Publications
471 results found
Wass PJ, Sumner TJ, Araújo HM, et al., 2023, Simulating the charging of isolated free-falling masses from TeV to eV energies: Detailed comparison with LISA Pathfinder results, Physical Review D, Vol: 107, ISSN: 2470-0010
A model is presented that explains the charging rate of the LISA Pathfinder test masses by the interplanetary cosmic ray environment. The model incorporates particle-tracking from TeV to eV energies using a combination of geant4 and a custom low-energy particle generation and tracking code. The electrostatic environment of the test mass is simulated allowing for a comparison of the test-mass charging-rate dependence on local electric fields with observations made in orbit. The model is able to reproduce the observed charging behavior with good accuracy using gold surface properties compatible with literature values. The results of the model confirm that a significant fraction of the net charging current is caused by a population of low-energy (∼eV) electrons produced by electron- and ion-induced kinetic emission from the test mass and surrounding metal surfaces. Assuming a gold work function of 4.2 eV, the unbalanced flow of these electrons to and from the unbiased test mass contributes ∼10% of the overall test mass charging rate. Their contribution to the charging-current shot noise is disproportionately higher, and it adds ∼40% to the overall predicted noise. However, even with this increased noise contribution, the overall charging-current noise is still only 40% of that measured in-orbit, and this remains an unsolved issue.
Apple SM, Kenyon SP, Barke S, et al., 2022, Measurement of stray electric fields in a capacitive inertial sensor using contactless test-mass charge modulation, Physical Review D, Vol: 106, ISSN: 2470-0010
We present a new technique for measuring the stray electric field in precision space inertial sensors by modulating the electric charge of a free-falling test mass and measuring the resulting coherent Coulomb force. The free charge of the test mass is controlled by ultraviolet photoemission using a pulsed light source synchronized with an oscillating potential capacitively induced on the test mass. We can modulate the test mass charge sinusoidally at an arbitrarily chosen frequency by varying the phase of the UV light pulses relative to the induced test mass potential at the appropriate rate. This technique allows us to optimize the precision of the measurement by choosing a modulation frequency that is within the most sensitive band of the sensor. We present an experimental validation of this approach using an inertial sensor integrated with a torsion pendulum, measuring the equivalent stray potential of the sensor with milliVolt precision in 104 s. We discuss the applicability of this technique for the upcoming Laser Interferometer Space Antenna (LISA) gravitational-wave observatory.
Akerib DS, Alsum S, Araujo HM, et al., 2022, Fast and flexible analysis of direct dark matter search data with machine learning, PHYSICAL REVIEW D, Vol: 106, ISSN: 2470-0010
Touboul P, Metris G, Rodrigues M, et al., 2022, Result of the MICROSCOPE weak equivalence principle test, CLASSICAL AND QUANTUM GRAVITY, Vol: 39, ISSN: 0264-9381
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- Citations: 8
Armano M, Audley H, Baird J, et al., 2022, Sensor noise in LISA Pathfinder: An extensive in-flight review of the angular and longitudinal interferometric measurement system, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 106, Pages: 1-34, ISSN: 1550-2368
In a previous article [1], we have reported on the first subpicometer interferometer flown in space as part of ESA’s LISA Pathfinder mission, and have shown the residual sensor noise to be on the level of 32.0+2.4−1.7 fm/√Hz. This review provides a deeper and more complete overview of the full system and its interferometric mission performance under varying operational conditions, allowing a much more detailed view on the noise model. We also include the optical measurements of rotations through differential wave front sensing (DWS), which reached a sensitivity of as good as 100 prad/√Hz. We present more evidence for the long-term stability of the interferometric performance and components. This proves a solid foundation for future interferometry in space such as the LISA mission.
Touboul P, Métris G, Rodrigues M, et al., 2022, MICROSCOPE mission: final results of the test of the equivalence principle, Physical Review Letters, Vol: 129, ISSN: 0031-9007
The MICROSCOPE mission was designed to test the weak equivalence principle (WEP), stating the equality between the inertial and the gravitational masses, with a precision of 10^{-15} in terms of the Eötvös ratio η. Its experimental test consisted of comparing the accelerations undergone by two collocated test masses of different compositions as they orbited the Earth, by measuring the electrostatic forces required to keep them in equilibrium. This was done with ultrasensitive differential electrostatic accelerometers onboard a drag-free satellite. The mission lasted two and a half years, cumulating five months worth of science free-fall data, two-thirds with a pair of test masses of different compositions-titanium and platinum alloys-and the last third with a reference pair of test masses of the same composition-platinum. We summarize the data analysis, with an emphasis on the characterization of the systematic uncertainties due to thermal instabilities and on the correction of short-lived events which could mimic a WEP violation signal. We found no violation of the WEP, with the Eötvös parameter of the titanium and platinum pair constrained to η(Ti,Pt)=[-1.5±2.3(stat)±1.5(syst)]×10^{-15} at 1σ in statistical errors.
