The BiPo detector for ultralow radioactivity measurements

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in 208Tl and 214Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 m2 of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in 208Tl. After more than one year of background measurement, a surface activity of the scintillators of A(208Tl) = 1.5 \muBq/m2 is reported here. Given this level of background, a larger BiPo3 detector having 3.25 m2 of active surface area, will able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of A(208Tl) < 3-4 \mu Bq/kg (90% C.L.) with a six month measurement. This detector is actually under construction and will be installed in the Canfranc Underground Laboratory mid 2011.Comment: Proceeding - Low Radioactivity Techniques (LRT) Workshop - SNOLab - 201

Results of the NEMO-3 Double Beta Decay Experiment

The NEMO-3 experiment is searching for neutrinoless double beta decay for 2 main isotopes (100Mo and 82Se) and is studying the two-neutrino double beta decay of seven isotopes. The experiment has been taking data since 2003 and, up to the end of 2009, showed no evidence for neutrinoless double beta decay. Two 90 % CL lower limits on the half-lives of the transitions were obtained : T_{1/2}^{0\nu} > 1.0 10^{24} yr for 100Mo and T_{1/2}^{0\nu} > 3.2 10^{23}$ yr for 82Se. The corresponding limits on the effective Majorana neutrino mass are respectively | m_nu | < 0.47 - 0.96 eV and | m_nu | < 0.94 - 2.5 eV. The measurements of the two-neutrino double beta decays for all the isotopes have also reached the highest precision to date.Comment: Proceeding - 22nd Rencontres de Blois - 201

Synergies and Prospects for Early Resolution of the Neutrino Mass Ordering

The measurement of neutrino Mass Ordering (MO) is a fundamental element for the understanding of leptonic flavour sector of the Standard Model of Particle Physics. Its determination relies on the precise measurement of $\Delta m^2_{31}$ and $\Delta m^2_{32}$ using either neutrino vacuum oscillations, such as the ones studied by medium baseline reactor experiments, or matter effect modified oscillations such as those manifesting in long-baseline neutrino beams (LB$\nu$B) or atmospheric neutrino experiments. Despite existing MO indication today, a fully resolved MO measurement ($\geq$5$\sigma$) is most likely to await for the next generation of neutrino experiments: JUNO, whose stand-alone sensitivity is $\sim$3$\sigma$, or LB$\nu$B experiments (DUNE and Hyper-Kamiokande). Upcoming atmospheric neutrino experiments are also expected to provide precious information. In this work, we study the possible context for the earliest full MO resolution. A firm resolution is possible even before 2028, exploiting mainly vacuum oscillation, upon the combination of JUNO and the current generation of LB$\nu$B experiments (NOvA and T2K). This opportunity is possible thanks to a powerful synergy boosting the overall sensitivity where the sub-percent precision of $\Delta m^2_{32}$ by LB$\nu$B experiments is found to be the leading order term for the MO earliest discovery. We also found that the comparison between matter and vacuum driven oscillation results enables unique discovery potential for physics beyond the Standard Model.Comment: Entitled in arXiv:2008.11280v1 as "Earliest Resolution to the Neutrino Mass Ordering?

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of &gt;50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022

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

JUNO Sensitivity to Invisible Decay Modes of Neutrons

We explore the bound neutrons decay into invisible particles (e.g., $n\rightarrow 3 \nu$ or $nn \rightarrow 2 \nu$) in the JUNO liquid scintillator detector. The invisible decay includes two decay modes: $n \rightarrow { inv}$ and $nn \rightarrow { inv}$. The invisible decays of $s$-shell neutrons in $^{12}{\rm C}$ will leave a highly excited residual nucleus. Subsequently, some de-excitation modes of the excited residual nuclei can produce a time- and space-correlated triple coincidence signal in the JUNO detector. Based on a full Monte Carlo simulation informed with the latest available data, we estimate all backgrounds, including inverse beta decay events of the reactor antineutrino $\bar{\nu}_e$, natural radioactivity, cosmogenic isotopes and neutral current interactions of atmospheric neutrinos. Pulse shape discrimination and multivariate analysis techniques are employed to further suppress backgrounds. With two years of exposure, JUNO is expected to give an order of magnitude improvement compared to the current best limits. After 10 years of data taking, the JUNO expected sensitivities at a 90% confidence level are $\tau/B( n \rightarrow { inv} ) > 5.0 \times 10^{31} \, {\rm yr}$ and $\tau/B( nn \rightarrow { inv} ) > 1.4 \times 10^{32} \, {\rm yr}$.Comment: 28 pages, 7 figures, 4 table

Mesure de processus de double désintégration bêta du 130Te dans l'expérience NEMO 3. RetD du projet SuperNEMO : étude d'un détecteur BiPo.

