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

EVENT RECONSTRUCTION IN JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton liquid scintillator experiment currently under construction in the vicinity of the Pearl River Delta in Southern China. Its main focus lies on the determination of the Neutrino Mass Ordering via measuring the oscillated spectrum of electron anti-neutrinos from two nuclear power plants in 53 km distance each. JUNO requires to measure the prompt positron signal of the coincident inverse beta decay reaction used for the anti-neutrino detection with an unprecedented energy resolution of 3% at 1 MeV. To be able to achieve this challenging energy resolution, the scintillation volume is densely instrumented with 17,612 large 20''-PMT's and 25,600 small 3''-PMT's. In case of a particle interaction in the detector, the digitized electronic pulses from the readout electronics of the large PMT's will be recorded. From the reconstruction of these pulses, it is possible to obtain the number and detection times of PMT photon hits, which are then used to reconstruct the particle energy, the time and vertex of the light emission, and the particle type. This presentation will show the development status of the reconstruction algorithms in JUNO with the focus on low energy events from the reactor spectrum. These will include conventional approaches, as well as novel approaches using deep learning methods

Physics potential of the JUNO experiment

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment currently under construction in Southern China, expecting to start data-taking in 2023. As its primary goal, it aims to address the determination of the Neutrino Mass Ordering with the study of the oscillated reactor electron anti-neutrino spectrum at a baseline of about 53 km. To acquire a sufficient event statistic and the required unprecedented energy resolution of 3% at 1 MeV, the main detector consists of a large 20 kt liquid scintillator target, instrumented with 17,612 20”-PMTs and 25,600 3” PMTs and will be placed 700 m underground. This exceptional experimental setup provides the opportunity for JUNO to give significant contributions to various topics in modern particle- and astrophysics. Besides the precision measurement of neutrino oscillation parameters, JUNO aims to measure geo-neutrinos, solar neutrinos, atmospheric neutrinos, and galactic core-collapse supernova neutrinos. Furthermore, JUNO has the potential to be sensitive to the diffuse supernova neutrino background as well as nucleon decays, if existent. This poster gives an overview of the JUNO experiment with a focus on its physics potential on the various topics

STATUS AND PHYSICS OF THE JUNO EXPERIMENT

The Jiangmen Underground Neutrino Observatory is a next-generation neutrino experiment under construction in China expected to start data taking in late 2021. As the main goal it aims to address the determination of the neutrino mass hierarchy with 3-4 sigma significance in 6 years. Therefore, it will measure the oscillated energy spectrum of electron anti-neutrinos from two nuclear power plants at 53km baseline with an unprecedented energy resolution of 3% at 1 MeV. A large target size of 20 kt liquid scintillator instrumented by 18000 large 20”-PMTs and 25000 small 3”-PMTs will give the opportunity to contribute to various other current physics topics. These include the measurement of geo-neutrinos, solar-neutrinos, atmospheric neutrinos, and supernova neutrinos. In addition to that JUNO aims to precisely measure the oscillation parameters $θ_{12}$, $Δm^2_{21}$, and$Δm^2_{ee}$ with sub-percent uncertainties and to search for the proton decay channel into kaons

Energy scale non-linearity and event reconstruction for the neutrino mass ordering measurement of the JUNO experiment

