Aromatic organic compounds, because of their small excitation energies ~ O(few eV) and scintillating properties, are promising targets for detecting dark matter of mass ~ O(few MeV). Additionally, their planar molecular structures lead to large anisotropies in the electronic wavefunctions, yielding a significant daily modulation in the event rate expected to be observed in crystals of these molecules. We characterize the daily modulation rate of dark matter interacting with an anisotropic scintillating organic crystal such as trans-stilbene, and show that daily modulation is an ~ O(1) fraction of the total rate for small DM masses and comparable to, or larger than, the ~ 10% annual modulation fraction at large DM masses. As we discuss in detail, this modulation provides significant leverage for detecting or excluding dark matter scattering, even in the presence of a non-negligible background rate. Assuming a non-modulating background rate of 1/min/kg that scales with total exposure, we find that a 100 kg yr experiment is sensitive to the cross section corresponding to the correct relic density for dark matter masses between 1.3-14 MeV (1.5-1000 MeV) if dark matter interacts via a heavy (light) mediator. This modulation can be understood using an effective velocity scale v* = Delta E/q*, where Delta E is the electronic transition energy and q* is a characteristic momentum scale of the electronic orbitals. We also characterize promising future directions for development of scintillating organic crystals as dark matter detectors.
Channeling of recoil ions in various crystals strongly depends on their direction. This, along with the WIMP wind due to the rotation of the galactic disc generates {\it daily} modulations of the channeling. Since channeling affect the characteristics of the WIMP induced recoil events these modulations may be observed in single crystal detectors and serve as a WIMP signature. We suggest in particular searching for such modulations in the DAMA scintillation data.
We study the effect of gravitational focusing of the earth on dark matter. We find that the effect can produce a detectable diurnal modulation in the dark matter signal for part of the parameter space which for high dark matter masses is larger than the diurnal modulation induced by the fluctuations in the flux of dark matter particles due to the rotation of the earth around its own axis. The two sources of diurnal modulation have different phases and can be distinguished from each other. We demonstrate that the diurnal modulation can potentially check the self-consistency of experiments that …
We point out that for a range of parameters, the flux of DM may be stopped significantly by its interactions with the Earth. This can significantly degrade the sensitivity of direct detection experiments to DM candidates with large interactions with terrestrial nuclei. We find that a significant region of parameter space remains unconstrained for DM $\lesssim $ a few GeV. For DM candidates with moderate levels of stopping power, the flux of DM may be blocked from below but not above a detector thereby producing a novel daily modulation. This can be explored by low threshold detectors placed on…
Statistics of Daily Modulation in Dark Matter Direct Detection Experiments
The Pennsylvania State University（宾夕法尼亚州立大学）；Princeton University（普林斯顿大学）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；University of Toronto（多伦多大学）；University of Oregon（俄勒冈大学）
Low threshold detectors with single-electron excitation sensitivity to nuclear recoil events in solid-state detectors are also sensitive to the crystalline structure of the target and, therefore, to the recoil direction via the anisotropic energy threshold for defect creation in the detector material. We investigate this effect and the resulting daily and annual modulation of the observable event rate for dark matter mass range from 0.2 to 5 GeV/c$^{2}$ in a silicon detector. We show that the directional dependence of the threshold energy and the motion of the laboratory result in modulation o…
Single phonon excitations are sensitive probes of light dark matter in the keV-GeV mass window. For anisotropic target materials, the signal depends on the direction of the incoming dark matter wind and exhibits a daily modulation. We discuss in detail the various sources of anisotropy, and carry out a comparative study of 26 crystal targets, focused on sub-MeV dark matter benchmarks. We compute the modulation reach for the most promising targets, corresponding to the cross section where the daily modulation can be observed for a given exposure, which allows us to combine the strength of DM-ph…
Dirac materials, because of their small ${\cal O}(\mbox{meV})$ band gap, are a promising target for dark photon-mediated scattering and absorption of light dark matter. In this paper, we characterize the daily modulation rate of dark matter interacting with a Dirac material due to anisotropies in their crystal structure. We show that daily modulation is an ${\cal O}(1)$ fraction of the total rate for dark matter scattering in the Dirac material ZrTe$_5$. When present, the modulation is dominated by the orientation of the material's dielectric tensor with respect to the dark matter wind, and is…
SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Institut für Hochenergiephysik der Österreichischen Akademie der Wissenschaften（奥地利科学院高能物理研究所）；Technische Universität Wien（维也纳工业大学）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）；Tel-Aviv University（特拉维夫大学）；University of Oregon（俄勒冈大学）；Stony Brook University（石溪大学）
We study the new mechanism of the axion production suggested recently in [1,2]. This mechanism is based on the so-called Axion Quark Nugget (AQN) dark matter model, which was originally invented to explain the similarity of the dark and visible cosmological matter densities. We perform numerical simulations to evaluate the axion flux on the Earth's surface. We examine annual and daily modulations, which have been studied previously and are known to occur for any type of dark matter. We also discuss a novel type of short time enhancements which are unique to the AQN model: the statistical fluct…
Dark Matter Weather: Probing Sub-GeV Interactions with Earth-Shielding Modulation
