[A NASA / University Joint Venture in Space Science]

MILAGRO is a water-Cherenkov detector for observing cosmic gamma rays over a broad energy range of 100 GeV to 100 TeV. MILAGRO will be the first detector that has sensitivity overlapping both air-Cherenkov and air-shower detectors. With this detector scientists in the collaboration will study previously observed celestial sources at their known emission energies, extend these observations into a new energy regime, and search for new sources at unexplored energies. The diffuse gamma-radiation component in our galaxy, which originates from interactions of cosmic rays with interstellar gas and photons, provides important information about the density, distribution, and spectrum of the cosmic rays that pervade the interstellar medium. Events in the Compton Gamma Ray Observatory (GRO) are being observed up to about 30 GeV, differing by slightly more than order of magnitude from the low energy threshold of MILAGRO. By looking in coincidence at sources, correlated observations will greatly extend the astrophysics potential of MILAGRO and NASA's GRO. A survey of cosmic-ray observatories is being prepared for scientists and others to provide a resource and reference which describes high energy cosmic-ray research activities around the world. This summary presents information about each research group, such as names of principal investigators, number of persons in the collaboration, energy range, sensitivity, angular resolution, and surface area of detector. Similarly, a survey of gamma-ray telescopes is being prepared to provide a resource and reference which describes gamma-ray telescopes for investigating galactic diffuse gamma-ray flux currently observed in the GeV energy range, but is expected to extend into the TeV range. Two undergraduate students are compiling information about gamma-ray telescopes and high energy cosmic-ray observatories for these surveys. Funding for this project was provided by the Arkansas Space Grant Consortium. Also enclosed Appendix A, B, C, D and E

Monte Carlo Simulation of the Scintillating Optical Fiber Calorimeter (SOFCAL)

A scintillating optical fiber calorimeter (SOFCAL) is being developed by NASA/Marshall Space Flight Center for use in balloon-borne emulsion chambers to study the spectrum of high-energy cosmic rays and gamma rays. SOFCAL will not saturate for long exposures, and the detector will be helpful for the study of primary cosmic-ray nuclei energies from 100 GeV to 1,000 TeV. For a given incident particle and energy, computer simulations of electromagnetic cascades allow computation of energy deposited in different regions of the calorimeter. For these initial simulations, a 5-cm x 5-cm x 7-cm calorimeter was used. Each subsection contained a 0.4-cm thick lead plate or two 0.2-cm lead plates and two layers of optical fibers, 90° to each other. There were 100 square fibers in a layer, and the length of an edge was 0.5 mm. For incident gamma ray energies of 0.5 to 1.5 TeV, the energy deposited in each layer of fibers was computed. Due to the limited dynamic range of the imaging electronics, a window for the energy deposition (SigmaEgamma) in the fibers was explored to determine the best measure of energy deposition in the calorimeter

Using FRITIOF to Model Nucleus-Nucleus Interactions in a Cosmic Ray Detector

Ascintillating optical fiber calorimeter (SOFCAL) isbeing developed by NASA/Marshall Space Flight Center for use in experiments to study the spectrum of high-energy cosmic rays and gamma rays from 100 GeV to 1,000 TeV. SOFCAL willnot saturate for long exposures and this calorimeter inthese balloon-borne emulsion chambers willbe helpful for the study of the composition of primary cosmic-ray nuclei. For primary nuclei with energies much greater than 1014 eV, nucleus-nucleus interactions are likely to exhibit characteristics of a quark-gluon plasma (QGP). Aparticle event generator was used tomodel the collision of a cosmic-ray nucleus with a target nucleus inan emulsion chamber. FRITIOF withLUCIAE was chosen tomodel collisions of primary cosmic rays inan emulsion chamber with SOFCAL. Pseudo-rapidity distributions were computed for protons on lead at 200 GeV/c and compared with experimental data. Pseudo-rapidity distributions were computed for protons or iron incident on a carbon or silver nucleus. For gamma-rays from nucleus-nucleus interactions, the total energy of the electromagnetic component Z£y was computed. The partial coefficient ofinelasticity kr defined by L£ y = kY E0 ,was computed from the primary energy Eo of the cosmic rays. The f(ky )-distributions were computed and compared with existing calorimeter data. Funding was provided by the NASA/University Joint Venture (JOVE) Program

