Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “WIMPS”

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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A database for storing the results of material radiopurity measurements

Searches for rare nuclear processes, such as neutrinoless double beta-decay and the interactions of WIMP dark matter, are motivating experiments with ever-decreasing levels of radioactive backgrounds. These background reductions are achieved using various techniques, but amongst the most important is minimizing radioactive contamination in the materials from which the experiment is constructed. To this end there have been decades of advances in material sourcing, manufacture and certification, during which researchers have accumulated many thousands of measurements of material radiopurity. Some of these assays are described in publications, others are in databases, but many are still communicated informally. Until this work, there has been no standard format for encoding assay results and no effective, central location for storing them. The aim of this paper is to address these long-standing problems by creating a concise and flexible material assay data format and powerful software application to manipulate it. Finally, a public installation of this software, available at http://www.radiopurity.org, is the largest database of assay results ever compiled and is intended as a long-term repository for the community's data.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Toward single electron resolution phonon mediated ionization detectors

Experiments seeking to detect rare event interactions such as dark matter or coherent elastic neutrino nucleus scattering are striving for large mass detectors with very low detection threshold. Using Neganov-Luke phonon amplification effect, the Cryogenic Dark Matter Search (CDMS) experiment is reaching unprecedented RMS resolutions of ~14 eV ee . CDMSlite is currently the most sensitive experiment to WIMPs of mass ~5 GeV/c 2 but is limited in achieving higher phonon gains due to an early onset of leakage current into Ge crystals. The contact interface geometry is particularly weak for blocking hole injection from the metal, and thus a new design is demonstrated that allows high voltage bias via vacuum separated electrode. With an increased bias voltage and a×2 Luke phonon gain, world best RMS resolution of sigma ~7 eV ee for 0.25 kg (d=75 mm, h=1 cm) Ge detectors was achieved. Since the leakage current is a function of the field and the phonon gain is a function of the applied voltage, appropriately robust interface blocking material combined with thicker substrate (25 mm) will reach a resolution of ~2.8 eV ee . In order to achieve better resolution of ~ eV, we are investigating a layer of insulator between the phonon readout surface and the semiconductor crystals.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

LUX trigger efficiency

The Large Underground Xenon experiment (LUX) searches for dark matter using a dual-phase xenon detector. LUX uses a custom-developed trigger system for event selection. Here, the trigger efficiency, which is defined as the probability that an event of interest is selected for offline analysis, is studied using raw data obtained from both electron recoil (ER) and nuclear recoil (NR) calibrations. The measured efficiency exceeds 98% at a pulse area of 90 detected photons, which is well below the WIMP analysis threshold on the S2 pulse area. The efficiency also exceeds 98% at recoil energies of 1.3 keV and above, for both ER and NR. In conclusion, the measured trigger efficiency varies between 99% and 100% over the fiducial volume of the detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

The LUX experiment

We present the status and prospects of the LUX experiment, which employs approximately 300 kg of two-phase xenon to search for WIMP dark matter interactions. The LUX detector was commissioned at the surface laboratory of the Sanford Underground Research Facility in Lead, SD, between December 2011 and February 2012 and the detector has been operating underground since January, 2013. These proceedings review the results of the commissioning run as well as the status of underground data-taking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

The LUX direct dark matter search

As evidenced by the numerous contributions on the topic at this meeting, the IX International Conference on Interconnections between Particle Physics and Cosmology (PPC2015), the direct detection of dark matter remains as one of the highest priorities in both particle physics and cosmology. In 2013 the LUX direct dark matter search collaboration reported the most stringent constraints to-date on the spin-independent WIMP–nucleon interaction cross section. Here we present a summary of that work, describe recent technical improvements, and results from new calibrations. Prospects for the future of the LUX scientific program are reported, together with the outlook for its successor project, LZ.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

What can(not) be measured with ton-scale dark matter direct detection experiments

Direct searches for dark matter have prompted in recent years a great deal of excitement within the astroparticle physics community, but the compatibility between signal claims and null results of different experiments is far from being a settled issue. In this context, we study here the prospects for constraining the dark matter parameter space with the next generation of ton-scale detectors. Using realistic experimental capabilities for a wide range of targets (including fluorine, sodium, argon, germanium, iodine and xenon), the role of target complementarity is analysed in detail while including the impact of astrophysical uncertainties in a self-consistent manner. We show explicitly that a multi-target signal in future direct detection facilities can determine the sign of the ratio of scalar couplings f{sub n}/f{sub p}, but not its scale. This implies that the scalar-proton cross-section is left essentially unconstrained if the assumption f{sub p} ∼ f{sub n} is relaxed. Instead, we find that both the axial-proton cross-section and the ratio of axial couplings a{sub n}/a{sub p} can be measured with fair accuracy if multi-ton instruments using sodium and iodine will eventually come online. Moreover, it turns out that future direct detection data can easily discriminate between elastic and inelastic scatterings. Finally, we argue that, with weak assumptions regarding the WIMP couplings and the astrophysics, only the dark matter mass and the inelastic parameter (i.e. mass splitting) may be inferred from the recoil spectra — specifically, we anticipate an accuracy of tens of GeV (tens of keV) in the measurement of the dark matter mass (inelastic parameter)

