Nuclear Recoil Research Articles

Impact of shell model interactions on nuclear responses to WIMP elastic scattering

Nuclear recoil from scattering with weakly interacting massive particles (WIMPs) is a signature searched for in direct detection of dark matter. The underlying WIMP-nucleon interactions could be spin and/or orbital angular momentum (in)dependent. Evaluation of nuclear recoil rates through these interactions requires accounting for nuclear structure, e.g., through shell model calculations. We evaluate nuclear response functions induced by these interactions for F19, Na23, Si28,29,30, Ar40, Ge70,72,73,74,76, I127, and Xe128,129,130,131,132,134,136 nuclei that are relevant to current direct detection experiments, and estimate their sensitivity to shell model interactions. Shell model calculations are performed with the NuShellX solver. Nuclear response functions from nonrelativistic effective field theory are evaluated and integrated over transferred momentum for quantitative comparisons. We show that although the standard spin-independent response is barely sensitive to the structure of the nuclei, large variations with the shell model interaction are often observed for the other channels. Significant uncertainties may arise from the nuclear components of WIMP-nucleus scattering amplitudes due to nuclear structure theory and modeling. These uncertainties should be accounted for in analyses of direct detection experiments. Published by the American Physical Society 2024

The Landé g factors of highly charged Sn47+ and Bi80+ ions

The wavefunctions and eigenvalues of the ground states of Sn47+, and Bi80+ ions are calculated using the fully relativistic multiconfiguration Dirac-Hartree–Fock (MCDHF) method. Detailed investigation are carried out to study the effects of electron correlation, Breit interaction, quantum electrodynamics (QED), and nuclear recoil. Based on these calculations, the theoretical predictions for the g factors of the ground states of Sn47+ and Bi80+ ions are 1.980429 and 1.934759, respectively. The accuracy of these calculations is expected to be on the order of 10−5.

Atomic line spectra and the conservation laws

By conservation of linear momentum an atom recoils after it de-excites by giving out a photon. The de-excitation energy is shared by the photon and the recoiling atom. There was no mention in textbooks of this recoil energy when discussing atomic line spectra. We illustrate why it is valid to assume that the de-excitation energy is the energy of the emitted photon in line spectra around the visible light region.

Study of low-energy nuclear recoils in liquid argon with the ReD experiment

Liquid Argon (LAr) Time Projection Chambers (TPC) operating in double-phase can detect the nuclear recoils (NR) possibly caused by the elastic scattering of WIMP dark matter particles via light signals from both scintillation and ionization processes. In the scenario of a low-mass WIMP (< 2 GeV/c2), the energy range for the NRs would be below 20 keV, thus making it crucial to characterize the ionization response in LAr TPCs as the lone available detection channel at such low energy. The Recoil Directionality (ReD) project, within the Global Argon Dark Matter Collaboration, aims to measure the ionization yield of a LAr TPC in the recoil energy range of 2–5 keV. The measurement was performed in winter 2023 at the INFN Sezione of Catania and the analysis is ongoing.

Charge amplification in sub-atmospheric CF4:He mixtures for directional dark matter searches

Low pressure gaseous Time Projection Chambers (TPCs) are a viable technology for directional Dark Matter (DM) searches and have the potential for exploring the parameter space below the neutrino fog [1,2]. Gases like CF4 are advantageous because they contain flourine which is predicted to have heightened elastic scattering rates with a possible Weakly Interacting Massive Particle (WIMP) DM candidate [3,4,5]. The low pressure of CF4 must be maintained, ideally lower than 100 Torr, in order to elongate potential Nuclear Recoil (NR) tracks which allows for improved directional sensitivity and NR/Electron Recoil (ER) discrimination [6]. Recent evidence suggests that He can be added to heavier gases, like CF4, without significantly affecting the length of 12C and 19F recoils due to its lower mass. Such addition of He has the advantage of improving sensitivity to lower mass WIMPs [1]. Simulations can not reliably predict operational stability in these low pressure gas mixtures and thus must be demonstrated experimentally. In this paper we investigate how the addition of He to low pressure CF4 affects the gas gain and energy resolution achieved with a single Thick Gaseous Electron Multiplier (ThGEM).

