60 research outputs found
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
Zodiacal Exoplanets in Time. X. The Orbit and Atmosphere of the Young "Neptune Desert"-Dwelling Planet K2-100b
We obtained high-resolution infrared spectroscopy and short-cadence
photometry of the 600-800 Myr Praesepe star K2-100 during transits of its
1.67-day planet. This Neptune-size object, discovered by the NASA K2 mission,
is an interloper in the "desert" of planets with similar radii on short period
orbits. Our observations can be used to understand its origin and evolution by
constraining the orbital eccentricity by transit fitting, measuring the
spin-orbit obliquity by the Rossiter-McLaughlin effect, and detecting any
extended, escaping hydrogen-helium envelope with the 10830A line of neutral
helium in the 2s3S triplet state. Transit photometry with 1-min cadence was
obtained by the K2 satellite during Campaign 18 and transit spectra were
obtained with the IRD spectrograph on the Subaru telescope. While the elevated
activity of K2-100 prevented us from detecting the Rossiter-McLaughlin effect,
the new photometry combined with revised stellar parameters allowed us to
constrain the eccentricity to e < 0.15/0.28 with 90%/99% confidence. We modeled
atmospheric escape as an isothermal, spherically symmetric Parker wind, with
photochemistry driven by UV radiation that we estimate by combining the
observed spectrum of the active Sun with calibrations from observations of
K2-100 and similar young stars in the nearby Hyades cluster. Our non-detection
(<5.7mA) of a transit-associated He I line limits mass loss of a
solar-composition atmosphere through a T<10000K wind to <0.3Me/Gyr. Either
K2-100b is an exceptional desert-dwelling planet, or its mass loss is occurring
at a lower rate over a longer interval, consistent with a core
accretion-powered scenario for escape.Comment: Accepted to MNRA
Measurement of the differential cross section for the production of an isolated photon with associated jet in ppbar collisions at sqrt(s)=1.96 TeV
The process ppbar -> photon + jet + X is studied using 1.0 fb^-1 of data
collected by the D0 detector at the Fermilab Tevatron ppbar collider at a
center-of-mass energy sqrt(s)=1.96 TeV. Photons are reconstructed in the
central rapidity region |y_gamma|<1.0 with transverse momenta in the range
30<Pt_gamma<400 GeV while jets are reconstructed in either the central
|y_jet|15 GeV.
The differential cross section d^3sigma/dPt_gamma dy_gamma dy_jet is measured
as a function of Pt_gamma in four regions, differing by the relative
orientations of the photon and the jet in rapidity. Ratios between the
differential cross sections in each region are also presented. Next-to-leading
order QCD predictions using different parameterizations of parton distribution
functions and theoretical scale choices are compared to the data. The
predictions do not simultaneously describe the measured normalization and
Pt_gamma dependence of the cross section in any of the four measured regions.Comment: 13 pages, 10 figure
Existing data on the 216-Z liquid waste sites
During 36 years of operation at the Hanford Site, the ground has been used for disposal of liquid and solid transuranic and/or low-level wastes. Liquid waste was disposed in surface and subsurface cribs, trenches, French drains, reverse wells, ditches and ponds. Disposal structures associated with Z Plant received liquid waste from plutonium finishing and reclamation, waste treatment and laboratory operations. The nineteen 216-Z sites have received 83% of the plutonium discharged to 325 liquid waste facilities at the Hanford Site. The purpose of this document is to support the Hanford Defense Waste Environmental Impact Statement by drawing the existing data together for the 216-Z liquid waste disposal sites. This document provides an interim reference while a sitewide Waste Information Data System (WIDS) is developed and put on line. Eventually these and additional site data for all Hanford waste disposal sites will be available on WIDS. Compilation of existing data is the first step in evaluating the need and developing the technology for long-term management of these waste sites. The scope of this document is confined to data describing the status of the 216-Z waste sites as of December 31, 1979. Information and sketches are taken from existing documents and drawings
Effect of High-Energy Electron Irradiation of Chicken Meat on Thiobarbituric Acid Values, Shear Values, Odor, and Cooked Yield
The impact of longitudinal studies on understanding development from young adulthood to old age
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