Two techniques to enhance particle reconstruction in JUNO: Liquid Scintillator purification and Waveform analysis

This thesis describes two techniques to enhance the particle reconstruction in large antineutrino experiments where large target masses are pivotal to compensate for neutrinos’ extremely elusive nature. The main obstacle for the correct characterization of the antineutrino crossing the experiment is the radioactive background. In the first section of this thesis, It is described the design, construction principles and operations of a distillation and a stripping plant for the purification of Liquid Scintillator. The main goal of these plants is to remove radio impurities from the liquid scintillator while increasing its optical attenuation length. Such a combined system will aim at obtaining a total attenuation length greater than 20 m @430 nm, and a bulk radiopurity for 238U and 232Th in the 10−15 ÷ 10−17 g/g range. In order to better understand the purification capability of these techniques two pilot plant were built and operated at the Daya Bay laboratories. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single Photo Multiplier Tube in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (pes) to pile-up at the anode. In such scenario, the signal generated by each pe is entangled to the others, and an accurate charge reconstruction becomes challenging. Thus, leads to a degradation of the resolution of the antineutrino energy spectrum. In the second part of this manuscript, it is described an experimental method able to address the charge reconstruction in the case of large pe pile-up, providing an unbiased charge estimator at the permille level up to 15 detected pes. The method is based on a signal filtering technique (Wiener filter) which suppresses the noise due to both pmt and readout electronics, and on a Fourier-based deconvolution able to minimize the influence of signal distortions — such as an overshoot.Questa tesi descrive due tecniche che possono essere utilizzate per migliorare la ricostruzione delle caratteristiche delle particelle interagenti all’interno di esperimenti per la rivelazione di antineutrini, in cui le grandi masse bersaglio sono fondamentali per compensare la natura estremamente sfuggente di queste particelle. L'ostacolo principale per la corretta caratterizzazione dell'antineutrino è il fondo radioattivo. Nella prima sezione di questa tesi, viene descritto la progettazione, i principi costruttivi e le operazioni di un impianto di distillazione e strippaggio per la purificazione si Scintillatore Liquido. L'obiettivo principale di questi impianti è rimuovere le radio-impurità dallo scintillatore liquido aumentandone contemporaneamente la lunghezza di attenuazione ottica. Tale sistema combinato mirerà ad ottenere una lunghezza di attenuazione totale maggiore di 20 m @430 nm, e una radiopurezza, espressa in concentrazione massica, per 238U e 232Th nell'intervallo 10−15 ÷ 10−17 g/g. Per comprendere meglio la capacità di purificazione di queste tecniche sono stati costruiti e messi in funzione due impianti pilota presso i laboratori di Daya Bay. A seconda della resa luminosa del rivelatore, è probabile che diversi fotoni di scintillazione derivanti dalla stessa interazione di neutrini colpiscano un singolo tubo fotomoltiplicatore in poche decine/centinaia di nanosecondi, con il risultato che diversi fotoelettroni (pes) si accumulino all'anodo. In tale scenario, il segnale generato da ciascun pe è sovrapposto agli altri, e una ricostruzione accurata della carica diventa impegnativa, comportando quindi un degrado della risoluzione dello spettro energetico dell'antineutrino. Nella seconda parte di questo manoscritto, viene descritto un metodo sperimentale in grado ricostruire la carica generata da multipli foto-elettroni incidenti sul PMT nel caso di pile-up, fornendo uno stimatore della carica con una precisione a livello del permille. Il metodo si basa su una tecnica di filtraggio del segnale (filtro Wiener) che sopprime il rumore dovuto sia al PMT che all'elettronica di lettura del segnale, e su una deconvoluzione basata sull’analisi di Fourier in grado di minimizzare l'influenza delle distorsioni del segnale

Breathomics can discriminate between anti IgE-treated and non-treated severe asthma adults

