Calibration and Analysis of the 2007 Data

The physics program of the NA61/SHINE (SHINE = SPS Heavy Ion and Neutrino Experiment) experiment at the CERN SPS consists of three subjects. In the first stage of data taking (2007-2009) measurements of hadron production in hadron-nucleus interactions needed for neutrino (T2K) and cosmic-ray (Pierre Auger and KASCADE) experiments will be performed. In the second stage (2009-2010) hadron production in proton-proton and proton-nucleus interactions needed as reference data for a better understanding of nucleus-nucleus reactions will be studied. In the third stage (2009-2013) energy dependence of hadron production properties will be measured in p+p, p+Pb interactions and nucleus-nucleus collisions, with the aim to identify the properties of the onset of deconfinement and find evidence for the critical point of strongly interacting matter. The NA61 experiment was approved at CERN in June 2007. The first pilot run was performed during October 2007. Calibrations of all detector components have been performed successfully and preliminary uncorrected spectra have been obtained. High quality of track reconstruction and particle identification similar to NA49 has been achieved. The data and new detailed simulations confirm that the NA61 detector acceptance and particle identification capabilities cover the phase space required by the T2K experiment. This document reports on the progress made in the calibration and analysis of the 2007 dat a

Low Redshift Intergalactic Absorption Lines in the Spectrum of HE0226-4110

We present an analysis of the FUSE and STIS E140M spectra of HE0226-4110 (z=0.495). We detect 56 Lyman absorbers and 5 O VI absorbers. The number of intervening O VI systems per unit redshift with W>50 m\AA is dN(O VI)/dz~ 11. The O VI systems unambiguously trace hot gas only in one case. For the 4 other O VI systems, photoionization and collisional ionization models are viable options to explain the observed column densities of the O VI and the other ions. If the O VI systems are mostly photoionized, only a fraction of the observed O VI will contribute to the baryonic density of the warm-hot ionized medium (WHIM) along this line of sight. Combining our results with previous ones, we show that there is a general increase of N(O VI) with increasing b(O VI). Cooling flow models can reproduce the N-b distribution but fail to reproduce the observed ionic ratios. A comparison of the number of O I, O II, O III, O IV, and O VI systems per unit redshift show that the low-z IGM is more highly ionized than weakly ionized. We confirm that photoionized O VI systems show a decreasing ionization parameter with increasing H I column density. O VI absorbers with collisional ionization/photoionization degeneracy follow this relation, possibly suggesting that they are principally photoionized. We find that the photoionized O VI systems in the low redshift IGM have a median abundance of 0.3 solar. We do not find additional Ne VIII systems other than the one found by Savage et al., although our sensitivity should have allowed the detection of Ne VIII in O VI systems at T~(0.6-1.3)x10^6 K (if CIE applies). Since the bulk of the WHIM is believed to be at temperatures T>10^6 K, the hot part of the WHIM remains to be discovered with FUV--EUV metal-line transitions.Comment: Accepted for publication in the ApJS. Full resolution figures available at http://www.journals.uchicago.edu/ApJ/journal/preprints/ApJS63975.preprint.pd

FUSE Observations of the Magellanic Bridge Gas toward Two Early-Type Stars: Molecules, Physical Conditions, and Relative Abundance

We discuss FUSE observations of two early-type stars, DI1388 and DGIK975, in the low density and low metallicity gas of Magellanic Bridge (MB). Toward DI1388, the FUSE observations show molecular hydrogen, O VI, and numerous other atomic or ionic transitions in absorption, implying the presence of multiple gas phases in a complex arrangement. The relative abundance pattern in the MB is attributed to varying degrees of depletion onto dust similar to that of halo clouds. The N/O ratio is near solar, much higher than N/O in damped Ly-alpha systems, implying subsequent stellar processing to explain the origin of nitrogen in the MB. The diffuse molecular cloud in this direction has a low column density and low molecular fraction. H2 is observed in both the Magellanic Stream and the MB, yet massive stars form only in the MB, implying significantly different physical processes between them. In the MB some of the H2 could have been pulled out from the SMC via tidal interaction, but some also could have formed in situ in dense clouds where star formation might have taken place. Toward DGIK975, the presence of neutral, weakly and highly ionized species suggest that this sight line has also several complex gas phases. The highly ionized species of O VI, C IV, and Si IV toward both stars have very broad features, indicating that multiple components of hot gas at different velocities are present. Several sources (a combination of turbulent mixing layer, conductive heating, and cooling flows) may be contributing to the production of the highly ionized gas in the MB. Finally, this study has confirmed previous results that the high-velocity cloud HVC 291.5-41.2+80 is mainly ionized composed of weakly and highly ions. The high ion ratios are consistent with a radiatively cooling gas in a fountain flow model.Comment: Accepted for publication in the ApJ (October 10, 2002). Added reference (Gibson et al. 2000

Discovery of Enhanced Germanium Abundances in Planetary Nebulae with FUSE

We report the discovery of Ge III $\lambda$1088.46 in the planetary nebulae (PNe) SwSt 1, BD+30$^{\rm o}$3639, NGC 3132, and IC 4593, observed with the Far Ultraviolet Spectroscopic Explorer. This is the first astronomical detection of this line and the first measurement of Ge (Z = 32) in PNe. We estimate Ge abundances using S and Fe as reference elements, for a range of assumptions about gas-phase depletions. The results indicate that Ge, which is synthesized in the initial steps of the s-process and therefore can be self-enriched in PNe, is enhanced by factors of > 3-10. The strongest evidence for enrichment is seen for PNe with Wolf-Rayet central stars, which are likely to contain heavily processed material.Comment: 11 pages, 1 figure, accepted for publication in ApJ Letter

Characterization of high purity germanium point contact detectors with low net impurity concentration

High Purity germanium point-contact detectors have low energy thresholds and excellent energy resolution over a wide energy range, and are thus widely used in nuclear and particle physics. In rare event searches, such as neutrinoless double beta decay, the point-contact geometry is of particular importance since it allows for pulse-shape discrimination, and therefore for a significant background reduction. In this paper we investigate the pulse-shape discrimination performance of ultra-high purity germanium point contact detectors. It is demonstrated that a minimal net impurity concentration is required to meet the pulse-shape performance requirements