Observation of the shadows of the moon and sun using 100 TeV cosmic rays

Journal ArticleThe Chicago Air Shower Array (CASA) is a large ground-based scintillation detector [1-4]. It is located at the Dugway Proving Ground is west central Utah, latitude 40°N and mean atmospheric depth 870 g / c m 2. A schematic aerial view of CASA is shown in Fig. 1. Each dot represents one scintillation station of the array

Elemental Composition of Cosmic Rays near the Knee by Multiparameter Measurement of Air Showerss

The small change in the spectral slope of the overall intensity of cosmic rays near 1 PeV may be associated with the endpoint energy of supernova shock acceleration. A crucial test of this connection and other ideas of the origin of the spectral `knee' is the reliable determination of the variation of elemental composition in this region. Recent measurements at the DICE/CASA/MIA air shower installation in Dugway, Utah, USA have provided several independent air shower parameters for each event. The derivation of elemental composition from a combination of Cherenkov size, depth of shower maximum in the atmosphere, muon size and electron size at ground level and the reliability of these results are discussed. There is no evidence from these data for a large change in the mean mass of cosmic rays across the `knee'. These measurements show the cosmic rays are composed of ~ 70% protons and alpha-particles near total energies of 10PeV.Comment: 29 pages including 10 figures Accepted for publication by Astroparticle Physics, 17th Sept. 199

Exploration of a 100 TeV gamma-ray northern sky using the Tibet air-shower array combined with an underground water-Cherenkov muon-detector array

Aiming to observe cosmic gamma rays in the 10 - 1000 TeV energy region, we propose a 10000 m^2 underground water-Cherenkov muon-detector (MD) array that operates in conjunction with the Tibet air-shower (AS) array. Significant improvement is expected in the sensitivity of the Tibet AS array towards celestial gamma-ray signals above 10 TeV by utilizing the fact that gamma-ray-induced air showers contain far fewer muons compared with cosmic-ray-induced ones. We carried out detailed Monte Carlo simulations to assess the attainable sensitivity of the Tibet AS+MD array towards celestial TeV gamma-ray signals. Based on the simulation results, the Tibet AS+MD array will be able to reject 99.99% of background events at 100 TeV, with 83% of gamma-ray events remaining. The sensitivity of the Tibet AS+MD array will be ~20 times better than that of the present Tibet AS array around 20 - 100 TeV. The Tibet AS+MD array will measure the directions of the celestial TeV gamma-ray sources and the cutoffs of their energy spectra. Furthermore, the Tibet AS+MD array, along with imaging atmospheric Cherenkov telescopes as well as the Fermi Gamma-ray Space Telescope and X-ray satellites such as Suzaku and MAXI, will make multiwavelength observations and conduct morphological studies on sources in the quest for evidence of the hadronic nature of the cosmic-ray acceleration mechanism.Comment: Accepted by Astroparticle Physic

La conciliation médicamenteuse de sortie : intérêt pour réduire la iatrogénie chez la personne âgée et tisser des liens ville-hôpital

Introduction: Good command of iatrogenic events, especially with the elderly is a public health problem to reduce morbi-mortality and the induced costs.Objective: Assuming that an hospitalisation in geriatric departments reduces iatrogenic events we aim to prove that the introduction of a paragraph in the hospitalisation reports dedicated to the therapeutic changes could improve their follow up by general practitioners.Methods: Our study was realized in a geriatric medical department of after-care and rehabilitation in Paris. The first step was to analyse retrospectively 36 hospitalisation reports to study the changes applied as well as the percentage of which modifications were maintained after the exit. Secondly we included in the study 36 new patients whose reports contained a dedicated paragraph and we applied the same methodology as previously.Results: Although hospitalisation improves the quality of prescription, improvements needs to be done regarding the prescription by hospital habits. We demonstrated that the addition of a dedicated paragraph improves significantly the percentage of justified changes in the CRH from 40% to 60%. In the same way, the continued implementation of needed changes raised from 87.5% to 95%.Conclusion: Adding a dedicated paragraph to the therapeutic changes in the hospitalisation reports allows the general practitioner to better understand them and thus maintain them. It also reinforces the link between city and hospital. This paragraph still needs to be formalized and its ability to reduce iatrogenic events is to be demonstrated.Contexte : La maîtrise de la iatrogénie médicale en particulier chez les personnes âgées est un problème de santé publique pour réduire la morbi-mortalité et le coût qu’elle induit.Objectif : Le but de notre étude est de démontrer que le maintien en ville des modifications réalisées à l’hôpital, peut être amélioré par l’introduction d’un paragraphe dédié aux changements de thérapeutiques dans le compte-rendu d’hospitalisation (CRH).Méthodes : Notre étude unicentrique a été réalisée dans un service de soins de suite et de rééducation gériatrique à Paris. Dans un premier temps, nous avons analysé de manière rétrospective les CRH de 36 patients pour analyser les modifications effectuées, ainsi que le taux de maintien de ces modifications après la sortie. Dans un deuxième temps, nous avons inclus de manière prospective 36 patients après avoir appliqué la rédaction d’un paragraphe dédié dans le compte-rendu d’hospitalisation et nous les avons analysés selon la même méthodologie.Résultats : Si l’hospitalisation améliore globalement la qualité de l’ordonnance, des améliorations restent à faire concernant la prescription par habitude hospitalière. Le paragraphe spécifique améliore significativement le pourcentage de modifications justifiées dans le compte-rendu qui augmente de 40% à 60%. De même, le maintien des modifications pertinentes depuis la sortie a été amélioré de 87.5% à 95%.Conclusion : L’ajout d’un paragraphe dédié aux modifications thérapeutiques dans le compte-rendu d’hospitalisation permet d’améliorer leur compréhension et leur maintien par les médecins traitants ainsi que de renforcer le lien ville-hôpital. Il reste à formaliser ce paragraphe et à démontrer son efficacité pour réduire la iatrogénie