University of Liverpool（利物浦大学）；SLAC National Accelerator Laboratory, Stanford University（斯坦福大学 SLAC 国家加速器实验室）；Kavli Institute for Particle Astrophysics and Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）
The signals in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in direct detection signals, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail for both WIMP and WISP dark matter searches, examining both …
The count rate at dark-matter direct-detection experiments should modulate annually due to the motion of the Earth around the Sun. We show that higher-frequency modulations, including daily modulation, are also present and in some cases are nearly as strong as the annual modulation. These higher-order modes are particularly relevant if (i) the dark matter is light, O(10) GeV, (ii) the scattering is inelastic, or (iii) velocity substructure is present; for these cases, the higher-frequency modes are potentially observable at current and ton-scale detectors. We derive simple expressions for the …
Because of their tiny band gaps Dirac materials promise to improve the sensitivity for dark matter particles in the sub-MeV mass range by many orders of magnitude. Here we study several candidate materials and calculate the expected rates for dark matter scattering via light and heavy dark photons as well as for dark photon absorption. A particular emphasis is placed on how to distinguish a dark matter signal from background by searching for the characteristic daily modulation of the signal, which arises from the directional sensitivity of anisotropic materials in combination with the rotation…
We investigate the velocity and recoil momentum dependence of dark matter interactions with ordinary matter. In particular we focus on the single-electron resolution semiconductor detectors, which allow experimental assessment of sub-GeV dark matter masses. We find that, within a specific mass range depending on the detector material, the dark matter interactions result in a signal characterized by daily modulation. Furthermore, we find that the detailed structure of this modulation is sensitive to the velocity and momentum dependence of dark matter interactions. We identify the optimal mass r…
The next generation of ultralight dark matter (DM) direct detection experiments, which could confirm sub-eV bosons as the dominant source of DM, will feature multiple detectors operating at various terrestrial locations. As a result of the wave-like nature of ultralight DM, spatially separated detectors will each measure a unique DM phase. When the separation between experiments is comparable to the DM coherence length, the spatially-varying phase contains information beyond that which is accessible at a single detector. We introduce a formalism to extract this information, which performs inte…
We advocate an idea that the presence of the daily and annual modulations of the axion flux on the Earth surface may dramatically change the strategy of the axion searches. Our computations are based on the so-called Axion Quark Nugget (AQN) dark matter model which was originally put forward to explain the similarity of the dark and visible cosmological matter densities $Ω_{\rm dark}\sim Ω_{\rm visible}$. In our framework, the population of galactic axions with mass $ 10^{-6} {\rm eV}\lesssim m_a\lesssim 10^{-3}{\rm eV}$ and velocity $< v_a>\sim 10^{-3} c$ will be always accompanied by the axi…
We derive spectral line shapes of the expected signal for a haloscope experiment searching for axionlike dark matter. The knowledge of these line shapes is needed to optimize an experimental design and data analysis procedure. We extend the previously known results for the axion-photon and axion-gluon couplings to the case of gradient (axion-fermion) coupling. A unique feature of the gradient interaction is its dependence not only on magnitudes but also on directions of velocities of galactic halo particles, which leads to the directional sensitivity of the corresponding haloscope. We also dis…
The magnetic inelastic dark matter (MiDM) model, in which dark matter inelastically scatters off nuclei through a magnetic dipole interaction, has previously been shown to reconcile the DAMA/LIBRA annual modulation signal with null results from other experiments. In this work, we explore the unique directional detection signature of MiDM. After the dark matter scatters into its excited state, it decays with a lifetime of order 1 microsecond and emits a photon with energy ~100 keV. Both the nuclear recoil and the corresponding emitted photon can be detected by studying delayed coincidence event…
A search for an annual variation of a daily sidereal modulation of the frequency difference between co-located ${}^{129}$Xe and ${}^{3}$He Zeeman masers sets a stringent limit on boost-dependent Lorentz and CPT violation involving the neutron, consistent with no effect at the level of 150 nHz. In the framework of the general Standard-Model Extension, the present result provides the first clean test for the fermion sector of the symmetry of spacetime under boost transformations at a level of $10^{-27}$ GeV.
Multi-component dark matter particles may have a more intricate direct detection signal than simple elastic scattering on nuclei. In a broad class of well-motivated models the inelastic excitation of dark matter particles is followed by de-excitation via $γ$-decay. In experiments with fine energy resolution, such as many $0ν2β$ decay experiments, this motivates a highly model-independent search for the sidereal daily modulation of an unexpected $γ$ line. Such a signal arises from two-step WIMP interaction: the WIMP is first excited in the lead shielding and subsequently decays back to the grou…
The channeling of the recoiling nucleus in crystalline detectors after a WIMP collision would produce a larger scintillation or ionization signal in direct detection experiments than otherwise expected. I present estimates of channeling fractions obtained using analytic models developed from the 1960's onwards to describe channeling and blocking effects. We find the fractions to be too small to affect the fits to potential WIMP candidates. I also examine the possibility of detecting a daily modulation of the dark matter signal due to channeling.
