Radioactivity is understood to be described by a Poisson process, yet some measurements of nuclear decays appear to exhibit unexpected variations. Generally, the isotopes reporting these variations ...have long half lives, which are plagued by large measurement uncertainties. In addition to these inherent problems, there are some reports of time-dependent decay rates and even claims of exotic neutrino-induced variations. We present a dedicated experiment for the stable long-term measurement of gamma emissions resulting from \(\beta\) decays, which will provide high-quality data and allow for the identification of potential systematic influences. Radioactive isotopes are monitored redundantly by thirty-two 76 mm \(\times\) 76 mm NaI(Tl) detectors in four separate temperature-controlled setups across three continents. In each setup, the monitoring of environmental and operational conditions facilitates correlation studies. The deadtime-free performance of the data acquisition system is monitored by LED pulsers. Digitized photomultiplier waveforms of all events are recorded individually, enabling a study of time-dependent effects spanning microseconds to years, using both time-binned and unbinned analyses. We characterize the experiment's stability and show that the relevant systematics are accounted for, enabling precise measurements of effects at levels well below \(\mathcal{O}(10^{-4})\).
Brothers (1990) has proposed that the amygdala is an important component of the neural network that underlies social behavior. Kemper and Bauman (1993) identified neuropathology in the amygdala of ...the postmortem autistic brain. These findings, along with recent functional neuroimaging data, have led Baron-Cohen et al. (2000) to propose that dysfunction of the amygdala may be responsible, in part, for the impairment of social behavior that is a hallmark feature of autism. Recent data from studies in our laboratory on the effects of amygdala lesions in the adult and infant macaque monkey do not support a fundamental role for the amygdala in social behavior. If the amygdala is not essential for the component processes of social behavior, as seems to be case in both non-human primates and selected patients with bilateral amygdala damage, then it is unlikely to be the primary substrate for the impaired social behavior of autism. However, damage to the amygdala does have an effect on a monkey's response to normally fear-inducing stimuli, such as snakes, and removes a natural reluctance to engage novel conspecifics in social interactions. These findings lead to the conclusion that an important role for the amygdala is in the detection of threats and mobilizing an appropriate behavioral response, part of which is fear. Interestingly, an important comorbid feature of autism is anxiety (Muris et al. 1998). If the amygdala is pathological in subjects with autism, it may contribute to their abnormal fears and increased anxiety rather than their abnormal social behavior.
In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon (\(^{222}\)Rn), thoron (\(^{220}\)Rn) and krypton (\(^{85}\)Kr). We detail the event ...selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of \(\sim\) 4 years, from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode.
The XENON100 experiment has completed a dark matter search with 100.9 live days of data, taken from January to June 2010. Events with energies between 8.4 and 44.6 keVnr in a fiducial volume ...containing 48 kg of liquid xenon have been analyzed. A total of three events have been found in the predefined signal region, compatible with the background prediction of (1.8±0.6) events. Based on this analysis we present limits on the WIMP-nucleon cross section for inelastic dark matter. With the present data we are able to rule out the explanation for the observed DAMA/LIBRA modulation as being due to inelastic dark matter scattering off iodine, at a 90% confidence level.
Phys. Rev. Lett. 121, 111302 (2018) We report on a search for Weakly Interacting Massive Particles (WIMPs) using
278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T
utilizes a ...liquid xenon time projection chamber with a fiducial mass of $(1.30
\pm 0.01)$ t, resulting in a 1.0 t$\times$yr exposure. The energy region of
interest, 1.4, 10.6 $\mathrm{keV_{ee}}$ (4.9, 40.9 $\mathrm{keV_{nr}}$),
exhibits an ultra-low electron recoil background rate of $(82\substack{+5 \\
-3}\textrm{ (sys)}\pm3\textrm{ (stat)})$
events/$(\mathrm{t}\times\mathrm{yr}\times\mathrm{keV_{ee}})$. No significant
excess over background is found and a profile likelihood analysis parameterized
in spatial and energy dimensions excludes new parameter space for the
WIMP-nucleon spin-independent elastic scatter cross-section for WIMP masses
above 6 GeV/c^2$, with a minimum of $4.1\times10^{-47}$ cm$^2$ at 30
GeV/c^2$ and 90% confidence level.
