Search

Dual-phase xenon time projection chamber (TPC) detectors have demonstratedsuperior search sensitivities to dark matter over a wide range of particlemasses. To extend their sensitivity to include low-mass dark matterinteractions, it is critical to characterize both the light and chargeresponses of liquid xenon to sub-keV nuclear recoils. In this work, we report anew nuclear recoil calibration in the LUX detector $\textit{in situ}$ usingneutron events from a pulsed Adelphi Deuterium-Deuterium neutron generator. Wedemonstrate direct measurements of light and charge yields down to 0.45 keV(1.4 scintillation photons) and 0.27 keV (1.3 ionization electrons),respectively, approaching the physical limit of liquid xenon detectors. Wediscuss the implication of these new measurements on the physics reach ofdual-phase xenon TPCs for nuclear-recoil-based low-mass dark matter detection.

The performance of superconducting qubits is degraded by a poorlycharacterized set of energy sources breaking the Cooper pairs responsible forsuperconductivity, creating a condition often called ``quasiparticlepoisoning". Both superconducting qubits and low threshold dark mattercalorimeters have observed excess bursts of quasiparticles or phonons thatdecrease in rate with time. Here, we show that a silicon crystal glued to itsholder exhibits a rate of low-energy phonon events that is more than two ordersof magnitude larger than in a functionally identical crystal suspended from itsholder in a low-stress state. The excess phonon event rate in the glued crystaldecreases with time since cooldown, consistent with a source of phonon burstswhich contributes to quasiparticle poisoning in quantum circuits and thelow-energy events observed in cryogenic calorimeters. We argue that relaxationof thermally induced stress between the glue and crystal is the source of theseevents.

Transmission electron microscopy (TEM) is a potent technique for thedetermination of three-dimensional atomic scale structure of samples instructural biology and materials science. In structural biology,three-dimensional structures of proteins are routinely determined usingphase-contrast single-particle cryo-electron microscopy from thousands ofidentical proteins, and reconstructions have reached atomic resolution forspecific proteins. In materials science, three-dimensional atomic structures ofcomplex nanomaterials have been determined using a combination of annular darkfield (ADF) scanning transmission electron microscopic (STEM) tomography andsubpixel localization of atomic peaks, in a method termed atomic electrontomography (AET). However, neither of these methods can determine thethree-dimensional atomic structure of heterogeneous nanomaterials containinglight elements. Here, we perform mixed-state electron ptychography from 34.5million diffraction patterns to reconstruct a high-resolution tilt series of adouble wall-carbon nanotube (DW-CNT), encapsulating a complex $\mathrm{ZrTe}$sandwich structure. Class averaging of the resulting reconstructions andsubpixel localization of the atomic peaks in the reconstructed volume revealsthe complex three-dimensional atomic structure of the core-shellheterostructure with 17 picometer precision. From these measurements, we solvethe full $\mathrm{Zr_{11}Te_{50}}$ structure, which contains a previouslyunobserved $\mathrm{ZrTe_{2}}$ phase in the core. The experimental realizationof ptychographic atomic electron tomography (PAET) will allow for structuraldetermination of a wide range of nanomaterials which are beam-sensitive orcontain light elements.

The computational cost for high energy physics detector simulation in futureexperimental facilities is going to exceed the current available resources. Toovercome this challenge, new ideas on surrogate models using machine learningmethods are being explored to replace computationally expensive components.Additionally, differentiable programming has been proposed as a complementaryapproach, providing controllable and scalable simulation routines. In thisdocument, new and ongoing efforts for surrogate models and differentialprogramming applied to detector simulation are discussed in the context of the2021 Particle Physics Community Planning Exercise (`Snowmass').

Today's world of scientific software for High Energy Physics (HEP) is poweredby x86 code, while the future will be much more reliant on accelerators likeGPUs and FPGAs. The portable parallelization strategies (PPS) project of theHigh Energy Physics Center for Computational Excellence (HEP/CCE) isinvestigating solutions for portability techniques that will allow the codingof an algorithm once, and the ability to execute it on a variety of hardwareproducts from many vendors, especially including accelerators. We think withoutthese solutions, the scientific success of our experiments and endeavors is indanger, as software development could be expert driven and costly to be able torun on available hardware infrastructure. We think the best solution for thecommunity would be an extension to the C++ standard with a very low entry barfor users, supporting all hardware forms and vendors. We are very far from thatideal though. We argue that in the future, as a community, we need to requestand work on portability solutions and strive to reach this ideal.

The nature of dark matter and properties of neutrinos are among the mostpressing issues in contemporary particle physics. The dual-phase xenontime-projection chamber is the leading technology to cover the availableparameter space for Weakly Interacting Massive Particles (WIMPs), whilefeaturing extensive sensitivity to many alternative dark matter candidates.These detectors can also study neutrinos through neutrinoless double-beta decayand through a variety of astrophysical sources. A next-generation xenon-baseddetector will therefore be a true multi-purpose observatory to significantlyadvance particle physics, nuclear physics, astrophysics, solar physics, andcosmology. This review article presents the science cases for such a detector.

