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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Automatic segmentation of head and neck CT images for radiotherapy treatment planning using multiple atlases, statistical appearance models, and geodesic active contours

Purpose: Accurate delineation of organs at risk (OARs) is a precondition for intensity modulated radiation therapy. However, manual delineation of OARs is time consuming and prone to high interobserver variability. Because of image artifacts and low image contrast between different structures, however, the number of available approaches for autosegmentation of structures in the head-neck area is still rather low. In this project, a new approach for automated segmentation of head-neck CT images that combine the robustness of multiatlas-based segmentation with the flexibility of geodesic active contours and the prior knowledge provided by statistical appearance models is presented. Methods: The presented approach is using an atlas-based segmentation approach in combination with label fusion in order to initialize a segmentation pipeline that is based on using statistical appearance models and geodesic active contours. An anatomically correct approximation of the segmentation result provided by atlas-based segmentation acts as a starting point for an iterative refinement of this approximation. The final segmentation result is based on using model to image registration and geodesic active contours, which are mutually influencing each other. Results: 18 CT images in combination with manually segmented labels of parotid glands and brainstem were used in a leave-one-out cross validation scheme in order to evaluate the presented approach. For this purpose, 50 different statistical appearance models have been created and used for segmentation. Dice coefficient (DC), mean absolute distance and max. Hausdorff distance between the autosegmentation results and expert segmentations were calculated. An average Dice coefficient of DC = 0.81 (right parotid gland), DC = 0.84 (left parotid gland), and DC = 0.86 (brainstem) could be achieved. Conclusions: The presented framework provides accurate segmentation results for three important structures in the head neck area. Compared to a segmentation approach based on using multiple atlases in combination with label fusion, the proposed hybrid approach provided more accurate results within a clinically acceptable amount of time.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Electron efficiency measurements with the ATLAS detector using 2012 LHC proton–proton collision data

This paper describes the algorithms for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC). These algorithms were used for all ATLAS results with electrons in the final state that are based on the 2012 pp collision data produced by the LHC at s = 8 TeV. The efficiency of these algorithms, together with the charge misidentification rate, is measured in data and evaluated in simulated samples using electrons from Z→ ee, Z→ eeγ and J/ ψ→ ee decays. For these efficiency measurements, the full recorded data set, corresponding to an integrated luminosity of 20.3 fb - 1 , is used. Based on a new reconstruction algorithm used in 2012, the electron reconstruction efficiency is 97% for electrons with E T = 15 GeV and 99% at E T = 50 GeV. Combining this with the efficiency of additional selection criteria to reject electrons from background processes or misidentified hadrons, the efficiency to reconstruct and identify electrons at the ATLAS experiment varies from 65 to 95%, depending on the transverse momentum of the electron and background rejection.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Jet energy scale and resolution measured in proton–proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Jet energy scale and resolution measurements with their associated uncertainties are reported for jets using 36–81 fb -1 of proton–proton collision data with a centre-of-mass energy of √s=13 TeV collected by the ATLAS detector at the LHC. Jets are reconstructed using two different input types: topo-clusters formed from energy deposits in calorimeter cells, as well as an algorithmic combination of charged-particle tracks with those topo-clusters, referred to as the ATLAS particle-flow reconstruction method. The anti-k t jet algorithm with radius parameter R=0.4 is the primary jet definition used for both jet types. This result presents new jet energy scale and resolution measurements in the high pile-up conditions of late LHC Run 2 as well as a full calibration of particle-flow jets in ATLAS. Jets are initially calibrated using a sequence of simulation-based corrections. Next, several in situ techniques are employed to correct for differences between data and simulation and to measure the resolution of jets. The systematic uncertainties in the jet energy scale for central jets (|η|<1.2) vary from 1% for a wide range of high-p T jets (250 T <2000 GeV), to 5% at very low p T (20 GeV) and 3.5% at very high p T (>2.5 TeV). The relative jet energy resolution is measured and ranges from (24±1.5)% at 20 GeV to (6±0.5)% at 300 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

The ATLAS inner detector trigger performance in pp collisions at 13 TeV during LHC Run 2

