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We discuss our recent progress on improving the theoretical description of the pp \to t\bar{t}W^\pm p p → t t ‾ W ± process with particular focus on fiducial signatures that include top-quark decays. We employ a wide range of techniques from parton shower matching, narrow width approximation to full off-shell computations to assess the importance of the different modeling approaches.
NREL's new imaging tool could provide manufacturers with insight on their processes.
Municipal wastewater treatment facilities have typically been limited to the role of accepting wastewater, treating it to required levels, and disposing of its treatment residuals. However, a new view is emerging which includes wastewater treatment facilities as regional resource recovery centers. This view is a direct result of increasingly stringent regulations, concerns over energy use, carbon footprint, and worldwide depletion of fossil fuel resources. Resources in wastewater include chemical and thermal energy, as well as nutrients, and water. A waste stream such as residual grease, which concentrates in the drainage from restaurants (referred to as Trap Waste), is a good example of a resource with an energy content that can be recovered for beneficial reuse. If left in wastewater, grease accumulates inside of the wastewater collection system and can lead to increased corrosion and pipe blockages that can cause wastewater overflows. Also, grease in wastewater that arrives at the treatment facility can impair the operation of preliminary treatment equipment and is only partly removed in the primary treatment process. In addition, residual grease increases the demand in treatment materials such as oxygen in the secondary treatment process. When disposed of in landfills, grease is likely to undergo anaerobic decay prior to landfill capping, resulting in the atmospheric release of methane, a greenhouse gas (GHG). This research project was therefore conceptualized and implemented by the San Francisco Public Utilities Commission (SFPUC) to test the feasibility of energy recovery from Trap Waste in the form of Biodiesel or Methane gas.
This work describes the ongoing work to develop a molten salt reactor (MSR) model and associated tools for safeguards analysis. A new flowsheet was developed in collaboration with Oak Ridge National Laboratory (ORNL) for the Molten Salt Demonstration Reactor (MSDR). This design was chosen by ORNL as a generic baseline design that could be used for safeguards research. The model has simple chemical processing that is less extensive than the two-fluid flowsheet developed in the last year. A detailed TRITON reactor physics model, provided by ORNL, was implemented into the process model. The process model now includes reactor parameters such as K-eff and decay heat, which could be used as part of an advanced safeguards approach. Finally, a set of generic safeguards tools based on current safeguards approaches were developed. These tools are flexible and can be used with most MSR flowsheets. ACKNOWLEDGEMENTS This work was funded by the Materials Protection Accounting and Control Technologies (MPACT) working group as part of the Fuel Cycle Technologies Program under the U.S. Department of Energy, Office of Nuclear Energy. The authors would also like to acknowledge Ben Betz ler for his work on the reactor physics models that were incorporated into the work and the continued collaboration with ORNL staff.
This internship involved the design and assembly of a mechanical system for testing skipper-Charge Couple Devices (CCDs) for the DarkNESS project. Skipper-CCDs are highly-sensitive sensors with ultra-low readout noise that are deployed for direct detection of dark matter. DarkNESS is a CubeSat that aims to use skipper CCDs to search for dark matter decaying into X-rays. Currently, in the testing phase, the design process involved creating 3D models of mechanical adapters to operate a prototype space Multi Chip Module (sMCM) package in existing testing chambers in the CCD lab at Fermilab's IERC. The drawings were sent out to be machined, and while waiting to receive the finished adapters, we assembled a vacuum chamber for skipper-CCD testing and performed initial testing of a single CCD controlled by the space Low Threshold Acquisition (sLTA) board that will be employed on the CubeSat. The results showed that the testing conditions are optimal for data to start being taken and analyzed.
Two independent methods for measuring the electron intensity in interstellar space are proposed. The positron method involves the production of pions in proton-proton collisions, the decay of the pions into muons, and the subsequent decay of the muons into positrons. Results from detailed calculations of these processes are given in graphical form. The second method involves cosmic electron emitted synchrotron radiation in the interstellar magnetic field. These two methods are also used to analyze the spatial and temporal constancy of cosmic ray electrons in the galaxy.
