Nanoseconds Timing System Based on IEEE 1588 FPGA Implementation

Clock synchronization procedures are mandatory in most physical experiments where event fragments are readout by spatially dislocated sensors and must be glued together to reconstruct key parameters (e.g. energy, interaction vertex etc.) of the process under investigation. These distributed data readout topologies rely on an accurate time information available at the frontend, where raw data are acquired and tagged with a precise timestamp prior to data buffering and central data collecting. This makes the network complexity and latency, between frontend and backend electronics, negligible within upper bounds imposed by the frontend data buffer capability. The proposed research work describ…

Solar neutrino physics with Borexino

We present the most recent solar neutrino results from the Borexino experiment at the Gran Sasso underground laboratory. In particular, refined measurements of all neutrinos produced in the {\it pp} fusion chain have been made. It is the first time that the same detector measures the entire range of solar neutrinos at once. These new data weakly favor a high-metallicity Sun. Prospects for measuring CNO solar neutrinos are also discussed.

Recent Borexino results and perspectives of the SOX measurement

International audience; Borexino is a liquid scintillator detector sited underground in the Laboratori Nazionali del Gran Sasso (Italy). Its physics program, until the end of this year, is focussed on the study of solar neutrinos, in particular from the Beryllium, pp, pep and CNO fusion reactions. Knowing the reaction chains in the sun provides insights towards physics disciplines such as astrophysics (star physics, star formation, etc.), astroparticle and particle physics. Phase II started in 2011 and its aim is to improve the phase I results, in particular the measurements of the neutrino fluxes from the pep and CNO processes. By the end of this year, data taking from the sun will be over…

The measurement of the pp chain solar neutrinos in Borexino

Calibration strategy of the JUNO experiment

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. [Figure not available: see fulltext.]

Search for low-energy neutrinos from astrophysical sources with Borexino

We report on searches for neutrinos and antineutrinos from astrophysical sources performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. Electron antineutrinos ($\bar{\nu}_e$) are detected in an organic liquid scintillator through the inverse $\beta$-decay reaction. In the present work we set model-independent upper limits in the energy range 1.8-16.8 MeV on neutrino fluxes from unknown sources that improve our previous results, on average, by a factor 2.5. Using the same data set, we first obtain experimental constraints on the diffuse supernova $\bar{\nu}_e$ fluxes in the previously unexplored region below 8 MeV. A search for $\bar{\nu}_e$ in the solar ne…

Seasonal Modulation of the $^7$Be Solar Neutrino Rate in Borexino

We detected the seasonal modulation of the $^7$Be neutrino interaction rate with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. The period, amplitude, and phase of the observed time evolution of the signal are consistent with its solar origin, and the absence of an annual modulation is rejected at 99.99\% C.L. The data are analyzed using three methods: the sinusoidal fit, the Lomb-Scargle and the Empirical Mode Decomposition techniques, which all yield results in excellent agreement.

Perspectives for CNO neutrino detection in Borexino

International audience; Borexino measured with unprecedented accuracy the fluxes of solar neutrinos emitted at all the steps of the pp fusion chain. Still missing is the measurement of the flux of neutrinos produced in the CNO cycle. A positive measurement of the CNO neutrino flux is of fundamental importance for understanding the evolution of stars and addressing the unresolved controversy on the solar abundances. The measurement of the CNO neutrino flux in Borexino is challenging because of the low intensity of this component (CNO cycle accounts for about 1% of the energy emitted by Sun), the lack of prominent spectral features and the presence of background sources. The main background c…

Charge reconstruction in large-area photomultipliers

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction …

CeSOX: An experimental test of the sterile neutrino hypothesis with Borexino

International audience; The third phase of the Borexino experiment that’s referred to as SOX is devoted to test the hypothesis of the existence of one (or more) sterile neutrinos at a short baseline (~5–10m). The experimental measurement will be made with artificial sources namely with a 144Ce–144Pr antineutrino source at the first stage (CeSOX) and possibly with a 51Cr neutrino source at the second one. The fixed 144Ce–144Pr sample will be placed beneath the detector in a special pit and the initial activity will be about 100 – 150 kCi. The start of data taking is scheduled for April 2018. The article gives a short description of the preparation for the first stage and shows the expected s…

The Design and Sensitivity of JUNO's scintillator radiopurity pre-detector OSIRIS

The European physical journal / C 81(11), 973 (2021). doi:10.1140/epjc/s10052-021-09544-4

Radioactivity control strategy for the JUNO detector

JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day, therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration…

Limiting neutrino magnetic moments with Borexino Phase-II solar neutrino data

A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of $\mu_{\nu}^{eff}$ $<$ 2.8$\cdot$10$^{-11}$ $\mu_{B}$ at 90\% c.l. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments.Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magne…

GIGJ: a crustal gravity model of the Guangdong Province for predicting the geoneutrino signal at the JUNO experiment

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. …

Solar neutrino spectroscopy in Borexino

International audience; In more than ten years of operation, Borexino has performed a precision measurement of the solar neutrino spectrum, resolving almost all spectral components originating from the proton-proton fusion chain. The presentation will review the results recently released for the second data taking phase 2012–2016 during which the detector excelled by its unprecedentedly low background levels. New results on the rate of pp, 7Be, pep and 8B neutrinos as well as their implications for solar neutrino oscillations and metallicity are discussed.

JUNO sensitivity to low energy atmospheric neutrino spectra

Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric $\nu_e$ and $\nu_\mu$ fluxes is presented in this paper. In this study, a sample of atmospheric neutrino Monte Carlo events has been generated, starting from theoretical models, and then pro…

The Monte Carlo simulation of the Borexino detector

We describe the Monte Carlo (MC) simulation package of the Borexino detector and discuss the agreement of its output with data. The Borexino MC 'ab initio' simulates the energy loss of particles in all detector components and generates the resulting scintillation photons and their propagation within the liquid scintillator volume. The simulation accounts for absorption, reemission, and scattering of the optical photons and tracks them until they either are absorbed or reach the photocathode of one of the photomultiplier tubes. Photon detection is followed by a comprehensive simulation of the readout electronics response. The algorithm proceeds with a detailed simulation of the electronics c…

Distillation and stripping pilot plants for the JUNO neutrino detector: Design, operations and reliability

Abstract This paper describes the design, construction principles and operations of the distillation and stripping pilot plants tested at the Daya Bay Neutrino Laboratory, with the perspective to adapt these processes, system cleanliness and leak-tightness standards to the final full scale plants to be used for the purification of the liquid scintillator of the JUNO neutrino detector. The main goal of these plants is to remove radio impurities from the liquid scintillator while increasing its optical attenuation length. Purification of liquid scintillator will be performed with a system combining alumina oxide, distillation, water extraction and steam (or N 2 gas) stripping. Such a combined…