The CUPID-Mo experiment to search for 0$u\beta\beta$ decay in $^{100}$Mohas been recently completed after about 1.5 years of operation at LaboratoireSouterrain de Modane (France). It served as a demonstrator for CUPID, a nextgeneration 0$u\beta\beta$ decay experiment. CUPID-Mo was comprised of 20enriched Li$_2$$^{100}$MoO$_4$ scintillating calorimeters, each with a mass of$\sim$ 0.2 kg, operated at $\sim$20 mK. We present here the final analysis withthe full exposure of CUPID-Mo ($^{100}$Mo exposure of 1.47 kg$\times$yr) usedto search for lepton number violation via 0$u\beta\beta$ decay. We report onvarious analysis improvements since the previous result on a subset of data,reprocessing all data with these new techniques. We observe zero events in theregion of interest and set a new limit on the $^{100}$Mo 0$u\beta\beta$ decayhalf-life of $T^{0u}_{1/2} > 1.8 \times 10^{24}$ year (stat.+syst.) at 90%CI. Under the light Majorana neutrino exchange mechanism this corresponds to aneffective Majorana neutrino mass of $\left <(0.28$--$0.49)$ eV, dependent upon the nuclear matrix element utilized.

CUPID will be a next generation experiment searching for the neutrinolessdouble $\beta$ decay, whose discovery would establish the Majorana nature ofthe neutrino. Based on the experience achieved with the CUORE experiment,presently taking data at LNGS, CUPID aims to reach a background freeenvironment by means of scintillating Li$_{2}$$^{100}$MoO$_4$ crystals coupledto light detectors. Indeed, the simultaneous heat and light detection allows usto reject the dominant background of $\alpha$ particles, as proven by theCUPID-0 and CUPID-Mo demonstrators. In this work we present the results of thefirst test of the CUPID baseline module. In particular, we propose a newoptimized detector structure and light sensors design to enhance theengineering and the light collection, respectively. We characterized the heatdetectors, achieving an energy resolution of (5.9 $\pm$ 0.2) keV FWHM at the$Q$-value of $^{100}$Mo (about 3034 keV). We studied the light collection ofthe baseline CUPID design with respect to an alternative configuration whichfeatures gravity-assisted light detectors' mounting. In both cases we obtainedan improvement in the light collection with respect to past measures and wevalidated the particle identification capability of the detector, which ensuresan $\alpha$ particle rejection higher than 99.9%, fully satisfying therequirements for CUPID.

We present the results from combining machine learning with the profilelikelihood fit procedure, using data from the Large Underground Xenon (LUX)dark matter experiment. This approach demonstrates reduction in computationtime by a factor of 30 when compared with the previous approach, without lossof performance on real data. We establish its flexibility to capture non-linearcorrelations between variables (such as smearing in light and charge signalsdue to position variation) by achieving equal performance using pulse areaswith and without position-corrections applied. Its efficiency and scalabilityfurthermore enables searching for dark matter using additional variableswithout significant computational burden. We demonstrate this by including alight signal pulse shape variable alongside more traditional inputs such aslight and charge signal strengths. This technique can be exploited by futuredark matter experiments to make use of additional information, reducecomputational resources needed for signal searches and simulations, and makeinclusion of physical nuisance parameters in fits tractable.

FASER is a new experiment designed to search for new light weakly-interactinglong-lived particles (LLPs) and study high-energy neutrino interactions in thevery forward region of the LHC collisions at CERN. The experimental apparatusis situated 480 m downstream of the ATLAS interaction-point aligned with thebeam collision axis. The FASER detector includes four identical trackerstations constructed from silicon microstrip detectors. Three of the trackerstations form a tracking spectrometer, and enable FASER to detect the decayproducts of LLPs decaying inside the apparatus, whereas the fourth station isused for the neutrino analysis. The spectrometer has been installed in the LHCcomplex since March 2021, while the fourth station is not yet installed. FASERwill start physics data taking when the LHC resumes operation in early 2022.This paper describes the design, construction and testing of the trackingspectrometer, including the associated components such as the mechanics,readout electronics, power supplies and cooling system.

The FASER experiment is a new small and inexpensive experiment that is placed480 meters downstream of the ATLAS experiment at the CERN LHC. FASER isdesigned to capture decays of new long-lived particles, produced outside of theATLAS detector acceptance. These rare particles can decay in the FASER detectortogether with about 500-1000 Hz of other particles originating from the ATLASinteraction point. A very high efficiency trigger and data acquisition systemis required to ensure that the physics events of interest will be recorded.This paper describes the trigger and data acquisition system of the FASERexperiment and presents performance results of the system acquired duringinitial commissioning.

The Forward Physics Facility (FPF) is a proposal to create a cavern with thespace and infrastructure to support a suite of far-forward experiments at theLarge Hadron Collider during the High Luminosity era. Located along the beamcollision axis and shielded from the interaction point by at least 100 m ofconcrete and rock, the FPF will house experiments that will detect particlesoutside the acceptance of the existing large LHC experiments and will observerare and exotic processes in an extremely low-background environment. In thiswork, we summarize the current status of plans for the FPF, including recentprogress in civil engineering in identifying promising sites for the FPF andthe experiments currently envisioned to realize the FPF's physics potential. Wethen review the many Standard Model and new physics topics that will beadvanced by the FPF, including searches for long-lived particles, probes ofdark matter and dark sectors, high-statistics studies of TeV neutrinos of allthree flavors, aspects of perturbative and non-perturbative QCD, andhigh-energy astroparticle physics.