The design and performance of the inner detector trigger for the high level trigger of the ATLAS experiment at the Large Hadron Collider during the 2016–2018 data taking period is discussed. In 2016, 2017, and 2018 the ATLAS detector recorded 35.6 fb –1 , 46.9 fb –1 , and 60.6 fb –1 respectively of proton–proton collision data at a centre-of-mass energy of 13 TeV. In order to deal with the very high interaction multiplicities per bunch crossing expected with the 13 TeV collisions the inner detector trigger was redesigned during the long shutdown of the Large Hadron Collider from 2013 until 2015. An overview of these developments is provided and the performance of the tracking in the trigger for the muon, electron, tau and b-jet signatures is discussed. The high performance of the inner detector trigger with these extreme interaction multiplicities demonstrates how the inner detector tracking continues to lie at the heart of the trigger performance and is essential in enabling the ATLAS physics programme.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurement of the energy response of the ATLAS calorimeter to charged pions from $W^{\pm }\rightarrow \tau ^{\pm }(\rightarrow \pi ^{\pm }\nu _{\tau })\nu _{\tau }$ events in Run 2 data

The energy response of the ATLAS calorimeter is measured for single charged pions with transverse momentum in the range 10 < p T < 300 GeV. The measurement is performed using 139 fb –1 of LHC proton–proton collision data at √s = 13 TeV taken in Run 2 by the ATLAS detector. Charged pions originating from τ-lepton decays are used to provide a sample of high-p T isolated particles, where the composition is known, to test an energy regime that has not previously been probed by in situ single-particle measurements. The calorimeter response to single-pions is observed to be overestimated by ~2% across a large part of the p T spectrum in the central region and underestimated by ~4% in the endcaps in the ATLAS simulation. The uncertainties in the measurements are ≲1% for 15 < p T < 185 GeV in the central region. To investigate the source of the discrepancies, the width of the distribution of the ratio of calorimeter energy to track momentum, the energies per layer and response in the hadronic calorimeter are also compared between data and simulation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Determination of the parton distribution functions of the proton using diverse ATLAS data from pp collisions at $$\sqrt{s} = 7$$, 8 and 13 TeV

This paper presents an analysis at next-to-next-to-leading order in the theory of quantum chromodynamics for the determination of a new set of proton parton distribution functions using diverse measurements in pp collisions at $\sqrt{s}$ = 7, 8 and 13 TeV, performed by the ATLAS experiment at the Large Hadron Collider, together with deep inelastic scattering data from ep collisions at the HERA collider. The ATLAS data sets considered are differential cross-section measurements of inclusive W ± and Z/γ* boson production, W ± and Z boson production in association with jets, $t\bar{t}$ production, inclusive jet production and direct photon production. In the analysis, particular attention is paid to the correlation of systematic uncertainties within and between the various ATLAS data sets and to the impact of model, theoretical and parameterisation uncertainties. The resulting set of parton distribution functions is called ATLASpdf21.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of exclusive pion pair production in proton–proton collisions at $\sqrt{s}={7}\,\text {TeV}$ with the ATLAS detector

The exclusive production of pion pairs in the process $pp$ → $pp π$ + $π$ - has been measured at $\sqrt{s}={7}\,\text {TeV}$ with the ATLAS detector at the LHC, using $80 µb$ -1 of low-luminosity data. The pion pairs were detected in the ATLAS central detector while outgoing protons were measured in the forward ATLAS ALFA detector system. This rep resents the first use of proton tagging to measure an exclusive hadronic final state at the LHC. A cross-section measurement is performed in two kinematic regions defined by the pro ton momenta, the pion rapidities and transverse momenta, and the pion–pion invariant mass. Cross-section values of $4.8 ± 1.0$ ${(stat)}^{+0.3}_{-0.2}$ $(syst) µ b$ and $9 ± 6$ ${(stat)}^{+2}_{-2}$ $(syst) µ b$ are obtained in the two regions; they are compared with theoretical models and provide a demonstration of the feasibility of measurements of this type.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Dijet production in s = 7 TeV p p collisions with large rapidity gaps at the ATLAS experiment

CERN-LHC. Measurements of the pseudorapidity gap and xi distributions for dijet production in diffractive events which are defined by large gaps devoid of activity seen in the ATLAS detector, based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV of integrated luminosity of 6.8 nb-1 collected in 2010. The final state consists of two jets found by the anti-kt jet algorithm with transverse momentum greater than 20 GeV and empty regions in the acceptance of the ATLAS detector. The pseudorapidity gap variable, denoted here as DELTA(C=RAPGAP), is defined as the larger of the pseudorapidity regions extending to the limits of the ATLAS detector sensitivity at eta=+-4.8, in which no final state particles are observed above a (transverse) momentum threshold. The xi variable is calculated using M**2/S and for Single Diffraction DELTA(C=RAPGAP)~=-ln(xi). See PLBXX (2015) YY for more details.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for heavy resonances decaying to a photon and a hadronically decaying Z / W / H boson in p p collisions at s = 13 TeV with the ATLAS detector