Using GEANT to Model Calrimeter Response for Electromagnetic Cascades from Nucleus-Nucleus Interactions in a Cosmic Ray Detector

Ascintillating optical fiber calorimeter (SOFCAL) is being developed by NASA/Marshall Space Flight Center for use in balloon-borne experiments to study the spectrum of high-energy cosmic rays and gamma rays. SOFCAL will not saturate for long exposures and the calorimeter willbe useful in emulsion chambers to study primary cosmic-ray nuclei with energies from 100 GeV to 1,000 TeV. The event generator FRITIOF was used to model the collision of a cosmic-ray projectile with a target nucleus inan emulsion chamber. The measurements of charged particles from the interaction in the emulsions are related to the energy of the primary cosmic ray nucleus-nucleus interaction, computer simulations of electromagnetic cascades allow computation of the energy ££y deposited indifferent regions of the calorimeter. The Monte Carlo program GEANT was used to model SOFCAL response to incident gamma rays and to compute the measure of energy deposition X£y in different layers ofthe calorimeter within the emulsion chamber. The partial coefficient o finelasticity kr defined by 1JE Y = kY E0 ,was computed for different energies Eo of primary cosmic rays. The were computed and compared with existing calorimeter data. Funding was provided by the NASA/University Joint Venture (JOVE) Program

Using FRITIOF to Model Nucleus-Nucleus Interactions in a Cosmic Ray Detector

Ascintillating optical fiber calorimeter (SOFCAL) isbeing developed by NASA/Marshall Space Flight Center for use in experiments to study the spectrum of high-energy cosmic rays and gamma rays from 100 GeV to 1,000 TeV. SOFCAL willnot saturate for long exposures and this calorimeter inthese balloon-borne emulsion chambers willbe helpful for the study of the composition of primary cosmic-ray nuclei. For primary nuclei with energies much greater than 1014 eV, nucleus-nucleus interactions are likely to exhibit characteristics of a quark-gluon plasma (QGP). Aparticle event generator was used tomodel the collision of a cosmic-ray nucleus with a target nucleus inan emulsion chamber. FRITIOF withLUCIAE was chosen tomodel collisions of primary cosmic rays inan emulsion chamber with SOFCAL. Pseudo-rapidity distributions were computed for protons on lead at 200 GeV/c and compared with experimental data. Pseudo-rapidity distributions were computed for protons or iron incident on a carbon or silver nucleus. For gamma-rays from nucleus-nucleus interactions, the total energy of the electromagnetic component Z£y was computed. The partial coefficient ofinelasticity kr defined by L£ y = kY E0 ,was computed from the primary energy Eo of the cosmic rays. The f(ky )-distributions were computed and compared with existing calorimeter data. Funding was provided by the NASA/University Joint Venture (JOVE) Program

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals

On the variability of quasars: a link between Eddington ratio and optical variability?

Repeat scans by the Sloan Digital Sky Survey (SDSS) of a 278 square degree stripe along the Celestial equator have yielded an average of over 10 observations each for nearly 8,000 spectroscopically confirmed quasars. Over 2500 of these quasars are in the redshift range such that the CIV emission line is visible in the SDSS spectrum. Utilising the width of these CIV lines and the luminosity of the nearby continuum, we estimate black hole masses for these objects. In an effort to isolate the effects of black hole mass and luminosity on the photometric variability of our dataset, we create several subsamples by binning in these two physical parameters. By comparing the ensemble structure functions of the quasars in these bins, we are able to reproduce the well-known anticorrelation between luminosity and variability, now showing that this anticorrelation is independent of the black hole mass. In addition, we find a correlation between variability and the mass of the central black hole. By combining these two relations, we identify the Eddington ratio as a possible driver of quasar variability, most likely due to differences in accretion efficiency.Comment: 13 pages, 5 figures, Accepted for publication in MNRA