Initial performance of the COSINE-100 experiment Adhikari, G.; Adhikari, P.; de Souza, E. Barbosa ...
European physical journal. C, Particles and fields,
02/2018, Volume:
78, Issue:
2
Journal Article
Peer reviewed
Open access
COSINE is a dark matter search experiment based on an array of low background NaI(Tl) crystals located at the Yangyang underground laboratory. The assembly of COSINE-100 was completed in the summer ...of 2016 and the detector is currently collecting physics quality data aimed at reproducing the DAMA/LIBRA experiment that reported an annual modulation signal. Stable operation has been achieved and will continue for at least 2 years. Here, we describe the design of COSINE-100, including the shielding arrangement, the configuration of the NaI(Tl) crystal detection elements, the veto systems, and the associated operational systems, and we show the current performance of the experiment.
This paper presents a model of factors influencing levels of human losses from natural hazards at the global scale, for the period 1980-2000. This model was designed for the United Nations ...Development Programme as a building stone of the Disaster Risk Index (DRI), which aims at monitoring the evolution of risk. Assessing what countries are most at risk requires considering various types of hazards, such as droughts, floods, cyclones and earthquakes. Before assessing risk, these four hazards were modelled using GIS and overlaid with a model of population distribution in order to extract human exposure. Human vulnerability was measured by crossing exposure with selected socio-economic parameters. The model evaluates to what extent observed past losses are related to population exposure and vulnerability. Results reveal that human vulnerability is mostly linked with country development level and environmental quality. A classification of countries is provided, as well as recommendations on data improvement for future use of the model.
The COSINE-100 dark matter search experiment is an array of NaI(Tl) crystal detectors located in the Yangyang Underground Laboratory (Y2L). To understand measured backgrounds in the NaI(Tl) crystals ...we have performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides. The background models are based on comparisons of measurement data with Monte Carlo simulations that are guided by a campaign of material assays and are used to evaluate backgrounds and identify their sources. The average background level for the six crystals (70 kg total mass) that are studied is 3.5 counts/day/keV/kg in the (2–6) keV energy interval. The dominant contributors in this energy region are found to be
210
Pb and
3
H.
We present new constraints on the dark matter-induced annual modulation signal using 1.7 years of COSINE-100 data with a total exposure of 97.7 kg yr. The COSINE-100 experiment, consisting of 106 kg ...of NaI(Tl) target material, is designed to carry out a model-independent test of DAMA/LIBRA's claim of WIMP discovery by searching for the same annual modulation signal using the same NaI(Tl) target. The crystal data show a 2.7 cpd/kg/keV background rate on average in the 2-6 keV energy region of interest. Using a χ-squared minimization method we observe best fit values for modulation amplitude and phase of 0.0092±0.0067 cpd/kg/keV and 127.2±45.9 d, respectively.
“Weeds amongst the wheat”: Oswald Pirow and the New Order for South Africa, 1940–1943 In 1940, after Germany’s crushing victory over France, and with Britain fighting for survival, South Africa was ...facing a period of political uncertainty. The popular feeling amongst many Afrikaners was that Britain had lost the war, and that for its own safety South Africa had to cut ties with the British Empire. Such a step required a new political order to replace the collapsing system of a British-dominated liberal-democratic capitalism. It was against this backdrop that Oswald Pirow (1890–1959), a former minister in the J.B.M. Hertzog government between 1929 and 1939, and a member of the Herenigde Nasionale Party (HNP), formed the New Order for South Africa (NO) on 25 September 1940 as a study group within the party to espouse national-socialistic ideals. Pirow was no conviction fascist and the founding of the NO represented an opportunistic trimming of the sails to prevailing political winds, to advance his own career. Highly intelligent, charismatic and an outstanding orator, at emotional mass meetings he was treated as a messianic figure, given his message that the Afrikaner had to follow the example of an authoritarian political system based on “staatsgesag” and “volksdissipline” which had emerged in Germany, Italy, Spain and Portugal. At the beginning of 1941 Pirow and the NO seemed unstoppable. And yet, by the end of the year he was marginalised, and by 1943 had become a pariah trapped in the political wilderness. This article argues that, after