CERN-ATLAS. Search for heavy resonances decaying to a photon and a hadronically decaying Z/W/H boson in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector. Many extensions of the Standard Model predict new resonances decaying to a Z, W, or Higgs boson and a photon. This paper presents a search for such resonances produced in pp collision at sqrt{s}=13 TeV using a dataset with an integrated luminosity of 36.1/fb collected by the ATLAS detector at the Large Hadron Collider. The Z/W/H bosons are identified through their decays to hadrons. The data are found to be consistent with the Standard Model expectation in the entire investigated mass range. Upper limits are set on the production cross section times branching fraction for resonance decays to Z/W+gamma in the mass range from 1.0 to 6.8 TeV, and for the first time into H+gamma in the mass range from 1.0 to 3.0 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Physics motivation and detector upgrades for the new era of the ATLAS experiment

The ATLAS experiment at CERN’s Large Hadron Collider (LHC) will be upgraded in two stages to prepare first for the Run~3 data-taking campaign, during which the integrated luminosity will roughly double, and then for the High-Luminosity LHC program with an ultimate integrated luminosity of up to 4 ab ^{{-1}} − 1 . These upgrades and high-statistics datasets will allow ATLAS to perform searches and precision measurements to constrain the Standard Model in yet-unexplored phase spaces and in the Higgs sector. This contribution summarizes the ATLAS detector upgrades and selected physics prospects for Run~3 and the HL-LHC.

Nielsen, Jason↗
DOE OSTI2014

Vector and Scalar Bosons at DØ and ATLAS

Vector Boson Fusion (VBF) has never been measured in hadron collisions, but it is one of the most sensitive modes for low mass Standard Model Higgs production at ATLAS. The objective of this proposal is to measure VBF production of W and Z bosons at the DØ Experiment taking place at the Tevatron Collider near Chicago, Illinois, and at the ATLAS Experiment, running at the Large Hadron Collider in Geneva, Switzerland. The framework developed in these measurements will be used to discover and study the Higgs Boson produced through the same mechanism (VBF) at ATLAS.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Energy Frontier Research With ATLAS: Final Report

The Boston University (BU) group is playing key roles across the ATLAS experiment: in detector operations, the online trigger, the upgrade, computing, and physics analysis. Our team has been critical to the maintenance and operations of the muon system since its installation. During Run 1 we led the muon trigger group and that responsibility continues into Run 2. BU maintains and operates the ATLAS Northeast Tier 2 computing center. We are actively engaged in the analysis of ATLAS data from Run 1 and Run 2. Physics analyses we have contributed to include Standard Model measurements (W and Z cross sections, t\bar{t} differential cross sections, WWW^* production), evidence for the Higgs decaying to \tau^+\tau^-, and searches for new phenomena (technicolor, Z' and W', vector-like quarks, dark matter).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Research on the ATLAS Experiment at the University of Illinois: Final Report

The goal of particle physics is to understand the Universe at its most fundamental level, including the constituents of matter and their interactions, and the nature of space and time itself. The quest to understand the fundamental building blocks of nature, and their interactions, is one of the most ambitious and enduring of human endeavors. Recent developments in particle physics and cosmology raise the exciting prospect that we are on the threshold of a major step forward in this pursuit. Facilities such as CERN's Large Hadron Collider (LHC) provide a unique window into the subatomic world to pursue this understanding. Mark Neubauer and his research group at the University of Illinois were supported over a nine-month period (07/01/2017 through 03/31/2018) to perform high-energy particle physics research on the ATLAS experiment at the LHC. The primary focus of this research was to search for physics beyond the standard model through an analysis of high-energy proton-proton collision data from the ATLAS experiment, with an emphasis on the Higgs boson as a sensitive tool for this search, and development of fast particle tracking systems for use the ATLAS trigger system.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Comment on "An implementation of neural simulation-based inference for parameter estimation in ATLAS''

The paper titled "An implementation of neural simulation-based inference for parameter estimation in ATLAS" by the ATLAS collaboration (arXiv:2412.01600v1 [hep-ex]) describes the implementation of neural simulation-based inference for a measurement analysis performed by ATLAS. The uncertainties in the analysis arising from the finiteness of the simulated datasets are estimated using a novel double-bootstrapping technique described in that work. In the present comment, it is claimed and demonstrated, using a toy example, that the double-bootstrapping technique does not actually capture the aforementioned uncertainties.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