In our quest to understand the nature of dark matter and discover itsnon-gravitational interactions with ordinary matter, we propose an experimentusing a \pbo ~calorimeter to search for or set new limits on the productionrate of i) hidden sector particles in the $3 - 60$ MeV mass range via their$e^+e^-$ decay (or $\gamma\gamma$ decay with limited tracking), and ii) thehypothetical X17 particle, claimed in multiple recent experiments. The searchfor these particles is motivated by new hidden sector models and dark mattercandidates introduced to account for a variety of experimental andobservational puzzles: the small-scale structure puzzle in cosmologicalsimulations, anomalies such as the 4.2$\sigma$ disagreement between experimentsand the standard model prediction for the muon anomalous magnetic moment, andthe excess of $e^+e^-$ pairs from the $^8$Be M1 and $^4$He nuclear transitionsto their ground states observed by the ATOMKI group. In these models, the $1 -100$ MeV mass range is particularly well-motivated and the lower part of thisrange still remains unexplored. Our proposed direct detection experiment willuse a magnetic-spectrometer-free setup (the PRad apparatus) to detect all threefinal state particles in the visible decay of a hidden sector particle allowingfor an effective control of the background and will cover the proposed massrange in a single setting. The use of the well-demonstrated PRad setup allowsfor an essentially ready-to-run and uniquely cost-effective search for hiddensector particles in the $3 - 60$ MeV mass range with a sensitivity of8.9$\times$10$^{-8}$ - 5.8$\times$10$^{-9}$ to $\epsilon^2$, the square of thekinetic mixing interaction constant between hidden and visible sectors. Thisupdated proposal includes our response to the PAC49 comments.

26,000 3-inch photomultiplier tubes (PMTs) have been produced for Jiangmen Underground Neutrino Observatory (JUNO) by the Hainan Zhanchuang Photonics Technology Co., Ltd (HZC) company in China and passed all acceptance tests with only 15 tubes rejected. The mass production began in 2018 and elapsed for about 2 years at a rate of ∼1,000 PMTs per month. The characterization of the PMTs was performed in the factory concurrently with production as a joint effort between HZC and JUNO. Fifteen performance parameters were tracked at different sampling rates, and novel working strategies were implemented to improve quality assurance. This constitutes the largest sample of 3-inch PMTs ever produced and studied in detail to date.

UCGretina, a GEANT4 simulation of the GRETINA gamma-ray tracking array of highly-segmented high-purity germanium detectors is described. We have developed a model of the array, in particular of the Quad Module and the capsules, that gives good agreement between simulated and measured photopeak efficiencies over a broad range of gamma-ray energies and reproduces the shape of the measured Compton continuum. Both of these features are needed in order to accurately extract gamma-ray yields from spectra collected in in-beam gamma-ray spectroscopy measurements with beams traveling at v∕c≳0.3 at the National Superconducting Cyclotron Laboratory and the Facility for Rare Isotope Beams. In the process of developing the model, we determined that millimeter-scale layers of passive germanium surrounding the active volumes of the simulated crystals must be included in order to reproduce measured photopeak efficiencies. We adopted a simple model of effective passive layers and developed heuristic methods of determining passive-layer thicknesses by comparison of simulations and measurements for a single crystal and for the full array. Prospects for future development of the model are discussed.

The dual-phase xenon time projection chamber (TPC) is a powerful tool fordirect-detection experiments searching for WIMP dark matter, other dark mattermodels, and neutrinoless double-beta decay. Successful operation of such a TPCis critically dependent on the ability to hold high electric fields in the bulkliquid, across the liquid surface, and in the gas. Careful design andconstruction of the electrodes used to establish these fields is thereforerequired. We present the design and production of the LUX-ZEPLIN (LZ)experiment's high-voltage electrodes, a set of four woven mesh wire grids. Griddesign drivers are discussed, with emphasis placed on design of the electronextraction region. We follow this with a description of the grid productionprocess and a discussion of steps taken to validate the LZ grids prior tointegration into the TPC.

This manuscript describes the commissioning of the Mini-CAPTAIN liquid argon detector in a neutron beam at the Los Alamos Neutron Science Center (LANSCE), which led to a first measurement of high-energy neutron interactions in argon. The Mini-CAPTAIN detector consists of a Time Projection Chamber (TPC) with an accompanying photomultiplier tube (PMT) array sealed inside a liquid-argon-filled cryostat. The liquid argon is constantly purified and recirculated in a closed-loop cycle during operation. The specifications and assembly of the detector subsystems and an overview of their performance in a neutron beam are reported.