Armano M, Audley H, Baird J, et al., 2022, Transient acceleration events in LISA Pathfinder data: Properties and possible physical origin, Physical Review D, Vol: 106, ISSN: 2470-0010
We present an in depth analysis of the transient events, or glitches, detected at a rate of about one per day in the differential acceleration data of LISA Pathfinder. We show that these glitches fall in two rather distinct categories: fast transients in the interferometric motion readout on one side, and true force transient events on the other. The former are fast and rare in ordinary conditions. The second may last from seconds to hours and constitute the majority of the glitches. We present an analysis of the physical and statistical properties of both categories, including a cross-analysis with other time series like magnetic fields, temperature, and other dynamical variables. Based on these analyses we discuss the possible sources of the force glitches and identify the most likely, among which the outgassing environment surrounding the test-masses stands out. We discuss the impact of these findings on the LISA design and operation, and some risk mitigation measures, including experimental studies that may be conducted on the ground, aimed at clarifying some of the questions left open by our analysis.
Aalbers J, Akerib DS, Al Musalhi AK, et al., 2022, Cosmogenic production of 37Ar in the context of the LUX-ZEPLIN experiment, Physical Review D, Vol: 105, Pages: 1-8, ISSN: 2470-0010
We estimate the amount of 37Ar produced in natural xenon via cosmic-ray-induced spallation, an inevitable consequence of the transportation and storage of xenon on the Earth’s surface. We then calculate the resulting 37Ar concentration in a 10-tonne payload (similar to that of the LUX-ZEPLIN experiment) assuming a representative schedule of xenon purification, storage, and delivery to the underground facility. Using the spallation model by Silberberg and Tsao, the sea-level production rate of 37Ar in natural xenon is estimated to be 0.024 atoms/kg/day. Assuming the xenon is successively purified to remove radioactive contaminants in 1-tonne batches at a rate of 1 tonne/month, the average 37Ar activity after 10 tons are purified and transported underground is 0.058−0.090 μBq/kg, depending on the degree of argon removal during above-ground purification. Such cosmogenic 37Ar will appear as a noticeable background in the early science data, while decaying with a 35-day half-life. This newly noticed production mechanism of 37Ar should be considered when planning for future liquid-xenon-based experiments.
Akerib DS, Akerlof CW, Akimov DY, et al., 2022, The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs (vol 80, 1044, 2020), EUROPEAN PHYSICAL JOURNAL C, Vol: 82, ISSN: 1434-6044
Akerib DS, Al Musalhi AK, Alsum SK, et al., 2021, Projected sensitivities of the LUX-ZEPLIN experiment to new physics via low-energy electron recoils, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-16, ISSN: 1550-2368
LUX-ZEPLIN is a dark matter detector expected to obtain world-leading sensitivity to weakly-interacting massive particles interacting via nuclear recoils with a ∼7-tonne xenon target mass. This paper presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment, and 2) an effective neutrino millicharge, both for pp-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axionlike particles forming the Galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6 t 1000 d exposure and low expected rate of electron-recoil backgrounds in the <100 keV energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout.
Akerib DS, Al Musalhi AK, Alsum SK, et al., 2021, Projected sensitivity of the LUX-ZEPLIN experiment to the two-neutrino and neutrinoless double β decays of Xe134, Physical Review C, Vol: 104, Pages: 1-11, ISSN: 2469-9985
The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrino and neutrinoless double β decay of 134Xe is presented. LZ is a 10-tonne xenon time-projection chamber optimized for the detection of dark matter particles and is expected to start operating in 2021 at Sanford Underground Research Facility, USA. Its large mass of natural xenon provides an exceptional opportunity to search for the double β decay of 134Xe, for which xenon detectors enriched in 136Xe are less effective. For the two-neutrino decay mode, LZ is predicted to exclude values of the half-life up to 1.7×1024 years at 90% confidence level (CL) and has a three-sigma observation potential of 8.7×1023 years, approaching the predictions of nuclear models. For the neutrinoless decay mode LZ, is projected to exclude values of the half-life up to 7.3×1024 years at 90% CL.