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Cosmological consequences of nearly conformal dynamics at the TeV scale

Nearly conformal dynamics at the TeV scale as motivated by the hierarchy problem can be characterized by a stage of significant supercooling at the electroweak epoch. This has important cosmological consequences. In particular, a common assumption about the history of the universe is that the reheating temperature is high, at least high enough to assume that TeV-mass particles were once in thermal equilibrium. However, as we discuss in this paper, this assumption is not well justified in some models of strong dynamics at the TeV scale. We then need to reexamine how to achieve baryogenesis in these theories as well as reconsider how the dark matter abundance is inherited. We argue that baryonic and dark matter abundances can be explained naturally in these setups where reheating takes place by bubble collisions at the end of the strongly first-order phase transition characterizing conformal symmetry breaking, even if the reheating temperature is below the electroweak scale ∼ 100 GeV. In particular, non-thermal production of heavy WIMPs during bubble collisions becomes a well-motivated possibility. We also discuss inflation as well as gravity wave smoking gun signatures of this class of models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Constraints on ultracompact minihalos from extragalactic γ-ray background

It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the γ-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transitions (i.e., electroweak symmetry breaking, QCD confinement and e{sup +}e{sup −} annihilation) to the extragalactic γ-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic γ-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Global fits of the cMSSM including the first LHC and XENON100 data

We present updated global fits of the constrained Minimal Supersymmetric Standard Model (cMSSM), including the most recent constraints from the ATLAS and CMS detectors at the LHC, as well as the most recent results of the XENON100 experiment. Our robust analysis takes into account both astrophysical and hadronic uncertainties that enter in the calculation of the rate of WIMP-induced recoils in direct detection experiment. We study the consequences for neutralino Dark Matter, and show that current direct detection data already allow to robustly rule out the so-called Focus Point region, therefore demonstrating the importance of particle astrophysics experiments in constraining extensions of the Standard Model of Particle Physics. We also observe an increased compatibility between results obtained from a Bayesian and a Frequentist statistical perspective. We find that upcoming ton-scale direct detection experiments will probe essentially the entire currently favoured region (at the 99% level), almost independently of the statistical approach used. Prospects for indirect detection of the cMSSM are further reduced.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

The low energy spectrum of TeO{sub 2} bolometers: results and dark matter perspectives for the CUORE-0 and CUORE experiments

We collected 19.4 days of data from four 750 g TeO{sub 2} bolometers, and in three of them we were able to set the energy threshold around 3 keV using a new analysis technique. We found a background rate ranging from 25 cpd/keV/kg at 3 keV to 2 cpd/keV/kg at 25 keV, and a peak at 4.7 keV. The origin of this peak is presently unknown, but its presence is confirmed by a reanalysis of 62.7 kg·days of data from the finished CUORICINO experiment. Finally, we report the expected sensitivities of the CUORE-0 (52 bolometers) and CUORE (988 bolometers) experiments to a WIMP annual modulation signal.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Dark radiation constraints on mixed Axion/Neutralino dark matter

Recent analyses of CMB data combined with the measurement of BAO and H{sub 0} show that dark radiation — parametrized by the apparent number of additional neutrinos ΔN{sub eff} contributing to the cosmic expansion — is bounded from above by about ΔN{sub eff}∼<1.6 at 95% CL. We consider the mixed axion/neutralino cold dark matter scenario which arises in R-parity conserving supersymmetric (SUSY) models wherein the strong CP problem is solved by hadronic axions with a concommitant axion(a)/saxion(s)/axino(ã) supermultiplet. Our new results include improved calculations of thermal axion and saxion production and include effects of saxion decay to axinos and axions. We show that the above bound on ΔN{sub eff} is easily satisfied if saxions are mainly thermally produced and m{sub LSP} < m{sub ã}∼<m{sub s}. However, if the dominant mechanism of saxion production is through coherent oscillations, the CMB data provides a strong bound on saxion production followed by saxion decays to axions. Furthermore we show that scenarios with mixed neutralino/axion dark matter are highly constrained by combined CMB, BBN and Xe-100 constraints. In particular, supersymmetric models with a standard overabundance of neutralino dark matter are excluded for all values of the Peccei-Quinn breaking scale. Next generation WIMP direct detection experiments may be able to discover or exclude mixed axion-neutralino CDM scenarios where s → aa is the dominant saxion decay mode.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Spectral study of the HESS J1745-290 gamma-ray source as dark matter signal

