Experimental limits on particle dark-matter candidates Jelley, N. A.
Philosophical transactions of the Royal Society of London. Series A: Mathematical and physical sciences,
12/1986, Letnik:
320, Številka:
1556
Journal Article
Recenzirano
The experimental limits on some of the particle candidates for the dark matter are discussed. The main part of the paper is about neutrinos, which are the only particles known to exist that are ...possible candidates, and the present evidence about neutrino mass is reviewed. This is followed by a discussion of the limits on two candidates that have provoked considerable experimental interest: the magnetic monopole, and the supersymmetric particle, the photino. The paper concludes with a brief account of a recently developed calorimetric detector and of its possible use in detecting dark-matter candidates, such as the photino.
The evidence for neutrino flavour change and for the LMA solution for the neutrino mixing parameters is briefly summarized. Recent results and current research from SNO and SK are then described ...along with the potential for KamLAND, Borexino and planned new experiments to extend our knowledge by studying low energy solar neutrinos. The sensitivity of reactor experiments in determining
θ
13
is discussed and the detection technique and principal backgrounds are explained. Finally the status of proposed and funded reactor
θ
13
experiments is presented.
The synthesis and the 5-HT receptor activity of a novel series of N,N-dimethyltryptamines substituted in the 5-position with an imidazole, triazole, or tetrazole ring are described. The objective of ...this work was to identify potent and selective 5-HT1D receptor agonists with high oral bioavailability and low central nervous system penetration. Compounds have been prepared in which the azole ring is attached through either nitrogen or carbon to the indole. Conjugated and methylene-bridged derivatives have been studied (n = 0 or 1). Substitution of the azole ring has been explored either alpha or beta to the point of attachment to indole. In a series of N-linked azoles (X = N), simple unsubstituted compounds have high affinity and selectivity for 5-HT1D receptors. It is proposed that for good affinity and selectivity a hydrogen bond acceptor interaction with the 5-HT1D receptor, through a beta-nitrogen in the azole ring, is required. In a series of C-linked triazoles and tetrazoles (X = C), optimal affinity and selectivity for the 5-HT1D receptor was observed when the azole ring is substituted at the 1-position with a methyl or ethyl group. This study has led to the discovery of the 1,2,4-triazole 10a (MK-462) as a potent and selective 5-HT1D receptor agonist which has high oral bioavailability and rapid oral absorption. The in vitro activity and the preliminary pharmacokinetics of compounds in this series are presented.
Phys. Rev. D 102, 062006 (2020) A search has been performed for neutrinos from two sources, the $hep$
reaction in the solar $pp$ fusion chain and the $\nu_e$ 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 $\Phi_{hep} <
30\times10^{3}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}$ 90% credible interval (CI).
No events are observed in the DSNB search region, and we set an improved upper
bound on the $\nu_e$ component of the DSNB flux of $\Phi^\mathrm{DSNB}_{\nu_e}
< 19~\textrm{cm}^{-2}~\textrm{s}^{-1}$ (90% CI) in the energy range $22.9 <
E_\nu < 36.9$~MeV.
Four methods for determining the composition of low-level uranium- and thorium-chain surface contamination are presented. One method is the observation of Cherenkov light production in water. In two ...additional methods a position-sensitive proportional counter surrounding the surface is used to make both a measurement of the energy spectrum of alpha particle emissions and also coincidence measurements to derive the thorium-chain content based on the presence of short-lived isotopes in that decay chain. The fourth method is a radiochemical technique in which the surface is eluted with a weak acid, the eluate is concentrated, added to liquid scintillator and assayed by recording beta-alpha coincidences. These methods were used to characterize two `hotspots' on the outer surface of one of the He-3 proportional counters in the Neutral Current Detection array of the Sudbury Neutrino Observatory experiment. The methods have similar sensitivities, of order tens of ng, to both thorium- and uranium-chain contamination.
The existing hydrous titanium oxide (HTiO) technique for the measurement of 224Ra and 226Ra in the water at the Sudbury Neutrino Observatory (SNO) has been changed to make it faster and less ...sensitive to trace impurities in the HTiO eluate. Using HTiO-loaded filters followed by cation exchange adsorption and HTiO co-precipitation, Ra isotopes from 200-450 tonnes of heavy water can be extracted and concentrated into a single sample of a few millilitres with a total chemical efficiency of 50%. Combined with beta-alpha coincidence counting, this method is capable of measuring 2.0x10^3 uBq/kg of 224Ra and 3.7x10^3 uBq/kg of 226Ra from the 232Th and 238U decay chains, respectively, for a 275 tonne D2O assay, which are equivalent to 5x10^16 g Th/g and 3x10^16 g U/g in heavy water.
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