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 >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

Neutrino Physics with JUNO

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purposeunderground liquid scintillator detector, was proposed with the determinationof the neutrino mass hierarchy as a primary physics goal. It is also capable ofobserving neutrinos from terrestrial and extra-terrestrial sources, includingsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,atmospheric neutrinos, solar neutrinos, as well as exotic searches such asnucleon decays, dark matter, sterile neutrinos, etc. We present the physicsmotivations and the anticipated performance of the JUNO detector for variousproposed measurements. By detecting reactor antineutrinos from two power plantsat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4sigma significance with six years of running. The measurement of antineutrinospectrum will also lead to the precise determination of three out of the sixoscillation parameters to an accuracy of better than 1\%. Neutrino burst from atypical core-collapse supernova at 10 kpc would lead to ~5000inverse-beta-decay events and ~2000 all-flavor neutrino-proton elasticscattering events in JUNO. Detection of DSNB would provide valuable informationon the cosmic star-formation rate and the average core-collapsed neutrinoenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400events per year, significantly improving the statistics of existing geoneutrinosamples. The JUNO detector is sensitive to several exotic searches, e.g. protondecay via the $p\to K^++\bar\nu$ decay channel. The JUNO detector will providea unique facility to address many outstanding crucial questions in particle andastrophysics. It holds the great potential for further advancing our quest tounderstanding the fundamental properties of neutrinos, one of the buildingblocks of our Universe

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

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

ESSν\nuSB Neutrino Oscillation Project

International audienceThe recent measurements of the last mixing angle performed by the reactor experiments in the neutrino sector enable the search for CP violation in the leptonic sector. The next generation of experiments will require new intense neutrino beams and large detector infrastructures. In this context, a new facility is proposed using the European Spallation Source (ESS), currently under construction in Lund (Sweden), to produce the world’s most intense neutrino beam with a megaton Water Cherenkov detector installed 1000 m down in a mine at a distance of about 500 km. This detector will also extent the physics program to proton-decay, atmospheric neutrinos and astrophysics searches

The ESSν\nuSB Switchyard, Target Station, and Facility Performance

International audienceOne of the next challenges in fundamental physics is to understand the origin of matter/antimatter asymmetry in the Universe. Neutrinos could play an important role to elucidate this mystery and better understand the expansion of the Universe. In this context, intense neutrino beams are fundamental tools to study the properties of these particles. The ESS$\nu$SB collaboration proposes to use the proton LINAC of the European Spallation Source currently under construction in Lund (Sweden) to produce a very intense neutrino super beam, in parallel with the spallation neutron production. A very challenging part of the proposed facility is the Target Station which will use 5 MW proton beam power. This paper presents an overview of the facility

The Veto System of the JUNO Experiment

International audienceThe Jiangmen Underground Neutrino Observatory (JUNO) is a new generation of reactor based experiments located in the Guangdong province in China. This experiment offers a rich physics program and will bring significant contributions in many neutrino areas, in particular concerning the determination of the neutrino mass ordering and the measurement of the oscillation parameters at the percent level.The central detector consists of a sphere filled with 20 kilo-tons of liquid scintillator surrounded by about 17612photomultipliers (20’’) and 25600 small photomultipliers (3’’) for reading the light produced by the event interactions. Even if the detector is located at 700 m depth in an underground laboratory, the remaining background imposes the use of a Veto System for its characterization and to ensure an efficient event selection. In particular, the cosmogenic induced background due to the muons passing through the central detector represents the most dangerous contribution and needs to be precisely characterized. The Veto System is assigned to this task and consists of two subsystems, the Outer Veto (OV) and the Top Tracker (TT). The OV is a Water Cherenkov type detector surrounding the central detector and is equipped with 2400 large photomultipliers (20’’) fixed on the support structure looking outward. The JUNO-TT uses the modules from the decommissioned OPERA experiment which are based on the well-known plastic scintillator technology equipped with wavelength shifting fibers. It will be placed on the top of the central detector for an efficient muon track reconstruction. In this poster, the status of the Veto System will be presented with some elements on the trigger strategy

Future of neutrino based reactor experiments

International audienceThe last angle of the PMNS mixing matrix has been measured by the neutrino reactor experiments. This important result opens the door to the precision era in the neutrino oscillation landscape. In this context, the next generation of reactor experiments at the kilo ton scale will significantly improve the measurements on the oscillation parameters and will give an answer on the mass hierarchy (MH) in the next decades. After a brief summary of the last results, these experiments will be presented with their technological challenges to reach the required sensitivity

The ESSν\nuSB High Intensity Neutrino Super Beam

International audienceThe measurement of the matter/antimatter asymmetry in the leptonic sector is one of the highest priority of the particle physics community in the next decades. The ESSnuSB collaboration proposes to design a long baseline experiment based on the European Spallation Source at Lund in Sweden. This experiment will be able to measure the delta_CP parameter with an unprecedent sensitivity thanks to a very intense neutrino superbeam and to the observation of the nu_mu to nu_e oscillation at the second oscillation maximum. To reach this goal, the European Spallation Source facility will be upgraded to provide an additional 5 MW proton beam by doubling the linac pulse frequency from 14 Hz to 28 Hz. The pulse time width will be reduced thanks to an accumulator ring from 2.86 ms to 1.3 microseconds and shared in four parts by a beam switchyard before entering into the target station. The produced neutrino superbeam will be sent to a large 538kt fiducial mass Far Detector based on water Cherenkov technology. The global overview of the project with its physics potentials will be reviewed and additional possibilities offered by this high intensity facility for complementary R&D activities will also be discussed