We study the main spectral features of the gamma-ray fluxes observed by the High Energy Stereoscopic System (HESS) from the J1745-290 Galactic Center source during the years 2004, 2005 and 2006. In particular, we show that these data are well fitted as the secondary gamma-rays photons generated from dark matter annihilating into Standard Model particles in combination with a simple power law background. We present explicit analyses for annihilation in a single standard model particle-antiparticle pair. In this case, the best fits are obtained for the uū and d d-bar quark channels and for the W{sup +}W{sup −} and ZZ gauge bosons, with background spectral index compatible with the Fermi-Large Area Telescope (LAT) data from the same region. The fits return a heavy WIMP, with a mass above ∼ 10 TeV, but well below the unitarity limit for thermal relic annihilation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Gamma-ray lines and one-loop continuum from s-channel dark matter annihilations

The era of indirect detection searches for dark matter has begun, with the sensitivities of gamma-ray detectors now approaching the parameter space relevant for weakly interacting massive particles. In particular, gamma ray lines would be smoking gun signatures of dark matter annihilation, although they are typically suppressed compared to the continuum. In this paper, we pay particular attention to the 1-loop continuum generated together with the gamma-ray lines and investigate under which conditions a dark matter model can naturally lead to a line signal that is relatively enhanced. We study generic classes of models in which DM is a fermion that annihilates through an s-channel mediator which is either a vector or scalar and identify the coupling and mass conditions under which large line signals occur. We focus on the ''forbidden channel mechanism'' advocated a few years ago in the ''Higgs in space'' scenario for which tree level annihilation is kinematically forbidden today. Detailed calculations of all 1-loop annihilation channels are provided. We single out very simple models with a large line over continuum ratio and present general predictions for a large range of WIMP masses that are relevant not only for Fermi and Hess II but also for the next generation of telescopes such as CTA and Gamma-400. Constraints from the relic abundance, direct detection and collider bounds are also discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Minimal decaying Dark Matter and the LHC

We consider a minimal Dark Matter model with just two additional states, a Dark Matter Majorana fermion and a colored or electroweakly charged scalar, without introducing any symmetry to stabilize the DM state. We identify the parameter region where an indirect DM signal would be within the reach of future observations and the DM relic density generated fits the observations. We find in this way two possible regions in the parameter space, corresponding to a FIMP/SuperWIMP or a WIMP DM. We point out the different collider signals of this scenario and how it will be possible to measure the different couplings in case of a combined detection.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Axion searches with the EDELWEISS-II experiment

We present new constraints on the couplings of axions and more generic axion-like particles using data from the EDELWEISS-II experiment. The EDELWEISS experiment, located at the Underground Laboratory of Modane, primarily aims at the direct detection of WIMPs using germanium bolometers. It is also sensitive to the low-energy electron recoils that would be induced by solar or dark matter axions. Using a total exposure of up to 448 kg.d, we searched for axion-induced electron recoils down to 2.5 keV within four scenarios involving different hypotheses on the origin and couplings of axions. We set a 95 % CL limit on the coupling to photons g{sub Aγ} < 2.15 × 10{sup −9} GeV{sup −1} in a mass range not fully covered by axion helioscopes. We also constrain the coupling to electrons, g{sub Ae} < 2.59 × 10{sup −11}, similar to the more indirect solar neutrino bound. Finally we place a limit on g{sub Ae} × g{sub AN}{sup eff} < 4.82 × 10{sup −17}, where g{sub AN}{sup eff} is the effective axion-nucleon coupling for {sup 57}Fe. Combining these results we fully exclude the mass range 0.92 eV < m{sub A} < 80 keV for DFSZ axions and 5.78 eV < m{sub A} < 40 keV for KSVZ axions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Direct detection of light anapole and magnetic dipole DM

We present comparisons of direct detection data for ''light WIMPs'' with an anapole moment interaction (ADM) and a magnetic dipole moment interaction (MDM), both assuming the Standard Halo Model (SHM) for the dark halo of our galaxy and in a halo-independent manner. In the SHM analysis we find that a combination of the 90% CL LUX and CDMSlite limits or the new 90% CL SuperCDMS limit by itself exclude the parameter space regions allowed by DAMA, CoGeNT and CDMS-II-Si data for both ADM and MDM. In our halo-independent analysis the new LUX bound excludes the same potential signal regions as the previous XENON100 bound. Much of the remaining signal regions is now excluded by SuperCDMS, while the CDMSlite limit is much above them. The situation is of strong tension between the positive and negative search results both for ADM and MDM. We also clarify the confusion in the literature about the ADM scattering cross section.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Bayesian reconstruction of the velocity distribution of weakly interacting massive particles from direct dark matter detection data

In this paper, we extended our earlier work on the reconstruction of the (time-averaged) one-dimensional velocity distribution of Galactic Weakly Interacting Massive Particles (WIMPs) and introduce the Bayesian fitting procedure to the theoretically predicted velocity distribution functions. In this reconstruction process, the (rough) velocity distribution reconstructed by using raw data from direct Dark Matter detection experiments directly, i.e. measured recoil energies, with one or more different target materials, has been used as ''reconstructed-input'' information. By assuming a fitting velocity distribution function and scanning the parameter space based on the Bayesian analysis, the astronomical characteristic parameters, e.g. the Solar and Earth's Galactic velocities, will be pinned down as the output results.

79 ASTRONOMY AND ASTROPHYSICS↗