Associated particle imaging (API) is a non-destructive nuclear technique for the 3D determination of isotopic distributions. By detecting the alpha particle associated with the emitted neutron in the deuterium-tritium fusion reaction with a position- and time-resolving detector, the direction of the 14.1 MeV neutron and its time of emission can be determined. Employing this method, isotope characteristic gamma rays emitted in inelastic neutron scattering events can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and characterized. The system was tested with common soil elements and shown to be sensitive to 12C, 16O, 28Si, 27Al, and 56Fe. New aspects of our approach are the use of a yttrium-aluminum-perovskite scintillator, using a sapphire window instead of a fiber-optic faceplate for light transport to the photomultiplier, and the all-digital data acquisition system. We present a description of the system with simulations and experimental results that show a position resolution on the alpha detector of 1 mm, a depth resolution using a LaBr3 detector of 6.2 cm, and an angular resolution of 4.5°. Additionally, we present single-element gamma response measurements for the elements mentioned above together with a comparison to Monte Carlo simulations (MCNP6).

Associated particle imaging (API) is a non-destructive nuclear technique for the 3D determination of isotopic distributions. By detecting the alpha particle associated with the emitted neutron in the deuterium-tritium fusion reaction with a position- and time-resolving detector, the direction of the 14.1 MeV neutron and its time of emission can be determined. Employing this method, isotope characteristic gamma rays emitted in inelastic neutron scattering events can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and characterized. The system was tested with common soil elements and shown to be sensitive to 12C, 16O, 28Si, 27Al, and 56Fe. New aspects of our approach are the use of a yttrium-aluminum-perovskite scintillator, using a sapphire window instead of a fiber-optic faceplate for light transport to the photomultiplier, and the all-digital data acquisition system. We present a description of the system with simulations and experimental results that show a position resolution on the alpha detector of 1 mm, a depth resolution using a LaBr3 detector of 6.2 cm, and an angular resolution of 4.5°. Additionally, we present single-element gamma response measurements for the elements mentioned above together with a comparison to Monte Carlo simulations (MCNP6).

Optical frequency stabilization is a critical component for precisionscientific systems including quantum sensing, precision metrology, and atomictimekeeping. Ultra-high quality factor photonic integrated optical resonatorsare a prime candidate for reducing their size, weight and cost as well asmoving these systems on chip. However, integrated resonators suffer fromtemperature-dependent resonance drift due to the large thermal response as wellas sensitivity to external environmental perturbations. Suppression of thecavity resonance drift can be achieved using precision interrogation of thecavity temperature through the dual-mode optical thermometry. This approachenables measurement of the cavity temperature change by detecting the resonancedifference shift between two polarization or optical frequency modes. Yet thisapproach has to date only been demonstrated in bulk-optic whispering gallerymode and fiber resonators. In this paper, we implement dual-mode opticalthermometry using dual polarization modes in a silicon nitride waveguideresonator for the first time, to the best of our knowledge. The temperatureresponsivity and sensitivity of the dual-mode TE/TM resonance difference is180.7$\pm$2.5 MHz/K and 82.56 $\mu$K, respectively, in a silicon nitrideresonator with a 179.9E6 intrinsic TM mode Q factor and a 26.6E6 intrinsic TEmode Q factor. Frequency stabilization is demonstrated by locking a laser tothe TM mode cavity resonance and applying the dual-mode resonance difference toa feedforward laser frequency drift correction circuit with a drift rateimprovement to 0.31 kHz/s over the uncompensated 10.03 kHz/s drift rate. Allandeviation measurements with dual-mode feedforward-correction engaged shows thata fractional frequency instability of 9.6E-11 over 77 s can be achieved.

The underlying physics behind an experimental observation often lacks asimple analytical description. This is especially the case for scanning probemicroscopy techniques, where the interaction between the probe and the sampleis nontrivial. Realistic modeling to include the details of the probe is alwaysexponentially more difficult than its "spherical cow" counterparts. On theother hand, a well-trained artificial neural network based on real data cangrasp the hidden correlation between the signal and sample properties. In thiswork, we show that, via a combination of model calculation and experimentaldata acquisition, a physics-infused hybrid neural network can predict thetip-sample interaction in the widely used scattering-type scanning near-fieldoptical microscope. This hybrid network provides a long-sought solution foraccurate extraction of material properties from tip-specific raw data. Themethodology can be extended to other scanning probe microscopy techniques aswell as other data-oriented physical problems in general.

FASER$\nu$ at the CERN Large Hadron Collider (LHC) is designed to directlydetect collider neutrinos for the first time and study their cross sections atTeV energies, where no such measurements currently exist. In 2018, a pilotdetector employing emulsion films was installed in the far-forward region ofATLAS, 480 m from the interaction point, and collected 12.2 fb$^{-1}$ ofproton-proton collision data at a center-of-mass energy of 13 TeV. We describethe analysis of this pilot run data and the observation of the first neutrinointeraction candidates at the LHC. This milestone paves the way for high-energyneutrino measurements at current and future colliders.

The deep underground neutrino experiment (DUNE), a 40-kton underground liquid argon time projection chamber experiment, will be sensitive to the electron-neutrino flavor component of the burst of neutrinos expected from the next Galactic core-collapse supernova. Such an observation will bring unique insight into the astrophysics of core collapse as well as into the properties of neutrinos. The general capabilities of DUNE for neutrino detection in the relevant few- to few-tens-of-MeV neutrino energy range will be described. As an example, DUNE’s ability to constrain the νe spectral parameters of the neutrino burst will be considered.