a few months during which Pirow was given free and uncritical passage to propagate national-socialism, the Afrikaans churches and the HNP launched an effective counterattack by condemning the principles of the NO as pagan and alien to the democratic traditions of the Afrikaner, while exposing Pirow’s opportunism. Ultimately, the Afrikaner churches and the HNP’s rejection of the principles of national-socialism, in a period when Nazi Germany was still winning the war, was the main factor leading to the collapse of the NO.Hierdie artikel bied ’n ontleding van die redes waarom dit aanvanklik in 1940 vir Oswald Pirow – wat weens opportunistiese redes nasionaal-sosialisme aangehang het met die stigting van die Nuwe Orde vir Suid-Afrika – moontlik was om hierdie ideologie suksesvol te verkondig. Daar word aangevoer dat unieke omstandighede die politieke veld vir enkele maande vir hom oopgelaat het om nasionaal-sosialisme te propageer. Ná die Afrikaanse kerke en die Herenigde Nasionale Party daarop gewys het dat dit ’n heidense en totalitêre ideologie was wat teenstrydig was met die demokratiese tradisies en volksaard van die Afrikaner, is die Nuwe Orde met ’n toenemende kritiese houding bejeën. Gevolglik was Pirow teen die einde van 1941 ’n randfiguur en teen 1943 ’n gebrokene, vasgevang in die politieke wildernis. Alhoewel die aanklag dat Pirow ’n opportunis was wel ’n rol gespeel het, was die Afrikaanse kerke en die HNP se verwerping van die totalitêre aard van nasionaal-sosialisme (in ’n tydperk toe dit gelyk het asof Nazi-Duitsland besig was om die oorlog te wen) die beslissende rede waarom die Nuwe Orde ten gronde sou gaan.
We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most sensitive, directional, dark matter detector. Several improvements were made relative to our previous ...work including a lower threshold for detection, a more robust analysis and a tenfold improvement in our gamma rejection factor. After analysis, no events remain in our fiducial region leading to an exclusion curve for spin-dependent WIMP-proton interactions which reaches 0.28pb at 100GeV/c2, a fourfold improvement on our previous work. We also present results from a 45.4 live-day unshielded run of the DRIFT-IId detector during which 14 nuclear recoil-like events were observed. We demonstrate that the observed nuclear recoil rate of 0.31 ± 0.08 events per day is consistent with detection of ambient, fast neutrons emanating from the walls of the Boulby Underground Science Facility.
A search for inelastic boosted dark matter (IBDM) using the COSINE-100 detector with 59.5 days of data is presented. This relativistic dark matter is theorized to interact with the target material ...through inelastic scattering with electrons, creating a heavier state that subsequently produces standard model particles, such as an electron-positron pair. In this study, we search for this electron-positron pair in coincidence with the initially scattered electron as a signature for an IBDM interaction. No excess over the predicted background event rate is observed. Therefore, we present limits on IBDM interactions under various hypotheses, one of which allows us to explore an area of the dark photon parameter space that has not yet been covered by other experiments. This is the first experimental search for IBDM using a terrestrial detector.
The addition of O2 to gas mixtures in time projection chambers containing CS2 has recently been shown to produce multiple negative ions that travel at slightly different velocities. This allows a ...measurement of the absolute position of ionising events in the z (drift) direction. In this work, we apply the z-fiducialisation technique to a directional dark matter search. We present results from a 46.3 live-day source-free exposure of the DRIFT-IId detector run in this new mode. With full-volume fiducialisation, we have achieved the first background-free operation of a directional detector. The resulting exclusion curve for spin-dependent WIMP-proton interactions reaches 1.1 pb at 100 GeV/c2, a factor of 2 better than our previous work. We describe the automated analysis used here, and argue that detector upgrades, implemented after the acquisition of these data, will bring an additional factor of ≳3 improvement in the near future.
As leader of the United Party and the official parliamentary opposition between 1956 and 1977, Sir De Villiers Graaff bolstered the apartheid state and destroyed his own party in the process. This ...essay, by investigating Graaff's personality and politics, concludes that he was a man of integrity and decency who loathed the impractical, vicious and cruel nature of apartheid, but that his lack of political acumen, vision and ruthlessness, made him a disastrous party leader. Despite his honest intentions he was the best leader of the parliamentary opposition the apartheid state could have wished for.
PDF