Neutrino Mass^2 Inferred from the Cosmic Ray Spectrum and Tritium Beta Decay

An earlier prediction of a cosmic ray neutron line right at the energy of the knee of the cosmic ray spectrum was based on the speculation that the electron neutrino is a tachyon whose mass is reciprocally related to the energy of the knee, $E_k$. Given the large uncertainty in $E_k$, the values of ${m_\nu}^2$ corresponding to it are consistent with values recently reported in tritium beta decay experiments.Comment: Published as Phys. Lett. B 493 (2000) 1-

A Measurement of the Cosmic Ray Spectrum and Composition at the Knee

The energy spectrum and primary composition of cosmic rays with energy between $3\times 10^{14}$ and 3\times10^{16}\unit{eV} have been studied using the CASA-BLANCA detector. CASA measured the charged particle distribution of air showers, while BLANCA measured the lateral distribution of Cherenkov light. The data are interpreted using the predictions of the CORSIKA air shower simulation coupled with four different hadronic interaction codes. The differential flux of cosmic rays measured by BLANCA exhibits a knee in the range of 2--3 PeV with a width of approximately 0.5 decades in primary energy. The power law indices of the differential flux below and above the knee are $-2.72\pm0.02$ and $-2.95\pm0.02$. We present our data both as a mean depth of shower maximum and as a mean nuclear mass. A multi-component fit using four elemental species shows the same composition trends given by the mean quantities, and also indicates that QGSJET and VENUS are the preferred hadronic interaction models. We find that an initially mixed composition turns lighter between 1 and 3 PeV, and then becomes heavier with increasing energy above 3 PeV.Comment: 25 pages, 10 figures. Submitted to Astroparticle Physic

Detection of Atmospheric Cherenkov Radiation Using Solar Heliostat Mirrors

The gamma-ray energy region between 20 and 250 GeV is largely unexplored. Ground-based atmospheric Cherenkov detectors offer a possible way to explore this region, but large Cherenkov photon collection areas are needed to achieve low energy thresholds. This paper discusses the development of a Cherenkov detector using the heliostat mirrors of a solar power plant as the primary collector. As part of this development, we built a prototype detector consisting of four heliostat mirrors and used it to record atmospheric Cherenkov radiation produced in extensive air showers created by cosmic ray particles.Comment: 16 latex pages, 8 postscript figures, uses psfig.sty, to be published in Astroparticle Physic

Galactic Point Sources of TeV Antineutrinos

High energy cosmic ray experiments have identified an excess from the region of the Galactic Plane in a limited energy range around $10^{18}$ eV (EeV). This is very suggestive of neutrons as candidate primaries, because the directional signal requires relatively-stable neutral primaries, and time-dilated neutrons can reach Earth from typical Galactic distances when the neutron energy exceeds an EeV. We here point out that if the Galactic messengers are neutrons, then those with energies below an EeV will decay in flight, providing a flux of cosmic antineutrinos above a TeV which is {\it observable} at a kilometer-scale neutrino observatory. The expected event rate per year above 1 TeV in a detector such as IceCube, for example, is 20 antineutrino showers (all flavors) and a $1^\circ$ directional signal of 4 $\bar \nu_\mu$ events. A measurement of this flux can serve to identify the first extraterrestrial point source of TeV antineutrinos.Comment: matches published versio

A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts

A small air shower array operating over many years has been used to search for ultra-high energy (UHE) gamma radiation ($\geq 50$ TeV) associated with gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each burst are presented for seven GRBs located with zenith angles $\theta < 20^{\circ}$. A $4.3\sigma$ excess over background was observed between 10 and 20 minutes following the onset of a GRB on 11 May 1991. The confidence level that this is due to a real effect and not a background fluctuation is 99.8\%. If this effect is real then cosmological models are excluded for this burst because of absorption of UHE gamma rays by the intergalactic radiation fields.Comment: 4 pages LaTeX with one postscript figure. This version does not use kluwer.sty and will allow automatic postscript generatio