The establishment of a possible connection between neutrino emission and gravitational-wave (GW) bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge. In the Daya Bay experiment, using the data collected from December 2011 to August 2017, a search was performed for electron-Antineutrino signals that coincided with detected GW events, including GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817. We used three time windows of 10, 500, and 1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates. The detected electron-Antineutrino candidates were consistent with the expected background rates for all the three time windows. Assuming monochromatic spectra, we found upper limits (90% confidence level) of the electron-Antineutrino fluence of (1.13-2.44)×1011 cm-2 at 5 MeV to 8.0×107 cm-2 at 100 MeV for the three time windows. Under the assumption of a Fermi-Dirac spectrum, the upper limits were found to be (5.4-7.0)×109 cm-2 for the three time windows.

The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrinoand neutrinoless double beta decay of $^{134}$Xe is presented. LZ is a 10-tonnexenon time projection chamber optimized for the detection of dark matterparticles, that is expected to start operating in 2021 at Sanford UndergroundResearch Facility, USA. Its large mass of natural xenon provides an exceptionalopportunity to search for the double beta decay of $^{134}$Xe, for which xenondetectors enriched in $^{136}$Xe are less effective. For the two-neutrino decaymode, LZ is predicted to exclude values of the half-life up to1.7$\times$10$^{24}$ years at 90% confidence level (CL), and has a three-sigmaobservation potential of 8.7$\times$10$^{23}$ years, approaching thepredictions of nuclear models. For the neutrinoless decay mode LZ, is projectedto exclude values of the half-life up to 7.3$\times$10$^{24}$ years at 90% CL.

Using a series of detector measurements taken at different locations tolocalize a source of radiation is a well-studied problem. The source ofradiation is sometimes constrained to a single point-like source, in which casethe location of the point source can be found using techniques such as maximumlikelihood. Recent advancements have shown the ability to locate point sourcesin 2D and even 3D, but few have studied the effect of intervening material onthe problem. In this work we examine gamma-ray data taken from a freely movingsystem and develop voxelized 3-D models of the scene using data from theonboard LiDAR. Ray casting is used to compute the distance each gamma raytravels through the scene material, which is then used to calculate attenuationassuming a single attenuation coefficient for solids within the geometry.Parameter estimation using maximum likelihood is performed to simultaneouslyfind the attenuation coefficient, source activity, and source position thatbest match the data. Using a simulation, we validate the ability of this methodto reconstruct the true location and activity of a source, along with the trueattenuation coefficient of the structure it is inside, and then we apply themethod to measured data with sources and find good agreement.

The KamLAND-Zen 800 experiment is searching for the neutrinoless double-betadecay of $^{136}$Xe by using $^{136}$Xe-loaded liquid scintillator. The liquidscintillator is enclosed inside a balloon made of thin, transparent,low-radioactivity film that we call Inner Balloon (IB). The IB, apart fromguaranteeing the liquid containment, also allows to minimize the backgroundfrom cosmogenic muon-spallation products and $^{8}$B solar neutrinos. Indeedthese events could contribute to the total counts in the region of interestaround the Q-value of the double-beta decay of $^{136}$Xe. In this paper, wepresent an overview of the IB and describe the various steps of itscommissioning minimizing the radioactive contaminations, from the materialselection, to the fabrication of the balloon and its installation inside theKamLAND detector. Finally, we show the impact of the IB on the KamLANDbackground as measured by the KamLAND detector itself.

We propose the use of silicon carbide (SiC) for direct detection of sub-GeV dark matter. SiC has properties similar to both silicon and diamond but has two key advantages: (i) it is a polar semiconductor which allows sensitivity to a broader range of dark matter candidates; and (ii) it exists in many stable polymorphs with varying physical properties and hence has tunable sensitivity to various dark matter models. We show that SiC is an excellent target to search for electron, nuclear and phonon excitations from scattering of dark matter down to 10 keV in mass, as well as for absorption processes of dark matter down to 10 meV in mass. Combined with its widespread use as an alternative to silicon in other detector technologies and its availability compared to diamond, our results demonstrate that SiC holds much promise as a novel dark matter detector.

We have developed an experimental system to simultaneously measure surface structure, morphology, composition, chemical state, and chemical activity for samples in gas phase environments. This is accomplished by simultaneously measuring x-ray photoelectron spectroscopy (XPS) and grazing incidence x-ray scattering in gas pressures as high as the multi-Torr regime while also recording mass spectrometry. Scattering patterns reflect near-surface sample structures from the nano-scale to the meso-scale, and the grazing incidence geometry provides tunable depth sensitivity of structural measurements. Scattered x rays are detected across a broad range of angles using a newly designed pivoting-UHV-manipulator for detector positioning. At the same time, XPS and mass spectrometry can be measured, all from the same sample spot and under ambient conditions. To demonstrate the capabilities of this system, we measured the chemical state, composition, and structure of Ag-behenate on a Si(001) wafer in vacuum and in O2 atmosphere at various temperatures. These simultaneous structural, chemical, and gas phase product probes enable detailed insights into the interplay between the structure and chemical state for samples in gas phase environments. The compact size of our pivoting-UHV-manipulator makes it possible to retrofit this technique into existing spectroscopic instruments installed at synchrotron beamlines. Because many synchrotron facilities are planning or undergoing upgrades to diffraction limited storage rings with transversely coherent beams, a newly emerging set of coherent x-ray scattering experiments can greatly benefit from the concepts we present here.

