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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Electroweak loop contributions to the direct detection of wino dark matter

Electroweak loop corrections to the matrix elements for the spin-independent scattering of cold dark matter particles on nuclei are generally small, typically below the uncertainty in the local density of cold dark matter. However, as shown in this paper, there are instances in which the electroweak loop corrections are relatively large, and change significantly the spin-independent dark matter scattering rate. An important example occurs when the dark matter particle is a wino, e.g., in anomaly-mediated supersymmetry breaking (AMSB) and pure gravity mediation (PGM) models. We find that the one-loop electroweak corrections to the spin-independent wino LSP scattering cross section generally interfere constructively with the tree-level contribution for AMSB models with negative Higgsino mixing, μ < 0, and in PGM-like models for both signs of μ, lifting the cross section out of the neutrino fog and into a range that is potentially detectable in the next generation of direct searches for cold dark matter scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

t -channel dark matter models – a whitepaper

This report, summarising work achieved in the context of the LHC Dark Matter Working Group, investigates the phenomenology of t -channel dark matter models, spanning minimal setups with a single dark matter candidate and mediator to more complex constructions closer to UV-complete models. For each considered class of models, we examine collider, cosmological and astrophysical implications. In addition, we explore scenarios with either promptly decaying or long-lived particles, as well as featuring diverse dark matter production mechanisms in the early universe. By providing a unified analysis framework, numerical tools and guidelines, this work aims to support future experimental and theoretical efforts in exploring t -channel dark matter models at colliders and in cosmology.

Arina, Chiara [Universite Catholique de Louvain, L↗
DOE OSTI2020

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. This paper is based on a submission (v1) in response to the Call for White Papers for the Voyage 2050 long-term plan in the ESA Science Programme. ESA limited the number of White Paper authors to 30. However, in this version (v2) we have welcomed as supporting authors participants in the Workshop on Atomic Experiments for Dark Matter and Gravity Exploration held at CERN: ({\tt https://indico.cern.ch/event/830432/}), as well as other interested scientists, and have incorporated additional material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Bulk Viscosity in Dense Nuclear Matter

NEUTRON star mergers are an extreme environment where, within milliseconds, the cold, dense matter in neutron stars is dramatically heated to some of the hottest temperatures encountered in astrophysics. Matter in neutron star mergers is located solidly in the interior of the QCD phase diagram, and therefore, the observation and simulation of these mergers provides an opportunity to learn about the strong interaction at a set of densities and temperatures that compliment those obtained in relativistic heavy-ion collisions. Matter during the merger of two neutron stars is far from hydrostatic equilibrium, allowing for the study of not only the equation of state of dense matter, but of transport properties as well. Perhaps the most likely transport property to play a role in neutron star mergers is the bulk viscosity, which acts to resist changes in density. Furthermore, the bulk viscosity of matter at high densities has long been anticipated to damp oscillations in isolated neutron stars, and the study of its role in neutron star mergers is just beginning.

Harris, Steven P.↗
DOE OSTI2019

Soft matter and nanomaterials characterization by cryogenic transmission electron microscopy

Soft matter has historically been an unlikely candidate for investigation by electron microscopy techniques due to damage by the electron beam as well as inherent instability under a high vacuum environment. Characterization of soft matter has often relied on ensemble-scattering techniques. The recent development of cryogenic transmission electron microscopy (cryo-TEM) provides the soft matter community with an exciting opportunity to probe the structure of soft materials in real space. Cryo-TEM reduces beam damage and allows for characterization in a native, frozen-hydrated state, providing direct visual representation of soft structure. This article reviews cryo-TEM in soft materials characterization and illustrates how it has provided unique insights not possible by traditional ensemble techniques. Soft matter systems that have benefited from the use of cryo-TEM include biological-based “soft” nanoparticles (e.g., viruses and conjugates), synthetic polymers, supramolecular materials as well as the organic–inorganic interface of colloidal nanoparticles. We conclude that while many challenges remain, such as combining structural and chemical analyses; the opportunity for soft matter research to leverage newly developed cryo-TEM techniques continues to excite.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Les Houches Lectures on Indirect Detection of Dark Matter

These lectures, presented at the 2021 Les Houches Summer School on Dark Matter, provide an introduction to key methods and tools of indirect dark matter searches, as well as a status report on the field circa summer 2021. Topics covered include the possible effects of energy injection from dark matter on the early universe, methods to calculate both the expected energy distribution and spatial distribution of particles produced by dark matter interactions, an outline of theoretical models that predict diverse signals in indirect detection, and a discussion of current constraints and some claimed anomalies. These notes are intended as an introduction to indirect dark matter searches for graduate students, focusing primarily on intuition-building estimates and useful concepts and tools.