Rationale: Omalizumab, an anti-IgE monoclonal antibody, is indicated in adults with severe persistent allergic asthma. Exhaled molecular markers can provide phenotypic information in asthma. Objectives: Determine whether adults with severe asthma on omalizumab (anti-IgE+) have a different breathprint compared with those who were not on anti-IgE therapy (anti-IgE-) as assessed by eNoses and gas chromatography/mass spectrometry (GC/MS) (breathomics). Methods: This was a cross-sectional analysis of the U- BIOPRED adult cohort. Severe asthma was defined by IMI-criteria [Bel, Thorax 2011]. Anti-IgE+ patients were on a regular treatment with s.c. omalizumab (150-375 mg) every 2-4 weeks. Exhaled volatile compounds trapped on adsorption tubes were analysed by a centralized eNose platform (Owlstone Lonestar, two Cyranose 320, Comon Invent, Tor Vergata TEN), including a total of 190 sensors, and GC/MS. Recursive feature elimination (http://topepo.github.io/caret/rfe.html) was used for feature selection and random forests, more robust to overfitting, for classification. Results: 9 anti- IgE+ (females/males 2/7, age 52.6±16.3 years, mean±SD, 1/2/6 current/ex/nonsmokers, pre-bronchodilator FEV1 70.6±21.1% predicted value) and 30 anti-IgE- patients (18/12 females/males, age 53.2±14.2 years, 0/16/14 current/ex/nonsmokers, pre-bronchodilator FEV1 59.6±30.7% predicted value) were studied. Conclusions: Preliminary results suggest that breathomics can distinguish between anti-IgE+ and anti-IgE- severe asthma patients

Borexino : geo-neutrino measurement at Gran Sasso, Italy

Geo-neutrinos, electron anti-neutrinos produced in beta-decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. After a brief introduction of the geo-neutrinos' properties and of the main aims of their study, we discuss the features of a detector which has recently provided breakthrough achievements in the field, Borexino, a massive, calorimetric liquid scintillator detector installed at the underground Gran Sasso Laboratory. With its unprecedented radiopurity levels achieved in the core of the detection medium, it is the only experiment in operation able to study in real time solar neutrino interactions in the challenging sub-MeV energy region. Its superior technical properties allowed Borexino also to provide a clean detection of terrestrial neutrinos. Therefore, the description of the characteristics of the detected geo-neutrino signal and of the corresponding geological implications are the main core of the discussion contained in this work

Mass testing of the JUNO experiment 20-inch PMTs readout electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose, large size, liquid scintillator experiment under construction in China. JUNO will perform leading measurements detecting neutrinos from different sources (reactor, terrestrial and astrophysical neutrinos) covering a wide energy range (from 200 keV to several GeV). This paper focuses on the design and development of a test protocol for the 20-inch PMT underwater readout electronics, performed in parallel to the mass production line. In a time period of about ten months, a total number of 6950 electronic boards were tested with an acceptance yield of 99.1%

Implementation and performances of the IPbus protocol for the JUNO Large-PMT readout electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a large neutrino detector currently under construction in China. Thanks to the tight requirements on its optical and radio-purity properties, it will be able to perform leading measurements detecting terrestrial and astrophysical neutrinos in a wide energy range from tens of keV to hundreds of MeV. A key requirement for the success of the experiment is an unprecedented 3% energy resolution, guaranteed by its large active mass (20 kton) and the use of more than 20,000 20-inch photo-multiplier tubes (PMTs) acquired by high-speed, high-resolution sampling electronics located very close to the PMTs. As the Front-End and Read-Out electronics is expected to continuously run underwater for 30 years, a reliable readout acquisition system capable of handling the timestamped data stream coming from the Large-PMTs and permitting to simultaneously monitor and operate remotely the inaccessible electronics had to be developed. In this contribution, the firmware and hardware implementation of the IPbus based readout protocol will be presented, together with the performances measured on final modules during the mass production of the electronics

Validation and integration tests of the JUNO 20-inch PMTs readout electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a large neutrino detector currently under construction in China. JUNO will be able to study the neutrino mass ordering and to perform leading measurements detecting terrestrial and astrophysical neutrinos in a wide energy range, spanning from 200 keV to several GeV. Given the ambitious physics goals of JUNO, the electronic system has to meet specific tight requirements, and a thorough characterization is required. The present paper describes the tests performed on the readout modules to measure their performances.Comment: 20 pages, 13 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