792 research outputs found
Neutrinoless Double Beta Decay, the Inverted Hierarchy and Precision Determination of theta(12)
Ruling out the inverted neutrino hierarchy with neutrinoless double beta
decay experiments is possible if a limit on the effective mass below the
minimal theoretically possible value is reached. We stress that this lower
limit depends strongly on the value of the solar neutrino mixing angle: it
introduces an uncertainty of a factor of 2 within its current 3 sigma range. If
an experiment is not background-free, a factor of two in effective mass
corresponds to a combined factor of 16 improvement for the experimental
parameters running time, detector mass, background level and energy resolution.
Therefore, a more precise determination of theta(12) is crucial for the
interpretation of experimental results and the evaluation of the potential and
requirements for future experiments. We give the required half-lifes to exclude
(and touch) the inverted hierarchy regime for all double beta decay isotopes
with a Q-value above 2 MeV. The nuclear matrix elements from 6 different groups
and, if available, their errors are used and compared. We carefully put the
calculations on equal footing in what regards various convention issues. We
also use our compilation of matrix elements to give the reachable values of the
effective mass for a given half-life value.Comment: 26 pages, 6 figures. v2: error corrected (misprint in paper we took a
value from), slightly modifying the result
Rejection of randomly coinciding events in ZnMoO scintillating bolometers
Random coincidence of events (particularly from two neutrino double beta
decay) could be one of the main sources of background in the search for
neutrinoless double beta decay with cryogenic bolometers due to their poor time
resolution. Pulse-shape discrimination by using front edge analysis, mean-time
and methods was applied to discriminate randomly coinciding events in
ZnMoO cryogenic scintillating bolometers. These events can be effectively
rejected at the level of 99% by the analysis of the heat signals with rise-time
of about 14 ms and signal-to-noise ratio of 900, and at the level of 92% by the
analysis of the light signals with rise-time of about 3 ms and signal-to-noise
ratio of 30, under the requirement to detect 95% of single events. These
rejection efficiencies are compatible with extremely low background levels in
the region of interest of neutrinoless double beta decay of Mo for
enriched ZnMoO detectors, of the order of counts/(y keV kg).
Pulse-shape parameters have been chosen on the basis of the performance of a
real massive ZnMoO scintillating bolometer. Importance of the
signal-to-noise ratio, correct finding of the signal start and choice of an
appropriate sampling frequency are discussed
Characterization of a ZnSe scintillating bolometer prototype for neutrinoless double beta decay search
As proposed in the LUCIFER project, ZnSe crystals are attractive materials to realize scintillating bolometers aiming at the search for neutrinoless double beta decay of the promising isotope 82Se. However, the optimization of the ZnSe-based detectors is rather complex and requires a wide-range investigation of the crystal features: optical properties, crystalline quality, scintillation yields and bolometric behaviour. Samples tested up to now show problems in the reproducibility of crucial aspects of the detector performance. In this work, we present the results obtained with a scintillating bolometer operated aboveground at about 25 mK. The detector energy absorber was a single 1 cm3 ZnSe crystal. The good energy resolution of the heat channel (about 14 keV at 1460 keV) and the excellent alpha/beta discrimination capability are very encouraging for a successful realization of the LUCIFER program. The bolometric measurements were completed by optical tests on the crystal (optical transmission and luminescence measurements down to 10 K) and investigation of the crystalline structure. The work here described provides a set of parameters and procedures useful for a complete pre-characterization of ZnSe crystals in view of the realization of highly performing scintillating bolometers
Applied genomics: the brazilian experience.
