SENSEI: Characterization of Single-Electron Events Using a Skipper-CCD

We use a science-grade Skipper Charge Coupled Device (Skipper-CCD) operating in a low-radiation background environment to develop a semi-empirical model that characterizes the origin of single-electron events in CCDs. We identify, separate, and quantify three independent contributions to the single-electron events, which were previously bundled together and classified as ``dark counts'': dark current, amplifier light, and spurious charge. We measure a dark current, which depends on exposure, of (5.89+-0.77)x10^-4 e-/pix/day, and an unprecedentedly low spurious charge contribution of (1.52+-0.07)x10^-4 e-/pix, which is exposure-independent. In addition, we provide a technique to study events produced by light emitted from the amplifier, which allows the detector's operation to be optimized to minimize this effect to a level below the dark-current contribution. Our accurate characterization of the single-electron events allows one to greatly extend the sensitivity of experiments searching for dark matter or coherent neutrino scattering. Moreover, an accurate understanding of the origin of single-electron events is critical to further progress in ongoing R&D efforts of Skipper and conventional CCDs.Comment: 9 pages, 6 figures, 4 table

Modeling and characterization of TES-based detectors for the Ricochet experiment

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) offers a valuable approach in searching for physics beyond the Standard Model. The Ricochet experiment aims to perform a precision measurement of the CE$\nu$NS spectrum at the Institut Laue-Langevin nuclear reactor with cryogenic solid-state detectors. The experiment plans to employ an array of cryogenic thermal detectors, each with a mass around 30 g and an energy threshold of sub-100 eV. The array includes nine detectors read out by Transition-Edge Sensors (TES). These TES based detectors will also serve as demonstrators for future neutrino experiments with thousands of detectors. In this article we present an update in the characterization and modeling of a prototype TES detector.Comment: Submitted to LTD20 proceedin

Applying Superfluid Helium to Light Dark Matter Searches: Demonstration of the HeRALD Detector Concept

The SPICE/HeRALD collaboration is performing R&D to enable studies of sub-GeV dark matter models using a variety of target materials. Here we report our recent progress on instrumenting a superfluid $^4$He target mass with a transition-edge sensor based calorimeter to detect both atomic signals (e.g. scintillation) and $^4$He quasiparticle (phonon and roton) excitations. The sensitivity of HeRALD to the critical "quantum evaporation" signal from $^4$He quasiparticles requires us to block the superfluid film flow to the calorimeter. We have developed a heat-free film-blocking method employing an unoxidized Cs film, which we implemented in a prototype "HeRALD v0.1" detector of $\sim$10~g target mass. This article reports initial studies of the atomic and quasiparticle signal channels. A key result of this work is the measurement of the quantum evaporation channel's gain of $0.15 \pm 0.012$, which will enable $^4$He-based dark matter experiments in the near term. With this gain the HeRALD detector reported here has an energy threshold of 145~eV at 5 sigma, which would be sensitive to dark matter masses down to 220~MeV/c$^2$.Comment: 14 pages, 9 figure

The factors influencing the decision to list on Abu Dhabi securities exchange

The Abu Dhabi Securities Exchange is established to fund corporates, investments and economic growth. However, many companies operating in Abu Dhabi do not take the opportunity and list in the market. In this paper we survey a sample 145 chief executive officers and deputies of the CEO’s in order to explain why firms refrain from going public and float their equity in the market. Our findings indicate that the poor quality of the Abu Dhabi equity market in terms of its inefficiency and inadequate liquidity plays a crucial role in discouraging firms to list in the market. Moreover, management do not list in order to avoid dilution of ownership as well as to retain control of the company. Finally, we find that knowledgeable managers in big companies are more likely to list in the market particularly when they operate in a competitive industry

A Stress Induced Source of Phonon Bursts and Quasiparticle Poisoning

The performance of superconducting qubits is degraded by a poorly characterized set of energy sources breaking the Cooper pairs responsible for superconductivity, creating a condition often called "quasiparticle poisoning." Recently, a superconductor with one of the lowest average quasiparticle densities ever measured exhibited quasiparticles primarily produced in bursts which decreased in rate with time after cooldown. Similarly, several cryogenic calorimeters used to search for dark matter have also observed an unknown source of low-energy phonon bursts that decrease in rate with time after cooldown. Here, we show that a silicon crystal glued to its holder exhibits a rate of low-energy phonon events that is more than two orders of magnitude larger than in a functionally identical crystal suspended from its holder in a low-stress state. The excess phonon event rate in the glued crystal decreases with time since cooldown, consistent with a source of phonon bursts which contributes to quasiparticle poisoning in quantum circuits and the low-energy events observed in cryogenic calorimeters. We argue that relaxation of thermally induced stress between the glue and crystal is the source of these events, and conclude that stress relaxation contributes to quasiparticle poisoning in superconducting qubits and the athermal phonon background in a broad class of rare-event searches.Comment: 13 pages, 6 figures. W. A. Page and R. K. Romani contributed equally to this work. Correspondence should be addressed to R. K. Roman