Oxygen isotope analysis of anhydrous high-temperature phases from carbonaceous meteorite chondrites indicates a high degree of O(17) and O(18) isotope depletion. The isotope decay is believed to be a result of nuclear rather than chemical processes caused by the admixture of a component consisting of almost pure O(16). It is theorized that this component may predate the solar system and may represent interstellar dust with a separate history of nucleosynthesis.
Measurements are presented for processes occurring in XeF self-sustained discharges including fluorescence, gain, and absorption at different wavelengths as a function of F2, Xe, and He partial pressures. Time-correlated oscillograms are given for the laser discharge current, metastable XeF small-signal gain at 351.1 nm, transient absorptions at 333.6 and 363.8 nm, metastable-XeF B-state sidelight emission at about 350 nm, metastable-F emission at 634.8 nm, and metastable-F emission at 731.1 nm. It is found that He atoms are necessary for the production of metastable-XeF in its lower vibrational levels and that radiative processes and He quenching are the primary mechanisms for metastable-XeF decay. For small-signal gains of as low as about 8%/cm, the transient absorption at the laser wavelength may be as large as about 1-2%/cm.
The behavior and time evolution of the large-scale magnetic fields and plasma of the dayside Venus ionosphere are studied using a one-dimensional model. The coupled continuity, momentum, and Maxwell's equations are solved simultaneously for O(+), O2(+), and H(+), and the magnetic field. The calculated magnetic field profiles are in good agreement with Pioneer Venus orbiter magnetometer observations. The magnetic field structure is quasi-steady for slow changes of the solar wind dynamic pressure. The peak at 165 km is maintained by downward convection from higher altitudes. The time scale for the decay of the field by the pure one-dimensional vertical diffusion/convection process is several hours unless the flux is resupplied from the top of the ionosphere.
The asymptotic solutions of Navier-Stokes equations for vortex filaments of finite strength with small effective vortical cores are summarized with special emphasis placed on the physical meaning and the practical limit to the applicability of the asymptotic solution. Finite-difference solutions of Navier-Stokes equations for the marging of the filament(s) are described with a focus on the development of the approximate boundary conditions for the computational domain. An efficiency study employing a model problem is used to assess the advantages of the present approximate boundary condition method over previously used techniques. Applications of the present method are presented for the motion and decay of a 3:1 elliptic vortex ring, and for the merging process of a pair of coaxial vortex rings. A numerical procedure for the problem of local merging of vortex filaments, which requires the asymptotic analysis as well as the numerical Navier-Stokes solver, is also presented.
Numerical solution of two-dimensional incompressible hydrodynamics shows that states of near minimal ratio of enstrophy to energy can be attained in times short compared with the flow decay time, confirming the simplest turbulent selective decay conjecture, and suggesting that coherent vortex structures do not terminate nonlinear processes. After all possible vortex mergers occur, the vorticity attains a particlelike character, suggested by the late-time similarity of the streamlines to Ewald potential contours.
Characteristics of relativistic electron precipitation bursts observed by the Heavy Ion Large Telescope (HILT) experiment onboard the Solar, Anomalous, and Magnetospheric Partical Explorer (SAMPEX) satellite were examined. Relatively narrow, persitent, latitudinal bands of precipitation with time scales of 10 to approximately 30 sec near the outer edge of the radiation belt which develop and decay with a time scale of a few hours are reported. Acceleration processes more effective than the usual radial diffusion process or scattering process would be needed to explain this strong precipitation band phenomenon. Another prominent signature is microbursts with a time scale down to a few hundred milliseconds. It is suggested that these microbursts are due to wave-particle interaction involving a relaxation-oscillator type of mechanism.
