Search NASA⌕ Search

SEARCH · Search NASA

Results for “Particle Nature of Dark Matter”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7

Projected sensitivity of the LUX-ZEPLIN experiment to the two-neutrino and neutrinoless double $\beta$ decays of $^{134}$Xe

The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrino and neutrinoless double beta decay of 134 Xe is presented. LZ is a 10-tonne xenon time projection chamber optimized for the detection of dark matter particles, that 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 beta decay of 134 Xe, for which xenon detectors enriched in 136 Xe are less effective. For the two-neutrino decay mode, LZ is predicted to exclude values of the half-life up to 1.7 x 10 24 years at 90% confidence level (CL), and has a three-sigma observation potential of 8.7 x 10 23 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 x 10 24 years at 90% CL.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Primordial black holes arise when the inflaton falls

Primordial Black Holes (PBHs) have entered the forefront of theoretical cosmology, due their potential role in phenomena ranging from gravitational waves, to dark matter, to galaxy formation. While producing PBHs from inflationary fluctuations naively would seem to require a large deceleration of the inflaton from its velocity at the horizon exit of CMB scales, in this work we demonstrate that an acceleration from a relatively small downward step in the potential that is transited in much less than an e-fold amplifies fluctuations as well. Depending on the location of the step, such PBHs could explain dark matter or the black holes detected by the gravitational wave interferometers. Furthermore, the perturbation enhancement has a natural interpretation as particle production due to the non-adiabatic transition associated with the step.

79 ASTRONOMY AND ASTROPHYSICS↗

Natural anomaly mediation from the landscape with implications for LHC SUSY searches

Supersymmetric models with the anomaly-mediated supersymmetry (SUSY) breaking (AMSB) form for soft SUSY breaking terms arise in two different settings: (1) extra-dimensional models where SUSY breaking occurs in a sequestered sector, and (2) 4 − d models with dynamical SUSY breaking in a hidden sector where scalars gain masses of order the gravitino mass m 3 / 2 , but gaugino masses and trilinear soft terms are assumed to be of the AMSB form. Both models run into serious conflicts with (1) LHC sparticle and Higgs mass constraints, (2) constraints from winolike weakly interacting massive particle dark matter searches, and (3) bounds from naturalness. These conflicts may be avoided by introducing minor changes to the underlying phenomenological models consisting of nonuniversal bulk scalar Higgs masses and A terms, providing a setting for natural anomaly mediation (nAMSB). In nAMSB, the wino is still expected to be the lightest of the gauginos, but the Higgsinos are expected to be the lightest electroweakinos (EWinos) in accord with naturalness. We examine what sorts of spectra are expected to emerge when nAMSB arises from a string landscape setting: While model 2 can only be natural for a Higgs mass m h ≲ 123 GeV , model 1 can accommodate naturalness along with m h ∼ 125 GeV while still respecting LHC bounds on sparticle masses. We explore the LHC phenomenology of nAMSB models where we find that for Higgsino pair production, typically larger dilepton mass gaps arise from the soft dilepton-plus-jets signature than in models with gaugino mass unification. For wino-pair production, the higher m 3 / 2 portion of nAMSB parameter space is excluded by recent LHC bounds from gaugino pair production searches. We characterize the dominant LHC signatures arising from the remaining lower m 3 / 2 ∼ 90 – 200 TeV range of parameter space, which should be fully testable at high-luminosity LHC via EWino pair production searches. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

Muon track reconstruction in a segmented bolometric array using multi-objective optimization

Recent advances in segmented solid-state detector arrays for rare-event searches have allowed the technology to approach the ton-scale in detector mass and the scale of meters in size. Often focused around searches for neutrinoless double-beta decay or direct dark matter detection, such experiments also have the capability to search for exotic particles that leave track-like signatures across their volume. However, the segmented nature of such detector arrays often sets the spatial resolution and makes the problem of reconstructing track-like paths non-trivial. Here, in this paper, we present an algorithm that improves reconstruction of track-like events in segmented detectors using multi-objective optimization — a computational technique that optimizes more than one cost function at a time without specifying a quantitative weighting between them. Such a technique allows the reconstruction of tracks through a detector and the determination of path-lengths through individual elements. When combined with the reconstructed energy depositions in each element this allows for a calculation of the stopping power of track-like particles and opens the door to searches for particles with abnormal stopping power like monopoles or lightly-ionizing particles (LIPs). Results are presented which evaluate the precision of the reconstruction tools as they currently stand against Monte Carlo generated data. The algorithm is presented in the context of the CUORE experiment, but has applications to other segmented calorimeter detectors.