GanESS: detecting coherent elastic neutrino-nucleus scattering with noble gases

The recent detection of the coherent elastic neutrino-nucleus scattering (CEνNS) opens the possibility to use neutrinos to explore physics beyond standard model with small size detectors. However, the CEνNS process generates signals at the few keV level, requiring very sensitive detecting technologies for its detection. The European Spallation Source (ESS) has been identified as an optimal source of low energy neutrinos offering an opportunity for a definitive exploration of all phenomenological applications of CEνNS.GanESS will use a high-pressure noble gas time projection chamber to measure CEνNS at ESS in gaseous Xe, Ar and Kr. Such technique appears extraordinarily promising for detecting the process, although characterization of the response to few-keV nuclear recoils will be necessary. With this goal, we are currently commissioning GaP, a small prototype capable of operating up to 50 bar. GaP will serve to fully evaluate the low energy response of the technique, with a strong focus on measuring the quenching factor for the different noble gases that will later be used at GanESS. An overview of the GanESS project with a focus on the status of GaP and its short-term plans is presented.

Phenomenological study of a gauged Lμ−Lτ model with a scalar leptoquark

A Z′ gauge boson with sub-GeV mass has acquired a significant interest in phenomenology, particularly in view of the muon g−2 anomaly and coherent elastic neutrino-nucleon scattering. The latter is challenged by the nuclear recoil energy of a few tens of keV but has been observed by the COHERENT experiment. To further reconcile the observed excesses in R(D(*)) from semileptonic charmful B decays and in the W boson mass, we investigate a model with a gauged U(1)Lμ−Lτ symmetry and a scalar leptoquark. In contrast to the mechanism that involves kinetic mixing between the gauge bosons of U(1)em and U(1)Lμ−Lτ, we adopt a dynamical symmetry breaking of U(1)Lμ−Lτ by incorporating an additional Higgs doublet. Through mixing with the U(1)Lμ−Lτ-charged Higgs doublet, new Higgs decay channels h→Z1Z1/Z1Z2 occur at percent-level branching ratios, which could be accessible at the LHC. The W-mass anomaly observed by CDF II can be potentially resolved through the enhancement in the oblique parameter T. Due to the flavored gauge symmetry, the introduced scalar leptoquark S13=(3¯,1,2/3) exhibits a unique coupling to the τ lepton, offering an explanation for the excesses observed in R(D(*)). Moreover, τ→μ(Z1→)e−e+ via the resonant light gauge boson decay can reach the sensitivity of Belle II at an integrated luminosity of 50 ab−1. Published by the American Physical Society 2024

First Measurement of Discrimination between Helium and Electron Recoils in Liquid Xenon for Low-Mass Dark Matter Searches.

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading α particles from ^{210}Po with a gold foil situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events.

Search for the Migdal effect in liquid xenon with keV-level nuclear recoils

The Migdal effect predicts that a nuclear recoil interaction can be accompanied by atomic ionization, allowing many dark matter direct detection experiments to gain sensitivity to sub-GeV masses. We report the first direct search for the Migdal effect for M- and L-shell electrons in liquid xenon using nuclear recoils produced by tagged neutron scatters. Despite an observed background rate lower than that of expected signals in the region of interest, we do not observe a signal consistent with predictions. We discuss possible explanations, including inaccurate predictions for either the Migdal rate or the signal response in liquid xenon. We comment on the implications for direct dark matter searches and future Migdal characterization efforts. Published by the American Physical Society 2024

QUEST-DMC superfluid 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He detector for sub-GeV dark matter

The focus of dark matter searches to date has been on Weakly Interacting Massive Particles (WIMPs) in the GeV/c2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c^2$$\\end{document}-TeV/c2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c^2$$\\end{document} mass range. The direct, indirect and collider searches in this mass range have been extensive but ultimately unsuccessful, providing a strong motivation for widening the search outside this range. Here we describe a new concept for a dark matter experiment, employing superfluid 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He as a detector for dark matter that is close to the mass of the proton, of order 1 GeV/c2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c^2$$\\end{document}. The QUEST-DMC detector concept is based on quasiparticle detection in a bolometer cell by a nanomechanical resonator. In this paper we develop the energy measurement methodology and detector response model, simulate candidate dark matter signals and expected background interactions, and calculate the sensitivity of such a detector. We project that such a detector can reach sub-eV nuclear recoil energy threshold, opening up new windows on the parameter space of both spin-dependent and spin-independent interactions of light dark matter candidates.