Abstract: Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low $$^{39}$$ 39 K contamination of 4.3 ± 0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1 ± 0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of $$^{226}$$ 226 Ra and $$^{228}$$ 228 Th inside the crystal to be $$5.9\pm 0.6~\upmu $$ 5.9 ± 0.6 μ Bq/kg and $$1.6\pm 0.3~\upmu $$ 1.6 ± 0.3 μ Bq/kg, respectively, which would indicate a contamination from $$^{238}$$ 238 U and $$^{232}$$ 232 Th at part-per-trillion level. We measured an activity of 0.51 ± 0.02 mBq/kg due to $$^{210}$$ 210 Pb out of equilibrium and a $$\alpha $$ α quenching factor of 0.63 ± 0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of $$\sim $$ ∼ 1 count/day/kg/keV in the [5–20] keV region.

The OSIRIS detector is a subsystem of the liquid scintillator fillling chainof the JUNO reactor neutrino experiment. Its purpose is to validate theradiopurity of the scintillator to assure that all components of the JUNOscintillator system work to specifications and only neutrino-grade scintillatoris filled into the JUNO Central Detector. The aspired sensitivity level of$10^{-16}$ g/g of $^{238}$U and $^{232}$Th requires a large ($\sim$20 m$^3$)detection volume and ultralow background levels. The present paper reports onthe design and major components of the OSIRIS detector, the detector simulationas well as the measuring strategies foreseen and the sensitivity levels to U/Ththat can be reached in this setup.

This report describes the conceptual design of the DUNE near detector

Imperfections in analog-to-digital conversion (ADC) cannot be ignored when signal digitization requirements demand both wide dynamic range and high resolution, as is the case for the Majorana Demonstrator 76Ge neutrinoless double-beta decay search. Enabling the experiment's high-resolution spectral analysis and efficient pulse shape discrimination required careful measurement and correction of ADC nonlinearities. A simple measurement protocol was developed that did not require sophisticated equipment or lengthy data-taking campaigns. A slope-dependent hysteresis was observed and characterized. A correction applied to digitized waveforms prior to signal processing reduced the differential and integral nonlinearities by an order of magnitude, eliminating these as dominant contributions to the systematic energy uncertainty at the double-beta decay Q value.

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.]

CUPID-Mo is a cryogenic detector array designed to search for neutrinoless double-beta decay (0νββ) of 100Mo. It uses 20 scintillating 100Mo-enriched Li2MoO4 bolometers instrumented with Ge light detectors to perform active suppression of α backgrounds, drastically reducing the expected background in the 0νββ signal region. As a result, pileup events and small detector instabilities that mimic normal signals become non-negligible potential backgrounds. These types of events can in principle be eliminated based on their signal shapes, which are different from those of regular bolometric pulses. We show that a purely data-driven principal component analysis based approach is able to filter out these anomalous events, without the aid of detector response simulations.

The ATLAS experiment at the Large Hadron Collider (LHC) employs a triggersystem consisting of a first-level hardware trigger (L1) and a software-basedhigh-level trigger. The L1 muon trigger system selects muon candidates, assignsthem to the correct LHC bunch crossing and classifies them into one of sixtransverse-momentum threshold classes. The L1 muon trigger system usesresistive-plate chambers (RPCs) to generate the muon-induced trigger signals inthe central (barrel) region of the ATLAS detector. The ATLAS RPCs are arrangedin six concentric layers and operate in a toroidal magnetic field with abending power of 1.5 to 5.5 Tm. The RPC detector consists of about 3700 gasvolumes with a total surface area of more than 4000 m$^2$. This paper reportson the performance of the RPC detector and L1 muon barrel trigger using 60.8fb$^{-1}$ of proton-proton collision data recorded by the ATLAS experiment in2018 at a centre-of-mass energy of 13 TeV. Detector and trigger performance arestudied using $Z$ boson decays into a muon pair. Measurements of the RPCdetector response, efficiency, and time resolution are reported. Measurementsof the L1 muon barrel trigger efficiencies and rates are presented, along withmeasurements of the properties of the selected sample of muon candidates.Measurements of the RPC currents, counting rates and mean avalanche charge areperformed using zero-bias collisions. Finally, RPC detector response andefficiency are studied at different high voltage and front-end discriminatorthreshold settings in order to extrapolate detector response to the higherluminosity expected for the High Luminosity LHC.

One of the primary uses for transmission electron microscopy (TEM) is to measure diffraction pattern images in order to determine a crystal structure and orientation. In nanobeam electron diffraction (NBED), we scan a moderately converged electron probe over the sample to acquire thousands or even millions of sequential diffraction images, a technique that is especially appropriate for polycrystalline samples. However, due to the large Ewald sphere of TEM, excitation of Bragg peaks can be extremely sensitive to sample tilt, varying strongly for even a few degrees of sample tilt for crystalline samples. In this paper, we present multibeam electron diffraction (MBED), where multiple probe-forming apertures are used to create multiple scanning transmission electron microscopy (STEM) probes, all of which interact with the sample simultaneously. We detail designs for MBED experiments, and a method for using a focused ion beam to produce MBED apertures. We show the efficacy of the MBED technique for crystalline orientation mapping using both simulations and proof-of-principle experiments. We also show how the angular information in MBED can be used to perform 3D tomographic reconstruction of samples without needing to tilt or scan the sample multiple times. Finally, we also discuss future opportunities for the MBED method.