Akerib DS, Alsum S, Araujo HM, et al., 2021, Constraints on effective field theory couplings using 311.2 days of LUX data, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-19, ISSN: 1550-2368
We report here the results of a nonrelativistic effective field theory (EFT) WIMP search analysis using LUX data. We build upon previous LUX analyses by extending the search window to include nuclear recoil energies up to ∼180 keVnr, requiring a reassessment of data quality criteria and background models. In order to use an unbinned profile likelihood statistical framework, the development of new analysis techniques to account for higher-energy backgrounds was required. With a 3.14×104 kg⋅day exposure using data collected between 2014 and 2016, we find our data is compatible with the background expectation and set 90% C.L. exclusion limits on nonrelativistic EFT WIMP-nucleon couplings, improving upon previous LUX results and providing constraints on a EFT WIMP interactions using the {neutron,proton} interaction basis. Additionally, we report exclusion limits on inelastic EFT WIMP-isoscalar recoils that are competitive and world-leading for several interaction operators.
Battelier B, Berge J, Bertoldi A, et al., 2021, Exploring the foundations of the physical universe with space tests of the equivalence principle, EXPERIMENTAL ASTRONOMY, Vol: 51, Pages: 1695-1736, ISSN: 0922-6435
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- Citations: 10
Akerib DS, Alsum S, Araujo HM, et al., 2021, Improving sensitivity to low-mass dark matter in LUX using a novel electrode background mitigation technique, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-15, ISSN: 1550-2368
This paper presents a novel technique for mitigating electrode backgrounds that limit the sensitivity of searches for low-mass dark matter (DM) using xenon time projection chambers. In the Large Underground Xenon (LUX) detector, signatures of low-mass DM interactions would be very low-energy (∼keV) scatters in the active target that ionize only a few xenon atoms and seldom produce detectable scintillation signals. In this regime, extra precaution is required to reject a complex set of low-energy electron backgrounds that have long been observed in this class of detector. Noticing backgrounds from the wire grid electrodes near the top and bottom of the active target are particularly pernicious, we develop a machine learning technique based on ionization pulse shape to identify and reject these events. We demonstrate the technique can improve Poisson limits on low-mass DM interactions by a factor of 1.7–3 with improvement depending heavily on the size of ionization signals. We use the technique on events in an effective 5 tonne·day exposure from LUX’s 2013 science operation to place strong limits on low-mass DM particles with masses in the range mχ∈0.15–10 GeV. This machine learning technique is expected to be useful for near-future experiments, such as LUX-ZEPLIN and XENONnT, which hope to perform low-mass DM searches with the stringent background control necessary to make a discovery.
Berge J, Baudis L, Brax P, et al., 2021, The local dark sector Probing gravitation's low-acceleration frontier and dark matter in the Solar System neighborhood, EXPERIMENTAL ASTRONOMY, Vol: 51, Pages: 1737-1766, ISSN: 0922-6435
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- Citations: 4
Armano M, Audley H, Baird J, et al., 2021, Sensor Noise in LISA Pathfinder: In-Flight Performance of the Optical Test Mass Readout, PHYSICAL REVIEW LETTERS, Vol: 126, ISSN: 0031-9007
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- Citations: 7
Kenyon SP, Letson B, Clark M, et al., 2021, A Charge Management System for Gravitational Reference Sensors - Design and Instrument Testing, ISSN: 1095-323X
Gravitational reference sensors (GRSs) are imperative to Earth geodesy missions and gravitational wave observations in space. A typical GRS consists of a test mass (TM) surrounded by a capacitive electrode housing to perform sensitive relative position measurements and to apply small forces to the TM. This paper specifically discusses advancements in the charge management system (CMS) for the GRS being used in the LISA mission. Space radiation accumulating charge on the TM will eventually generate unwanted forces on the TM due to stray electric fields in the spacecraft. Thus, the TM charge must be kept close to a zero potential. The TM charge will be controlled in a contact-free manner by shining UV light and exploiting the photoelectric effect. A major design improvement for future missions is using UV LEDs, which can be pulsed. This facilitates more advanced charge control schemes for a continuous science measurement. The UV LEDs are housed in an aluminum block and controlled with supporting electronics via the charge management device (CMD). The CMD needs to be integrated with the spacecraft computer and needs to contain redundancy to survive the 10+ year LISA mission. The CMD is a NASA deliverable for the ESA mission and has begun the process of technology advancement and testing. The unit has custom PCBs designed to supply both continuous and pulsed current to the UV LEDs, readback telemetry data, manage CMD power needs, and synchronize with the spacecraft computer to communicate with spacecraft operators. The system achieved TRL 4 at the end of 2018 and surpassed all requirements for performance, redundancy, and lifetime. The system is capable of generating stable and robust square UV light pulses, has the capacity to drive the UV LEDs at their full dynamic range, and meets requirements on power, pulse properties, stability, and commanding speed. This technology features novel discharge methods and improvements on past missions in terms of noise level and cont
