Search

The direction of individual B8 solar neutrinos has been reconstructed using the SNO+ liquid scintillator detector. Prompt, directional Cherenkov light was separated from the slower, isotropic scintillation light using time information, and a maximum likelihood method was used to reconstruct the direction of individual scattered electrons. A clear directional signal was observed, correlated with the solar angle. The observation was aided by a period of low primary fluor concentration that resulted in a slower scintillator decay time. This is the first time that event-by-event direction reconstruction in high light-yield liquid scintillator has been demonstrated in a large-scale detector.

The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240 km away in Ontario, Canada. This analysis uses events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190 days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5σ.

Eos is a technology demonstrator, designed to explore the capabilities of hybrid event detection technology, leveraging both Cherenkov and scintillation light simultaneously. With a fiducial mass of four tons, Eos is designed to operate in a high-precision regime, with sufficient size to utilize time-of-flight information for full event reconstruction, flexibility to demonstrate a range of cutting edge technologies, and simplicity of design to facilitate potential future deployment at alternative sites. Results from Eos can inform the design of future neutrino detectors for both fundamental physics and nonproliferation applications. This paper describes the conceptual design and potential applications of the Eos detector.

This paper reports results from a search for single and multinucleon disappearance from the O16 nucleus in water within the SNO+ detector using all of the available data. These so-called "invisible"decays do not directly deposit energy within the detector but are instead detected through their subsequent nuclear deexcitation and gamma-ray emission. New limits are given for the partial lifetimes: τ(n→inv)>9.0×1029 years, τ(p→inv)>9.6×1029 years, τ(nn→inv)>1.5×1028 years, τ(np→inv)>6.0×1028 years, and τ(pp→inv)>1.1×1029 years at 90% Bayesian credibility level (with a prior uniform in rate). All but the (nn→inv) results improve on existing limits by a factor of about 3.

SNO+ is a large-scale liquid scintillator experiment with the primary goal of searching for neutrinoless double beta decay, and is located approximately 2 km underground in SNOLAB, Sudbury, Canada. The detector acquired data for two years as a pure water Cherenkov detector, starting in May 2017. During this period, the optical properties of the detector were measured in situ using a deployed light diffusing sphere, with the goal of improving the detector model and the energy response systematic uncertainties. The measured parameters included the water attenuation coefficients, effective attenuation coefficients for the acrylic vessel, and the angular response of the photomultiplier tubes and their surrounding light concentrators, all across different wavelengths. The calibrated detector model was validated using a deployed tagged gamma source, which showed a 0.6% variation in energy scale across the primary target volume.

A liquid scintillator consisting of linear alkylbenzene as the solvent and 2,5-diphenyloxazole as the fluor was developed for the SNO+ experiment. This mixture was chosen as it is compatible with acrylic and has a competitive light yield to pre-existing liquid scintillators while conferring other advantages including longer attenuation lengths, superior safety characteristics, chemical simplicity, ease of handling, and logistical availability. Its properties have been extensively characterized and are presented here. This liquid scintillator is now used in several neutrino physics experiments in addition to SNO+.

A search has been performed for neutrinos from two sources, the hep reaction in the solar pp fusion chain and the νe component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton-years after fiducialization. The hep search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of φhep

The SNO+ experiment collected data as a low-threshold water Cherenkov detector from September 2017 to July 2019. Measurements of the 2.2-MeV γ's produced by neutron capture on hydrogen were made using an Am-Be calibration source, for which a large fraction of emitted neutrons are produced simultaneously with a 4.4-MeV γ. Analysis of the delayed coincidence between the 4.4-MeV γ and the 2.2-MeV capture γ revealed a neutron detection efficiency that is centered around 50% and varies at the level of 1% across the inner region of the detector, which to our knowledge is the highest efficiency achieved among pure water Cherenkov detectors. In addition, the neutron capture time constant was measured and converted to a thermal neutron-proton capture cross section of 336.3-1.5+1.2mb.

New developments in liquid scintillators, high-efficiency, fast photon detectors, and chromatic photon sorting have opened up the possibility for building a large-scale detector that can discriminate between Cherenkov and scintillation signals. Such a detector could reconstruct particle direction and species using Cherenkov light while also having the excellent energy resolution and low threshold of a scintillator detector. Situated deep underground, and utilizing new techniques in computing and reconstruction, this detector could achieve unprecedented levels of background rejection, enabling a rich physics program spanning topics in nuclear, high-energy, and astrophysics, and across a dynamic range from hundreds of keV to many GeV. The scientific program would include observations of low- and high-energy solar neutrinos, determination of neutrino mass ordering and measurement of the neutrino CP-violating phase δ, observations of diffuse supernova neutrinos and neutrinos from a supernova burst, sensitive searches for nucleon decay and, ultimately, a search for neutrinoless double beta decay, with sensitivity reaching the normal ordering regime of neutrino mass phase space. This paper describes Theia, a detector design that incorporates these new technologies in a practical and affordable way to accomplish the science goals described above.

Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of geant4 physics models. In addition, the cosmogenic neutron yield, in units of 10-4 cm2/(g·μ), is measured to be 7.28±0.09(stat)-1.12+1.59(syst) in pure heavy water and 7.30±0.07(stat)-1.02+1.40(syst) in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB.

Neutron production in GeV-scale neutrino interactions is a poorly studiedprocess. We have measured the neutron multiplicities in atmospheric neutrinointeractions in the Sudbury Neutrino Observatory experiment and compared themto the prediction of a Monte Carlo simulation using GENIE and a minimallymodified version of GEANT4. We analyzed 837 days of exposure corresponding toPhase I, using pure heavy water, and Phase II, using a mixture of Cl in heavywater. Neutrons produced in atmospheric neutrino interactions were identifiedwith an efficiency of $15.3\%$ and $44.3\%$, for Phase I and II respectively.The neutron production is measured as a function of the visible energy of theneutrino interaction and, for charged current quasi-elastic interactioncandidates, also as a function of the neutrino energy. This study is alsoperformed classifying the complete sample into two pairs of event categories:charged current quasi-elastic and non charged current quasi-elastic, and$\nu_{\mu}$ and $\nu_e$. Results show good overall agreement between data andMonte Carlo for both phases, with some small tension with a statisticalsignificance below $2\sigma$ for some intermediate energies.

The long baseline between Earth and the Sun makes solar neutrinos an excellent test beam for exploring possible neutrino decay. The signature of such decay would be an energy-dependent distortion of the traditional survival probability which can be fit for using well-developed and high-precision analysis methods. Here a model including neutrino decay is fit to all three phases of B8 solar neutrino data taken by the Sudbury Neutrino Observatory (SNO). This fit constrains the lifetime of neutrino mass state ν2 to be >8.08×10-5 s/eV at 90% confidence. An analysis combining this SNO result with those from other solar neutrino experiments results in a combined limit for the lifetime of mass state ν2 of >1.92×10-3 s/eV at 90% confidence.

This paper reports results from a search for nucleon decay through invisible modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently deexcite, often emitting detectable gamma rays. A search for such gamma rays yields limits of 2.5×1029 y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6×1029 y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of 1.3×1028 y for nn, 2.6×1028 y for pn and 4.7×1028 y for pp, an improvement over existing limits by close to 3 orders of magnitude for the latter two.

A measurement of the B8 solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25-0.07+0.09 events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03-0.12+0.13 events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53-0.28+0.31(stat)-0.10+0.13(syst)×106 cm-2 s-1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.

A measurement of the B8 solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25-0.07+0.09 events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03-0.12+0.13 events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53-0.28+0.31(stat)-0.10+0.13(syst)×106 cm-2 s-1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.

Experimental tests of Lorentz symmetry in systems of all types are critical for ensuring that the basic assumptions of physics are well founded. Data from all phases of the Sudbury Neutrino Observatory, a kiloton-scale heavy water Cherenkov detector, are analyzed for possible violations of Lorentz symmetry in the neutrino sector. Such violations would appear as one of eight possible signal types in the detector: six seasonal variations in the solar electron neutrino survival probability differing in energy and time dependence and two shape changes to the oscillated solar neutrino energy spectrum. No evidence for such signals is observed, and limits on the size of such effects are established in the framework of the standard model extension, including 38 limits on previously unconstrained operators and improved limits on 16 additional operators. This makes limits on all minimal, Dirac-type Lorentz violating operators in the neutrino sector available for the first time.

Tests on B-L symmetry breaking models are important probes to search for new physics. One proposed model with Δ(B-L)=2 involves the oscillations of a neutron to an antineutron. In this paper, a new limit on this process is derived for the data acquired from all three operational phases of the Sudbury Neutrino Observatory experiment. The search concentrated on oscillations occurring within the deuteron, and 23 events were observed against a background expectation of 30.5 events. These translated to a lower limit on the nuclear lifetime of 1.48×1031 yr at 90% C.L. when no restriction was placed on the signal likelihood space (unbounded). Alternatively, a lower limit on the nuclear lifetime was found to be 1.18×1031 yr at 90% C.L. when the signal was forced into a positive likelihood space (bounded). Values for the free oscillation time derived from various models are also provided in this article. This is the first search for neutron-Antineutron oscillation with the deuteron as a target.