In organic waste, numerous mold fungi and other microorganisms develop sometimes within a few hours only which decompose the organic material already in the collecting containers generating heat and ...odor. With regard to the emission of mold fungus spores out of garbage cans for bio-waste and the potential environmental-hygienic danger connected with it, considerable worries have been expressed recently. A wide spectrum of mold fungi can be found in bio-waste in strongly varying concentrations. No noticeable difference could be ascertained between the settlement structure areas and the cities respectively as to the fungus concentration in the bio-waste substrate. A. fumigatus and A. niger can be recommended as leading spores for the behavior of the total concentration of fungi in the bio-waste due to their frequency of detection and their seasonal dynamism. The intensity of the air spore pollution through emission of mold fungus spores correlates closely with the climatic conditions, such as variations of temperature, relative humidity and solar radiation. The airborne release of mold fungus spores out of garbage cans for bio-waste and the formation of a respective exposure connected with it is judged as harmless for healthy persons. Risk patients and persons having a weakened immune system or assumed to have such a one due to an existent basic illness and/or other reasons should avoid any handling of bio-waste as well as any other waste if possible.
We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92 V/cm, 154 V/cm and 366 V/cm using the XENON100 detector. A ...data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 V/cm are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xenon.
On August 17, 2017, the first gravitational wave signal from a binary neutron star inspiral (GW170817) was detected by Advanced LIGO and Advanced VIRGO. Here we present radioactive \(\beta\)-decay ...rates of three independent sources \(^{44}\)Ti, \(^{60}\)Co and \(^{137}\)Cs, monitored during the same period by a precision experiment designed to investigate the decay of long-lived radioactive sources. We do not find any significant correlations between decay rates in a 5\,h time interval following the GW170817 observation. This contradicts a previous claim published in this journal of an observed 2.5\(\sigma\) Pearson Correlation between fluctuations in the number of observed decays from two \(\beta\)-decaying isotopes (\(^{32}\)Si and \(^{36}\)Cl) in the same time interval. By correcting for the choice of an arbitrary time interval, we find no evidence of a correlation above 1.5\(\sigma\) confidence. In addition, we argue that such analyses on correlations in arbitrary time intervals should always correct for the so-called Look-Elsewhere effect by quoting the global significance.
We present the first search for dark matter-induced delayed coincidence signals in a dual-phase xenon time projection chamber, using the 224.6 live days of the XENON100 science run II. This very ...distinct signature is predicted in the framework of magnetic inelastic dark matter which has been proposed to reconcile the modulation signal reported by the DAMA/LIBRA collaboration with the null results from other direct detection experiments. No candidate event has been found in the region of interest and upper limits on the WIMP's magnetic dipole moment are derived. The scenarios proposed to explain the DAMA/LIBRA modulation signal by magnetic inelastic dark matter interactions of WIMPs with masses of 58.0 GeV/c\(^2\) and 122.7 GeV/c\(^2\) are excluded at 3.3 \(\sigma\) and 9.3 \(\sigma\), respectively.
We report the first dark matter search results from XENON1T, a \(\sim\)2000-kg-target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the Laboratori Nazionali del Gran ...Sasso in Italy and the first ton-scale detector of this kind. The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042\(\pm\)12) kg fiducial mass and in the 5, 40 \(\mathrm{keV}_{\mathrm{nr}}\) energy range of interest for WIMP dark matter searches, the electronic recoil background was \((1.93 \pm 0.25) \times 10^{-4}\) events/(kg \(\times\) day \(\times \mathrm{keV}_{\mathrm{ee}}\)), the lowest ever achieved in a dark matter detector. A profile likelihood analysis shows that the data is consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10 GeV/c\({}^2\), with a minimum of 7.7 \(\times 10^{-47}\) cm\({}^2\) for 35-GeV/c\({}^2\) WIMPs at 90% confidence level.
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