Bortoluzzi D, Vignotto D, Zambotti A, et al., 2021, In-flight testing of the injection of the LISA Pathfinder test mass into a geodesic, ADVANCES IN SPACE RESEARCH, Vol: 67, Pages: 504-520, ISSN: 0273-1177
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- Citations: 3
Akerib DS, Alsum S, Araujo HM, et al., 2020, Discrimination of electronic recoils from nuclear recoils in two-phase xenon time projection chambers, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-27, ISSN: 1550-2368
We present a comprehensive analysis of electronic recoil vs nuclear recoil discrimination in liquid/gas xenon time projection chambers, using calibration data from the 2013 and 2014–2016 runs of the Large Underground Xenon experiment. We observe strong charge-to-light discrimination enhancement with increased event energy. For events with S1=120 detected photons, i.e., equivalent to a nuclear recoil energy of ∼100 keV, we observe an electronic recoil background acceptance of <10−5 at a nuclear recoil signal acceptance of 50%. We also observe modest electric field dependence of the discrimination power, which peaks at a field of around 300 V/cm over the range of fields explored in this study (50–500 V/cm). In the weakly interacting massive particle search region of S1=1−80 phd, the minimum electronic recoil leakage we observe is (7.3±0.6)×10−4, which is obtained for a drift field of 240–290 V/cm. Pulse shape discrimination is utilized to improve our results, and we find that, at low energies and low fields, there is an additional reduction in background leakage by a factor of up to 3. We develop an empirical model for recombination fluctuations which, when used alongside the Noble Element Scintillation Technique simulation package, correctly reproduces the skewness of the electronic recoil data. We use this updated simulation to study the width of the electronic recoil band, finding that its dominant contribution comes from electron-ion recombination fluctuations, followed in magnitude of contribution by fluctuations in the S1 signal, fluctuations in the S2 signal, and fluctuations in the total number of quanta produced for a given energy deposition.
Yang F, Bai Y, Hong W, et al., 2020, A charge control method for space-mission inertial sensor using differential UV LED emission, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 91, ISSN: 0034-6748
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- Citations: 5
Akerib DS, Akerlof CW, Akimov DY, et al., 2020, The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs, European Physical Journal C: Particles and Fields, Vol: 80, Pages: 1-52, ISSN: 1124-1861
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4×10−48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Investigation of background electron emission in the LUX detector, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-17, ISSN: 1550-2368
Dual-phase xenon detectors, as currently used in direct detection dark matter experiments, have observed elevated rates of background electron events in the low energy region. While this background negatively impacts detector performance in various ways, its origins have only been partially studied. In this paper we report a systematic investigation of the electron pathologies observed in the LUX dark matter experiment. We characterize different electron populations based on their emission intensities and their correlations with preceding energy depositions in the detector. By studying the background under different experimental conditions, we identified the leading emission mechanisms, including photoionization and the photoelectric effect induced by the xenon luminescence, delayed emission of electrons trapped under the liquid surface, capture and release of drifting electrons by impurities, and grid electron emission. We discuss how these backgrounds can be mitigated in LUX and future xenon-based dark matter experiments.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Search for two neutrino double electron capture of(124)Xe and(126)Xe in the full exposure of the LUX detector, Journal of Physics G: Nuclear and Particle Physics, Vol: 47, Pages: 1-13, ISSN: 0954-3899
Two-neutrino double electron capture is a process allowed in the standard model of particle physics. This rare decay has been observed in 78Kr, 130Ba and more recently in 124Xe. In this publication we report on the search for this process in 124Xe and 126Xe using the full exposure of the large underground xenon (LUX) experiment, in a total of 27769.5 kg-days. No evidence of a signal was observed, allowing us to set 90% C.L. lower limits for the half-lives of these decays of 2.0 × 1021 years for 124Xe and 1.9 × 1021 years for 126Xe.