This review paper provides a summary of the published results of the SudburyNeutrino Observatory (SNO) experiment that was carried out by an internationalscientific collaboration with data collected during the period from 1999 to2006. By using heavy water as a detection medium, the SNO experimentdemonstrated clearly that solar electron neutrinos from $^8$B decay in thesolar core change into other active neutrino flavors in transit to Earth. Thereaction on deuterium that has equal sensitivity to all active neutrino flavorsalso provides a very accurate measure of the initial solar flux for comparisonwith solar models. This review summarizes the results from three phases ofsolar neutrino detection as well as other physics results obtained fromanalyses of the SNO data.

SNO+ is a large liquid scintillator-based experiment located 2 km underground at SNOLAB, Sudbury, Canada. It reuses the Sudbury Neutrino Observatory detector, consisting of a 12 m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pure liquid scintillator. Designed as a multipurpose neutrino experiment, the primary goal of SNO+ is a search for the neutrinoless double-beta decay (0ββ) of 130Te. In Phase I, the detector will be loaded with 0.3% natural tellurium, corresponding to nearly 800 kg of 130Te, with an expected effective Majorana neutrino mass sensitivity in the region of 55-133 meV, just above the inverted mass hierarchy. Recently, the possibility of deploying up to ten times more natural tellurium has been investigated, which would enable SNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future. Additionally, SNO+ aims to measure reactor antineutrino oscillations, low energy solar neutrinos, and geoneutrinos, to be sensitive to supernova neutrinos, and to search for exotic physics. A first phase with the detector filled with water will begin soon, with the scintillator phase expected to start after a few months of water data taking. The 0νββ Phase I is foreseen for 2017.

The US neutrino community gathered at the Workshop on the IntermediateNeutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 toexplore opportunities in neutrino physics over the next five to ten years.Scientists from particle, astroparticle and nuclear physics participated in theworkshop. The workshop examined promising opportunities for neutrino physics inthe intermediate term, including possible new small to mid-scale experiments,US contributions to large experiments, upgrades to existing experiments, R&Dplans and theory. The workshop was organized into two sets of parallel workinggroup sessions, divided by physics topics and technology. Physics workinggroups covered topics on Sterile Neutrinos, Neutrino Mixing, NeutrinoInteractions, Neutrino Properties and Astrophysical Neutrinos. Technologysessions were organized into Theory, Short-Baseline Accelerator Neutrinos,Reactor Neutrinos, Detector R&D and Source, Cyclotron and Meson Decay at Restsessions.This report summarizes discussion and conclusions from the workshop.

Purpose: To evaluate the microtensile bond strength (μTBS) of a one-step self-etch adhesive (1-SEA) to dentin and its interfacial nanomechanical properties after 8 years of water storage. Materials and Methods: Flat coronal dentin surfaces of extracted human third molars were bonded with a 1-SEA (Clearfil S3 Bond Plus, CS3+) and built up with a hybrid resin composite (Clearfil AP-X). After storage in water for 24 h or 8 years, non-trimmed stick-shaped specimens were fabricated from the central part of each bonded tooth and subjected to the μTBS test at a crosshead speed of 1.0 mm/min. Failure modes and the morphology of debonded interfaces were analyzed using a scanning electron microscope (SEM). In addition, the elastic modulus (E) and hardness (H) of the adhesive layer and the resin composite were determined by an instrumented nanoindentation test. The acquired μTBS, E, and H data were statistically analyzed using t-tests to examine the effect of storage time (α = 0.05). Results: The 8-year μTBS was slightly lower than that after 24 h, but the difference was not significant (p = 0.123). The SEM observation of debonded surfaces after 8 years revealed extrusions and lacunas. E and H of the adhesive layer and the resin composite significantly decreased over the 8-year water storage (p < 0.001). Conclusions: Although 8 years of water storage did not decrease the μTBS of CS3+ significantly, the observed failure mode patterns and significantly decreased nanomechanical properties indicated resin degradation of the adhesive and the resin composite. [ABSTRACT FROM AUTHOR]

Costimulation mediated by the CD28 receptor has been shown to play an important role in the development of a vigorous T cell immune response. Nevertheless, CD28-deficient mice can mount effective T cell-dependent immune responses. These data suggest that other costimulatory molecules may play a role in T cell activation. In a search for other costimulatory receptors on T cells, we have characterized a monoclonal antibody (mAb) that can costimulate T cells in the absence of accessory cells. Similar to CD28 antibodies, this mAb, R2/60, was found to synergize with T cell receptor engagement in inducing proliferation. Independent ligation of CD3 and the ligand recognized by R2/60 results in T cell proliferation, suggesting that the two molecules do not have to colocalize to activate the R2/60 costimulatory pathway. R2/60 does not react with CD28, and furthermore, R2/60 costimulates in a CD28-independent fashion since the mAb costimulates T cells from the CD28-deficient mice as well as wild-type mice. Expression cloning of the R2/60 antigen identified the ligand as murine CD43. Together, these data demonstrate that CD43 can serve as a receptor on T cells that can provide CD28-independent costimulation.