Slatyer, Tracy↗
DOE OSTI2023

Testing the mean field theory of scalar field dark matter

Scalar field dark matter offers an interesting alternative to the traditional WIMP dark matter picture. Astrophysical and cosmological simulations are useful to constraining the mass of the dark matter particle in this model. This is particularly true at low mass where the wavelike nature of the dark matter particle manifests on astrophysical scales. These simulations typical use a classical field approximation. In this work, we look at extending these simulations to include quantum corrections. We look into both the ways in which large corrections impact the predictions of scalar field dark matter, and the timescales on which these corrections grow large. Corrections tend to lessen density fluctuations and increase the effect of “quantum pressure”. During collapse, these corrections grow exponentially, quantum corrections would become important in about \sim 30 ∼ 30 dynamical times. This implies that the predictions of classical field simulations may differ from those with quantum corrections for systems with short dynamical times.

Eberhardt, Andrew↗
DOE OSTI2017

US Cosmic Visions: New Ideas in Dark Matter 2017 : Community Report

This white paper summarizes the workshop “U.S. Cosmic Visions: New Ideas in Dark Matter” held at University of Maryland from March 23-25. The flagships of the US Dark Matter search program are the G2 experiments ADMX, LZ, and SuperCDMS, which will cover well-motivated axion and WIMP dark matter over a range of masses. The workshop assumes that a complete exploration of this parameter space remains the highest priority of the dark matter community, and focuses instead on the science case for additional new small-scale projects in dark matter science that complement the G2 program (and other ongoing projects worldwide). It therefore concentrates on exploring distinct, well-motivated parameter space that will not be covered by the existing program; on surveying ideas for such projects (i.e. projects costing ~$10M or less); and on placing these ideas in a global context. The workshop included over 100 presentations of new ideas, proposals and recent science and R&D results from the US and international scientific community.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Dark Matter Science in the Era of LSST

Astrophysical observations currently provide the only robust, empirical measurements of dark matter. In the coming decade, astrophysical observations will guide other experimental efforts, while simultaneously probing unique regions of dark matter parameter space. This white paper summarizes astrophysical observations that can constrain the fundamental physics of dark matter in the era of LSST. We describe how astrophysical observations will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational interactions with the Standard Model, and compact object abundances. Additionally, we highlight theoretical work and experimental/observational facilities that will complement LSST to strengthen our understanding of the fundamental characteristics of dark matter.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

A Dark Matter Search Using the Final SuperCDMS Soudan Dataset and the Development of a Large-Format, Highly-Multiplexed, Athermal-Phonon-Mediated Particle Detector

Over the past eighty years, numerous complementary observations of our universe have indicated that our current description of physics is far from complete. The “or- dinary matter”, such as electrons, protons, photons and neutrons, that constitutes the bulk of all human physical experiences is actually only a minority (about 16%) of the total mass of the universe. The remaining 84% is very poorly understood, but has profound effects on the dynamics and evolution of our universe. Because it does not interact with light, and is not observable in telescopes on earth, this extra mass is usually referred to as “dark matter”. Although the dark matter is poorly understood, Weakly Interacting Massive Particles (WIMPs) are a well-motivated candidate that can be directly detected via a non-gravitational interaction with nor- mal matter, potentially allowing for direct terrestrial detection and characterization of this dark matter. This dissertation is focused on this direct WIMP detect ion and will be broken into two main parts. The first part focuses on the blinded analysis of roughly three years of data collected from March 2012 to November 2015 by the SuperCDMS Soudan experiment. SuperCDMS Soudan consists of an array of 15, 0.6-kg, cryogenic, Ge iZIP particle detectors situated in a decommissioned iron mine in remote northern Minnesota. This analysis is optimized to be sensitive to theoretical WIMP masses above 10 GeV/$c^2$ . This result set the strongest limits for WIMP–germanium-nucleus interac- tions for WIMP masses greater than 12 Gev/$c^2$ and can be found here [1]. The second part focuses on the development new kind of particle detector in the style of a SuperCDMS iZIP, designed to simplify fabrication and readout, improve phonon-based position reconstruction, and help to scale to larger target arrays. These detectors replace the TES-based phonon sensors of the iZIP with Microwave Kinetic Inductance Detectors (MKIDs).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The Origin of Matter (Final Scientific Report)

