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Register a new userGIGJ: a crustal gravity model of the Guangdong Province for predicting the geoneutrino signal at the JUNO experiment
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Gravimetric methods are expected to play a decisive role in geophysical modeling of the regional crustal structure applied to geoneutrino studies. GIGJ (GOCE Inversion for Geoneutrinos at JUNO) is a 3D numerical model constituted by ~46 x 10$^{3}$ voxels of 50 x 50 x 0.1 km, built by inverting gravimetric data over the 6{deg} x 4{deg} area centered at the Jiangmen Underground Neutrino Observatory (JUNO) experiment, currently under construction in the Guangdong Province (China). The a-priori modeling is based on the adoption of deep seismic sounding profiles, receiver functions, teleseismic P-wave velocity models and Moho depth maps, according to their own accuracy and spatial resolution. The inversion method allowed for integrating GOCE data with the a-priori information and regularization conditions through a Bayesian approach and a stochastic optimization. GIGJ fits the homogeneously distributed GOCE gravity data, characterized by high accuracy, with a ~1 mGal standard deviation of the residuals, compatible with the observation accuracy. Conversely to existing global models, GIGJ provides a site-specific subdivision of the crustal layers masses which uncertainties include estimation errors, associated to the gravimetric solution, and systematic uncertainties, related to the adoption of a fixed sedimentary layer. A consequence of this local rearrangement of the crustal layer thicknesses is a ~21% reduction and a ~24% increase of the middle and lower crust expected geoneutrino signal, respectively. Finally, the geophysical uncertainties of geoneutrino signals at JUNO produced by unitary uranium and thorium abundances distributed in the upper, middle and lower crust are reduced by 77%, 55% and 78%, respectively. The numerical model is available at http://www.fe.infn.it/u/radioactivity/GIGJ
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Constraints on the Earths composition and on its radiogenic energy budget come from the detection of geoneutrinos. The KamLAND and Borexino experiments recently reported the geoneutrino flux, which reflects the amount and distribution of U and Th inside the Earth. The KamLAND and Borexino experiments recently reported the geoneutrino flux, which reflects the amount and distribution of U and Th inside the Earth. The JUNO neutrino experiment, designed as a 20 kton liquid scintillator detector, will be built in an underground laboratory in South China about 53 km from the Yangjiang and Taishan nuclear power plants. Given the large detector mass and the intense reactor antineutrino flux, JUNO aims to collect high statistics antineutrino signals from reactors but also to address the challenge of discriminating the geoneutrino signal from the reactor background.The predicted geoneutrino signal at JUNO is 39.7 $^{+6.5}_{-5.2}$ TNU, based on the existing reference Earth model, with the dominant source of uncertainty coming from the modeling of the compositional variability in the local upper crust that surrounds (out to $sim$ 500 km) the detector. A special focus is dedicated to the 6{deg} x 4{deg} Local Crust surrounding the detector which is estimated to contribute for the 44% of the signal. On the base of a worldwide reference model for reactor antineutrinos, the ratio between reactor antineutrino and geoneutrino signals in the geoneutrino energy window is estimated to be 0.7 considering reactors operating in year 2013 and reaches a value of 8.9 by adding the contribution of the future nuclear power plants. In order to extract useful information about the mantles composition, a refinement of the abundance and distribution of U and Th in the Local Crust is required, with particular attention to the geochemical characterization of the accessible upper crust.
One of the main open issues of neutrino physics is the determination of the mass hierarchy, discriminating between the two possible ordering of the mass eigenvalues, known as Normal and Inverted Hierarchies. The solution of this puzzle would have a significant impact both on elementary particle physics and astrophysics. A possible way to investigate the problem is the study, with medium baseline reactor antineutrinos, of the mass dependent corrections to inverse $beta$ decays. This is the idea pursued by JUNO, a multipurpose underground liquid scintillator experiment that will start data taking in very few years from now. The main characteristics and the status of the experiment are discussed here, together with its rich physics program. We focus in particular on the potentiality for mass hierarchy determination, the main goal of the experiment, on the oscillation parameters accurate measurements and on the supernova and solar neutrinos and geoneutrino studies.
We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.
Models that envisage successful subduction channel transport of upper crustal materials below 300 km depth, past a critical phase transition in buoyant crustal lithologies, are capable of accumulating and assembling these materials into so-called second continents that are gravitationally stabilized at the base of the Transition Zone, at some 600 to 700 km depth. Global scale, Pacific-type subduction (ocean-ocean and ocean-continent convergence), which lead to super continent assembly, were hypothesized to produce second continents that scale to about the size of Australia, with continental upper crustal concentration levels of radiogenic power. Seismological techniques are incapable of imaging these second continents because of their negligible difference in seismic wave velocities with the surrounding mantle. We can image the geoneutrino flux linked to the radioactive decays in these second continents with land and/or ocean-based detectors. We present predictions of the geoneutrino flux of second continents, assuming different scaled models and we discuss the potential of current and future neutrino experiments to discover or constrain second continents. The power emissions from second continents were proposed to be drivers of super continental cycles. Thus, testing models for the existence of second continents will place constraints on mantle and plate dynamics when using land and ocean-based geoneutrino detectors deployed at strategic locations.
The determination of the neutrino mass hierarchy, whether the $ u _3$ neutrino mass eigenstate is heavier or lighter than the $ u _1$ and $ u _2$ mass eigenstates, is one of the remaining undetermined fundamental aspects of the Standard Model in the lepton sector. Furthermore the mass hierarchy determination will have an impact in the quest of the neutrino nature (Dirac or Majorana mass terms) towards the formulation of a theory of flavour. The Jiangmen Underground Neutrino Observatory (JUNO) is a reactor neutrino experiment under construction at Kaiping, Jiangmen in Southern China composed by a large liquid scintillator detector (sphere of 35.4 m of diameter) surronding by 18000 large PMTs and 25000 small PMTs, a water cherenkov detector and a top tracker detector. The large active mass (20 kton) and the unprecedented energy resolution (3% at 1 MeV) will allow to determine the neutrino mass hierarchy with good sensitivity and to precisely measure the neutrino mixing parameters, $theta _{12}$, $Delta m^2_{21} $, and $Delta m^2_{ee}$ below the 1% level. Moreover, a large liquid scintillator detector will allow to explore physics beyond mass hierarchy determination, in particular on many oyher topics such as in astroparticle physics, like supernova burst and diffuse supernova neutrinos, solar neutrinos, atmospheric neutrinos, geo-neutrinos, nucleon decay, indirect dark matter searches and a number of additional exotic searches. In this work the status and the perspectives of the JUNO experiment will be described, focusing also on the main physics aims and the other possible physics cases.
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