101 research outputs found
Ft values of the T = 1/2 mirror beta transitions
A complete survey is presented of all half-life and branching-ratio
measurements related to the isospin T = 1/2 mirror beta transitions ranging
from 3He to 83Mo. No measurements are ignored, although some are rejected for
cause. Using the decay energies obtained in the 2003 Mass Evaluation
experimental ft values are then determined for the transitions up to 45V. For
the first time also all associated theoretical corrections needed to convert
these results into "corrected" Ft values, similar to the superallowed 0+ -> 0+
pure Fermi beta transitions, were calculated. Precisions of the resulting
values are in most cases between 0.1 % and 0.4 %. These Ft(mirror) values can
now be used to extract precise weak interaction information from past and
ongoing correlation measurements in the beta decay of the T = 1/2 mirror beta
transitions
Precision measurements of the Co -asymmetry parameter in search for tensor currents in weak interactions
The -asymmetry parameter for the Gamow-Teller decay of
Co was measured by polarizing the radioactive nuclei with the brute
force low-temperature nuclear-orientation method. The Co activity was
cooled down to milliKelvin temperatures in a He-He dilution
refrigerator in an external 13 T magnetic field. The particles were
observed by a 500 thick Si PIN diode operating at a temperature of
about 10 K in a magnetic field of 0.6 T. Extensive GEANT4 Monte-Carlo
simulations were performed to gain control over the systematic effects. Our
result, , is in agreement with
the Standard-Model value of , which includes recoil-order
corrections that were addressed for the first time for this isotope. Further,
it enables limits to be placed on possible tensor-type charged weak currents as
well as other physics beyond the Standard Model
The Impact of COVID-19 on the Majority Population, Ethno-Racial Minorities, and Immigrants : A Systematic Literature Review on Threat Appraisals From an Inter-Group Perspective
The COVID-19 pandemic constitutes an unprecedented threat for individuals and societies, revealing stark inequalities in preparedness, exposure, and consequences. The present systematic literature review complements extant knowledge on disasters and pandemic diseases with programmatic research on the COVID-19 pandemic. Building upon an integrative definition of threat, we merge intra-personal threat regulation with group dynamics and inter-group relations. Via streamlined methods of knowledge synthesis, we first map out a broad taxonomy of threats, as appraised by the majority population and ethno-racial and immigrant minorities. Second, we delve into research linking threat appraisals with either conflict or prosociality within and across group boundaries. To conclude, we propose some guidelines for researchers to involve ethno-racial and immigrant minorities actively and for societies to cope cohesively with the impact of COVID-19
The WITCH experiment: completion of a set-up to investigate the structure of weak interactions with a Penning trap
The WITCH experiment aims to study a possible admixture of a scalar or tensor
type interaction in beta decay by determining the beta-neutrino angular
correlation from the shape of the recoil energy spectrum. The installation
period was completed and intensive commissioning of the set-up was performed
already. The lay-out of the WITCH set-up and results of commissioning tests
performed until now are described here, showing that the full set-up up to the
spectrometer is now operational, although several efficiencies are still to be
improved. Due to its feature of being able to measure the energy spectrum for
recoil ions, the WITCH experiment also opens possibilities for other
observables.Comment: 31 pages, 18 figures. International Journal of Mass Spectrometry, in
pres
WITCH: a recoil spectrometer for weak interaction and nuclear physics studies
An experimental set-up is described for the precise measurement of the recoil energy spectrum of the daughter ions from nuclear beta decay. The experiment is called WITCH, short for Weak Interaction Trap for CHarged particles, and is set up at the ISOLDE facility at CERN. The principle of the experiment and its realization are explained as well as the main physics goal. A cloud of radioactive ions stored in a Penning trap serves as the source for the WITCH experiment, leading to the minimization of scattering and energy loss of the decay products. The energy spectrum of the recoiling daughter ions from the --decays in this ion cloud will be measured with a retardation spectrometer. The principal aim of the WITCH experiment is to study the electroweak interaction by determining the beta--neutrino angular correlation in nuclear --decay from the shape of this recoil energy spectrum. This will be the first time that the recoil energy spectrum of the daughter ions from --decay can be measured for a wide variety of isotopes, independent of their specific properties
Progress at the WITCH experiment
The WITCH-experiment will measure the energy spectrum of the recoiling daughter ions in -decay to search for non-standard scalar and tensor type interaction. To facilitate this a Penning trap is used to store the radioactive ions. Thus the recoil ions can leave the source without any energy loss and their energy can be probed by the subsequent retardation spectrometer. The experiment is being set up at present at ISOLDE/CERN. The principle and the status of the WITCH-experiment will be presented. (12 refs)
Immigrant community integration in world cities
As a consequence of the accelerated globalization process, today major cities
all over the world are characterized by an increasing multiculturalism. The
integration of immigrant communities may be affected by social polarization and
spatial segregation. How are these dynamics evolving over time? To what extent
the different policies launched to tackle these problems are working? These are
critical questions traditionally addressed by studies based on surveys and
census data. Such sources are safe to avoid spurious biases, but the data
collection becomes an intensive and rather expensive work. Here, we conduct a
comprehensive study on immigrant integration in 53 world cities by introducing
an innovative approach: an analysis of the spatio-temporal communication
patterns of immigrant and local communities based on language detection in
Twitter and on novel metrics of spatial integration. We quantify the "Power of
Integration" of cities --their capacity to spatially integrate diverse
cultures-- and characterize the relations between different cultures when
acting as hosts or immigrants.Comment: 13 pages, 5 figures + Appendi
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