The research of this project was concerned with the matter content of the universe. The first topic we studied was the amount of CP violation in kaon decays into two pions; with a new analysis we decreased the theoretical uncertainty by more than an order of magnitude. This constitutes a milestone in our understanding of the matter-antimatter asymmetry among the known standard-model particles. Furthermore, we studied the energy scale dependence of the self-interactions of spinless dark matter for the first time. This allows to study the consistency of theoretical models for dark matter, and is an important ingredient in the interpretation of various dark matter experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Search for dark matter decaying to two displaced muons produced in proton-proton collisions at 13 TeV with the CMS detector, and for dark photons produced in electron-positron fixed-target collisions at 500 MeV with the PADME detector

Two novel searches for dark matter using particle accelerators are presented. The first is a search for inelastically-coupled dark matter with the CMS detector at CERN, relying on 137 fb$^{-1}$ of proton-proton collision data collected at 13 TeV center-of-mass energy between 2016 and 2018. The search strategy exploits the striking signature expected of inelastic dark matter: a pair of displaced, soft, and narrow muons collimated with missing transverse momentum and recoiled off an initial-state radiation jet. This is the first search for inelastic dark matter at a hadron collider. The second experiment is PADME, a small-scale detector to search for dark photons located in Frascati, Italy. PADME seeks to detect the production of dark photons in positron-electron collisions with a stationary diamond target and a 500 MeV positron beam. The missing-mass technique employed in the experiment relies on constraining all four-momenta in the system except for the dark photon and lookin g for a bump in the resulting invariant mass distribution corresponding to the dark photon's mass. The projected sensitivity for both experiments is compared in the context of highlighting the need for a comprehensive experimental search program for dark matter. Both analyses expect first public results by the end of 2020.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Report of the Topical Group on Cosmic Probes of Dark Matter for Snowmass 2021

Cosmological and astrophysical observations currently provide the only robust, positive evidence for dark matter. Cosmic probes of dark matter, which seek to determine the fundamental properties of dark matter through observations of the cosmos, have emerged as a promising means to reveal the nature of dark matter. This report summarizes the current status and future potential of cosmic probes to inform our understanding of the fundamental nature of dark matter in the coming decade.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Harnessing the Population Statistics of Subhalos to Search for Annihilating Dark Matter

The Milky Way's dark matter halo is expected to host numerous low-mass subhalos with no detectable associated stellar component. Such subhalos are invisible unless their dark matter annihilates to visible states such as photons. One of the established methods for identifying candidate subhalos is to search for individual unassociated gamma-ray sources with properties consistent with the dark matter expectation. However, robustly ruling out an astrophysical origin for any such candidate is challenging. In this work, we present a complementary approach that harnesses information about the entire population of subhalos—such as their spatial and mass distribution in the Galaxy—to search for a signal of annihilating dark matter. Using simulated data, we show that the collective emission from subhalos can imprint itself in a unique way on the statistics of observed photons, even when individual subhalos may be too dim to be resolved on their own. Additionally, we demonstrate that, for the models we consider, the signal can be identified even in the face of unresolved astrophysical point-source emission of extragalactic and Galactic origin. Furthermore, this establishes a new search technique for subhalos that is complementary to established methods, and that could have important ramifications for gamma-ray dark matter searches using observatories such as the Fermi Large Area Telescope and the Cerenkov Telescope Array.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Point-scale organic-matter decomposition in streambeds is weakly associated with reach-scale respiration

