Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session U9: Cosmic Rays II |
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Sponsoring Units: DAP Chair: Gary Zank, University of Riverside Room: Marriott Tampa Waterside Room 5 |
Monday, April 18, 2005 3:30PM - 3:42PM |
U9.00001: Particle Identification and Energy Measurementswith the TRACER Cosmic-Ray Detector D. Muller, M. Ave, P. Boyle, F. Gahbauer, C. Hoeppner, J. Hoerandel, M. Ichimura, A. Romero-Wolf, S. Wakely TRACER is currently the largest cosmic-ray detector for balloon-borne measurements of cosmic-ray nuclei at very high energies, exhibiting a geometric factor of $\sim$ 5 m$^2$ ster. For particle identification and energy measurements it employs a combination of plastic scintillators, acrylic Cherenkov counter, and arrays of gas-proportional tubes.Eight layers of tubes measure the specific ionization and its relativistic rise, and another eight layers are combined with radiator material to function as a transition radiation detector. This detector system provides measurements of heavy nuclei (8 $\leq$ Z $\leq$ 26) over the energy range $\sim$ 500 MeV/nucleon to $\sim$ 10 TeV/nucleon. Optimum response is achieved if the signal characteristics of the detector elements are well calibrated, and the correlations between signals are well understood. To accomplish this we employ calibrations in the laboratory and at accelerators, analytical studies and a complete simulation of the detector using GEANT, and the balloon flight data themselves. Subtle effects such as $\delta$-ray contributions and nuclear interactions in the detector material are taken into account in the analysis of the data. We describe our procedures and discuss how well the response characteristics of TRACER match the requirements of a cosmic-ray measurement. [Preview Abstract] |
Monday, April 18, 2005 3:42PM - 3:54PM |
U9.00002: A New Measurement of the Energy Spectra of Heavy Cosmic-Ray Nuclei up to Very High Energies Patrick Boyle, Maximo Ave, Florian Gahbauer, Christian Hoeppner, Joerg Hoerandel, Masakatsu Ichimura, Dietrich Muller, Andrew Romero-Wolf, Scott Wakely The TRACER cosmic-ray detector was exposed in a long-duration balloon flight from McMurdo, Antarctica in December 2003. The instrument, with a geometric factor of $\sim$ 5 m$^2$ ster, performed well and provided measurements for a duration of ten days with zero dead-time. TRACER measured the energy of cosmic ray nuclei at single charge resolution over the range oxygen to iron (8 $\leq$ Z $\leq$ 26). We shall present preliminary results on the energy spectra of these nuclei from $\sim$ 500 MeV/nucleon to $\sim$ 10 TeV/nucleon. The data will be compared with results from previous measurements, and discussed in the context of current models on the galactic propagation of cosmic rays. [Preview Abstract] |
Monday, April 18, 2005 3:54PM - 4:06PM |
U9.00003: A Fast Neutron Imager for Inner Heliosphere Measurements James Ryan, John Macri, Mark McConnell, Michael Moser, Robert Lin Inner heliosphere measurements of the Sun can be conducted with the proposed Solar Sentinel spacecraft and mission. One of the key measurements that can be made inside the orbit of Earth is that of lower energy neutrons that arise in flares from nuclear reactions. Solar flare neutrons below 10 MeV suffer heavy weak-decay losses before reaching 1 AU. For heliocentric radii as close as 0.3 AU, the number of surviving neutrons from a solar event is dramatically greater. Neutrons from 1-10 MeV provide a new measure of heavy ion interactions at low energies, where the vast majority of the energetic particle energy resides. Such measurements are difficult because of locally generated neutrons. We describe the potential of such neutron measurements in the context of the Solar Sentinel program and an instrument for performing these measurements employing neutron imaging techniques to optimize the signal-to-noise ratio. [Preview Abstract] |
Monday, April 18, 2005 4:06PM - 4:18PM |
U9.00004: On the Importance of Electromagnetic Dissociation for Cosmic Ray and Nuclear Transport Codes John Norbury A relativistic nucleus-nucleus reaction is mediated by the Strong interaction when the nuclei collide, i.e. when they come closer than 1 fm. However if the nuclei miss each other, a reaction can still occur via the long range Electromagnetic force. This is often called Electromagnetic Dissociation (EMD). Some nuclear transport codes only include Strong interactions for the nucleus- nucleus reaction component. It will be shown that for certain nuclei and energies it is a bad approximation to ignore EMD. [Preview Abstract] |
Monday, April 18, 2005 4:18PM - 4:30PM |
U9.00005: Cosmic Rays and Mountain Waves John Matthews, Charles Jui The High Resolution Fly's Eye (HiRes), AUGER South, and the Telescope Array (TA) cosmic ray experiments are all located on high plateaus leeward (down-wind) of a major mountain range. The obstructed air motion generates down-slope winds and gravity waves (analogous to deep ocean waves) called ``mountain waves'' or ``lee-waves''. The location of AUGER South in the southern Andes is a particularly active region for mountain waves. The waves generate an additional uncertainty which must either be measured or accounted for in the reconstruction of cosmic ray air showers. While the effect is significantly smaller in Utah -- Home to HiRes and TA, the new Telescope Array experiment will be measuring this effect and taking it into account. [Preview Abstract] |
Monday, April 18, 2005 4:30PM - 4:42PM |
U9.00006: Lorentz Invariance Violation and the Spectrum and Source Power of Ultrahigh Energy Cosmic Rays Floyd Stecker, Sean Scully Owing to their isotropy, it is generally believed that ultrahigh energy cosmic rays (UHECRs) are extragalactic in origin. It is then expected that interactions of these cosmic rays with photons of the cosmic background radiation (CBR) should produce a drastic reduction in their flux above and energy of about $5 \times 10^{19}$ eV (50 EeV), the so-called ``GZK effect.'' At present, the existence of this effect is uncertain owing to conflicting observational data and small number statistics. We show here that a small amount of Lorentz invariance violation (LIV), which could turn off photomeson interactions of UHECRs with the CBR, could explain the UHECR spectrum as measured by {\it AGASA} which shows an excess of UHECRs at energies above 100 EeV. If new results from the {\it Auger} array agree with the {\it AGASA} spectrum, this may be interpreted as evidence for a small amount of LIV. If, on the other hand, the new results are consistent with the {\it HiRes} results favoring a GZK effect, this would place severe constraints on LIV and, by implication, on some Planck scale quantum gravity models. We also discuss the power requirements needed to explain the UHECR spectrum for a range of assumptions, including source evolution and LIV and show that in all cases our results disfavor a $\gamma$-ray burst origin for the UHECRs. [Preview Abstract] |
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U9.00007: {\it p}--air Inelastic Cross-Section Measurement at $10^{18.5}$ eV Using Cosmic Ray Data Konstantin Belov Cosmic ray data can be used to measure hadronic cross-section at the energies unreachable by modern accelerators. Using high quality cosmic ray data provided by the High Resolution Fly's Eye stereo fluorescence detector we find the p-air inelastic cross-section value to be $456\pm17(stat)+39(sys)-11(sys)$ mb at $10^{18.5}$ eV. We discuss the result, and the statistical and systematic errors. [Preview Abstract] |
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