An expanded maize gene expression atlas based on RNA sequencing and its use to explore root development

Comprehensive and systematic transcriptome profiling provides valuable insight into biological and developmental processes that occur throughout the life cycle of a plant. We have enhanced our previously published microarray-based gene atlas of maize ( Zea mays L.) inbred B73 to now include 79 distinct replicated samples that have been interrogated using RNA sequencing (RNA-seq). The current version of the atlas includes 50 original array-based gene atlas samples, a time-course of 12 stalk and leaf samples postflowering, and an additional set of 17 samples from the maize seedling and adult root system. The entire dataset contains 4.6 billion mapped reads, with an average of 20.5 million mapped reads per biological replicate, allowing for detection of genes with lower transcript abundance. As the new root samples represent key additions to the previously examined tissues, we highlight insights into the root transcriptome, which is represented by 28,894 (73.2%) annotated genes in maize. Additionally, we observed remarkable expression differences across both the longitudinal (four zones) and radial gradients (cortical parenchyma and stele) of the primary root supported by fourfold differential expression of 9353 and 4728 genes, respectively. Among the latter were 1110 genes that encode transcription factors, some of which are orthologs of previously characterized transcription factors known to regulate root development in Arabidopsis thaliana (L.) Heynh., while most are novel, and represent attractive targets for reverse genetics approaches to determine their roles in this important organ. As a result, this comprehensive transcriptome dataset is a powerful tool toward understanding maize development, physiology, and phenotypic diversity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

ORIGIN OF THE CHAOTIC MOTION OF THE SATURNIAN SATELLITE ATLAS

We revisit the dynamics of Atlas. Using Cassini ISS astrometric observations spanning 2004 February to 2013 August, Cooper et al. found evidence that Atlas is currently perturbed by both a 54:53 corotation eccentricity resonance (CER) and a 54:53 Lindblad eccentricity resonance (LER) with Prometheus. They demonstrated that the orbit of Atlas is chaotic, with a Lyapunov time of order 10 years, as a direct consequence of the coupled resonant interaction (CER/LER) with Prometheus. Here we investigate the interactions between the two resonances using the CoraLin analytical model, showing that the chaotic zone fills almost all the corotation sites occupied by the satellite's orbit. Four 70:67 apse-type mean motion resonances with Pandora are also overlapping, but these resonances have a much weaker effect. Frequency analysis allows us to highlight the coupling between the 54:53 resonances, and confirms that a simplified system including the perturbations due to Prometheus and Saturn's oblateness only captures the essential features of the dynamics.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream

We present the first spectroscopic measurements of the ATLAS and Aliqa Uma streams from the Southern Stellar Stream Spectroscopic Survey (S 5), in combination with the photometric data from the Dark Energy Survey and astrometric data from Gaia. From the coherence of spectroscopic members in radial velocity and proper motion, we find that these two systems are extremely likely to be one stream with discontinuity in morphology and density on the sky (the “kink” feature). We refer to this entire stream as the ATLAS-Aliqa Uma stream, or the AAU stream. We perform a comprehensive exploration of the effect of baryonic substructures and find that only an encounter with the Sagittarius dwarf ∼0.5 Gyr ago can create a feature similar to the observed “kink.” In addition, we also identify two gaps in the ATLAS component associated with the broadening in the stream width (the “broadening” feature). These gaps have likely been created by small mass perturbers, such as dark matter halos, as the AAU stream is the most distant cold stream known with severe variations in both the stream surface density and the stream track on the sky. With the stream track, stream distance, and kinematic information, we determine the orbit of the AAU stream and find that it has been affected by the Large Magellanic Cloud, resulting in a misalignment between the proper motion and stream track. Together with the Orphan-Chenab Stream, AAU is the second stream pair that has been found to be a single stream separated into two segments by external perturbation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas

Far-ultraviolet (FUV; ~1200–2000 Å) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N 1500 Å ≳ 5/resel), high-resolution (R ~ 15,000) FUV spectral database of 45 nearby (0.002 < z < 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 < log M * (M ⊙ ) < 10.1), star formation rate (–2.0 < log SFR (M ⊙ yr –1 ) < +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization (0.5 < O 32 < 38.0), reddening (0.02 < E(B – V) < 0.67), and nebular density (10 < n e (cm –3 ) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the z ~ 0 mass–metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to z ≳ 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.

79 ASTRONOMY AND ASTROPHYSICS↗