3,586 research outputs found
Discovery potential for supernova relic neutrinos with slow liquid scintillator detectors
Detection of supernova relic neutrinos could provide key support for our
current understanding of stellar and cosmological evolution, and precise
measurements of these neutrinos could yield novel insights into the universe.
In this paper, we studied the detection potential of supernova relic neutrinos
using linear alkyl benzene (LAB) as a slow liquid scintillator. The linear
alkyl benzene features good separation of Cherenkov and scintillation lights,
thereby providing a new route for particle identification. We further addressed
key issues in current experiments, including (1) the charged current background
of atmospheric neutrinos in water Cherenkov detectors and (2) the neutral
current background of atmospheric neutrinos in typical liquid scintillator
detectors. A kiloton-scale LAB detector at Jinping with (10) years
of data could discover supernova relic neutrinos with a sensitivity comparable
to that of large-volume water Cherenkov detectors, typical liquid scintillator
detectors, and liquid argon detectors.Comment: 9 pages, 6 figure
Hybrid Functional Study Rationalizes the Simple Cubic Phase of Calcium at High Pressures
Simple cubic (SC) phase has been long experimentally determined as the
high-pressure phase III of elemental calcium (Ca) since 1984. However, recent
density functional calculations within semi-local approximation showed that
this SC phase is structurally unstable by exhibiting severely imaginary
phonons, and is energetically unstable with respect to a theoretical
body-centered tetragonal I41/amd structure over the pressure range of phase
III. These calculations generated extensive debates on the validity of SC
phase. Here we have re-examined the SC structure by performing more precise
density functional calculations within hybrid functionals of
Heyd-Scuseria-Erhzerhof (HSE) and PBE0. Our calculations were able to
rationalize fundamentally the phase stability of SC structure over all other
known phases by evidence of its actual energetic stability above 33 GPa and its
intrinsically dynamical stability without showing any imaginary phonons in the
entire pressure range studied. We further established that the long-thought
theoretical I41/amd structure remains stable in a narrow pressure range before
entering SC phase and is actually the structure of experimental Ca-III'
synthesized recently at low temperature 14 K as supported by the excellent
agreement between our simulated X-ray diffraction patterns and the experimental
data. Our results shed strong light on the crucial role played by the precise
electron exchange energy in a proper description of the potential energy of Ca.Comment: submitted to Physical Review
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