Comparing Proton Momentum Distributions in A = 2 and 3 Nuclei Via \u3csup\u3e2\u3c/sup\u3eH \u3csup\u3e3\u3c/sup\u3eH and \u3csup\u3e3\u3c/sup\u3eHe (e,e′p) Measurements

We report the first measurement of the (e, e\u27 p) reaction cross-section ratios for Helium-3 (3He), Tritium (3H), and Deuterium (d). The measurement covered a missing momentum range of 40 ≤ pmiss ≤ 550 MeV/c, at large momentum transfer ({Q2} ≈ 1.9 (GeV/c)2) and xB \u3e 1, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with planewave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for 3He/d and 3H/d extend to just above the typical nucleon Fermi-momentum (kF ≈ 250 MeV/c) and differ from each other by ∼ 20%, while for 3He/3H they agree within the measurement accuracy of about 3%. At momenta above kF , the measured 3He/3H ratios differ from the calculation by 20% −50%. Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the 3He/3H cross-section ratio for this measurement by less than 5%. If these calculations are correct, then the differences at large missing momenta between the 3He/3H experimental and calculated ratios could be due to the underlying NN interaction, and thus could provide new constraints on the previously loosely-constrained short-distance parts of the NN interaction

The GLAST Background Model

In order to estimate the ability of the GLAST/LAT to reject unwanted background of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the background particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible background components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the background are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect

Development and testing of an air quality model for Mexico City

Los Alamos National Laboratory and Instituto Mexicano del Petroleo have embarked on a joint study of options for improving air quality in Mexico City. The intent is to develop a modeling system which can address the behavior of pollutants in the region so that option for improving Mexico City air quality can be properly evaluated. In February of 1991, the project conducted a field program which yielded a variety of data which is being used to evaluate and improve the models. Normally the worst air quality for both primary and photochemical pollutants occurs in the winter Mexico City. During the field program, measurements included: (1) lidar measurements of aerosol transport and dispersion, (2) aircraft measurements of winds, turbulence, and chemical species aloft, (3) aircraft measurements of earth surface skin temperatures, and (4) tethersonde measurements of wind, temperature and ozone vertical profiles. A three-dimensional, prognostic, higher order turbulence meteorological model (HOTMAC) was modified to include an urban canopy and urban heat sources. HOTMAC is used to drive an Monte-Carlo kernel dispersion code (RAPTAD). HOTMAC also provides winds and mixing heights for the CIT photochemical model which was developed by investigators at the California Institute of Technology and Carnegie Mellon University

Measurement of the Cross Sections for Inclusive Electron Scattering in the E12-14-012 Experiment at Jefferson Lab

The E12-14-012 experiment performed at Jefferson Lab Hall A has collected inclusive electron-scattering data for different targets at the kinematics corresponding to beam energy 2.222 GeV and scattering angle 15.54°. Here we present a comprehensive analysis of the collected data and compare the double-differential cross sections for inclusive scattering of electrons, extracted using solid targets (aluminum, carbon, and titanium) and a closed argon-gas cell. The data extend over broad range of energy transfer, where quasielastic interaction, Δ-resonance excitation, and inelastic scattering yield contributions to the cross section. The double-differential cross sections are reported with high precision (∼3%) for all targets over the covered kinematic range

Swift Detects a Remarkable Gamma-Ray Burst, GRB 060614, That Introduces a New Classification Scheme

Gamma ray bursts (GRBs) are known to come in two duration classes, separated at {approx}2 s. Long bursts originate from star forming regions in galaxies, have accompanying supernovae (SNe) when near enough to observe and are likely caused by massive-star collapsars. Recent observations show that short bursts originate in regions within their host galaxies with lower star formation rates, consistent with binary neutron star (NS) or NS - black hole (BH) mergers. Moreover, although their hosts are predominantly nearby galaxies, no SNe have been so far associated with short GRBs. We report here on the bright, nearby GRB 060614 that does not fit in either class. Its {approx}102 s duration groups it with long GRBs, while its temporal lag and peak luminosity fall entirely within the short GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova, similar to short GRBs. This combination of a long duration event without accompanying SN poses a challenge to both a collapsar and merging NS interpretation and opens the door on a new GRB classification scheme that straddles both long and short bursts

ehm-lab/hipmapp: Health Impact Projections Shiny App Zenodo-DOI

This app reports projections of temperature-related mortality until the end of the century for 854 cities in 30 European countries