Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Effects of Revegetation on Soil Organic Carbon Storage and Erosion-Induced Carbon Loss under Extreme Rainstorms in the Hill and Gully Region of the Loess Plateau

px; &quot;&gt; &lt;Background: The Loess Plateau, an ecologically vulnerable region, has long been suffering from serious soil erosion. Revegetation has been implemented to control soil erosion and improve ecosystems in the Loess Plateau region through a series of ecological recovery programs. However, the increasing atmospheric CO2 as a result of human intervention is affecting the climate by global warming, resulting in the greater frequency and intensity of extreme weather events, such as storms that may weaken the effectiveness of revegetation and cause severe soil erosion. Most research to date has evaluated the effectiveness of revegetation on soil properties and soil erosion of different land use or vegetation types. Here, we study the effect of revegetation on soil organic carbon (SOC) storage and erosion-induced carbon loss related to different plant communities, particularly under extreme rainstorm events. Materials and methods: The erosion-pin method was used to quantify soil erosion, and soil samples were taken at soil depths of 0&ndash;5 cm, 5&ndash;10 cm and 10&ndash;20 cm to determine the SOC content for 13 typical hillside revegetation communities in the year of 2013, which had the highest rainfall with broad range, long duration and high intensity since 1945, in the Yanhe watershed. Results and discussion: The SOC concentrations of all plant communities increased with soil depth when compared with slope cropland, and significant increases (p &lt; 0.05) were observed for most shrub and forest communities, particularly for natural ones. Taking the natural secondary forest community as reference (i.e., soil loss and SOC loss were both 1.0), the relative soil loss and SOC loss of the other 12 plant communities in 2013 ranged from 1.5 to 9.4 and 0.30 to 1.73, respectively. Natural shrub and forest communities showed greater resistance to rainstorm erosion than grassland communities. The natural grassland communities with lower SOC content produced lower SOC loss even with higher soil loss, natural secondary forest communities produced higher SOC loss, primarily because of their higher SOC content, and the artificial R. pseudoacacia community with greater soil loss produced higher SOC loss. Conclusions: These results indicate that natural revegetation is more effective in enhancing SOC storage and reducing soil erosion than artificial vegetative recovery on hillsides. However, natural secondary forest communities, with higher SOC content and storage capacity, may also contribute to larger SOC loss under extreme rainstorms.</span

Successional Trajectory Over 10Years of Vegetation Restoration of Abandoned Slope Croplands in the Hill-Gully Region of the Loess Plateau

Revegetation has been the primary management approach for solving the problems caused by severe soil erosion in the Loess Plateau. The&nbsp;objectives of this work were to explore the successional trajectory of the different types of restoration and discuss their potential effectiveness&nbsp;for the control of soil erosion. The presence and coverage of plants in 40 permanent plots were investigated during two periods (2003&ndash;2006&nbsp;and 2013). The naturally and artificially revegetated communities studied in the two surveys were classified using two-way indicator species&nbsp;analysis, and their relationships were analyzed using detrended correspondence analysis. Under natural revegetation, the communities succeed in the following order: annual plants &rarr; perennial plants &rarr; short rhizome tufts and subshrubs. Under artificial revegetation, succession&nbsp;was interrupted by artificial planting, and a Gramineae herb layer persisted through the years with few changes in species composition. Additionally, species richness, diversity, and evenness increased, while ecological dominance decreased during succession in both revegetation&nbsp;types. Succession rate was rapid at the initial stage and then slowed down gradually. Succession followed different trajectories under natural and artificial revegetation, and based on the potential effects of the two approaches on soil erosion and soil desiccation, we suggest that natural revegetation is preferable over artificial revegetation.<br style="orphans: 2; text-align: -webkit-auto; widows: 2;" /

Accuracy Assessment of the Planar Morphology of Valley Bank Gullies Extracted with High Resolution Remote Sensing Imagery on the Loess Plateau, China

