Search results for " dark"
showing 10 items of 212 documents
Iepazīšanās portāla lietošanas motīvi un personības tumšā triāde
2020
Pētījuma mērķis bija noskaidrot kāda sakarība pastāv starp iepazīšanās portālu lietošanas motīviem un tumšās triādes personības iezīmēm. Pētījumā piedalījās 686 Latvijas iepazīšanās portāla Otrapuse.lv lietotāji, 420 sievietes un 266 vīrieši. Pētījumā tika uzmantotas divas aptaujas: Īsā tumšās triādes skala (Short Dark Triad Scale, Jones & Paulhus, 2014). Latvijā metodi adaptējusi Laima Baldiņa (Baldiņa, 2017); Iepazīšanās portāla Otrapuse.lv lietošanas motīvi aptauja ( Tinder Motives Scale (TMS), Timmermans & De Caluwé, 2017). Aptauja tika adaptēta maģistra darba ietvaros. Pētījumā izvirzītie jautājumi: 1. Kāda sakarība pastāv starp iepazīšanās portāla lietošanas motīviem un tumšās triādes…
$^{222}$Rn emanation measurements for the XENON1T experiment
2021
The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the $^{222}$Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a $^{222}$Rn activity concentration of 10 $\mu$Bq/kg in 3.2 t of xenon. The knowledge of the distribut…
Results from a calibration of XENON100 using a source of dissolved radon-220
2017
A Rn 220 source is deployed on the XENON100 dark matter detector in order to address the challenges in calibration of tonne-scale liquid noble element detectors. We show that the Pb 212 beta emission can be used for low-energy electronic recoil calibration in searches for dark matter. The isotope spreads throughout the entire active region of the detector, and its activity naturally decays below background level within a week after the source is closed. We find no increase in the activity of the troublesome Rn 222 background after calibration. Alpha emitters are also distributed throughout the detector and facilitate calibration of its response to Rn 222 . Using the delayed coincidence of R…
The DArk Matter Particle Explorer mission
2017
The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives include the study of galactic cosmic rays up to $\sim 10$ TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. In this paper we illustrate the layout of the DAMPE instrument, and discuss the results of beam tests and calib…
Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data
2017
We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 years, from January 2010 to January 2014. A profile likelihood method, which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of $431^{+16}_{-14}$ days in the low energy region of $(2.0-5.8)$ keV in the single scatter event sample, with a global significance of $1.9\,\sigma$, however no other more significant modulation is observed. The expected annual modulation of a dark matt…
Improved cosmological bound on the thermal axion mass
2007
Relic thermal axions could play the role of an extra hot dark matter component in cosmological structure formation theories. By combining the most recent observational data we improve previous cosmological bounds on the axion mass m_a in the so-called hadronic axion window. We obtain a limit on the axion mass m_a < 0.42eV at the 95% c.l. (m_a < 0.72eV at the 99% c.l.). A novel aspect of the analysis presented here is the inclusion of massive neutrinos and how they may affect the bound on the axion mass. If neutrino masses belong to an inverted hierarchy scheme, for example, the above constraint is improved to m_a < 0.38eV at the 95% c.l. (m_a < 0.67eV at the 99% c.l.). Future da…
Reconstructing WIMP properties with neutrino detectors
2008
If the dark matter of the Universe is constituted by weakly interacting massive particles (WIMP), they would accumulate in the core of astrophysical objects as the Sun and annihilate into particles of the Standard Model. High-energy neutrinos would be produced in the annihilations, both directly and via the subsequent decay of leptons, quarks and bosons. While Cherenkov neutrino detectors/telescopes can only count the number of neutrinos above some threshold energy, we study how, by exploiting their energy resolution, large magnetized iron calorimeter and, possibly, liquid argon and totally active scintillator detectors, planned for future long baseline neutrino experiments, have the capabi…
A mysterious Universe : revealing the bright and dark sides of the cosmos
2016
Why is our universe as we observe it? Will it be the same forever? Understanding the nature of the main constituents of the universe is crucial to obtain a precise description of the way in which it reached its present state. Nowadays, many independent observations support a picture in which the matter content of the universe is shared between an ordinary and observable baryonic component ( ~ 5?%) and an invisible dark matter ( ~ 23?%). The remaining ~ 72?% of the universe content is in the form of a completely mysterious dark energy field. This composition emphasizes that, while ~ 95?% of our universe represents a major uncertainty for us, even the minor contribution from normal and, appar…
Neutrino signatures on the high-transmission regions of the Lyman $\boldsymbol {\alpha }$ forest
2013
We quantify the impact of massive neutrinos on the statistics of low density regions in the intergalactic medium (IGM) as probed by the Lyman-� forest at redshifts z = 2.2– 4. Based on mock but realistic quasar (QSO) spectra extracted from hydrodynamic simulations with cold dark matter, baryons and neutrinos, we find that the probability distribution of weak Lyman-� absorption features, as sampled by Lyman-� flux regions at high transmissivity, is strongly affected by the presence of massive neutrinos. We show that systematic errors affecting the Lyman-� forest reduce but do not erase the neutrino signal. Using the Fisher matrix formalism, we conclude that the sum of the neutrino masses can…
EDGES result versus CMB and low-redshift constraints on ionization histories
2018
We examine the results from the Experiment to Detect the Global Epoch of Reionization Signature (EDGES), which has recently claimed the detection of a strong absorption in the 21 cm hyperfine transition line of neutral hydrogen, at redshifts demarcating the early stages of star formation. More concretely, we study the compatibility of the shape of the EDGES absorption profile, centered at a redshift of $z \sim 17.2$, with measurements of the reionization optical depth, the Gunn-Peterson optical depth, and Lyman-$\alpha$ emission from star-forming galaxies, for a variety of possible reionization models within the standard $\Lambda$CDM framework (that is, a Universe with a cosmological consta…