47 OTHER INSTRUMENTATION↗

Twin sterile neutrino dark matter

We propose that the dark matter of our Universe could be sterile neutrinos which reside within the twin sector of a mirror twin Higgs model. In our scenario, these particles are produced through a version of the Dodelson-Widrow mechanism that takes place entirely within the twin sector, yielding a dark matter candidate that is consistent with x-ray and gamma-ray line constraints. Furthermore, this scenario can naturally avoid the cosmological problems that are typically encountered in mirror twin Higgs models. In particular, if the sterile neutrinos in the Standard Model sector decay out of equilibrium, they can heat the Standard Model bath and reduce the contributions of the twin particles to N eff . Such decays also reduce the effective temperature of the dark matter, thereby relaxing constraints from large-scale structure. The sterile neutrinos included in this model are compatible with the seesaw mechanism for generating Standard Model neutrino masses. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Gravitational lenses and particle properties

The potential of observations of gravitational lens systems for the determination of cosmological constants and for tests of the nature and distribution of dark matter is illustrated. The advantages and disadvantages of gravitational lenses as cosmological probes are evaluated.

Turner, Edwin L.↗

Particle Theory and Cosmology

This project covered theoretical studies in particle physics, particle astrophysics and cosmology, aiming to bridge theoretical models with observable phenomena. The central focus was on exploring innovative mechanisms that could simultaneously address several outstanding puzzles in these areas, including the nature of dark matter, the muon g-2 anomaly, the existence of topologically stable monopoles, the generation of observable gravitational waves from early universe phenomena and high energy cosmic rays. One of the major achievements of this project was the development of models that predict new physics accessible through current and forthcoming experimental setups, both in particle colliders and astrophysical observations. These models have been instrumental in proposing verifiable predictions concerning supersymmetric extensions, the dynamics of cosmic strings and monopoles, and the intricate processes underpinning baryogenesis and reheating post-inflation. In tackling the dark matter conundrum, the project proposed several candidates within extended frameworks, such as light Z' models, pseudo-Goldstone dark matter, and scenarios integrating dark matter with inflationary cosmology. Each model outlined pathways for detection through direct, indirect, and collider search strategies, marking significant strides in the hunt for dark matter. Another cornerstone of the project was the in-depth analysis of inflationary models compliant with the Trans-Planckian Censorship Conjecture, highlighting the compatibility of axion dark matter within such frameworks. This not only provided a coherent picture of early universe cosmology but also delineated clear experimental signatures. The exploration of grand unified theories yielded insights into the potential discovery of monopoles and novel particle configurations at energy scales accessible to current and future colliders. This endeavor expanded the predictive power of these theories, particularly in the context of proton decay and the properties of Higgs-portal dark matter. Throughout the project, significant emphasis was placed on ensuring the theoretical developments were grounded in experimental testability. This led to a series of publications across prestigious journals, each contributing to the vibrant discourse at the intersection of particle physics and cosmology. In summary, this project has elucidated pathways beyond the Standard Model that are ripe for exploration through both ongoing and upcoming experimental efforts. The comprehensive approach adopted herein not only enhances our understanding of the fundamental forces and constituents of the universe but also propels the field towards new frontiers in high-energy physics and cosmology.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Mirror neutron stars

The fundamental nature of dark matter is entirely unknown. A compelling candidate is twin Higgs mirror matter, invisible hidden-sector cousins of the Standard Model particles and forces. This predicts mirror neutron stars made entirely of mirror nuclear matter. Here we find their structure using realistic equations of state, robustly modified based on first-principle quantum chromodynamic calculations, for the first time. This allows us to predict their gravitational wave signals, demonstrating an impressive discovery potential and ability to probe dark sectors connected to the hierarchy problem.

