分类： 核科学技术 >> 核科学与技术 提交时间： 2023-08-27
摘要： As a unique probe, precision measurement of textit{pp} solar neutrinos is important for studying the Sun's energy mechanism, monitoring thermodynamic equilibrium, and studying neutrino oscillation in the vacuum-dominated region. For a large-scale liquid scintillator detector, one bottleneck for textit{pp} solar neutrino detection comes from pile-up events of intrinsic $^{14}$C decays. This paper presents a few approaches to discriminate textit{pp} solar neutrinos and $^{14}$C pile-up events by considering the difference in their time and spatial distributions. In this work, a Geant4-based Monte Carlo simulation is constructed. Then multivariate analysis and deep learning technology were adopted respectively to investigate the capability of $^{14}$C pile-up reduction. As a result, the BDTG model and VGG network showed good performance in discriminating textit{pp} solar neutrinos and $^{14}$C double pile-up events. hl{At the $^{14}$C concentration assumption $5 times10^{-18} g/g$,} their signal significance can achieve 10.3 and 15.6 using only one day of statistics. In this case, the signal efficiency is 51.1 % for discrimination using the BDTG model when rejecting 99.18 % $^{14}$C double pile-up events, and the signal efficiency is 42.7 % for the case using the VGG network when rejecting 99.81 % $^{14}$C double pile-up events.
分类： 物理学 >> 核物理学 提交时间： 2023-07-18
Zhou, Xing
Qie, Xiaoyu
Guo, Siming
Huang, Yongbo
Shu, Ziyao
Huang, Shikui
Fan, Lipeng
Guo, Kaiyue
Yu, Tao
Wu, Jinjie
摘要： With the advancement in X-ray astronomical detection technology, various celestial polarization detection projects have been initiated. To meet the calibration requirements of polarimeters on the ground, a polarized X-ray radiation facility was designed for this study. The design was based on the principle that X-rays incident at 45$^\circ$ on a crystal produce polarized X-rays, and a second crystal was used to measure the polarization of the X-rays produced by the facility after rotation. The effects of different diaphragm sizes on the degree of polarization were compared, and the facility produced X-rays with polarization degrees of up to 99.55$\pm$0.96\% using LiF200 and LiF220 crystals. This result revealed that the polarization of incident X-rays is one of the factors affecting the diffraction efficiency of crystals. The replacement of different crystals can satisfy the calibration requirements of polarized X-ray detectors with more energy points in the energy range (410) keV. In the future, the facility should be placed in a vacuum environment to meet the calibration requirements at lower energies.
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