45 research outputs found
study of states in : Implications for new physics searches with xenon detectors
We used the Ba reaction to carry out an in-depth study of
states in Cs, up to around 2.5~MeV. In this work, we place emphasis on
hitherto unobserved states below the first level, which are important in
the context of solar neutrino and fermionic dark matter (FDM) detection in
large-scale xenon experiments. We identify for the first time candidate
metastable states in Cs, which would allow a real-time detection of
solar neutrino and FDM events in xenon detectors, with high background
suppression. Our results are also compared with shell-model calculations
performed with three Hamiltonians that were previously used to evaluate the
nuclear matrix element (NME) for Xe neutrinoless double beta decay. We
find that one of these Hamiltonians, which also systematically underestimates
the NME compared to the others, dramatically fails to describe the observed
low-energy Cs spectrum, while the other two show reasonably good
agreement
First Evidence of Axial Shape Asymmetry and Configuration Coexistence in Zn: Suggestion for a Northern Extension of the Island of Inversion
The excited states of Zn were investigated via -ray
spectroscopy following Cu decay. By exploiting -
angular correlation analysis, the , , and states
in Zn were firmly established. The -ray branching and
mixing ratios for transitions de-exciting the , and
states were measured, allowing for the extraction of relative values.
In particular, the and transitions were
observed for the first time. The results show excellent agreement with new
microscopic large-scale shell-model calculations, and are discussed in terms of
underlying shapes, as well as the role of neutron excitations across the
gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize
Zn in its ground state. Furthermore, an excited band with a
significantly larger softness in its shape is identified. A shore of the
``island of inversion'' appears to manifest above , previously thought as
its northern limit in the chart of the nuclides
An integrated online radioassay data storage and analytics tool for nEXO
Large-scale low-background detectors are increasingly used in rare-event
searches as experimental collaborations push for enhanced sensitivity. However,
building such detectors, in practice, creates an abundance of radioassay data
especially during the conceptual phase of an experiment when hundreds of
materials are screened for radiopurity. A tool is needed to manage and make use
of the radioassay screening data to quantitatively assess detector design
options. We have developed a Materials Database Application for the nEXO
experiment to serve this purpose. This paper describes this database, explains
how it functions, and discusses how it streamlines the design of the
experiment
Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO
Liquid xenon time projection chambers are promising detectors to search for
neutrinoless double beta decay (0), due to their response
uniformity, monolithic sensitive volume, scalability to large target masses,
and suitability for extremely low background operations. The nEXO collaboration
has designed a tonne-scale time projection chamber that aims to search for
0 of \ce{^{136}Xe} with projected half-life sensitivity of
~yr. To reach this sensitivity, the design goal for nEXO is
1\% energy resolution at the decay -value (~keV).
Reaching this resolution requires the efficient collection of both the
ionization and scintillation produced in the detector. The nEXO design employs
Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm
scintillation light of liquid xenon. This paper reports on the characterization
of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3
SiPMs specifically designed for nEXO, as well as new measurements on new test
samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters
(MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct
crosstalk, correlated avalanches and photon detection efficiency were measured
as a function of the applied over voltage and wavelength at liquid xenon
temperature (163~K). The results from this study are used to provide updated
estimates of the achievable energy resolution at the decay -value for the
nEXO design