There are 2 parts in this thesis: one analysis of the NEMO3 experiment data associated with a study of a BiPo detector for the SuperNEMO project. NEMO3 is searching for double beta decay process using direct detection of the two emitted electrons by a tracking detector coupled to a calorimeter. I completely studied the backgrounds and therefore gave the most precise measurement of the allowed process with neutrinos emission 2beta2nu for 130Te: T1/2(2nu) = 6.1±1.2(stat)±0.4(syst)x10^20 yr. This result also constraints theoretical calculations for the neutrino effective mass m_betabeta of 130Te: T1/2(0nu) >5.0x10^22 yr et m_betabeta10^26 yr, using the NEMO3 detection principle but improving efficiency, radiopurity, energy resolution and reducing backgrounds. This background will be then limited by natural radioactive contaminations inside the source foils. Thus the SuperNEMO specifications are very high (A(208Tl)5,0 10^22 ans et m_betabeta 10^26 ans, et qui reprend le principe de détection de NEMO3 en augmentant l'efficacité et la radiopureté du détecteur, en améliorant la résolution en énergie et en réduisant le bruit de fond. Ce dernier sera finalement dû aux contaminations radioactives naturelles internes aux sources, et les exigences de radiopureté sont élevées (A(208Tl)<2 microBq/kg) et au-dessous des limites de sensibilité actuelles. La collaboration étudie un détecteur BiPo pour la mesure du 208Tl, par identification de la cascade 212Bi→212Po→208Pb. La source à mesurer est déposée entre deux plans de scintillateurs donnant les énergies et les temps. J'ai mené l'étude du prototype BiPo1, démontré la faisabilité technique, validé le principe, et déterminé la sensibilité de mesure de sources par rapport au bruit de fond. L'analyse des données de BiPo1 permet d'envisager la mesure de 5 microBq/kg en 208Tl avec BiPo, ce qui est proche des exigences pour SuperNEMO et représente un gain d'un facteur 4 par rapport aux possibilités actuelles

Mesure des processus de double désintégration bêta du 130 Te dans l'expérience NEMO 3

Cette thèse comporte une analyse des données de l'expérience NEMO3 et l'étude d'un détecteur BiPo. NEMO3 recherche un signal de double désintégration bêta 2b0v par détection directe des 2 électrons émis, avec un trajectographe couplé à un calorimètre. J ai étudié complètement le bruit de fond, et fourni la mesure la plus précise de la période du processus avec émission de deux électrons et deux neutrinos 2b2v du 130Te : T1/2 2v = 6,1+-1,2(stat) +-0,4(syst)1020 ans. Ce résultat contraint aussi les calculs théoriques sur la masse effective du neutrino mbb du 130Te : T1/2 >5,0 1022 ans et mbb10 26 ans, et qui reprend le principe de détection de NEMO3 en augmentant l'efficacité et la radiopureté du détecteur, en améliorant la résolution en énergie et en réduisant le bruit de fond. Ce dernier sera finalement dû aux contaminations radioactives naturelles internes aux sources, et les exigences de radiopureté sont élevées (A(208Tl)212Po->208Pb. La source à mesurer est déposée entre deux plans de scintillateurs donnant les énergies et les temps. J ai mené l étude du prototype BiPo1, démontré la faisabilité technique, validé le principe, et déterminé la sensibilité de mesure de sources par rapport au bruit de fond. L analyse des données de BiPo1 permet d'envisager la mesure de 5 uBq/kg en 208Tl avec BiPo, ce qui est proche des exigences pour SuperNEMO et représente un gain d'un facteur 4 par rapport aux possibilités actuellesThere are 2 parts in this thesis: one analysis of the NEMO3 experiment data associated with a study of a BiPo detector for the SuperNEMO project. NEMO3 is searching for double beta decay process using direct detection of the two emitted electrons by a tracking detector coupled to a calorimeter. I completely studied the backgrounds and therefore gave the most precise measurement of the allowed process with neutrinos emission for 130Te: T1/2 = 6.1+-1.2(stat)+-0.4(syst)x1020 yr. This result also constraints theoretical calculations for the neutrino effective mass m of 130Te: T1/2 >5.0x1022 yr et m 1026 yr, using the NEMO3 detection principle but improving efficiency, radiopurity, energy resolution and reducing backgrounds. This background will be then limited by natural radioactive contaminations inside the source foils. Thus the SuperNEMO specifications are very high (A(208Tl)212Po->208Pb chain. Foil source to measure is put between two scintillator plans allowing energy and time measurements. I studied BiPo1 prototype, showed its technical feasibility, validated the principle and determined the sensitivity of the source measurement compared to backgrounds. Data analysis of BiPo1 showed the possibility to measure 5 Bq/kg of 208Tl with the final BiPo. This result is not so far from SuperNEMO requirements and already shows a gain factor of 4 compared to actual detection possibilities.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF