1,068 research outputs found
Does the enhancement observed in contain two -wave higher charmonia?
Solved is a new puzzle raised by the observation of an enhancement structure
Z(3930) in . If categorizing Z(3930) as
suggested by Belle and BaBar, we must explain why
dominantly decaying into is missing in the
invariant mass spectrum. In this work, we propose that the Z(3930)
enhancement structure may contain two -wave higher charmonia
{} and . We show that this assumption is
supported by our analysis of the invariant mass spectrum and
distribution of . This observation
would not only provide valuable information of two P-wave higher charmonia
and , but also serve as the crucial test of our
novel proposal to the observed enhancement structure Z(3930), especially at the
forthcoming BelleII and the approved SuperB.Comment: 5 pages, 2 tables, 3 figures. More contents and discussions adde
Acute effects of ambient nitrogen oxides and interactions with temperature on cardiovascular mortality in Shenzhen, China
Background: Though inconsistent, acute effects of ambient nitrogen oxides on cardiovascular mortality have been reported. Whereas, interactive roles of temperature on their relationships and joint effects of different indicators of nitrogen oxides were less studied. This study aimed to extrapolate the independent roles of ambient nitrogen oxides and temperature interactions on cardiovascular mortality.Methods: Data on mortality, air pollutants, and meteorological factors in Shenzhen from 2013 to 2019 were collected. Three indicators including nitric oxide (NO), nitrogen dioxide (NO2), and nitrogen oxides (NOX) were studied. Adjusted generalized additive models (GAMs) were applied to analyse their associations with cardiovascular mortality in different groups.Results: The average daily concentrations of NO, NO2, and NOX were 11.7 mu g/m(3), 30.7 mu g/m(3), and 53.2 mu g/m(3), respectively. Significant associations were shown with each indicator. Cumulative effects of nitrogen oxides were more obvious than distributed lag effects. Males, population under 65 years old, and population with stroke related condition were more susceptible to nitrogen oxides. Adverse effects of nitrogen oxides were more significant at low temperature. Impacts of NO2 on cardiovascular mortality, and NO on stroke mortality were the most robust in the multi-pollutant models, whereas variations were shown in the other relationships.Conclusions: Low levels of nitrogen oxides showed acute and adverse impacts and the interactive roles of temperature on cardiovascular mortality. Cumulative effects were most significant and joint effects of nitrogen oxides required more attention. Population under 65 years old and population with stroke-related health condition were susceptible, especially days at lower temperature
Anomalous x-ray diffraction study of disorders in epitaxial films of the Heusler alloy Co2 MnGe
The authors report a study of structural and chemical disorders in a ternary combinatorial epitaxial film of Cox Mny Ge1-x-y in the composition range that includes the Heusler alloy Co2 MnGe, using microbeam anomalous x-ray diffraction techniques. The structural and chemical ordering of the alloy has been found to be extremely stable over a large composition range, while elemental site swapping and sublattice vacancies have been identified. A model of anomalous diffraction around the Co and Ge edges is presented and shown to make possible the identification and quantification of these disorders in an epitaxial film
Structural and chemical ordering of Heusler C ox M ny G ez epitaxial films on Ge (111): Quantitative study using traditional and anomalous x-ray diffraction techniques
Epitaxial films of CoxMnyGez grown on Ge (111) substrates by molecular-beam-epitaxy techniques have been investigated as a continuous function of composition using combinatorial synchrotron x-ray diffraction (XRD) and x-ray fluorescence (XRF) spectroscopy techniques. A high-resolution ternary epitaxial phase diagram is obtained, revealing a small number of structural phases stabilized over large compositional regions. Ordering of the constituent elements in the compositional region near the full Heusler alloy Co2MnGe has been examined in detail using both traditional XRD and a new multiple-edge anomalous diffraction (MEAD) technique. Multiple-edge anomalous diffraction involves analyzing the energy dependence of multiple reflections across each constituent absorption edge in order to detect and quantify the elemental distribution of occupation in specific lattice sites. Results of this paper show that structural and chemical ordering are very sensitive to the Co: Mn atomic ratio, such that the ordering is the highest at an atomic ratio of 2 but significantly reduced even a few percent off this ratio. The in-plane lattice is nearly coherent with that of the Ge substrate, while the approximately 2% lattice mismatch is accommodated by the out-of-plane tetragonal strain. The quantitative MEAD analysis further reveals no detectable amount (<0.5%) of Co-Mn site swapping, but instead high levels (26%) of Mn-Ge site swapping. Increasing Ge concentration above the Heusler stoichiometry (Co0.5Mn0.25Ge0.25) is shown to correlate with increased lattice vacancies, antisites, and stacking faults, but reduced lattice relaxation. The highest degree of chemical ordering is observed off the Heusler stoichiometry with a Ge enrichment of 5 at.%