Detection of astrophysical neutrinos at prospective locations of dark matter detectors

We study the prospects for detection of solar, atmospheric neutrino, and diffuse supernova neutrino background (DSNB) fluxes at future large-scale dark matter detectors through both electron and nuclear recoils. We specifically examine how the detection prospects change for several prospective detector locations [Sanford Underground Research Facility (SURF), SNOlab, Gran Sasso, China Jinping Underground Laboratory (CJPL), and Kamioka] and improve upon the statistical methodologies used in previous studies. Because of its ability to measure lower neutrino energies than other locations, we find that the best prospects for the atmospheric neutrino flux are at the SURF location, while the prospects are weakest at CJPL because it is restricted to higher neutrino energies. On the contrary, the prospects for the DSNB are best at CJPL, due largely to the reduced atmospheric neutrino background at this location. Including full detector resolution and efficiency models, the CNO component of the solar flux is detectable via the electron recoil channel with exposures of ∼103 ton-yr for all locations. These results highlight the benefits for employing two detector locations, one at high and one at low latitude. Published by the American Physical Society 2024

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

The future Ricochet experiment aims to search for new physics in the electroweak sector by measuring the Coherent Elastic Neutrino-Nucleus Scattering process from reactor antineutrinos with high precision down to the sub-100 eV nuclear recoil energy range. While the Ricochet collaboration is currently building the experimental setup at the reactor site, it is also finalizing the cryogenic detector arrays that will be integrated into the cryostat at the Institut Laue Langevin in early 2024. In this paper, we report on recent progress from the Ge cryogenic detector technology, called the CryoCube. More specifically, we present the first demonstration of a 30 eVee (electron equivalent) baseline ionization resolution (RMS) achieved with an early design of the detector assembly and its dedicated High Electron Mobility Transistor (HEMT) based front-end electronics with a total input capacitance of about 40 pF. This represents an order of magnitude improvement over the best ionization resolutions obtained on similar phonon-and-ionization germanium cryogenic detectors from the EDELWEISS and SuperCDMS dark matter experiments, and a factor of three improvement compared to the first fully-cryogenic HEMT-based preamplifier coupled to a CDMS-II germanium detector with a total input capacitance of 250 pF. Additionally, we discuss the implications of these results in the context of the future Ricochet experiment and its expected background mitigation performance.

Pulse shape discrimination for the CONUS experiment in the keV and sub-keV regime

Point-contact p-type high-purity germanium detectors (PPC HPGe) are particularly suited for detection of sub-keV nuclear recoils from coherent elastic scattering of neutrinos or light dark matter particles. While these particles are expected to interact homogeneously in the entire detector volume, specific classes of external background radiation preferably deposit their energy close to the semi-active detector surface, in which diffusion processes dominate that subsequently lead to slower rising pulses compared to the ones from the fully active bulk volume. Dedicated studies of their shape are therefore highly beneficial for the understanding and the rejection of these unwanted events. This article reports about the development of a data-driven pulse shape discrimination (PSD) method for the four 1 kg size PPC HPGe detectors of the Conus experiment in the keV and sub-keV regime down to 210 eVee.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{ee}.$$\\end{document} The impact of the electronic noise at such low energies is carefully examined. It is shown that for an acceptance of 90% of the faster signal-like pulses from the bulk volume, approx. 50% of the surface events can be rejected at the energy threshold and that their contribution is fully suppressed above 800 eVee.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{ee}.$$\\end{document} Applied to the Conus background data, such a PSD rejection cut allows to achieve an overall (15-25)%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(15{-}25)\\%$$\\end{document} reduction of the total background budget. The new method allows to improve the sensitivity of future Conus analyses and to refine the corresponding background model in the sub-keV energy region.

Daily and annual modulation rate of low mass dark matter in silicon detectors

Low-threshold solid-state detectors with single electron excitation sensitivity can probe nuclear recoil energies in the sub-100 eV range, coinciding with the typical threshold displacement energies in the detector material. We investigate the daily and annual modulation of the observable event rate for dark matter mass ranging from 0.2 to 5 GeV/c2 in a silicon detector, considering the energy threshold and the direction of the nuclear recoil. The data for the energy threshold is obtained from a molecular dynamics simulation. It is shown that the directional dependence of the threshold energy and the motion of the laboratory result in the modulation of the interaction event rate. We demonstrate silicon’s average annual interaction rate is more considerable than germanium for low-mass dark matter. However, their event rates take a similar trend in large dark matter masses. Thus, silicon can be a reliable target to discriminate low-mass dark matter from backgrounds. We also find 8 h and 12h periodicities in the time series of event rates for silicon detectors due to the 45-degree symmetry in the silicon crystal structure.