79 ASTRONOMY AND ASTROPHYSICS↗

Test for the Origin of Solar Mass Black Holes

Solar-mass black holes with masses in the range of ~1–2.5 M ⊙ are not expected from conventional stellar evolution, but can be produced naturally via neutron star (NS) implosions induced by capture of small primordial black holes (PBHs) or from accumulation of some varieties of particle dark matter. We argue that a unique signature of such “transmuted” solar-mass BHs is that their mass distribution would follow that of the NSs. This would be distinct from the mass function of black holes in the solar-mass range predicted either by conventional stellar evolution or early Universe PBH production. We propose that analysis of the solar-mass BH population mass distribution in a narrow mass window of ~1–2.5 M ⊙ can provide a simple yet powerful test of the origin of these BHs. Recent LIGO/VIRGO gravitational wave (GW) observations of the binary merger events GW190425 and GW190814 are consistent with a BH mass in the range ~1.5–2.6 M ⊙ . Though these results have fueled speculation on dark matter-transmuted solar-mass BHs, we demonstrate that it is unlikely that the origin of these particular events stems from NS implosions. Data from upcoming GW observations will be able to distinguish between solar-mass BHs and NSs with high confidence. This capability will facilitate and enhance the efficacy of our proposed test.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Maximum entropy distributions of dark matter in ΛCDM cosmology

Context. Small-scale challenges to ΛCDM cosmology require a deeper understanding of dark matter physics. Aims. This paper aims to develop the maximum entropy distributions for dark matter particle velocity (denoted by X ), speed (denoted by Z ), and energy (denoted by E ) that are especially relevant on small scales where system approaches full virialization. Methods. For systems involving long-range interactions, a spectrum of halos of different sizes is required to form to maximize system entropy. While the velocity in halos can be Gaussian, the velocity distribution throughout the entire system, involving all halos of different sizes, is non-Gaussian. With the virial theorem for mechanical equilibrium, we applied the maximum entropy principle to the statistical equilibrium of entire system, such that the maximum entropy distribution of velocity (the X distribution) could be analytically derived. The halo mass function was not required in this formulation, but it did indeed result from the maximum entropy. Results. The predicted X distribution involves a shape parameter α and a velocity scale, v 0 . The shape parameter α reflects the nature of force ( α → 0 for long-range force or α → ∞ for short-range force). Therefore, the distribution approaches Laplacian with α → 0 and Gaussian with α → ∞. For an intermediate value of α , the distribution naturally exhibits a Gaussian core for v ≪ v 0 and exponential wings for v ≫ v 0 , as confirmed by N -body simulations. From this distribution, the mean particle energy of all dark matter particles with a given speed, v , follows a parabolic scaling for low speeds (∝ v 2 for v ≪ v 0 in halo core region, i.e., “Newtonian”) and a linear scaling for high speeds (∝ v for v ≫ v 0 in halo outskirt, i.e., exhibiting “non-Newtonian” behavior due to long-range gravity). We compared our results against N -body simulations and found a good agreement.

79 ASTRONOMY AND ASTROPHYSICS↗

Searches for New Long-Lived Particles and Upgrade to the ATLAS Inner Detector (Final Technical Report)