First demonstration of 30 eVee ionization energy resolution with Ricochet germanium cryogenic bolometers

The future Ricochet experiment aims to search for new physics in the electroweak sector by measuring the Coherent Elastic Neutrino-Nucleus Scattering process from reactor antineutrinos with high precision down to the sub-100 eV nuclear recoil energy range. While the Ricochet collaboration is currently building the experimental setup at the reactor site, it is also finalizing the cryogenic detector arrays that will be integrated into the cryostat at the Institut Laue Langevin in early 2024. In this paper, we report on recent progress from the Ge cryogenic detector technology, called the CryoCube. More specifically, we present the first demonstration of a 30~eVee (electron equivalent) baseline ionization resolution (RMS) achieved with an early design of the detector assembly and its dedicated High Electron Mobility Transistor (HEMT) based front-end electronics. This represents an order of magnitude improvement over the best ionization resolutions obtained on similar heat-and-ionization germanium cryogenic detectors from the EDELWEISS and SuperCDMS dark matter experiments, and a factor of three improvement compared to the first fully-cryogenic HEMT-based preamplifier coupled to a CDMS-II germanium detector. Additionally, we discuss the implications of these results in the context of the future Ricochet experiment and its expected background mitigation performance.Comment: 10 pages, 5 figures, 1 tabl

Fast neutron background characterization of the future Ricochet experiment at the ILL research nuclear reactor

The future Ricochet experiment aims at searching for new physics in the electroweak sector by providing a high precision measurement of the Coherent Elastic Neutrino-Nucleus Scattering (CENNS) process down to the sub-100 eV nuclear recoil energy range. The experiment will deploy a kg-scale low-energy-threshold detector array combining Ge and Zn target crystals 8.8 meters away from the 58 MW research nuclear reactor core of the Institut Laue Langevin (ILL) in Grenoble, France. Currently, the Ricochet collaboration is characterizing the backgrounds at its future experimental site in order to optimize the experiment's shielding design. The most threatening background component, which cannot be actively rejected by particle identification, consists of keV-scale neutron-induced nuclear recoils. These initial fast neutrons are generated by the reactor core and surrounding experiments (reactogenics), and by the cosmic rays producing primary neutrons and muon-induced neutrons in the surrounding materials. In this paper, we present the Ricochet neutron background characterization using $^3$He proportional counters which exhibit a high sensitivity to thermal, epithermal and fast neutrons. We compare these measurements to the Ricochet Geant4 simulations to validate our reactogenic and cosmogenic neutron background estimations. Eventually, we present our estimated neutron background for the future Ricochet experiment and the resulting CENNS detection significance.Comment: 14 pages, 14 figures, 1 tabl

Emerging trends in government venture capital policies in smaller peripheral economies: lessons from Finland, New Zealand, and Estonia

Emerging trends from the developing venture capital industries of three smaller peripheral economies (Finland, New Zealand, and Estonia), demonstrate that government policy can overcome scale and distance barriers to assist in establishing venture capital to support innovative potential high growth ventures. Eight common policy themes for successful venture capital development are: new venture stimulation; dedicated finance policy institutions; stable, internationally harmonized tax and regulations; business angel development; inward investment; international venture capital fund development; smooth pipeline of investment; effective investment exit market. Venture capital policy development themes are interconnected, requiring a holistic ecosystem approach. A blueprint for successful small peripheral economy venture capital development requires an initial phase of new venture demand stimulation and ensuing simultaneity of policies to engineer venture capital development

Coherent elastic neutrino-nucleus scattering: Terrestrial and astrophysical applications

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) is a process in which neutrinos scatter on a nucleus which acts as a single particle. Though the total cross section is large by neutrino standards, CE$\nu$NS has long proven difficult to detect, since the deposited energy into the nucleus is $\sim$ keV. In 2017, the COHERENT collaboration announced the detection of CE$\nu$NS using a stopped-pion source with CsI detectors, followed up the detection of CE$\nu$NS using an Ar target. The detection of CE$\nu$NS has spawned a flurry of activities in high-energy physics, inspiring new constraints on beyond the Standard Model (BSM) physics, and new experimental methods. The CE$\nu$NS process has important implications for not only high-energy physics, but also astrophysics, nuclear physics, and beyond. This whitepaper discusses the scientific importance of CE$\nu$NS, highlighting how present experiments such as COHERENT are informing theory, and also how future experiments will provide a wealth of information across the aforementioned fields of physics