Constraints on directionality effect of nuclear recoils in a liquid argon time projection chamber

The direct search for dark matter in the form of weakly interacting massive particles (WIMP) is performed by detecting nuclear recoils produced in a target material from the WIMP elastic scattering. The experimental identification of the direction of the WIMP-induced nuclear recoils is a crucial asset in this field, as it enables unmistakable modulation signatures for dark matter. The Recoil Directionality (ReD) experiment was designed to probe for such directional sensitivity in argon dual-phase time projection chambers (TPC), that are widely considered for current and future direct dark matter searches. The TPC of ReD was irradiated with neutrons at the INFN Laboratori Nazionali del Sud. Data were taken with nuclear recoils of known directions and kinetic energy of 72 keV, which is within the range of interest for WIMP-induced signals in argon. The direction-dependent liquid argon charge recombination model by Cataudella et al. was adopted and a likelihood statistical analysis was performed, which gave no indications of significant dependence of the detector response to the recoil direction. The aspect ratio R of the initial ionization cloud is R<1.072\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R < 1.072$$\\end{document} with 90 % confidence level.

Formula omitted][formula omitted] MCDHF/RCI calculations of mass- and field shifts isotopes parameters of the [formula omitted][formula omitted][formula omitted] and [formula omitted][formula omitted][formula omitted] transitions in He-like ions for the sequence 2 [formula omitted][formula omitted][formula omitted] 83

Based on the multiconfiguration Dirac–Hartree–Fock method, the field shift and mass shift parameters of the 1s21S0−1s2p1P1o and 1s21S0−1s2p3P0,1,2o transitions in He-like ions for the sequence 2 ≤Z≤ 83 are calculated with high precision. The total value of the isotope shift is determined by the sum of the mass- and field-shifts. With the inclusion of the Breit interaction and the leading QED corrections, we find that the mass shift parameters of these transitions do not change monotonously along the isoelectronic sequence in the high-Z range due to the relativistic nuclear recoil effects. In addition, the field shifts and mass shifts of these four transitions are estimated and compared along the isoelectronic sequence.

Precise measurements of electron &lt;i&gt;g&lt;/i&gt; factors in bound states of few-electron ions

&lt;sec&gt;The electron &lt;i&gt;g&lt;/i&gt; factor is an important fundamental structural parameter in atomic physics, as it reveals various mechanisms of interactions between electrons and external fields. Precise measurements of &lt;i&gt;g&lt;/i&gt; factors of bound electrons in simple atomic and molecular systems provide an effective method for investigating the bound-state quantum electrodynamics (QED) theory. Especially in highly-charged heavy ions (HCIs), the strong electromagnetic interactions between the nuclei and inner-shell electrons provide unique opportunities to test QED under extremely strong fields. Accurate measurements of the &lt;i&gt;g&lt;/i&gt; factors of the bound-state electrons are also important for determining nuclear effects, nuclear parameters and fundamental constants. The research on &lt;i&gt;g&lt;/i&gt; factors of the bound-state electrons has become a frontier topic in fundamental physics. A Penning trap, which uses steady-state electromagnetic fields to confine charged particles, is utilized to precisely measure the &lt;i&gt;g&lt;/i&gt; factor. This paper presents a comprehensive review of the experiments on &lt;i&gt;g&lt;/i&gt; factors for few-electron simple systems in Penning traps, including experimental principles, experimental setups, measurement methods, and a summary of important research findings. The physical concept of the electron &lt;i&gt;g&lt;/i&gt; factor and its historical research background are introduced. The electron &lt;i&gt;g&lt;/i&gt; factor is considered as an effective probe to study higher-order QED effects. Through high-precision measurements of the free electron g factor, discrepancies between the fine-structure constants and other experimental results in atomic physics are identified. Notably, the &lt;i&gt;g&lt;/i&gt; factor of the 1s electron in HCIs deviates significantly from the value for free electrons as the atomic number increases. Experimental principles, including the principle of the Penning trap and the principle of measuring the bound-state electron &lt;i&gt;g&lt;/i&gt; factors are discussed. A double-trap experiment setup and related precision measurement techniques are also introduced.&lt;/sec&gt;&lt;sec&gt;This paper reviews several milestone experiments including (1) the stringent test of bound-state QED by precise measurement of bound-state electron &lt;i&gt;g&lt;/i&gt; factor of a &lt;sup&gt;118&lt;/sup&gt;Sn&lt;sup&gt;49+&lt;/sup&gt; ion, (2) measurement of the &lt;i&gt;g&lt;/i&gt; factors of lithium-like and boron-like ions and their applications, and (3) measurement of the &lt;i&gt;g&lt;/i&gt;-factor isotope shift by using an advanced two-ion balance technique in the Penning trap, providing an insight into the QED effects in nuclear recoil. Finally, this paper summarizes the challenges currently faced in measuring the &lt;i&gt;g&lt;/i&gt; factors of bound-state electrons in few-electron ion systems and provides the prospects for the future developments of this field.&lt;/sec&gt;

