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• PICO bubble chambers at the 40 liter/50 kg scale can be made background-free • PICO setting world-leading constraints on spin-dependent WIMP proton coupling • Moving on to the next phase of the program
The bright objects we observe in the night sky make up less than 20% of the matter in the Universe. More than 80% of matter is invisible dark matter [1], which was postulated because the amount of visible matter in galaxy clusters could not account for the galaxies’ velocities [2]. Observations from cosmology and astrophysics that converge on the existence of dark matter include the cosmic microwave background power spectrum [3], cluster and galactic rotation curves [2], gravitational lensing [4,5] and large-scale structure formation [6]. The existence of dark matter is one of the biggest unsolved mysteries in physics, providing concrete evident for physics beyond the Standard Model (SM) of particle physics. Many particle candidates have been introduced, including weakly interacting massive particles (WIMPs) and ultralight bosons, such as the axion [7]. No candidates have been discovered, despite many searches, and the nature of dark matter is still unknown. The axion is a new fundamental spin-0 particle, which was originally motivated by explaining the strong charge-parity ( CP ) problem of quantum chromodynamics (QCD) [7], the theory of the strong nuclear force within nucleons. The CP -violating term in QCD within the SM is expected to generate a sizable neutron electric dipole moment (EDM), while the experimental upper bound is roughly one trillionth that size [8]. The strong CP problem is the non-observation of this neutron EDM. Discovery of axions would aid in understanding both the cosmological dark matter problem and the strong CP problem.
NEXUS (Northwestern EXperimental Underground Site) is a dark matter detector prototyping and calibration facility at Fermilab. It is part of the SuperCDMS collaboration, which is focused on exploring light-WIMP parameter space. The NEXUS cryostat, typically operated at temperatures of about 10 mK, is located 107 meters underground in the MINOS Near Detector Hall to reduce cosmic ray backgrounds. We characterized the vibrational and electro-magnetic frequency (EMF) backgrounds surrounding the cryostat and investigated how these backgrounds transfer into the detector itself.
Single-phase liquid argon time projection chambers (LArTPCs) are an important part of Fermilab's neutrino experimental program. Current LArTPCs are able to detect interactions producing energy deposits above the MeV scale, and focus on neutrinos at GeV energies. The Liquid Argon Charge Amplification Device, or LArCADe, program aims to employ modified anode geometries in order to obtain electron avalanches that would help reduce detection thresholds, opening the door to new physics opportunities at the keV scale (e.g. CEvNS and dark-matter WIMP searches). To model and quantify this phenomenon, a simulation of electron transport in LAr was built, able to simulate excitations and ionizations in non-uniform fields. Using COMSOL simulations of the anode structures, the built simulation produced quantitative and realistic estimates of LAr charge amplification near different tip geometries. These results will inform the next generation of tips produced for LArCADe.
Liquid xenon time projection chambers (LXe-TPCs) currently lead the direct-detection search for dark matter (DM) in the form of weakly interacting massive particles (WIMPs). However, sensitivity is currently limited to DM with masses above 5 GeV/c². Hydrogen doping in LXe-TPCs would allow for better kinematic matching between light DM particles and target nuclei, expanding sensitivity to DM masses down to 200 MeV/c². Additionally, this method would introduce sensitivity to spindependent DM. So far, no major experiments have explored this parameter space. Plans are underway to dope an existing small-scale LXe-TPC (XELDA) with H₂ to study behavior and mixing properties in LXe. This will include measuring the Henry coefficient and characterizing the charge-to-light spectrum of H₂ recoils in LXe. Prior to this, it is important to determine an expected time scale of H₂ diffusion and saturation in our TPC.
Researchers at Stony Brook University (Stony Brook) and the Fermi National Accelerator Laboratory (Fermilab) have proposed a new experiment called the Sub-Electron Noise Skipper-CCD Experimental Instrument (SENSEI). Uncovering the identity of dark matter (DM), which makes up about 85% of the matter in the Universe, is among the most important goals of particle physics today. Laboratory-based experimental searches, which have mostly focused on Weakly Interacting Massive Particles (WIMPs) with masses above the GeV-scale (proton mass), have turned up empty thus far. Stony Brook and Fermilab have agreed to provide most of the infrastructure and technical support that will be needed by the collaboration to construct and operate two detectors for the experiment -- SENSEI-10 and SENSEI-100. The Heising-Simons Foundation is providing partial support for the experiment, through a grant to Stony Brook University, which will be used to procure the detector components, support a graduate student to work full-time on the SENSEI experiment, and support travel for collaborators to work on the experiment.
