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

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

SENSEI: Direct-Detection Constraints on Sub-GeV Dark Matter from a Shallow Underground Run Using a Prototype Skipper CCD

We present new direct-detection constraints on eV-to-GeV dark matter interacting with electrons using a prototype detector of the Sub-Electron-Noise Skipper-CCD Experimental Instrument. The results are based on data taken in the MINOS cavern at the Fermi National Accelerator Laboratory. We focus on data obtained with two distinct readout strategies. For the first strategy, we read out the Skipper CCD continuously, accumulating an exposure of 0.177 g day. While we observe no events containing three or more electrons, we find a large one- and two-electron background event rate, which we attribute to spurious events induced by the amplifier in the Skipper-CCD readout stage. For the second strategy, we take five sets of data in which we switch off all amplifiers while exposing the Skipper CCD for 120 ks, and then read out the data through the best prototype amplifier. We find a one-electron event rate of (3.51±0.10)×10^{-3}  events/pixel/day, which is almost 2 orders of magnitude lower than the one-electron event rate observed in the continuous-readout data, and a two-electron event rate of (3.18_{-0.55}^{+0.86})×10^{-5}  events/pixel/day. We again observe no events containing three or more electrons, for an exposure of 0.069 g day. We use these data to derive world-leading constraints on dark matter-electron scattering for masses between 500 keV and 5 MeV, and on dark-photon dark matter being absorbed by electrons for a range of masses below 12.4 eV

SENSEI: Direct-Detection Results on sub-GeV Dark Matter from a New Skipper CCD

We present the first direct-detection search for sub-GeV dark matter using a new ∼2-gram high-resistivity Skipper CCD from a dedicated fabrication batch that was optimized for dark matter searches. Using 24 days of data acquired in the MINOS cavern at the Fermi National Accelerator Laboratory, we measure the lowest rates in silicon detectors of events containing one, two, three, or four electrons, and achieve world-leading sensitivity for a large range of sub-GeV dark matter masses. Data taken with different thicknesses of the detector shield suggest a correlation between the rate of high-energy tracks and the rate of single-electron events previously classified as "dark current."We detail key characteristics of the new Skipper CCDs, which augur well for the planned construction of the ∼100-gram SENSEI experiment at SNOLAB.Fil: Barak, Liron. Universitat Tel Aviv; IsraelFil: Bloch, Itay M.. Universitat Tel Aviv; IsraelFil: Cababie, Mariano Ruben. Universidad de Buenos Aires; Argentina. Fermi National Accelerator Laboratory; Estados UnidosFil: Cancelo, Gustavo Indalecio. Fermi National Accelerator Laboratory; Estados UnidosFil: Chaplinsky, Luke. Stony Brook University; Estados UnidosFil: Chierchie, Fernando. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Crisler, Michael. Fermi National Accelerator Laboratory; Estados UnidosFil: Drlica Wagner, Alex. University of Chicago; Estados Unidos. Fermi National Accelerator Laboratory; Estados UnidosFil: Essig, Rouven. Stony Brook University; Estados UnidosFil: Estrada, Juan. Fermi National Accelerator Laboratory; Estados UnidosFil: Etzion, Erez. Universitat Tel Aviv; IsraelFil: Fernández Moroni, Guillermo. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Gift, Daniel. Stony Brook University; Estados UnidosFil: Munagavalasa, Sravan. Stony Brook University; Estados UnidosFil: Orly, Aviv. Universitat Tel Aviv; IsraelFil: Rodrigues, Dario. Fermi National Accelerator Laboratory; Estados Unidos. Universidad de Buenos Aires; ArgentinaFil: Singal, Aman. Stony Brook University; Estados UnidosFil: Sofo Haro, Miguel Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fermi National Accelerator Laboratory; Estados Unidos. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Stefanazzi, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; Argentina. Fermi National Accelerator Laboratory; Estados UnidosFil: Tiffenberg, Javier Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fermi National Accelerator Laboratory; Estados UnidosFil: Uemura, Sho. Universitat Tel Aviv; IsraelFil: Volansky, Tomer. Universitat Tel Aviv; IsraelFil: Yu, Tien Tien. University of Oregon; Estados UnidosFil: SENSEI collaboration. No especifíca

SENSEI: Search for Millicharged Particles produced in the NuMI Beam

International audienceMillicharged particles appear in several extensions of the Standard Model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultra-relativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target. The absence of any ionization events with 3 to 6 electrons in the SENSEI data allow us to place world-leading constraints on millicharged particles for masses between 30 MeV to 380 MeV. This work also demonstrates the potential of utilizing low-threshold detectors to investigate new particles in beam-dump experiments, and motivates a future experiment designed specifically for this purpose

SENSEI: Search for Millicharged Particles produced in the NuMI Beam

International audienceMillicharged particles appear in several extensions of the Standard Model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultra-relativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target. The absence of any ionization events with 3 to 6 electrons in the SENSEI data allow us to place world-leading constraints on millicharged particles for masses between 30 MeV to 380 MeV. This work also demonstrates the potential of utilizing low-threshold detectors to investigate new particles in beam-dump experiments, and motivates a future experiment designed specifically for this purpose

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