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Irreducible Axion Background.
Phys Rev Lett
December 2022
Theoretical Physics Department, CERN, 1 Esplanade des Particules, CH-1211 Geneva 23, Switzerland.
Searches for dark matter decaying into photons constrain its lifetime to be many orders of magnitude larger than the age of the Universe. A corollary statement is that the abundance of any particle that can decay into photons over cosmological timescales is constrained to be much smaller than the cold dark-matter density. We show that an irreducible freeze-in contribution to the relic density of axions is in violation of that statement in a large portion of the parameter space.
View Article and Find Full Text PDFMeasuring Changes in the Atmospheric Neutrino Rate over Gigayear Timescales.
Phys Rev Lett
December 2020
University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, USA.
Measuring the cosmic ray flux over timescales comparable to the age of the Solar System, ∼4.5 Gyr, could provide a new window on the history of the Earth, the Solar System, and even our Galaxy. We present a technique to indirectly measure the rate of cosmic rays as a function of time using the imprints of atmospheric neutrinos in "paleo-detectors," natural minerals that record damage tracks from nuclear recoils.
View Article and Find Full Text PDFAirborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017.
Proc Natl Acad Sci U S A
August 2019
Infrastructural Group for Ionizing Radiation Measurements, Institut "Jožef Stefan", 1000 Ljubljana, Slovenia.
In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (Ru). The range of concentrations varied from some tenths of µBq·m to more than 150 mBq·m The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location.
View Article and Find Full Text PDFPremarital sexual practice and associated factors among adolescents in the refugee camps in Tigray, northern Ethiopia.
BMC Res Notes
July 2019
Department of Medical Laboratory Sciences, College of Health Science, Aksum University, Aksum, Ethiopia.
Objective: Premarital sexual practice during adolescence time may lead to different sexual and reproductive health problems including HIV/AIDS. This study was aimed to assess the prevalence of premarital sexual practice and associated factors among adolescents living in the refugee camps in Tigray, northern Ethiopia.
Result: The prevalence of premarital sexual practice was 47.
Two-neutrino double electron capture (2νECEC) is a second-order weak-interaction process with a predicted half-life that surpasses the age of the Universe by many orders of magnitude. Until now, indications of 2νECEC decays have only been seen for two isotopes, Kr and Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance. The 2νECEC half-life is an important observable for nuclear structure models and its measurement represents a meaningful step in the search for neutrinoless double electron capture-the detection of which would establish the Majorana nature of the neutrino and would give access to the absolute neutrino mass.
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