Akerib DS, Akerlof CW, Alqahtani A, et al., 2020, Projected sensitivity of the LUX-ZEPLIN experiment to the 0νββ decay of 136Xe, Physical Review C, Vol: 102, Pages: 014602 – 1-014602 – 13, ISSN: 2469-9985
The LUX-ZEPLIN (LZ) experiment will enable a neutrinoless double β decay search in parallel to the main science goal of discovering dark matter particle interactions. We report the expected LZ sensitivity to 136Xe neutrinoless double β decay, taking advantage of the significant (>600 kg) 136Xe mass contained within the active volume of LZ without isotopic enrichment. After 1000 live-days, the median exclusion sensitivity to the half-life of 136Xe is projected to be 1.06×1026 years (90% confidence level), similar to existing constraints. We also report the expected sensitivity of a possible subsequent dedicated exposure using 90% enrichment with 136Xe at 1.06×1027 years.
Collaboration TLUX-ZEPLIN, Akerib DS, Akerlof CW, et al., 2020, Simulations of Events for the LUX-ZEPLIN (LZ) Dark Matter Experiment, Astroparticle Physics, ISSN: 0927-6505
The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to theWIMP-nucleon spin-independent cross-section down to (1-2) $\times$ $10^{-12}$pb at a WIMP mass of 40 GeV/$c^2$. This paper describes the simulationsframework that, along with radioactivity measurements, was used to support thisprojection, and also to provide mock data for validating reconstruction andanalysis software. Of particular note are the event generators, which allow usto model the background radiation, and the detector response physics used inthe production of raw signals, which can be converted into digitized waveformssimilar to data from the operational detector. Inclusion of the detectorresponse allows us to process simulated data using the same analysis routinesas developed to process the experimental data.
Yang F, Bai Y, Hong W, et al., 2020, Investigation of charge management using UV LED device with a torsion pendulum for TianQin, CLASSICAL AND QUANTUM GRAVITY, Vol: 37, ISSN: 0264-9381
Armano M, Audley H, Baird J, et al., 2020, Spacecraft and interplanetary contributions to the magnetic environment on-board LISA Pathfinder, Monthly Notices of the Royal Astronomical Society, Vol: 494, Pages: 3014-3027, ISSN: 0035-8711
LISA Pathfinder (LPF) has been a space-based mission designed to test new technologies that will be required for a gravitational wave observatory in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime (mHz and below), the measurement band of interest for a space-based observatory. The magnetic field can couple to the magnetic susceptibility and remanent magnetic moment from the test masses and disturb them from their geodesic movement. LPF carried on-board a dedicated magnetic measurement subsystem with noise levels of 10 nT Hz−1/2 from 1 Hz down to 1 mHz. In this paper we report on the magnetic measurements throughout LPF operations. We characterize the magnetic environment within the spacecraft, study the time evolution of the magnetic field and its stability down to 20 μHz, where we measure values around 200 nT Hz−1/2, and identify two different frequency regimes, one related to the interplanetary magnetic field and the other to the magnetic field originating inside the spacecraft. Finally, we characterize the non-stationary component of the fluctuations of the magnetic field below the mHz and relate them to the dynamics of the solar wind.
Armano M, Audley H, Baird J, et al., 2020, Analysis of the accuracy of actuation electronics in the laser interferometer space antenna pathfinder, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 91, ISSN: 0034-6748
Akerib DS, Alsum S, Araújo HM, et al., 2020, An effective field theory analysis of the first LUX dark matter search, Publisher: arXiv
The Large Underground Xenon (LUX) dark matter search was a 250-kg active massdual-phase time projection chamber that operated by detecting light andionization signals from particles incident on a xenon target. In December 2015,LUX reported a minimum 90% upper C.L. of 6e-46 cm^2 on the spin-independentWIMP-nucleon elastic scattering cross section based on a 1.4e4 kg*day exposurein its first science run. Tension between experiments and the absence of adefinitive positive detection suggest it would be prudent to search for WIMPsoutside the standard spin-independent/spin-dependent paradigm. Recenttheoretical work has identified a complete basis of 14 independent effectivefield theory (EFT) operators to describe WIMP-nucleon interactions. In additionto spin-independent and spin-dependent nuclear responses, these operators canproduce novel responses such as angular-momentum-dependent and spin-orbitcouplings. Here we report on a search for all 14 of these EFT couplings withdata from LUX's first science run. Limits are placed on each coupling as afunction of WIMP mass.
El-Neaj YA, Alpigiani C, Amairi-Pyka S, et al., 2020, AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space, EPJ QUANTUM TECHNOLOGY, Vol: 7, ISSN: 2662-4400
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