Projeto/Plano de Ação: 01.06.10602-03
Background suppression in massive TeO bolometers with Neganov-Luke amplified light detectors
Bolometric detectors are excellent devices for the investigation of
neutrinoless double-beta decay (0). The observation of such
decay would demonstrate the violation of lepton number, and at the same time it
would necessarily imply that neutrinos have a Majorana character. The
sensitivity of cryogenic detectors based on TeO is strongly limited by the
alpha background in the region of interest for the 0 of
Te. It has been demonstrated that particle discrimination in TeO
bolometers is possible measuring the Cherenkov light produced by particle
interactions. However an event-by-event discrimination with NTD-based light
detectors has to be demonstrated. We will discuss the performance of a
highly-sensitive light detector exploiting the Neganov-Luke effect for signal
amplification. The detector, being operated with NTD-thermistor and coupled to
a 750 g TeO crystal, shows the ability for an event-by-event identification
of electron/gamma and alpha particles. The extremely low detector baseline
noise, RMS 19 eV, demonstrates the possibility to enhance the sensitivity of
TeO-based 0 experiment to an unprecedented level
Rejection of randomly coinciding events in LiMoO scintillating bolometers using light detectors based on the Neganov-Luke effect
Random coincidences of nuclear events can be one of the main background
sources in low-temperature calorimetric experiments looking for neutrinoless
double-beta decay, especially in those searches based on scintillating
bolometers embedding the promising double-beta candidate Mo, because of
the relatively short half-life of the two-neutrino double-beta decay of this
nucleus. We show in this work that randomly coinciding events of the
two-neutrino double decay of Mo in enriched LiMoO
detectors can be effectively discriminated by pulse-shape analysis in the light
channel if the scintillating bolometer is provided with a Neganov-Luke light
detector, which can improve the signal-to-noise ratio by a large factor,
assumed here at the level of on the basis of preliminary
experimental results obtained with these devices. The achieved pile-up
rejection efficiency results in a very low contribution, of the order of counts/(keVkgy), to the background counting rate
in the region of interest for a large volume ( cm)
LiMoO detector. This background level is very encouraging in
view of a possible use of the LiMoO solution for a bolometric
tonne-scale next-generation experiment as that proposed in the CUPID project
Mapping quantitative trait loci in Gallus gallus using principal components.
Projeto/Plano de Ação: 01.06.10.602-03
Thyroid hormone treated astrocytes induce maturation of cerebral cortical neurons through modulation of proteoglycan levels
Proper brain neuronal circuitry formation and synapse development is dependent on specific cues, either genetic or epigenetic, provided by the surrounding neural environment. Within the sesignals, thyroid hormones (T3 and T4) play crucial role in several steps of brain morphogenesis including proliferation of progenitor cells, neuronal differentiation, maturation, migration, and synapse formation. the lack of thyroid hormones during childhood is associated with several impair neuronal connections, cognitive deficits, and mental disorders. Many of the thyroid hormones effects are mediated by astrocytes, although the mechanisms underlying these events are still unknown. in this work, we investigated the effect of 3,5,3'-triiodothyronine-treated (T3-treated) astrocytes on cerebral cortex neuronal differentiation. Culture of neural progenitors from embryonic cerebral cortex mice onto T3-treated astrocyte monolayers yielded an increment in neuronal population, followed by enhancement of neuronal maturation, arborization and neurite outgrowth. in addition, real time PCR assays revealed an increase in the levels of the heparan sulfate proteoglycans, Glypican 1(GPC-1) and Syndecans 3 e 4 (SDC-3 e SDC-4), followed by a decrease in the levels of the chondroitin sulfate proteoglycan, Versican. Disruption of glycosaminoglycan chains by chondroitinase AC or heparanase III completely abolished the effects of T3-treated astrocytes on neuronal morphogenesis. Our work provides evidence that astrocytes are key mediators of T3 actions on cerebral cortex neuronal development and identified potential molecules and pathways involved in neurite extension; which might eventually contribute to a better understanding of axonal regeneration, synapse formation, and neuronal circuitry recover.Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional para o Desenvolvimento Cientifico e TecnologicoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Rio de Janeiro, Inst Ciencias Biomed, BR-21949590 Rio de Janeiro, RJ, BrazilUniv Fed Rio de Janeiro, Inst Bioquim Med, BR-21949590 Rio de Janeiro, RJ, BrazilUniv Fed Rio de Janeiro, Hosp Univ Clementino Fraga Filho, BR-21949590 Rio de Janeiro, RJ, BrazilUniversidade Federal de São Paulo, Dept Bioquim, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Bioquim, São Paulo, BrazilWeb of Scienc
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