Dasmeusa pauperata (Fabricius). Scanning electron microscopy was employed for a detailed study of the integument of the type-species, including sensilla, surface sculpturing, brochosomes, organ of Evans, and other structures. The phylogenetic analysis with equal weights resulted in nine most parsimonious trees. The implied weighting method resulted in two trees, both with the same ingroup topology as observed in one of the nine equal-weights trees. This preferred topology is as follows: ((D. basseti (D. mendica (D. rafaeli sp. nov., D. falcifera sp. nov.))) (D. isabellina (D. oriximina sp. nov. (D. pauperata (D. imperialis, D. dinizi sp. nov.))))). Dasmeusa was recovered as monophyletic in all trees, being supported by five apomorphic characters

Search for two-neutrino double electron capture on 124^{124}Xe with the XMASS-I detector

Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on $^{124}$Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as $4.7 \times 10^{21}$ years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the $^{126}$Xe two-neutrino double electron capture half-life of $4.3 \times 10^{21}$ years at 90% confidence level as well.Comment: 6 pages, 3 figures, accepted for publication in Physics Letters

Search for solar axions in XMASS, a large liquid-xenon detector

XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent limit on the coupling for mass $\ll$ 1keV is $|g_{aee}|< 5.4\times 10^{-11}$ (90% C.L.), which is a factor of two stronger than the existing experimental limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are 1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced the most stringent limit, which is better than that previously derived from astrophysical arguments regarding the Sun to date

Direct dark matter search by annual modulation in XMASS-I

A search for dark matter was conducted by looking for an annual modulation signal due to the Earth's rotation around the Sun using XMASS, a single phase liquid xenon detector. The data used for this analysis was 359.2 live days times 832 kg of exposure accumulated between November 2013 and March 2015. When we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically scattering on the target nuclei, the exclusion upper limit of the WIMP-nucleon cross section 4.3$\times$10$^{-41}$cm$^2$ at 8 GeV/c$^2$ was obtained and we exclude almost all the DAMA/LIBRA allowed region in the 6 to 16 GeV/c$^2$ range at $\sim$10$^{-40}$cm$^2$. The result of a simple modulation analysis, without assuming any specific dark matter model but including electron/$\gamma$ events, showed a slight negative amplitude. The $p$-values obtained with two independent analyses are 0.014 and 0.068 for null hypothesis, respectively. we obtained 90\% C.L. upper bounds that can be used to test various models. This is the first extensive annual modulation search probing this region with an exposure comparable to DAMA/LIBRA.Comment: 5 pages, 4 figure