Large Liquid Scintillator Neutrino Detector Research Articles

20-inch photomultiplier tube timing study for JUNO

Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator neutrino detector now under construction at Jiangmen, Guangdong, China for determination of neutrino mass ordering with 3% energy resolution at 1 MeV, a precise measurement of neutrino oscillation parameters, and other neutrino physics. The central detector is made up of a 35.4-meter diameter acrylic sphere which contains 20 kton of liquid scintillator and is surrounded by about 18k 20-inch photomultiplier tubes (PMTs). The PMTs performance is one of the JUNO’s key successes to reach the high resolution goal. In this study, the PMT characteristic and its timing related responses were determined via the PMT generated signals, extracted from the PMT in a scanning station system. About 2,400 of micro-channel plate PMTs (MCP-PMTs) and dynode PMTs were analyzed for their responses with LED source such as rise time, fall time, transit time spread (TTS), gain, etc., which relate to photon incident on different positions of PMT’s glass surface. Furthermore, we also observed the fluctuation of PMT performance under magnetic field which can decrease the PMT photon detection efficiency (PDE).

Search for reactor neutrino directionality using a LAB-based Gd-loaded liquid scintillation detector

Recently, several interesting phenomena related to neutrinos have been found using reactor neutrinos and we have learned much about the properties of neutrinos. Ultrapure water or liquid scintillator is generally used to detect neutrinos. Since a detector filled with water can use the Cherenkov light emitted in a conical shape based on the direction of a charged particle, the direction of the incident neutrinos can be reconstructed relatively well. However, in a detector filled with the liquid scintillator, the reactor neutrino signal can be reconstructed using information from the Inverse Beta Decay (IBD) process. In this case, it is not easy to determine the direction of an incident neutrino because light is emitted in all directions. In this study, we briefly investigated the possibility of the directional reconstruction of reactor neutrinos in the Linear Alkyl Benzene (LAB)-based Gadolinium (Gd)-loaded liquid scintillator using a Monte Carlo simulation technique. The LAB was used in place of existing, conventional liquid scintillation detector solution. It has a high flash point and is environmentally friendly. The purpose of this study was to show a practical and interesting application of neutrino direction reconstruction for reactor neutrinos that could be used in future large liquid scintillator neutrino detectors.

Exploring detection of nuclearites in a large liquid scintillator neutrino detector

We take the JUNO experiment as an example to explore nuclearites in the future large liquid scintillator detector. Comparing to the previous calculations, the visible energy of nuclearites across the liquid scintillator will be reestimated for the liquid scintillator based detector. Then the JUNO sensitivities to the nuclearite flux are presented. It is found that the JUNO projected sensitivities can be better than $7.7 \times 10^{-17} {\rm cm^{-2} s^{-1} sr^{-1}}$ for the nuclearite mass $10^{15} \; {\rm GeV} \leq M \leq 10^{24}$ GeV and initial velocity $10^{-4} \leq \beta_0 \leq 10^{-1}$ with a 20 year running. Note that the JUNO will give the most stringent limits for downgoing nuclearites with $1.6 \times 10^{13} \; {\rm GeV} \leq M \leq 4.0 \times 10^{15}$ GeV and a typical galactic velocity $\beta_0 = 10^{-3}$.

Prompt directional detection of galactic supernova by combining large liquid scintillator neutrino detectors

Core-collapse supernovae produce an intense burst of electron antineutrinos in the few-tens-of-MeV range. Several Large Liquid Scintillator-based Detectors (LLSD) are currently operated worldwide, being very effective for low energy antineutrino detection through the Inverse Beta Decay (IBD) process. In this article, we develop a procedure for the prompt extraction of the supernova location by revisiting the details of IBD kinematics over the broad energy range of supernova neutrinos. Combining all current scintillator-based detector, we show that one can locate a canonical supernova at 10 kpc with an accuracy of 45 degrees (68% C.L.). After the addition of the next generation of scintillator-based detectors, the accuracy could reach 12 degrees (68% C.L.), therefore reaching the performances of the large water Čerenkov neutrino detectors. We also discuss a possible improvement of the SuperNova Early Warning System (SNEWS) inter-experiment network with the implementation of a directionality information in each experiment. Finally, we discuss the possibility to constrain the neutrino energy spectrum as well as the mass of the newly born neutron star with the LLSD data.

Densities, isobaric thermal expansion coefficients and isothermal compressibilities of linear alkylbenzene

We report the measurements of the densities of linear alkylbenzene at three temperatures over 4 to 23 °C with pressures up to 10 MPa. The measurements have been analysed to yield the isobaric thermal expansion coefficients and, so far for the first time, isothermal compressibilities of linear alkylbenzene. Relevance of results for current generation (i.e., Daya Bay) and next generation (i.e. JUNO) large liquid scintillator neutrino detectors are discussed.

Optical scattering lengths in large liquid-scintillator neutrino detectors

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents phenylxylylethane, linear alkylbenzene (LAB), and dodecane, which are under discussion for next-generation experiments such as SNO+ (Sudbury Neutrino Observatory), HanoHano, or LENA (Low Energy Neutrino Astronomy). Results comprise the wavelength range of 415-440 nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Measurements of charged current reactions ofνμon12C

Charged current scattering of ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ on ${}^{12}\mathrm{C}$ has been studied using a ${\ensuremath{\pi}}^{+}$ decay-in-flight ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ beam at the Los Alamos Neutron Science Center. A sample of $66.9\ifmmode\pm\else\textpm\fi{}9.1$ events satisfying criteria for the exclusive reaction ${}^{12}\mathrm{C}({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.}$ was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section $(5.6\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41} {\mathrm{cm}}^{2}$ agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible ${}^{12}\mathrm{N}$ states ${}^{12}\mathrm{C}({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}})X.$ This flux-averaged cross section is $(10.6\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40} {\mathrm{cm}}^{2}$ which is lower than present theoretical calculations.

Measurements of the reactions12C(νμ,μ−)12Ng.s.and12C(νμ,μ−)X

Charged current scattering of ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ on ${}^{12}\mathrm{C}$ has been studied using a ${\ensuremath{\pi}}^{+}$ decay-in-flight ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ beam at the Los Alamos Meson Physics Facility. A sample of 56.8 $\ifmmode\pm\else\textpm\fi{}9.6$ events satisfying criteria for the exclusive reaction ${}^{12}{\mathrm{C}(\mathrm{\ensuremath{\nu}}}_{\mathrm{\ensuremath{\mu}}}{,\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.}$ was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section $(6.6\ifmmode\pm\else\textpm\fi{}1.0\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}{\mathrm{cm}}^{2}$ agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible ${}^{12}\mathrm{N}$ states ${}^{12}\mathrm{C}({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}})X.$ This flux-averaged cross section is $(11.2\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}{\mathrm{cm}}^{2},$ which is approximately half of that given by a recent continuum random-phase approximation calculation.

Measurements of the reactions12C(νe,e−)12Ng.s.and12C(νe,e−)12N*

Charged current reactions of nu_e on 12C have been studied using a mu decay-at-rest nu_e beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction 12C + nu_e -> e- + 12N g.s. were measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to 12N excited states, 12C + nu_e -> e- + 12N and compared with theoretical expectations. Results are consistent with a recent Continuum Random Phase Approximation (CRPA) calculation.