Respaldado nas teorias de coprodução de bens públicos, este artigo desenvolve e apresenta uma matriz de coprodução do serviço público. A partir desta matriz faz-se uma avaliação da participação do cidadão na implementação de uma política habitacional levada a efeito pela Companhia de Habitação do Estado de Santa Catarina (Cohab/SC), órgão vinculado à Secretaria de Estado do Desenvolvimento Social, Urbano e Meio Ambiente, com a execução do Programa Estadual de Promoção de Assentamentos Humanos e Moradias Populares no período 2003-06. Os resultados obtidos revelam que a participação do cidadão varia desde o contato inicial com o órgão, ou respectivo representante público, durante a execução das obras, até a entrega das casas. Análise pautada na matriz identificou que o tipo e a intensidade da coprodução do bem público ocorreram de formas distintas nos dois municípios observados - Palhoça e Rancho Queimado -, apresentando resultados mais abrangentes e substantivos em favor do último.

O objetivo deste trabalho foi avaliar a resistência à fratura de dentes restaurados com resina composta de alta viscosidade (Filtek P60 – 3M/ESPE) e resina composta indireta (BelleGlass - sds/Kerr) em preparos MOD. Trinta e dois pré-molares superiores foram divididos em 4 grupos, sendo: grupo 1 - dentes hígidos; grupo 2 - dentes com preparos MOD restaurados com resina composta P60; grupo 3 - dentes restaurados com BelleGlass; e grupo 4 - dentes apenas preparados (MOD). Todos os corpos de prova foram submetidos ao teste de resistência à fratura em máquina de ensaio universal com velocidade de 0,5 mm/min. Os resultados foram analisados estatisticamente através dos testes ANOVA e Tukey, com um nível de significância de 1%, que mostraram diferenças significativas entre todos os grupos, sendo o grupo 1 (dentes hígidos) mais resistente à fratura do que o grupo 2 (P60), o qual foi mais resistente que o grupo 3 (BelleGlass), que por sua vez apresentou maior resistência do que o grupo 4 (apenas preparados). Concluiu-se que o preparo cavitário reduziu a resistência à fratura de forma significativa e que as restaurações adesivas restituíram parcialmente a resistência perdida, sendo a performance da resina composta P60 superior à Belleglass.

Interferon (IFN) was found to be secreted by cloned lines of murine cytotoxic T lymphocytes in response to mitogenic or antigen specific stimulation. The IFN produced was shown to be of the immune type based on its sensitivity to pH 2.0 and on the ability of an antiserum to immune IFN to neutralize the antiviral activity.

A inoculação intraperitoneal de 3,8 x 10(9) CFU de Salmonella typhimurium viva causou 100% de mortalidade em ratos. Nesses animais, pequeno número de neutrófilos migraram para a cavidade peritoneal. A injeção intraperitoneal de tioglicolato (TG, 90 mg), carragenina (Cg, 500 mi g) ou salmonella morta pelo calor (KS, 1,9 x10(9) CFU) 24 horas antes do desafio com S. typhimurium viva causou maior (p < 0,01) migração de neutrófilos para a cavidade peritoneal após 6 horas e conferiu proteção aos animais contra os efeitos letais da bactéria que foram da ordem de 50%, 83% e 80%, respectivamente. Todavia, o tratamento semelhante dos animais com o meio de cultivo "infusão de cérebro e coração" (brain heart infusion-BHI) estéril exerceu proteção de apenas 23%. O número de neutrófilos que migraram para a cavidade peritoneal representou apenas 10% do verificado nos outros tratamentos. A atividade fagocitária não estava relacionada ao índice de sobrevivência dos animais, uma vez que tal atividade foi duas vezes maior no grupo KS do que nos grupos Tg e Cg, e a taxa de sobrevivência nesse grupo foi semelhante à observada no grupo Cg. Esses resultados sugerem que o aumento da migração de neutrófilos para o sítio infeccioso induzida pelas administrações prévias das diferentes substâncias é um importante fator associado com a proteção dos animais contra os efeitos letais da infecção bacteriana.