Neutrino constraints on inelastic dark matter captured in the Sun

The flux of neutrinos from annihilation of gravitationally captured dark matter in the Sun has significant constraints from direct-detection experiments. However, these constraints are relaxed for inelastic dark matter as inelastic dark matter interactions generate less energetic nuclear recoils compared to elastic dark matter interactions. In this paper, we explore the possibility for large volume underground neutrino experiments to detect the neutrino flux from captured inelastic dark matter in the Sun. The neutrino spectrum has two components: a mono-energetic “spike” from pion and kaon decays at rest and a broad-spectrum “shoulder” from prompt primary meson decays. We focus on detecting the shoulder neutrinos from annihilation of hadrophilic inelastic dark matter with masses in the range 4–100 GeV and the mass splittings in up to 300 keV. We determine the event selection criterion for DUNE to identify GeV-scale muon neutrinos and anti-neutrinos originating from hadrophilic dark matter annihilation in the Sun, and forecast the sensitivity from contained events. We also map the current bounds from Super-Kamiokande and IceCube on elastic dark matter, as well as the projected limits from Hyper-Kamiokande, to the parameter space of inelastic dark matter. We find that there is a region of parameter space that these neutrino experiments are more sensitive to than the direct-detection experiments. For dark matter annihilation to heavy-quarks, the projected sensitivity of DUNE is weaker than current (future) Super (Hyper) Kamiokande experiments. However, for the light-quark channel, only the spike is observable and DUNE will be the most sensitive experiment.

Временные изменения 234U/238U, 234U и концентраций элементов в минеральной воде из карбонатов в Олхинской скважине, юг Сибирской платформы: Условия проявления эффекта Чердынцева-Чалова

Based on monitoring results of 2013–2022, the time-varying ratios of components in mineral water from carbonates containing gypsum and anhydrite are determined, when the activities ratios 234U/238U (AR4/8) vary from 11.82 to 15.71. With increasing this indicator, the activity of 234U (A4) also increases in mineral water, with maxima and minima occurring in 2017–2022. Variations in A4 are consistent with changes in total mineralization, the contents of all macrocomponents (Ca, Na, Mg, Si, K, S, and Cl), and some microcomponents (U, Li, B, V, Mn, Br, Y, Rb, and Sr), with an inverse trends of the other microcomponents (Cu, Sc, Nb, Mo, Ba, Ti, Zr, and Cr). It is inferred that U isotopes vary in mineral water due to changes in the chemical dissolution of carbonates. Mineral water is enriched in 234U recoil atoms like other dissolving components, whereas OA4/8 is complicated by the dependence of U dissolution on oxidation-reduction potential (ORP).

Rare event searches with cryogenic detectors

Cryogenic detectors can detect the smallest energy depositions via the scattering of the incoming particle with the detector material. The deposited energy leads to minimal temperature rises of a few μ K , read out via transition edge sensors and SQUIDs. Using scintillating crystals as detector material offers the possibility of discriminating between nuclear recoils from dark matter scattering and electromagnetic background events. The CRESST experiment pioneered this technology and is still among the most sensitive experiments searching for sub-GeV dark matter particles. The technology is now also used by other experiments for dark matter searches (COSINUS) and for measuring coherent elastic neutrino-nucleus scattering (NUCLEUS). We discuss cryogenic detectors’ detection principle and their application. We present the latest dark matter results from CRESST, a new type of background, and the status of the COSINUS and NUCLEUS experiments. This article is part of the theme issue ‘The particle-gravity frontier’.