The background measured with space-borne gamma-ray spectrometers (GRS) in the 100 keV-10 MeV energy region consists of both discrete lines and continuum. The discrete lines originate in the decay of radioactive species. The continuum originates from a number of different processes and can be an important factor in the detection, for example, of weak gamma-ray lines from a planetary surface. Measurements of the gamma-ray background have been made during the cruise portion of a number of planetary missions. The three missions described here are the Apollo 15 and 16 missions each of which carried a 7 cm x 7 cm NaI scintillation detector, the Mars Observer (MO) mission which used a 5.5 cm X 5.5 cm high-purity germanium (HPGe) detector, and the Near Earth Rendezvous Asteroid (NEAR) mission that has a 2.54 cm x 7.6 cm NaI detector. A comparison of the intensity and spectral shape of these background spectra can be useful to help understand how these backgrounds vary with spacecraft size, detector position, and detector size. The use of shields to reduce the background components on these three missions is a test of the effectiveness of different shield designs.
Aquila X-1 is the most prolific of soft X-ray transients. It is believed to contain a rapidly spinning neutron star sporadically accreting near the Eddington limit from a low-mass companion star. The interest in studying the repeated X-ray outbursts from Aquila X-1 is twofold: (1) studying the relation between optical, soft and hard X-ray emission during the outburst onset, development and decay; (2) relating the spectral component to thermal and non-thermal processes occurring near the magnetosphere and in the boundary layer of a time-variable accretion disk. Our investigation is based on the BATSE monitoring of Aquila X-1 performed by our group. We observed Aquila X-1 in 1997 and re-analyzed archival information obtained in April 1994 during a period of extraordinary outbursting activity of the source in the hard X-ray range. Our results allow, for the first time for this important source, to obtain simultaneous spectral information from 2 keV to 200 keV. A black body (T = 0.8 keV) plus a broken power-law spectrum describe accurately the 1994 spectrum. Substantial hard X-ray emission is evident in the data, confirming that the accretion phase during sub-Eddington limit episodes is capable of producing energetic hard emission near 5 x 10(exp 35) ergs(exp -1). A preliminary paper summarizes our results, and a more comprehensive account is being written. We performed a theoretical analysis of possible emission mechanisms, and confirmed that a non-thermal emission mechanism triggered in a highly sheared magnetosphere at the accretion disk inner boundary can explain the hard X-ray emission. An anticorrelation between soft and hard X-ray emission is indeed prominently observed as predicted by this model.
A numerical procedure is presented to calculate transmittance degradation caused by contaminant films on spacecraft surfaces produced through the interaction of orbital atomic oxygen (AO) with volatile silicones and hydrocarbons from spacecraft components. In the model, contaminant accretion is dependent on the adsorption of species, depletion reactions due to gas-surface collisions, desorption, and surface reactions between AO and silicone producing SiO(x), (where x is near 2). A detailed description of the procedure used to calculate the constituents of the contaminant layer is presented, including the equations that govern the evolution of fractional coverage by specie type. As an illustrative example of film growth, calculation results using a prototype code that calculates the evolution of surface coverage by specie type is presented and discussed. An example of the transmittance degradation caused by surface interaction of AO with deposited contaminant is presented for the case of exponentially decaying contaminant flux. These examples are performed using hypothetical values for the process parameters.
Three-dimensional squirrel monkey eye movements were recorded during and immediately following rotation around an earth-vertical yaw axis (160 degrees/s steady state, 100 degrees/s2 acceleration and deceleration). To study interactions between the horizontal angular vestibulo-ocular reflex (VOR) and head orientation, postrotatory VOR alignment was changed relative to gravity by tilting the head out of the horizontal plane (pitch or roll tilt between 15 degrees and 90 degrees) immediately after cessation of motion. Results showed that in addition to post rotatory horizontal nystagmus, vertical nystagmus followed tilts to the left or right (roll), and torsional nystagmus followed forward or backward (pitch) tilts. When the time course and spatial orientation of eye velocity were considered in three dimensions, the axis of eye rotation always shifted toward alignment with gravity, and the postrotatory horizontal VOR decay was accelerated by the tilts. These phenomena may reflect a neural process that resolves the sensory conflict induced by this postrotatory tilt paradigm.