Gully erosion is a serious environmental problem worldwide, causing soil loss, land degradation, silting up of reservoirs and even catastrophic flooding. Mapping gully features from remote sensing imagery is crucial for assisting in understanding gully erosion mechanisms, predicting its development processes and assessing its environmental and socio-economic effects over large areas, especially under the increasing global climate extremes and intensive human activities. However, the potential of using increasingly available high-resolution remote sensing imagery to detect and delineate gullies has been less evaluated. Hence, 130 gullies occurred along a transect were selected from a typical watershed in the hilly and gully region of the Chinese Loess Plateau, and visually interpreted from a Pleiades-1B satellite image (panchromatic-sharpened image at 0.5 m resolution fused with 2.0 m multi-spectral bands). The interpreted gullies were compared with their measured data obtained in the field using a differential global positioning system (GPS). Results showed that gullies could generally be accurately interpreted from the image, with an average relative error of gully area and gully perimeter being 11.1% and 8.9%, respectively, and 74.2% and 82.3% of the relative errors for gully area and gully perimeter were within 15%. But involving field measurements of gullies in present imagery-based gully studies is still recommended. To judge whether gullies were mapped accurately further, a standard adopting one-pixel tolerance along the mapped gully edges was proposed and proved to be practical. Correlation analysis indicated that larger gullies could be interpreted more accurately but increasing gully shape complexity would decrease interpreting accuracy. Overall lower vegetation coverage in winter due to the withering and falling of vegetation rarely affected gully interpreting. Furthermore, gully detectability on remote sensing imagery in this region was lower than the other places of the world, due to the overall broken topography in the Loess Plateau, thus images with higher resolution than normally perceived are needed when mapping erosion features here. Taking these influencing factors (gully dimension and shape complexity, vegetation coverage, topography) into account will be favorable to select appropriate imagery and gullies (as study objects) in future imagery-based gully studies. Finally, two linear regression models were built to correct gully area (Aip, m2) and gully perimeter (Pip, m) visually extracted, by connecting them with the measured area (Ams, m2) and perimeter (Pms, m). The correction models were A m s = 1.021 A i p + 0.139 and P m s = 0.949 P i p + &nbsp; 0.722 , respectively. These models could be helpful for improving the accuracy of interpreting results, and further accurately estimating gully development and developing more effective automated gully extraction methods on the Loess Plateau of China

Mass Testing and Characterization of 20-inch PMTs for JUNO

Main goal of the JUNO experiment is to determine the neutrino mass ordering using a 20kt liquid-scintillator detector. Its key feature is an excellent energy resolution of at least 3 % at 1 MeV, for which its instruments need to meet a certain quality and thus have to be fully characterized. More than 20,000 20-inch PMTs have been received and assessed by JUNO after a detailed testing program which began in 2017 and elapsed for about four years. Based on this mass characterization and a set of specific requirements, a good quality of all accepted PMTs could be ascertained. This paper presents the performed testing procedure with the designed testing systems as well as the statistical characteristics of all 20-inch PMTs intended to be used in the JUNO experiment, covering more than fifteen performance parameters including the photocathode uniformity. This constitutes the largest sample of 20-inch PMTs ever produced and studied in detail to date, i.e. 15,000 of the newly developed 20-inch MCP-PMTs from Northern Night Vision Technology Co. (NNVT) and 5,000 of dynode PMTs from Hamamatsu Photonics K. K.(HPK)

Model Independent Approach of the JUNO 8^8B Solar Neutrino Program

The physics potential of detecting $^8$B solar neutrinos is exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the potential low background level, $^8$B solar neutrinos would be observable in the CC and NC interactions on $^{13}$C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC and ES channels to guarantee the $^8$B solar neutrino observation. From the sensitivity studies performed in this work, we show that one can reach the precision levels of 5%, 8% and 20% for the $^8$B neutrino flux, $\sin^2\theta_{12}$, and $\Delta m^2_{21}$, respectively, using ten years of JUNO data. It would be unique and helpful to probe the details of both solar physics and neutrino physics. In addition, when combined with SNO, the world-best precision of 3% is expected for the $^8$B neutrino flux measurement