The JUNO experiment is a next-generation neutrino experiment under construction in vicinity of the Pearl River Delta in Southern China. It is expected to start data-taking in 2022 and aims to address the determination of the Neutrino Mass Ordering with 3-4 $\sigma$ sensitivity in about 6 years as its main goal. For that, it will measure the oscillated energy spectrum of electron anti-neutrinos from two nuclear power plants at a baseline of about 53 km with a required energy resolution of 3 % at 1 MeV and a sub-percent uncertainty on the energy scale. In order to reach these requirements, the JUNO detector consists of a large 20 kton liquid scintillator detector, which is instrumented with a dense PMT array consisting of about 18,000 large 20''-PMT's and 25,000 small 3''-PMT's. Besides this main goal it aims to address a large variety of important topics in neutrino and astroparticle physics.The first part of this thesis gives an overview over the current status of neutrino physics and shows why the determination of the Neutrino Mass Ordering is a key to explore a large area of physics topics. Moreover, it gives an overview of the JUNO experiment: the detector design and its calibration, the simulation framework, and the various physics goals of the JUNO experiment. Besides the detector design, a meticulous data analysis is needed to ensure, that the JUNO experiment can meet the requirements on the precision and accuracy on the reconstructed energy. Such analysis methods are presented in the second part of this thesis. Here, a model is presented, which can be used to describe the non-linear light response of positrons in the liquid scintillator. Based on the non-linearity model of electrons, an algorithm is introduced to calculate the more complex non-linearity model of gammas and combine both eventually to the non-linearity model of positrons. As the amount of detected light for a constant energy varies with the position of the energy deposition in the detector, the energy resolution of JUNO is impacted by the uncertainty of the reconstructed light emission vertex. The vertex reconstruction finds the light emission vertex by minimizing a likelihood function, which contains the information on the times and charges of the PMT hits. It is shown, that the uncertainty on the reconstructed vertex is especially small at the outer parts of the volume, where the effect on the energy resolution is the largest. Additionally to the improvement of the energy resolution, it is shown how the vertex reconstruction can be used to reconstruct the direction of an electron anti-neutrino flux from a point-source. Another important effect, which leads to biases on the reconstructed energy on JUNO is the pile-up of signal events with $^{14}$C decays.The organic scintillator contains large amounts of natural, radioactive $^{14}$C. These $^{14}$C decays are able to timely coincide with measured signal events to cause a smearing of the measured energy spectrum. To reduce the impact of these $^{14}$C decays, two analysis methods are presented. A clusterization algorithm identifies different energy depositions in the PMT hit time distribution. This algorithm is optimized on the sensitivity of JUNO to determine the Neutrino Mass Ordering. For event coincidences, which can not be separated in time, the vertex reconstruction is used to perform a likelihood test to identify these

Reduction of the 14C-background in the JUNO experiment

The Jiangmen Underground Neutrino Observatory (JUNO) will be a 20kt liquid scintillator neutrino detector located at Kaiping, Jiangmen in South China. With the data aquisition starting in 2021, its main goal is the determination of the neutrino mass hierarchy from a precise measurement of the energy spectrum of anti-electron-neutrinos 53km away from the reactor. To precisely measure the oscillation pattern of the reactor spectrum an unpredecent energy resolution for this kind of detector of 3% at 1MeV is needed. Pile-up events with background from radioactive decays such as those from 14C can spoil the reconstruction of the neutrino energy. On this poster methods for detecting pile-up events are presented. In addition to a simple clusterization algorithm on the hit times, the utilization of spherical harmonics of the hit distribution as well as a Likelihood-test of the hit times are used to tag pile-up events

Ľudovít Turčan, Robert Klobucký: Denníky sociológov I. Alexander Hirner. 1953–1955

The Jiangmen Underground Neutrino Observatory (JUNO) is a next-generation neutrino experiment under construction in China expected to be completed in 2022. As the main goal it aims to determine the neutrino mass ordering with 3-4 $\sigma$ significance using a 20 kton liquid scintillator detector. It will measure the oscillated energy spectrum of electron anti-neutrinos from two nuclear power plants at about 53 km baseline with an unprecedented energy resolution of 3% at 1 MeV. A requirement of the JUNO experiment is the knowledge of the energy non-linearity of the detector with a sub-percent precision. As the light yield of the liquid scintillator is not fully linear to the energy of the detected particle and dependent on the particle type, a model for this light yield is presented in this paper. Based on an energy non-linearity model of electrons, this article provides the conversion to the more complex energy response of positrons and gammas. This conversion uses a fast and simple algorithm to calculate the spectrum of secondary electrons generated by a gamma, which is introduced here and made open access to potential users. It is also discussed how the positron non-linearity can be obtained from the detector calibration with gamma sources using the results presented in this article.Comment: 19 pages and 12 figures, submitted to Journal of Instrumentatio