The search for new fundamental particles is one of the defining goals of the Large Hadron Collider (LHC). The discovery of the Higgs Boson by the ATLAS and CMS collaborations provided the capstone of the Standard Model of particle physics, but outstanding questions remain. Why does the Higgs boson have a mass of 125 GeV when its natural mass would be many orders of magnitude larger? Is there a universal symmetry which unites all three forces described by the Standard Model? Can that symmetry be extended to include gravity? Is dark matter, evidenced by astronomical observations, made of a particle that interacts via Standard Model forces with the rest of matter? Together, these motivations provide compelling arguments that new physical processes await discovery. This project addressed some outstanding questions about the fundamental particles and their interactions with the ATLAS experiment at the Large Hadron Collider. In particular, the project improved the discovery potential for new, long- lived particles produced via electroweak processes in proton-proton collisions and set world-leading limits on their existence for certain values of their potential mass and lifetime. To achieve this, the project developed new data analysis methods, developed new triggers to select events with new long-lived particles during data-taking of the ATLAS experiment, and analyzed the largest proton–proton collision dataset ever produced. The project also supported significant development of the data acquisition software for the upgrade to the ATLAS inner detector, the Inner TracKer (ITk). The upgrade of the ATLAS inner detector is essential to the success of the entire Phase II physics program on ATLAS. Personnel supported by the project provided support for integration, assembly, and testing of the inner two layers of the ITk pixel system during its prototype and pre-production phase. Four PhD students and two post-doctoral scholars were supported by the grant and received invaluable scientific training as part of the research endeavor. The students and postdocs gained essential professional skills in the areas of advanced data analysis techniques, statistical analysis of data and simulation, programming in C++ and Python, hardware and instrumentation development, and presentation and collaboration skills. Additionally, approximately ten undergraduate students supported through other funding sources participated in research activities synergistic with the goals of this project, receiving essential mentorship from the personnel supported by this project.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Two-fluid simulations of galaxy formation

We investigate the formation of galaxies and larger structure with a simulation modeling two gravitationally coupled fluids representing dark matter and baryons. The baryon gas dynamics are calculated with a smoothed particle hydrodynamics (SPH) method, and the physics modeled includes thermal pressure, shock heating, and radiative cooling. We simulate a 16 Mpc periodic cube with 64(exp 3) particles in each fluid and 10% baryon mass fraction. We confirm, for the first time experimentally, disk formation as a natural consequence of hierarchical clustering in a large-scale cosmological environment. The majority of isolated galaxies exhibit centrifugally supported disks. A power-law relation between cold baryonic mass and maximum rotation velocity is found, M varies as nu(sub rot)(exp alpha) with alpha = 2.5 after correcting for differential numerical resolution. Both the spatial and velocity distributions of the simulated galaxies are biased with respect to the dark matter. A counts-in-cells analysis indicates that an unphysical degree of merging in the central cluster is likely responsible for the antibias signal in the correlation function. A robust, scale-dependent velocity bias is measured. The ratio of galaxy to dark matter pairwise velocity dispersions on a scale of 1 Mpc is 0.7. The amplitude is only mildly dependent on redshift or mass cutoff and scales with separation as r(exp 0.2). The degree to which these results depend on numerical parameters is discussed. Mass resolution plays a key role in controlling the resulting fraction of cold, dense baryons. The mass fraction associated with galaxies decreases by a factor of approximately greater than 3 when the mass per particle is increased by a factor 8. Photoionization and energy input from supernova will have to be included to determine more carefully the fraction of highly dissipated material and the characteristics of the stellar component of galaxies.

Evrard, August E.↗

Hidden Sectors from Cosmos to Colliders

The major aims of this project are to (i) to systematically explore the cosmological history of dark matter born out of a larger dark sector and to establish new discovery opportunities for dark matter in both astrophysical and terrestrial experiments, and (ii) to develop new techniques to discover very weakly coupled new physics at colliders, especially particles produced in exotic decays of the Higgs boson and/or with a macroscopic proper lifetime. This report summarizes how the research carried out in this project addresses these goals. Selected highlights from the final year of the project include (i) establishing new probes of dark sectors in the early universe through visible footprints in cosmic microwave background, big bang nucleosynthesis, and gravitational wave observables; (ii) developing new links between self-interacting dark sectors and dark matter microstructure; (iii) surveying progress in the search for exotic decays of the Higgs and discussing the resulting consequences for models of nature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan

Through the exploration of fundamental symmetries, and by using nuclei, neutrons, and neutrinos, nuclear physics addresses some of the most profound questions in science. Why does the universe contain so much more matter than antimatter? Are neutrinos their own antiparticles and where do their masses come from? What objects make up the dark matter that is responsible for most of the universe’s mass? Does nature contain more forces than the four we know about? Our Standard Model of nature’s particles and forces is incomplete because it does not answer these questions; new physics, from beyond the Standard Model (BSM) is needed. With that physics not appearing at the high energy frontier, it has become imperative to realize the potential of the burgeoning program of precision nuclear-physics measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Direct Detection of Dark Matter at the University of South Dakota