Evidence for strain compensation in stabilizing epitaxial growth of highly doped germanium
We report on a study of the epitaxial phase diagram of Co- and Mn-doped Ge(001) magnetic semiconductors. Complementary doping using dopants from different groups of elements can compensate for the effects of lattice strain caused by the doping species. Reducing lattice mismatch with the Ge host has been shown to be the key to stabilizing epitaxial growth and suppressing phase separation at higher doping levels. Applying this approach to other multidopant systems opens new prospects for tailoring highly doped electronic materials
Observation of Two New N* Peaks in J/psi -> and Decays
The system in decays of is limited to be
isospin 1/2 by isospin conservation. This provides a big advantage in studying
compared with and experiments which mix
isospin 1/2 and 3/2 for the system. Using 58 million decays
collected with the Beijing Electron Positron Collider, more than 100 thousand
events are obtained. Besides two well known
peaks at 1500 MeV and 1670 MeV, there are two new, clear peaks in
the invariant mass spectrum around 1360 MeV and 2030 MeV. They are the
first direct observation of the peak and a long-sought "missing"
peak above 2 GeV in the invariant mass spectrum. A simple
Breit-Wigner fit gives the mass and width for the peak as MeV and MeV, and for the new peak above 2 GeV
as MeV and MeV, respectively
Wave function mapping conditions in Open Quantum Dots structures
We discuss the minimal conditions for wave function spectroscopy, in which
resonant tunneling is the measurement tool. Two systems are addressed: resonant
tunneling diodes, as a toy model, and open quantum dots. The toy model is used
to analyze the crucial tunning between the necessary resolution in
current-voltage characteristics and the breakdown of the wave functions probing
potentials into a level splitting characteristic of double quantum wells. The
present results establish a parameter region where the wavefunction
spectroscopy by resonant tunneling could be achieved. In the case of open
quantum dots, a breakdown of the mapping condition is related to a change into
a double quantum dot structure induced by the local probing potential. The
analogy between the toy model and open quantum dots show that a precise control
over shape and extention of the potential probes is irrelevant for wave
function mapping. Moreover, the present system is a realization of a tunable
Fano system in the wave function mapping regime.Comment: 6 pages, 6 figure
Epitaxial growth of (FeCo)x Ge1-x (001)
The epitaxial growth of (FeCo)x Ge1-x films on Ge and GaAs (001) substrates has been studied systematically with x in the range between 0 and 17 at. %, using combinatorial molecular beam epitaxy (MBE) techniques. Complementary doping using the two transition metal dopants into Ge (001) during MBE growth is shown to produce high quality coherent epitaxial films for transition metal concentrations as high as 11 at. %. As the doping level increases, rough growth occurs, which is accompanied by an increasing amount of stacking faults along the 〈111〉 directions. The crystal lattice that resulted from the rough growth exhibits a large out-of-plane tetragonal distortion. There are no detectable secondary phases up to a combined transition metal concentration of 17 at. %. The behaviors are shown to be invariant with respect to the choice of substrates
Search for Invisible Decays of and in and
Using a data sample of decays collected with the BES
II detector at the BEPC, searches for invisible decays of and
in to and are performed.
The signals, which are reconstructed in final states, are used
to tag the and decays. No signals are found for the
invisible decays of either or , and upper limits at the 90%
confidence level are determined to be for the ratio
and for . These are the first
searches for and decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo
Structural and Magnetic Instabilities of LaSrCaCuO
A neutron scattering study of nonsuperconducting
LaSrCaCuO (x=0 and 0.2), a bilayer copper oxide without CuO
chains, has revealed an unexpected tetragonal-to-orthorhombic transition with a
doping dependent transition temperature. The predominant structural
modification below the transition is an in-plane shift of the apical oxygen. In
the doped sample, the orthorhombic superstructure is strongly disordered, and a
glassy state involving both magnetic and structural degrees of freedom develops
at low temperature. The spin correlations are commensurate.Comment: published versio
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