The Borexino Thermal Monitoring & Management System and simulations of the fluid-dynamics of the Borexino detector under asymmetrical, changing boundary conditions

A comprehensive monitoring system for the thermal environment inside the Borexino neutrino detector was developed and installed in order to reduce uncertainties in determining temperatures throughout the detector. A complementary thermal management system limits undesirable thermal couplings between the environment and Borexino's active sections. This strategy is bringing improved radioactive background conditions to the region of interest for the physics signal thanks to reduced fluid mixing induced in the liquid scintillator. Although fluid-dynamical equilibrium has not yet been fully reached, and thermal fine-tuning is possible, the system has proven extremely effective at stabilizing the detector's thermal conditions while offering precise insights into its mechanisms of internal thermal transport. Furthermore, a Computational Fluid-Dynamics analysis has been performed, based on the empirical measurements provided by the thermal monitoring system, and providing information into present and future thermal trends. A two-dimensional modeling approach was implemented in order to achieve a proper understanding of the thermal and fluid-dynamics in Borexino. It was optimized for different regions and periods of interest, focusing on the most critical effects that were identified as influencing background concentrations. Literature experimental case studies were reproduced to benchmark the method and settings, and a Borexino-specific benchmark was implemented in order to validate the modeling approach for thermal transport. Finally, fully-convective models were applied to understand general and specific fluid motions impacting the detector's Active Volume.Comment: arXiv admin note: substantial text overlap with arXiv:1705.09078, arXiv:1705.0965

Geoneutrinos in Borexino

This paper describes the Borexino detector and the high-radiopurity studies and tests that are integral part of the Borexino technology and development. The application of Borexino to the detection and studies of geoneutrinos is discussed.Comment: Conference: Neutrino Geophysics Honolulu, Hawaii December 14-16, 200

A Study of the Residual 39Ar Content in Argon from Underground Sources

The discovery of argon from underground sources with significantly less 39Ar than atmospheric argon was an important step in the development of direct-detection dark matter experiments using argon as the active target. We report on the design and operation of a low background detector with a single phase liquid argon target that was built to study the 39Ar content of the underground argon. Underground argon from the Kinder Morgan CO2 plant in Cortez, Colorado was determined to have less than 0.65% of the 39Ar activity in atmospheric argon.Comment: 21 pages, 10 figure

The Nylon Scintillator Containment Vessels for the Borexino Solar Neutrino Experiment

Borexino is a solar neutrino experiment designed to observe the 0.86 MeV Be-7 neutrinos emitted in the pp cycle of the sun. Neutrinos will be detected by their elastic scattering on electrons in 100 tons of liquid scintillator. The neutrino event rate in the scintillator is expected to be low (~0.35 events per day per ton), and the signals will be at energies below 1.5 MeV, where background from natural radioactivity is prominent. Scintillation light produced by the recoil electrons is observed by an array of 2240 photomultiplier tubes. Because of the intrinsic radioactive contaminants in these PMTs, the liquid scintillator is shielded from them by a thick barrier of buffer fluid. A spherical vessel made of thin nylon film contains the scintillator, separating it from the surrounding buffer. The buffer region itself is divided into two concentric shells by a second nylon vessel in order to prevent inward diffusion of radon atoms. The radioactive background requirements for Borexino are challenging to meet, especially for the scintillator and these nylon vessels. Besides meeting requirements for low radioactivity, the nylon vessels must also satisfy requirements for mechanical, optical, and chemical properties. The present paper describes the research and development, construction, and installation of the nylon vessels for the Borexino experiment

The SABRE project and the SABRE Proof-of-Principle

SABRE aims to directly measure the annual modulation of the dark matter interaction rate with NaI(Tl) crystals. A modulation compatible with the standard hypothesis, in which our Galaxy is immersed in a dark matter halo, has been measured by the DAMA experiment in the same target material. Other direct detection experiments, using different target materials, seem to exclude the interpretation of such modulation in the simplest scenario of WIMP-nucleon elastic scattering. The SABRE experiment aims to carry out an independent search with sufficient sensitivity to confirm or refute the DAMA claim. The goal of the SABRE experiment is to achieve the lowest background rate for a NaI(Tl) experiment (order of 0.1 cpd/kg/keV(ee) in the energy region of interest for dark matter). This challenging goal could be achievable by operating high-purity crystals inside a liquid scintillator veto for active background rejection. In addition, twin detectors will be located in the northern and southern hemispheres to identify possible contributions to the modulation from seasonal or site-related effects. The SABRE project includes an initial Proof-of-Principle phase at LNGS (Italy), to assess the radio-purity of the crystals and the efficiency of the liquid scintillator veto. This paper describes the general concept of SABRE and the expected sensitivity to WIMP annual modulation.The SABRE program is supported by funding from INFN (Italy), NSF (USA), and ARC (Australia Grants: LE170100162, LE16010080, DP170101675, LP150100075). F. Froborg has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 703650. We acknowledge the generous hospitality and constant support of the Laboratori Nazionali del Gran Sasso (Italy)

Snowmass CF1 Summary: WIMP Dark Matter Direct Detection

As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.Comment: Snowmass CF1 Final Summary Report: 47 pages and 28 figures with a 5 page appendix on instrumentation R&

Awe and Wonder in Scientific Practice: Implications for the Relationship Between Science and Religion

This paper examines the role of awe and wonder in scientific practice. Drawing on evidence from psychological research and the writings of scientists and science communicators, I argue that awe and wonder play a crucial role in scientific discovery. They focus our attention on the natural world, encourage open-mindedness, diminish the self (particularly feelings of self-importance), help to accord value to the objects that are being studied, and provide a mode of understanding in the absence of full knowledge. I will flesh out implications of the role of awe and wonder in scientific discovery for debates on the relationship between science and religion. Abraham Heschel argued that awe and wonder are religious emotions because they reduce our feelings of self-importance, and thereby help to cultivate the proper reverent attitude towards God. Yet metaphysical naturalists such as Richard Dawkins insist that awe and wonder need not lead to any theistic commitments for scientists. The awe some scientists experience can be regarded as a form of non-theistic spirituality, which is neither a reductive naturalism nor theism. I will attempt to resolve the tension between these views by identifying some common ground

Search for electron antineutrino interactions with the Borexino Counting Test Facility at Gran Sasso

Electron antineutrino interactions above the inverse beta decay energy of protons (E_\bar{\nu}_e>1.8) where looked for with the Borexino Counting Test Facility (CTF). One candidate event survived after rejection of background, which included muon-induced neutrons and random coincidences. An upper limit on the solar $\bar{\nu}_{e}$ flux, assumed having the $^8$B solar neutrino energy spectrum, of 1.1$\times10^{5}$ cm$^{-2}$~s$^{-1}$ (90% C.L.) was set with a 7.8 ton $\times$ year exposure. This upper limit corresponds to a solar neutrino transition probability, $\nu_{e} \to \bar{\nu}_{e}$, of 0.02 (90% C.L.). Predictions for antineutrino detection with Borexino, including geoneutrinos, are discussed on the basis of background measurements performed with the CTF.Comment: 10 pages, 9 figures, 5 table