Simulation study on the optical processes at deep-sea neutrino telescope sites

The performance of a large-scale water Cherenkov neutrino telescope relies heavily on the transparency of the surrounding water, quantified by its level of light absorption and scattering. A pathfinder experiment was carried out to measure the optical properties of deep seawater in South China Sea with light-emitting diodes (LEDs) as light sources, photon multiplier tubes (PMTs) and cameras as photon sensors. Here, we present an optical simulation program employing the Geant4 toolkit to understand the absorption and scattering processes in the deep seawater, which helps to extract the underlying optical properties from the experimental data. The simulation results are compared with the experimental data and show good agreements. We also verify the analysis methods that utilize various observables of the PMTs and the cameras with this simulation program, which can be easily adapted by other neutrino telescope pathfinder experiments and future large-scale detectors.Comment: 27 pages, 11 figure

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

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

Search for Dark Matter and Neutrino Events with the Darkside Liquid Argon Time Projection Chambers

Many astronomical observations found that atomic matter can account for only a small fraction of the matter in the Universe. Evidences from cosmology show that dark matter must be non-baryonic. Weakly interacting massive particles (WIMPs) is a leading candidate for dark matter. Searching for WIMPs has become a major activity of particle physics. DarkSide-50 did a search for WIMPs using a liquid argon time projection chamber (LAr TPC) with low-radioactivity underground argon (UAr). Null result was reported by DarkSide-50 for a 532-day data collection, corresponding to an exposure of ($16660 \pm 270$) kg$\cdot$day. At the best sensitivity, for WIMP mass around 100 GeV, a $90\%$ C.L. upper limit on the WIMP-nucleon spin-independent cross section of $1.14 \times 10^{−44}$ cm$^2$ was derived. Research on particle identification using machine learning techniques in DarkSide-50 data analysis is presented. Both supervised and unsupervised learning algorithms were developed. Monte Carlo simulation was used to generate training data for supervised learning. A greater power of suppressing ER backgrounds at $\sim 100$ PE was achieved. The unsupervised learning uses DarkSide-50 experimental data for training, whose result needs to be validated with more analysis. DarkSide-20k and Argo are the next two generations of LAr TPCs for WIMP searches, having an active mass of $38.6$ and $400$ tonnes, respectively. In these larger detectors, neutrinos become an irreducible background for WIMP searches. This dissertation presents a calculation of the neutrino event rate in the DarkSide-20k LAr TPC. A study on supernova neutrino detection with DarkSide-20k and Argo is presented. DarkSide-20k can make a 5-$\sigma$ detection of supernova neutrinos out to a distance of $\sim 20$ kpc, covering the entire Milky Way Galaxy. Argo can make a 5-$\sigma$ detection out to a distance of $\sim 40$ kpc. It is demonstrated that DarkSide-20k and Argo can measure the total energy emitted and average neutrino energy to a precision of a few percent, as well as significantly detect the neutronization burst out to great distances.Physics, Department o

Attacks Meet Interpretability (AmI) Evaluation and Findings

To investigate the effectiveness of the model explanation in detecting adversarial examples, we reproduce the results of two papers, Attacks Meet Interpretability: Attribute-steered Detection of Adversarial Samples and Is AmI (Attacks Meet Interpretability) Robust to Adversarial Examples. And then conduct experiments and case studies to identify the limitations of both works. We find that Attacks Meet Interpretability(AmI) is highly dependent on the selection of hyperparameters. Therefore, with a different hyperparameter choice, AmI is still able to detect Nicholas Carlini's attack. Finally, we propose recommendations for future work on the evaluation of defense techniques such as AmI.Comment: Need to withdraw it. The current work needs to be changed at a large extent which would take a longer tim

Optimization and simulation analysis of structure parameters of OPCM ultrasonic longitudinal wave actuating element

The force-electric coupling relationship of the mechanical and electrical properties of piezoelectric composites has been the main factor in the research and development of piezoelectric composites in practical application. A novel orthotropic piezoelectric composite material (OPCM) element is studied in this paper. The properties of the piezoelectric phase and the polymer phase and the influence of the geometrical dimensions of the OPCM on the longitudinal wave drive element are analyzed from the perspective of mechanics and electric power, respectively, and the structural design is optimized. This provides a theoretical basis for the development of OPCM and of new longitudinal ultrasonic phased array actuators