Sensors fabricated from high resistivity, float zone, silicon material have been the basis of vertex detectors and trackers for the last 30 years. The areas of these devices have increased from a few square cm to > 200m2 for the existing CMS tracker. High Luminosity Large Hadron Collider (HL-LHC), CMS and ATLAS tracker upgrades will each require more than 200 m2 of silicon and the CMS High Granularity Calorimeter (HGCAL) will require more than 600 m2. The cost and complexity of assembly of these devices is related to the area of each module, which in turn is set by the size of the silicon sensors. In addition to large area, the devices must be radiation hard, which requires the use of sensors thinned to 200 microns or less. The combination of wafer thinning and large wafer diameter is a significant technical challenge, and is the subject of this work. We describe work on development of thin sensors on 200 mm wafers using wafer bonding technology. Results of development runs with float zone, Silicon-on-Insulator and Silicon-Silicon bonded wafer technologies are reported.

The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for 8B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting 8B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background 238U and 232Th in the liquid scintillator can be controlled to 10-17g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If Δm221= 4.8 × 10-5(7.5 × 10-5) eV, JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3σ (2σ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure Δm221using 8B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Δm221reported by solar neutrino experiments and the KamLAND experiment.

A scintillating bolometer based on a large cubic Li$_{2}$$^{100}$MoO$_4$crystal (45 mm side) and a Ge wafer (scintillation detector) has been operatedin the CROSS cryogenic facility at the Canfranc underground laboratory inSpain. The dual-readout detector is a prototype of the technology that will beused in the next-generation $0\nu2\beta$ experiment CUPID. The measurementswere performed at 18 and 12 mK temperature in a pulse tube dilutionrefrigerator. This setup utilizes the same technology as the CUORE cryostatthat will host CUPID and so represents an accurate estimation of the expectedperformance. The Li$_{2}$$^{100}$MoO$_4$ bolometer shows a high energyresolution of 6 keV FWHM at the 2615 keV $\gamma$ line. The detection ofscintillation light for each event triggered by the Li$_{2}$$^{100}$MoO$_4$bolometer allowed for a full separation ($\sim$8$\sigma$) between$\gamma$($\beta$) and $\alpha$ events above 2 MeV. The Li$_{2}$$^{100}$MoO$_4$crystal also shows a high internal radiopurity with $^{228}$Th and $^{226}$Raactivities of less than 3 and 8 $\mu$Bq/kg, respectively. Taking also intoaccount the advantage of a more compact and massive detector array, which canbe made of cubic-shaped crystals (compared to the cylindrical ones), this testdemonstrates the great potential of cubic Li$_{2}$$^{100}$MoO$_4$ scintillatingbolometers for high-sensitivity searches for the $^{100}$Mo $0\nu2\beta$ decayin CROSS and CUPID projects.

A scintillating bolometer based on a large cubic Li$_{2}$$^{100}$MoO$_4$crystal (45 mm side) and a Ge wafer (scintillation detector) has been operatedin the CROSS cryogenic facility at the Canfranc underground laboratory inSpain. The dual-readout detector is a prototype of the technology that will beused in the next-generation $0u2\beta$ experiment CUPID. The measurementswere performed at 18 and 12 mK temperature in a pulse tube dilutionrefrigerator. This setup utilizes the same technology as the CUORE cryostatthat will host CUPID and so represents an accurate estimation of the expectedperformance. The Li$_{2}$$^{100}$MoO$_4$ bolometer shows a high energyresolution of 6 keV FWHM at the 2615 keV $\gamma$ line. The detection ofscintillation light for each event triggered by the Li$_{2}$$^{100}$MoO$_4$bolometer allowed for a full separation ($\sim$8$\sigma$) between$\gamma$($\beta$) and $\alpha$ events above 2 MeV. The Li$_{2}$$^{100}$MoO$_4$crystal also shows a high internal radiopurity with $^{228}$Th and $^{226}$Raactivities of less than 3 and 8 $\mu$Bq/kg, respectively. Taking also intoaccount the advantage of a more compact and massive detector array, which canbe made of cubic-shaped crystals (compared to the cylindrical ones), this testdemonstrates the great potential of cubic Li$_{2}$$^{100}$MoO$_4$ scintillatingbolometers for high-sensitivity searches for the $^{100}$Mo $0u2\beta$ decayin CROSS and CUPID projects.

The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li2100MoO4 crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of (6.7 ± 0.6) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of α particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this α-induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.

To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were increased in 12 steps from 0.5 g/L and

The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li2100MoO4 crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of (6.7 ± 0.6) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of α particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this α-induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.