The dearth of signals unambiguously attributable to WIMP dark matter motivates exploring new parameter space, particularly the ultra-light dark matter (ULDM) regime, where the signal is not scattering events but wave phenomena. The proliferation of quantum technologies has enabled searches for ULDM at previously inaccessible sensitivity. One such technology is atom interferometry which can measure time-dependent fluctuations in the energy spacing of atoms as well as in the light-travel time across the apparatus, enabling searches for ULDM and gravitational waves, respectively. In this talk, I will review the science case for long baseline atom interferometers, such as MAGIS-100 at Fermilab, provide an update on the experiment’s status, and discuss the need for a future, kilometer-scale atom interferometer which would achieve unprecedented sensitivity to ULDM and gravitational waves in the “Mid-Band” region between LIGO and LISA.
Detectors based upon the noble elements, especially liquid xenon as well as liquid argon, as both single- and dual-phase types, require reconstruction of the energies of interacting particles, both in the field of direct detection of dark matter (weakly interacting massive particles WIMPs, axions, etc.) and in neutrino physics. Experimentalists, as well as theorists who reanalyze/reinterpret experimental data, have used a few different techniques over the past few decades. In this paper, we review techniques based on solely the primary scintillation channel, the ionization or secondary channel available at non-zero drift electric fields, and combined techniques that include a simple linear combination and weighted averages, with a brief discussion of the application of profile likelihood, maximum likelihood, and machine learning. Comparing results for electron recoils (beta and gamma interactions) and nuclear recoils (primarily from neutrons) from the Noble Element Simulation Technique (NEST) simulation to available data, we confirm that combining all available information generates higher-precision means, lower widths (energy resolution), and more symmetric shapes (approximately Gaussian) especially at keV-scale energies, with the symmetry even greater when thresholding is addressed. Near thresholds, bias from upward fluctuations matters. For MeV-GeV scales, if only one channel is utilized, an ionization-only-based energy scale outperforms scintillation; channel combination remains beneficial. We discuss here what major collaborations use.
https://arxiv.org/abs/2311.04982This repository contains data products from the 14 year Fermi-LAT analysis of the Milky Way dSphs as described in McDaniel et al (2023) https://arxiv.org/abs/2311.04982. The included data products are the SED fits files and 2D TS profiles in the WIMP mass and cross section space. These are available for dSphs as well as the blank-field analysis, using both the standard likelihood and the weighted likelihood approach (see Appendix A). CSV data files are included containing relevant information about the dSphs (see table 1 of McDaniel+2024) and blank fields (RA & Dec). Also included is a python Jupyter Notebook to show basic usage of the data products. For Example, plotting the SED likelihoods, converting the SED likelihood to DM space, creating a combined TS profile, obtaining upper limits, etc. This is also stored as a static html file for easier viewing. SEDs are stored as fits files in the output format of fermipy (see https://fermipy.readthedocs.io/en/latest/advanced/sed.html) TS profiles are stored as numpy arrays covering 40 logarithmically spaced mass values over the 1 GeV - 1 TeV mass range and 60 logarithmically spaced cross-section values covering the $10^{-28}$ to $10^{-22}$ cm$^3$/s cross section range. TS profiles including the J-factor prior and without are available, and are labeled with "Jprior" or "noprior" respectively.
A motivation is presented for the idea that dense nuclear matter can burn to a new class of stable particles. One of several possibilities is an 'octet' particle which is the 16 baryon extension of alpha particle, but now composed of a pair of each of the two nucleons, (3Sigma, Delta, and 2Xi). Such 'tertiary' nuclear burning (here 'primary' is H-He and 'secondary' is He-Fe) may lead to neutron star explosions rather than collapse to a black hole, analogous to some Type I supernovae models wherein accreting white dwarfs are pushed over the Chandrasekhar mass limit but explode rather than collapse to form neutron stars. Such explosions could possibly give gamma-ray bursts and power quasars, with efficient particle acceleration in the resultant relativistic shocks. The new stable particles themselves could possibly be the sought-after weakly interacting, massive particles (WIMPs) or 'dark' matter.
