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  1. Non-thermal electron distributions, such as beams of electrons, are found in many laboratory and astrophysical plasma sources and can produce anisotropic and polarized emission. Theories used to model the emission require sublevel specific analysis, which can be difficult to verify experimentally. Using two polarization-sensitive Johann-type crystal spectrometers at the National Institute of Standards and Technology (NIST) electron beam ion trap facility, we measured the linear polarization of well-known dielectronic recombination satellite transitions from Li-like Ar ions and two blended features from Be-like ions. The spectrometers observed the plasma at 90◦ relative to the electron beam propagation direction, and the crystalmore »dispersion planes were oriented perpendicular relative to each other to allow for differing polarization sensitivities. Measurements were taken near the resonance energies of each line and compared with theoretical predictions based on relativistic magnetic sublevel atomic kinetics using the density-matrix theory. Most of the predictions are in excellent agreement with measured values.« less
  2. High-resolution x-ray spectra were recorded at the National Institute of Standards and Technology electron beam ion trap (EBIT) using two Johann-type crystal spectrometers, with their dispersion planes oriented parallel and perpendicular to the beam direction. The linear polarizations of the 1s2−1s2l transitions in He-like argon ions were determined from the measured spectra at electron beam energies of 3.87 and 7.91 keV. The theoretical analysis was performed using detailed collisional-radiative modeling of the non-Maxwellian EBIT plasma with the NOMAD code modified to account for magnetic sublevel atomic kinetics. Effects influencing the polarizations of the observed 1s2−1s2l lines were investigated, including radiativemore »cascades, the 1s2 1S0−1s2s 1S0 two-photon transition, and the charge exchange recombination of H-like argon ions. With these included, the measured polarizations of the resonance (1s2 1S0−1s2p 1P1), intercombination (1s2 1S0−1s2p 3P1), and forbidden lines (1s2 1S0−1s2s 3S1, 1s2 1S0−1s2p 3P2 ) were found to be in good agreement with the calculations.« less
  3. This paper investigates the psychological traits of individuals’ attraction to engaging in hacking behaviors (both ethical and illegal/unethical)upon entering the workforce.We examine the role of the Dark Triad, Opposition to Authority and Thrill-Seeking traits as regards the propensity of an individual to be interested in White Hat, Black Hat,and Grey Hat hacking. A new set of scales were developed to assist in the delineation of the three hat categories. We also developed a scale to measure each subject’s perception of the probability of being apprehended for violating privacy laws. Engaging in criminal activity involves a choice where there are consequencesmore »and opportunities, and individuals perceive them differently, but they can be deterred if there is a likelihood of punishment,and the punishment is severe. The results suggest that individuals that are White Hat, Grey Hat and Black Hat hackers score high on the Machiavellian and Psychopathy scales. We also found evidence that Grey Hatters oppose authority, Black Hatters score high on the thrill-seeking dimension and White Hatters, the good guys, tend to be Narcissists. Thrill-seeking was moderately important for White Hat hacking and Black hat hacking. Opposition to Authority was important for Grey Hat hacking. Narcissism was not statistically significant in any of the models. The probability of being apprehended had a negative effect on Grey Hat and Black Hat hacking. Several suggestions will be made on what organizations can do to address insider threats.« less
  4. This paper investigates the psychological traits of individuals’ attraction to engaging in hacking behaviors (both ethical and illegal/unethical)upon entering the workforce.We examine the role of the Dark Triad, Opposition to Authority and Thrill-Seeking traits as regards the propensity of an individual to be interested in White Hat, Black Hat,and Grey Hat hacking. A new set of scales were developed to assist in the delineation of the three hat categories. We also developed a scale to measure each subject’s perception of the probability of being apprehended for violating privacy laws. Engaging in criminal activity involves a choice where there are consequencesmore »and opportunities, and individuals perceive them differently, but they can be deterred if there is a likelihood of punishment,and the punishment is severe. The results suggest that individuals that are White Hat, Grey Hat and Black Hat hackers score high on the Machiavellian and Psychopathy scales. We also found evidence that Grey Hatters oppose authority, Black Hatters score high on the thrill-seeking dimension and White Hatters, the good guys, tend to be Narcissists. Thrill-seeking was moderately important for White Hat hacking and Black hat hacking. Opposition to Authority was important for Grey Hat hacking. Narcissism was not statistically significant in any of the models. The probability of being apprehended had a negative effect on Grey Hat and Black Hat hacking. Several suggestions will be made on what organizations can do to address insider threats.« less
  5. Free, publicly-accessible full text available March 1, 2023
  6. Free, publicly-accessible full text available January 1, 2023
  7. A bstract A search is presented for new particles produced at the LHC in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb − 1 , collected in 2017–2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with anmore »earlier search based on a data sample of 36 fb − 1 , collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.« less
    Free, publicly-accessible full text available November 1, 2022
  8. Free, publicly-accessible full text available September 1, 2022