The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to the WIMP-nucleon spin-independent cross-section down to (1–2)×10−12 pb at a WIMP mass of 40 GeV/c2. This paper describes the simulations framework that, along with radioactivity measurements, was used to support this projection, and also to provide mock data for validating reconstruction and analysis software. Of particular note are the event generators, which allow us to model the background radiation, and the detector response physics used in the production of raw signals, which can be converted into digitized waveforms similar to data from the operational detector. Inclusion of the detector response allows us to process simulated data using the same analysis routines as developed to process the experimental data.

Two-phase xenon detectors, such as that at the core of the forthcoming LZdark matter experiment, use photomultiplier tubes to sense the primary (S1) andsecondary (S2) scintillation signals resulting from particle interactions intheir liquid xenon target. This paper describes a simulation study exploringtwo techniques to lower the energy threshold of LZ to gain sensitivity tolow-mass dark matter and astrophysical neutrinos, which will be applicable toother liquid xenon detectors. The energy threshold is determined by the numberof detected S1 photons; typically, these must be recorded in three or morephotomultiplier channels to avoid dark count coincidences that mimic realsignals. To lower this threshold: a) we take advantage of the doublephotoelectron emission effect, whereby a single vacuum ultraviolet photon has a$\sim20\%$ probability of ejecting two photoelectrons from a photomultipliertube photocathode; and b) we drop the requirement of an S1 signal altogether,and use only the ionization signal, which can be detected more efficiently. Forboth techniques we develop signal and background models for the nominalexposure, and explore accompanying systematic effects, including the dependenceon the free electron lifetime in the liquid xenon. When incorporating doublephotoelectron signals, we predict a factor of $\sim 4$ sensitivity improvementto the dark matter-nucleon scattering cross-section at $2.5$ GeV/c$^2$, and afactor of $\sim1.6$ increase in the solar $^8$B neutrino detection rate.Dropping the S1 requirement may allow sensitivity gains of two orders ofmagnitude in both cases. Finally, we apply these techniques to even lowermasses by taking into account the atomic Migdal effect; this could lower thedark matter particle mass threshold to $80$ MeV/c$^2$.

Attosecond transient absorption spectroscopy (ATAS) is used to observe photoexcited dynamics with outstanding time resolution. The main experimental challenge of this technique is that high-harmonic generation sources show significant instabilities, resulting in sub-par sensitivity when compared to other techniques. This paper proposes edge-pixel referencing as a means to suppress this noise. Two approaches are introduced: the first is deterministic and uses a correlation analysis, while the second relies on singular value decomposition. Each method is demonstrated and quantified on a noisy measurement taken on WS2 and results in a fivefold increase in sensitivity. The combination of the two methods ensures the fidelity of the procedure and can be implemented on live data collection but also on existing datasets. The results show that edge-referencing methods bring the sensitivity of ATAS near the detector noise floor. An implementation of the post-processing code is provided to the reader.

Core-collapse supernovae are among the most magnificent events in theobservable universe. They produce many of the chemical elements necessary forlife to exist and their remnants -- neutron stars and black holes -- areinteresting astrophysical objects in their own right. However, despitemillennia of observations and almost a century of astrophysical study, theexplosion mechanism of core-collapse supernovae is not yet well understood.Hyper-Kamiokande is a next-generation neutrino detector that will be able toobserve the neutrino flux from the next galactic core-collapse supernova inunprecedented detail. We focus on the first 500 ms of the neutrino burst,corresponding to the accretion phase, and use a newly-developed, high-precisionsupernova event generator to simulate Hyper-Kamiokande's response to fivedifferent supernova models. We show that Hyper-Kamiokande will be able todistinguish between these models with high accuracy for a supernova at adistance of up to 100 kpc. Once the next galactic supernova happens, thisability will be a powerful tool for guiding simulations towards a precisereproduction of the explosion mechanism observed in nature.

The ATLAS Fast TracKer (FTK) was designed to provide full tracking for theATLAS high-level trigger by using pattern recognition based on AssociativeMemory (AM) chips and fitting in high-speed field programmable gate arrays. Thetracks found by the FTK are based on inputs from all modules of the pixel andsilicon microstrip trackers. The as-built FTK system and components aredescribed, as is the online software used to control them while running in theATLAS data acquisition system. Also described is the simulation of the FTKhardware and the optimization of the AM pattern banks. An optimization forlong-lived particles with large impact parameter values is included. A test ofthe FTK system with the data playback facility that allowed the FTK to becommissioned during the shutdown between Run 2 and Run 3 of the LHC isreported. The resulting tracks from part of the FTK system covering a limited$\eta$-$\phi$ region of the detector are compared with the output from the FTKsimulation. It is shown that FTK performance is in good agreement with thesimulation.

Dual phase xenon detectors are widely used in experimental searches forgalactic darkmatter particles. The origin of single electron backgroundsfollowing prompt scintillation and proportional scintillation signals in thesedetectors is not fully understood, although there has been progress in recentyears. In this paper, we describe single electron backgrounds in ${}^{83m}Kr$calibration events and their correlation with drift and extraction fields,using the Particle Identification in Xenon at Yale (PIXeY) dual-phase xenontime projection chamber. The single electron background induced by theFowler-Nordheim (FN) effect is measured, and its electric field dependence isquantified. The photoionization of grids and impurities by prompt scintillationand proportional scintillation also contributes to the single electronbackground.