The grant supports experimental research to address one of the pressing questions of our time is the nature and composition of the dark matter. Direct detection of dark matter is possible because the rotation curves of galaxies suggest the presence of a sufficiently-large weakly interacting massive particle (WIMP) density. However, the absence of any confirmed dark matter detection indicates the need for more sensitive experiments. SuperCDMS SNOLAB is a generation-2 dark matter search experiment that is designed to have vastly improved sensitivity to low-mass WIMPs. SuperCDMS SNOLAB unique capabilities also enable sensitivity to a broader range of science beyond WIMPs. The SuperCDMS SNOLAB experiment is being installed and integrated at SNOLAB, near Sudbury, Ontario in Canada. The University of South Dakota (USD) group is deeply invested in the installation, integration and planning for commissioning and operations of the SuperCDMS SNOLAB experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Dark Matter Search in Pu-241 Beta Decays

Our universe is predominantly composed of mysterious unknowns: Dark Matter (DM) and Dark Energy. DM constitutes approximately 27% of the universe, yet its nature and origins remain elusive. Among the various candidates for dark matter, this project focuses on the search for keV-scale sterile neutrinos. A sterile neutrino is a hypothetical particle that belongs to the neutrino family and may possess a higher mass than ordinary neutrinos. They are considered a compelling warm dark matter candidate if their mass is on the order of kilo-electronvolts. Existence of sterile neutrinos can be investigated via high precision beta spectroscopy. Sterile neutrinos can be produced during nuclear beta decay processes, similar to ordinary active neutrinos, but they uniquely alter the beta decay spectrum. The emission of sterile neutrinos will introduce a distinctive "kink" structure in the middle of the beta spectrum. This project investigated the existence of sterile neutrino dark matter by employing high-precision decay energy spectroscopy of Pu-241 beta decays using magnetic microcalorimeters (MMCs). The Pu-241 source material is embedded within the microcalorimeter detectors, enabling the measurement of full beta decay energies with ultra-high energy resolution. In this project, the most precise Pu-241 spectrum to date was obtained by collecting a total of 1 billion beta decay events in the MMC detectors. This extensive data set allows us to investigate evidence of keV sterile neutrino emission in beta decays with unprecedented sensitivity.

79 ASTRONOMY AND ASTROPHYSICS↗

Travel for SuperCDMS SNOLAB Operations (Final Technical Report)

The grant supported SuperCDMS SNOLAB experimental research to address the nature and composition of the dark matter. SuperCDMS SNOLAB is a generation-2 dark matter search experiment that is designed to have vastly improved sensitivity to low-mass weakly interacting massive particles (WIMPs). SuperCDMS SNOLAB unique capabilities also enable sensitivity to a broader range of science beyond WIMPs. The SuperCDMS SNOLAB experiment is being installed and integrated at SNOLAB, near Sudbury, Ontario in Canada. The scope of this grant was support of SuperCDMS members to travel to the experiment location to engage in installation, integration and operations of the SuperCDMS experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Freeze-in dark matter from secret neutrino interactions

We investigate a simplified freeze-in dark-matter model in which the dark matter only interacts with the standard-model neutrinos via a light scalar. The extremely small coupling for the freeze-in mechanism is naturally realized in several neutrino-portal scenarios with the secret neutrino interactions. We study possible evolution history of the hidden sector: the dark sector would undergo pure freeze-in production if the interactions between the dark-sector particles are negligible, while thermal equilibrium within the dark sector could occur if the reannihilation of the dark matter and the scalar mediator is rapid enough. We investigate the relic abundance in the freeze-in and dark freeze-out regimes, calculate evolution of the dark temperature, and study its phenomenological aspects on BBN and CMB constraints, the indirect-detection signature, as well as the potential to solve the small scale structure problem.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