28 research outputs found
Study of proton-unbound states in relevant for the reaction in novae
Background: The nucleosynthesis of several proton-rich nuclei is determined
by radiative proton-capture reactions on unstable nuclei in nova explosions.
One such reaction is , which links the
NeNa and MgAl cycles in oxygen-neon (ONe) novae.
Purpose: To extract resonance
strengths from a study of proton-unbound states in , produced
via the Mg(He,) reaction.
Methods: A beam of ions at 50.7 MeV was used to produce
the states of interest in Al. Proton-triton angular correlations were
measured with a QDD magnetic spectrometer and a silicon detector array,
located at iThemba LABS, South Africa.
Results: We measured the excitation energies of the four lowest
proton-unbound states in Al and place lower-limits on
values for these four states. Together with USD-C shell-model calculations of
partial gamma widths, the experimental data are also used to determine
resonance strengths for the three lowest
resonances.
Conclusions: The energy of the dominant first
resonance is determined to be keV, with a resonance
strength meV
Isospin mixing and the cubic isobaric multiplet mass equation in the lowest <i>T</i>=2, <i>A</i>=32 quintet
The isobaric multiplet mass equation (IMME) is known to break down in the
first T = 2, A = 32 isospin quintet. In this work we combine high-resolution
experimental data with state-of-the-art shell-model calculations to investigate
isospin mixing as a possible cause for this violation. The experimental data
are used to validate isospin-mixing matrix elements calculated with newly
developed shell-model Hamiltonians. Our analysis shows that isospin mixing with
nonanalog T = 1 states contributes to the IMME breakdown, making the
requirement of an anomalous cubic term inevitable for the multiplet
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
Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan
This whitepaper presents the research priorities decided on by attendees of
the 2022 Town Meeting for Fundamental Symmetries, Neutrons and Neutrinos, which
took place December 13-15, 2022 in Chapel Hill, NC, as part of the Nuclear
Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of
275 scientists registered for the meeting. The whitepaper makes a number of
explicit recommendations and justifies them in detail
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
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
Gazéification de Matières Organiques en milieu Eau Supercritique : Rendements expérimentaux et Equilibres thermodynamiques
National audienceno abstrac
Supercritical gasification and partial oxidation of beet residues in a continuous reactor
International audienceno abstrac