3,808 research outputs found

    Constraints on directionality effect of nuclear recoils in a liquid argon time projection chamber

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    Toward a Research Agenda on Digital Media and Humanity Well-Being

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    In the 2020s, an American citizen will spend an average of 6h35 a day on social media, compared to 3h35 for television. As for social networks, which were non-existent less than 20 years ago, about 40\% of US citizens use them at least once a week as source of news and they now have an estimated 60-70% penetration rate worldwide.This means that in less than a generation, digital media have radically transformed the way we inform and socialize, and that this transformation is still ongoing as older generations are gradually replaced by digital natives. From a scientific point of view, this transformation generates many phenomena to be studied, and even "unknown unknowns" whose effects will be revealed only with time.This roadmap covers the issues, impacts and future challenges of digital media as they relate to human well-being in the broadest sense, from mental health to the health of democracies.Its objective is to initiate a new interdisciplinary research community in this field, to define a research agenda, to formulate recommendations for future digital media policy and design, and to inspire future EU calls for projects to develop innovative and transdisciplinary research on these societal challenges.The roadmap is the result of the EU-funded project DIGEING conducted by an international consortium with the help of an interdisciplinary advisory group of international experts. Its writing was based on an hybrid methodology developped at CNRS and powered by GarganText, where the advisory group acted both as catalyst and guide for a larger collaborative mapping of the state-of-the-art and identification of challenges of that emerging field. More than forty researchers from fourteen European countries have contributed to the writing of this roadmap.This roadmap is complemented by online interactive maps that can be used by researchers to situate themselves in this evolving scientific landscape and by research funding agencies to launch new calls for projects

    Directionality of nuclear recoils in a liquid argon time projection chamber

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    International audienceThe direct search for dark matter in the form of weakly interacting massive particles (WIMP) is performed by detecting nuclear recoils (NR) produced in a target material from the WIMP elastic scattering. A promising experimental strategy for direct dark matter search employs argon dual-phase time projection chambers (TPC). One of the advantages of the TPC is the capability to detect both the scintillation and charge signals produced by NRs. Furthermore, the existence of a drift electric field in the TPC breaks the rotational symmetry: the angle between the drift field and the momentum of the recoiling nucleus can potentially affect the charge recombination probability in liquid argon and then the relative balance between the two signal channels. This fact could make the detector sensitive to the directionality of the WIMP-induced signal, enabling unmistakable annual and daily modulation signatures for future searches aiming for discovery. The Recoil Directionality (ReD) experiment was designed to probe for such directional sensitivity. The TPC of ReD was irradiated with neutrons at the INFN Laboratori Nazionali del Sud, and data were taken with 72 keV NRs of known recoil directions. The direction-dependent liquid argon charge recombination model by Cataudella et al. was adopted and a likelihood statistical analysis was performed, which gave no indications of significant dependence of the detector response to the recoil direction. The aspect ratio R of the initial ionization cloud is estimated to be 1.037 +/- 0.027 and the upper limit is R < 1.072 with 90% confidence leve

    Study on cosmogenic activation above ground for the DarkSide-20k project

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    International audienceThe activation of materials due to the exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k is a direct detection experiment for galactic dark matter particles, using a two-phase liquid argon time projection chamber filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the argon and other massive components of the set-up has been estimated; production of 120 t of radiopure UAr is foreseen. The expected exposure above ground and production rates, either measured or calculated, have been considered. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. Activation of titanium, considered in early designs but not used in the final design, is discussed. The activity of 39Ar induced during extraction, purification and transport on surface, in baseline conditions, is evaluated to be 2.8% of the activity measured in UAr from the same source, and thus considered acceptable. Other products in the UAr such as 37Ar and 3H are shown to not be relevant due to short half-life and assumed purification methods

    Study of cosmogenic activation above ground for the DarkSide-20k experiment

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    The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating 纬/尾 background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods

    Measurements of the Cherenkov effect in direct detection of charged particles with SiPMs

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    In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been tested with charged particles to characterize the Cherenkov light produced in the sensor protection layer. A careful position scan of the SiPM response has been performed with different prototypes, confirming the large number of firing cells and proving almost full efficiency, with the SiPM filling factor essentially negligible. This study also allowed us to study the time resolution of such devices as a function of the number of firing cells, reaching values below 20 ps. These measurements provide significant insight into the capabilities of SiPM sensors in direct detection of charged particles and their potential for several applications

    Toward a Research Agenda on Digital Media and Humanity Well-Being

    No full text
    In the 2020s, an American citizen will spend an average of 6h35 a day on social media, compared to 3h35 for television. As for social networks, which were non-existent less than 20 years ago, about 40\% of US citizens use them at least once a week as source of news and they now have an estimated 60-70% penetration rate worldwide.This means that in less than a generation, digital media have radically transformed the way we inform and socialize, and that this transformation is still ongoing as older generations are gradually replaced by digital natives. From a scientific point of view, this transformation generates many phenomena to be studied, and even "unknown unknowns" whose effects will be revealed only with time.This roadmap covers the issues, impacts and future challenges of digital media as they relate to human well-being in the broadest sense, from mental health to the health of democracies.Its objective is to initiate a new interdisciplinary research community in this field, to define a research agenda, to formulate recommendations for future digital media policy and design, and to inspire future EU calls for projects to develop innovative and transdisciplinary research on these societal challenges.The roadmap is the result of the EU-funded project DIGEING conducted by an international consortium with the help of an interdisciplinary advisory group of international experts. Its writing was based on an hybrid methodology developped at CNRS and powered by GarganText, where the advisory group acted both as catalyst and guide for a larger collaborative mapping of the state-of-the-art and identification of challenges of that emerging field. More than forty researchers from fourteen European countries have contributed to the writing of this roadmap.This roadmap is complemented by online interactive maps that can be used by researchers to situate themselves in this evolving scientific landscape and by research funding agencies to launch new calls for projects

    Temporal Structures in Electron Spectra and Charge Sign Effects in Galactic Cosmic Rays

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    International audienceWe present the precision measurements of 11聽years of daily cosmic electron fluxes in the rigidity interval from 1.00 to 41.9聽GV based on 2.0脳108 electrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The electron fluxes exhibit variations on multiple timescales. Recurrent electron flux variations with periods of 27聽days, 13.5聽days, and 9聽days are observed. We find that the electron fluxes show distinctly different time variations from the proton fluxes. Remarkably, a hysteresis between the electron flux and the proton flux is observed with a significance of greater than 6蟽 at rigidities below 8.5聽GV. Furthermore, significant structures in the electron-proton hysteresis are observed corresponding to sharp structures in both fluxes. This continuous daily electron data provide unique input to the understanding of the charge sign dependence of cosmic rays over an 11-year solar cycle
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