A number of recent studies have suggested that cosmions, or WIMPS, may play an important role in the energetics of the solar interior; in particular, it has been argued that these hypothetical particles may transport sufficient energy within the nuclear-burning solar core so as to depress the solar core temperature to the point of resolving the solar neutrino problem. Solutions to the solar neutrino problem have proven themselves to be quite nonunique, so that it is of some interest whether the cosmion solution can be tested in some independent manner. It is argued that if cosmions solve the solar neutrino problem, then they must also play an important role in the evolution of low mass main sequence stars; and, second, that if they do so, then a simple (long mean free path) model for the interaction of cosmions with baryons leads to changes in the structure of the nuclear-burning core which may be in principal observable. Such changes include suppression of a fully-convective core in very low mass main sequence stars; and a possible thermal runaway in the core of the nuclear burning region. Some of these changes may be directly observable, and hence may provide independent constraints on the properties of the cosmions required to solve the solar neutrino problem, perhaps even ruling them out.
Appropriate design of two dimensional user interfaces (2D U/I) utilizing the well known WIMP (Window, Icon, Menu, Pointing device) environment for computer software is well studied and guidance can be found in several standards. Three-dimensional U/I design is not nearly so mature as 2D U/I, and standards bodies have not reached consensus on what makes a usable interface. This is especially true when the tools for interacting with the virtual environment may include stereo viewing, real time trackers and pinch gloves instead of just a mouse & keyboard. Over the last several years the authors have created a 3D U/I system dubbed Pinchigator for navigating virtual worlds based on the dVise dV/Mockup visualization software, Fakespace Pinch Gloves and Pohlemus trackers. The current work is to test the usability of the system on several virtual worlds, suggest improvements to increase Pinchigator s usability, and then to generalize about what was learned and how those lessons might be applied to improve other 3D U/I systems.
Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking pbysics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.
Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
We explore the capability of the IceCube/Deepcore array to discover signal neutrinos resulting from the annihilations of Supersymmetric WIMPS that may be captured in the solar core. In this analysis, we use a previously generated set of {approx} 70k model points in the 19-dimensional parameter space of the pMSSM which satisfy existing experimental and theoretical constraints. Our calculations employ a realistic estimate of the IceCube/DeepCore effective area that has been modeled by the IceCube collaboration. We find that a large fraction of the pMSSM models are shown to have significant signal rates in the anticipated IceCube/DeepCore 1825 day dataset, including some prospects for an early discovery. Many models where the LSP only constitutes a small fraction of the total dark matter relic density are found to have observable rates. We investigate in detail the dependence of the signal neutrino fluxes on the LSP mass, weak eigenstate composition, annihilation products and thermal relic density, as well as on the spin-independent and spin-dependent scattering cross sections. Lastly, We compare the model coverage of IceCube/DeepCore to that obtainable in near-future direct detection experiments and to pMSSM searches at the 7 TeV LHC.
Argon is a powerful scintillator and an excellent medium for detection of ionization. Its high discrimination power against minimum ionization tracks, in favor of selection of nuclear recoils, makes it an attractive medium for direct detection of WIMP dark matter. However, cosmogenic {sup 39}Ar contamination in atmospheric argon limits the size of liquid argon dark matter detectors due to pile-up. The cosmic ray shielding by the earth means that Argon from deep underground is depleted in {sup 39}Ar. In Cortez Colorado a CO{sub 2} well has been discovered to contain approximately 500ppm of argon as a contamination in the CO{sub 2}. In order to produce argon for dark matter detectors we first concentrate the argon locally to 3-5% in an Ar, N{sub 2}, and He mixture, from the CO{sub 2} through chromatographic gas separation. The N{sub 2} and He will be removed by continuous cryogenic distillation in the Cryogenic Distillation Column recently built at Fermilab. In this talk we will discuss the entire extraction and purification process; with emphasis on the recent commissioning and initial performance of the cryogenic distillation column purification.
The DAMIC experiment uses fully depleted, high resistivity CCDs to search for dark matter particles. With an energy threshold $\sim$50 eV$_{ee}$, and excellent energy and spatial resolutions, the DAMIC CCDs are well-suited to identify and suppress radioactive backgrounds, having an unrivaled sensitivity to WIMPs with masses $<$6 GeV/$c^2$. Early results motivated the construction of a 100 g detector, DAMIC100, currently being installed at SNOLAB. This contribution discusses the installation progress, new calibration efforts near the threshold, a preliminary result with 2014 data, and the prospects for physics results after one year of data taking.