Stream and river ecosystems play a central role in the movement and decomposition of particulate organic matter, serving as a conduit between terrestrial hillslopes and coastal environments. Microbial-catalyzed decomposition generates simpler organic molecules that fuel respiration, often in the sediments of these ecosystems. However, the degree of connection between sediment-associated respiration (ER??d) and organic-matter decomposition remains poorly understood. How that relationship compares to decomposition’s relationship with whole ecosystem (ERtot) and water column (ERwc) respiration is also not clear. We examined the link between particulate organic matter decomposition—using cellulose-based cotton strips as a standardized substrate—and all three components of respiration across 48 sites in the environmentally diverse Yakima River Basin (Washington State, USA). We hypothesized that decomposition within sediments would be most strongly related to ERsed, but decomposition rates were more closely associated with ERtot, with little connection to ERsed or ERwc. This suggests that particulate organic matter decomposition within stream/river sediments reflects integrated system respiration rather than processes confined to sediments or the water column alone. Further, across the basin, decomposition rates nearly spanned the previously reported global range for streams and rivers and were best explained by total dissolved nitrogen (TDN), sediment grain size, and aridity of the upstream drainage area. These results highlight the strong influence of land cover and basin-scale biophysical variation on sediment-associated decomposition processes and indicate that mechanistic models of organic matter decomposition in streams/rivers should account for coupled sediment–water–land interactions.

Stegen, James C. (ORCID:0000000191357424)↗
DOE OSTI2024

Lambda-PFLOTRAN 1.0: a workflow for incorporating organic matter chemistry informed by ultra high resolution mass spectrometry into biogeochemical modeling

Abstract. Organic matter (OM) composition plays a central role in microbial respiration of dissolved organic matter and subsequent biogeochemical reactions. Here, a direct connection of organic matter chemistry and thermodynamics to reactive transport simulators has been achieved through the newly developed Lambda-PFLOTRAN workflow tool that succinctly incorporates carbon chemistry data generated from Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) into reaction networks to simulate organic matter degradation and the resulting biogeochemistry. Lambda-PFLOTRAN is a Python-based workflow, executed through a Jupyter notebook interface, that digests raw FTICR-MS data, develops a representative reaction network based on substrate-explicit thermodynamic modeling (also termed lambda modeling due to its key thermodynamic parameter λ used therein), and completes a biogeochemical simulation with the open source, reactive flow and transport code PFLOTRAN. The workflow consists of the following five steps: configuration, thermodynamic (lambda) analysis, sensitivity analysis, parameter estimation, and simulation output and visualization. Two test cases are provided to demonstrate the functionality of the Lambda-PFLOTRAN workflow. The first test case uses laboratory incubation data of temporal oxygen depletion to fit lambda parameters (i.e., maximum utilization rate and microbial carrying capacity). A slightly more complex second test case fits multiple lambda formulation and soil organic matter release parameters to temporal greenhouse gas generation measured during a soil incubation. Overall, the Lambda-PFLOTRAN workflow facilitates upscaling by using molecular-scale characterization to inform biogeochemical processes occurring at larger scales.

58 GEOSCIENCES↗
NASA NTRS1985

Recent heavy-particle decay in a matter-dominated universe

The cold matter scenario for galaxy formation solves the dark matter problem very nicely on small scales corresponding to galaxies and clusters of galaxies. It is, however, difficult to reconcile with a Universe with an Einstein-deSitter value of (UC OMEGA) = 1. Cold matter and (UC OMEGA) = 1 can be made compatible while retaining the feature that the Universe is matter dominated today. This is done by means of heavy (cold) particles whose decay subsequently leads to the unbinding of a large fraction of lighter clustered matter.

Olive, K. A.↗
NASA NTRS1987

Thematic mapper research in the earth sciences: Small scale patches of suspended matter and phytoplankton in the Elbe River Estuary, German Bight and Tidal Flats

A Thematic Mapper (TM) field experiment was followed by a data analysis to determine TM capabilities for analysis of suspended matter and phytoplankton. Factor analysis showed that suspended matter concentration, atmospheric scattering, and sea surface temperature can be retrieved as independent factors which determine the variation in the TM data over water areas. Spectral channels in the near infrared open the possibility of determining the Angstrom exponent better than for the coastal zone color scanner. The suspended matter distribution may then be calculated by the absolute radiance of channel 2 or 3 or the ratio of both. There is no indication of whether separation of chlorophyll is possible. The distribution of suspended matter and sea surface temperature can be observed with the expected fine structure. A good correlation between water depth and suspended matter distribution as found from ship data can now be analyzed for an entire area by the synoptic view of the TM scenes.

Grassl, H.↗