[en] Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper

[en] Solar Neutrinos from the decay of 8B have been detected at the Sudbury Neutrino Observatory (SNO) by charged current (CC) and neutral current (NC) interactions on deuterium and elastic scattering (ES) of electrons. The SNO data indicate that with the assumption of undistorted 8B shape, the flux for ve is φ_e = 1.76_-0.05^+0.05 (stat.)_-0.09^+0.09 (syst.) x 10⁶ cm^-2s^-1 for a kinetic energy threshold of 5 MeV. The non-ve flux is φ_μτ = 3.41_-0.45^+0.45 (stat.)_-0.45^+0.45 (syst.) x 10⁶ cm^-2s^-1. This provides strong evidence for solar ve flavor transformation. The day and night solar neutrino energy spectra and rates have also been measured. For CC events, the ve asymmetry is 14.0% ± 6.3% _-1.4^+1.5 %. By additionally constraining the total (NC) flux of active neutrinos to have no asymmetry, the ve asymmetry becomes 7.0% ± 4.9% _-1.2^+1.3 %. A global solar neutrino analysis strongly favors the Large Mixing Angle (LMA) solution in a two-flavor neutrino oscillation model

[en] Levels in ¹¹²Cd have been studied through the (n,n'γ) reaction with monoenergetic neutrons. An extended set of experiments that included excitation functions, γ-ray angular distributions, and γγ coincidence measurements was performed. A total of 375 γ rays were placed in a level scheme comprising 200 levels (of which 238 γ-ray assignments and 58 levels are newly established) up to 4 MeV in excitation. No evidence to support the existence of 47 levels as suggested in previous studies was found, and these have been removed from the level scheme. From the results, a comparison of the level density is made with the constant temperature and back-shifted Fermi gas models. The back-shifted Fermi gas model with the Gilbert-Cameron spin cutoff parameter provided the best overall fit. Without using the neutron resonance information and only fitting the cumulative number of low-lying levels, the level density parameters extracted are a sensitive function of the maximum energy used in the fit

[en] After the first direct observation of neutrino flavor transformations at the Sudbury Neutrino Observatory, future planned neutrino experiments are focusing on the understanding of the neutrino oscillation mechanism by determining key neutrino parameters, such as the mass differences and mass hierarchy, the mixing angles, and the possibility of CP violation. Organic liquid scintillators (LS) have been the detection medium of choice for neutrinos since the early discovery experiment of Reines and Cowan. For the delayed neutron-capture signal following antineutrino capture, the advantages of adding a metallic element to the LS (to form M-LS) are significant. Chemically, there are challenges to adding inorganic salts of metal directly to the LS. Key aspects of the metal-loaded LS for neutrino detection are (a) long-term chemical stability, (b) high optical transparency, (c) high photon production by the LS, and (d) ultra-low impurity content, mainly of natural radioactive contaminants, such as U, Th, Ra, and Rn. The BNL Neutrino and Nuclear Chemistry group has a long history of neutrino research since Ray Davis's pioneering Homestake experiment. The group has developed new chemical techniques of loading metals, such as In, Yb, Gd, Nd, and currently Li and other low-Z elements, in organic liquid scintillator that can be used for low-energy solar neutrino, reactor antineutrino, terrestrial antineutrino or double-beta decay experiments. Metals at different concentrations in a series of liquid scintillators have been studied systematically at BNL. We have successfully prepared many metal-doped scintillators, with long attenuation lengths (10-15 m) and high light yields. These have been stable for long period of time since synthesis (>2 years for Gd-LS and Nd-LS, and >3 years for In-LS), a crucial characteristic in experiments that are planned to run for at least 3 years. Our chemical-doping technologies and the performance of different organometallic liquid scintillators for different experiments will be presented.

[en] Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can be used under stable conditions for many years even in ton scale experiments. Applications of metal loaded scintillators in neutrino experiments are reviewed and the performance as well as the prospects of different scintillator types are compared. (topical review)

[en] Recent exciting results have shown that neutrinos oscillate between their weak eigenstates and thus must not only be massive but their mass and flavor eigenstates do no coincide. This has opened a whole new area of experimental physics where one strives to precisely measure the mixing parameters, search for potential CP symmetry violation in the lepton sector and understand secondary effects, such as how the oscillations are affected when the neutrinos pass through matter. It is possible to measure all of the oscillation parameters in a single experiment by employing a 1-MW wide-band neutrino super-beam, a very long baseline of ∼2500 km and a 500-kton massive far detector

[en] Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper.

[en] Negative-parity excitations in the 2.5 MeV region in ¹¹²Cd have been investigated with the (n,n'γ reaction. Several of these states exhibit enhanced B(E2) values for decay to the 3₁^- octupole state, indicative of quadrupole-octupole coupled (2⁺x3^-) structures. The B(E1) values observed are typically in the range of 1-5x10^-4 W.u., irrespective of the final state. (author)

[en] We describe precise optical attenuation measurements of LAB based liquid scintillators using a custom-built photometer with variable pathlengths up to 2 m. Results are presented for linear alkyl benzene (LAB) and LAB based liquid scintillators at wave lengths of 405, 430, 450, and 470 nm. For these measurements much care was exercised to control the purity of the liquids and additives, as well as the materials of the photometer to control contaminations. These data should be valuable for design of large detectors, such as underground neutrino detectors, using these materials as the media.

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