The Hanford Site's Long-Term Stewardship (LTS) Program is responsible for 220 square miles of the Site's River Corridor, which includes 1,527 waste sites, 6 Manhattan Project Era production reactors that have been placed in interim safe storage, and 46 miles of Columbia River shoreline. More than 24,000 cleanup and historic documents have been identified, indexed, and tagged in the LTS records and document libraries. The LTS program, operated by the Mission Support Alliance, LLC (MSA) manages and provides surveillance and maintenance of facilities and institutional controls and all associated monitoring to ensure continued protectiveness of human health and the environment. Since 2010, through collaborative efforts with DOE and its prime contractors, land in 14 geographic areas and six cocooned reactor facilities were transitioned (mid-contract) from the River Corridor Closure Contractor to the LTS program. This accomplishment relied heavily on Site contractors and DOE working together to address challenges. Other stakeholders were informed of LTS progress through the Hanford LTS web site, presentations, and briefings. Hanford's LTS program is responsible for ensuring the protectiveness of cleanup remedies and the management of institutional controls once cleanup objectives have been achieved. LTS accomplishes this by adhering to post-cleanup requirements specified in the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and the Resource Conservation and Recovery Act of 1976 (RCRA) cleanup decision documents. The LTS program conducted inspection and surveillance and maintenance (S and M) activities of the cocooned 105-F Reactor in October 2014 and the other five reactors in 2015 and 2016. Reactor entries and internal inspections typically are conducted at 5-year intervals to assess the condition of the structures and evaluate potential deterioration of the reactor core, shield walls, and roof. The cocooning process is designed to protect the reactor for 75 years while radioactive decay continues, ultimately making the structures safe for demolition and removal. The results of the recent 5-year inspections allowed DOE to negotiate an extended 10-year inspection cycle, which led to a $5 million avoidance in lifecycle inspection costs. Hanford's LTS program is successfully shifting from a program focused on transitioning land and waste sites to a program focused on data management and S and M activities for those buildings and waste sites within the program. This paper will highlight the accomplishments and collaborative efforts in addressing the challenges faced by Hanford's LTS program. (authors)
The Heavy Photon Search Experiment (HPS) is a fixed-target experiment at Jefferson Lab’s Hall B, designed to explore a hidden sector (HS) of particles containing dark matter and a new force mediator known as the “heavy photon” (A'). The A' is a massive spin-1 gauge boson associated with a new U (1)D symmetry in the HS that kinetically mixes with the Standard Model () photon with a weak coupling strength parameterized by ¿, with ¿2 ~ 10-2 -10-10. HPS utilizes a high-intensity electron beam on a thin tungsten target to produce heavy photons in the MeV-GeV mass range via “dark bremsstrahlung,” a process analogous to SM bremsstrahlung but suppressed by ¿2. The A' can decay resonantly to SM leptons, allowing HPS to conduct both mass resonance searches for prompt decays (large ¿) and displaced vertex searches for long-lived particles (small ¿). In addition to the minimal A' model, HPS probes more complex extensions such as the QCD-like strongly-interacting massive particles (SIMPs) HS containing “dark” pions (pD) and vector mesons (VD), with pD as dark matter candidates. These particles introduce new thermal dark matter freeze- out scenarios and visible signals through long-lived VD decays to SM leptons, which are accessible to HPS. This analysis conducted a displaced vertex search for VD ¿ e-e+ in the mass range 30 MeV to 124 MeV and ¿ between 10-6 < ¿ < 10-2 using data from the 2016 Engineering Run (10.753 nb-1) at 2.3 GeV. Unlike the minimal A' search, SIMP signal kinematics required new approaches to signal normalization and SM background rejection. The strongest signal evidence was a local p-value of 0.01317 for mVD = 119 MeV, corresponding to a global significance of 0.9s. Although no signal was found, this search excluded a region of the SIMP parameter space at 90 % confidence. This work demonstrates HPS’s competitive capability to probe SIMP sectors within cosmologically significant parameters and introduces a new method for HPS displaced vertex searches using track vertical impact parameter cuts