The Potential of Spaced-based High-Energy Neutrino Measurements via the Airshower Cherenkov Signal

Future space-based experiments, such as OWL and JEM-EUSO, view large atmospheric and terrestrial neutrino targets. With energy thresholds slightly above 10^19 eV for observing airshowers via air fluorescence, the potential for observing the cosmogenic neutrino flux associated with the GZK effect is limited. However, the forward Cherenkov signal associated with the airshower can be observed at much lower energies. A simulation was developed to determine the Cherenkov signal strength and spatial extent at low-Earth orbit for upward-moving airshowers. A model of tau neutrino interactions in the Earth was employed to determine the event rate of interactions that yielded a tau lepton which would induce an upward-moving airshower observable by a space-based instrument. The effect of neutrino attenuation by the Earth forces the viewing of the Earth's limb to observe the nu_tau-induced Cherenkov airshower signal at above the OWL Cherenkov energy threshold of ~10^16.5 eV for limb-viewed events. Furthermore, the neutrino attenuation limits the effective terrestrial neutrino target area to ~3x10^5 km^2 at 10^17 eV, for an orbit of 1000 km and an instrumental full Field-of-View of 45 degrees. This translates into an observable cosmogenic neutrino event rate of ~1/year based upon two different models of the cosmogenic neutrino flux, assuming neutrino oscillations and a 10% duty cycle for observation.Comment: Contribution to the 32nd ICRC, Beijing, China, August 2011; Paper#1331, 4 pages, 4 figure

Cross-Cohort Differences in Health on the Verge of Retirement

Baby Boomers have left a unique imprint on US culture and society in the last 60 years, and it might be anticipated that they will also put their own stamp on retirement, the last phase of the life cycle. Yet because Boomers have not all fully retired, we cannot yet judge how they will fare as retirees. Instead, we focus on how this group compares with prior groups on the verge of retirement, that is, at ages 51-56. Accordingly, this chapter evaluates the stock of health which Early Boomers bring to retirement and compare these to the circumstances of two prior cohorts at the same point in their life cycles. Using three sets of responses from the Health and Retirement Study, we find some interesting patterns. Overall, the raw evidence indicates that Boomers on the verge of retirement are in poorer health their counterparts 12 years ago. Using a summary health index designed for this study, we find that those born 1948 to 1953 share health risks with the War Baby cohort. This suggests that most of the health decline instead began before the late 1940's. A more complex set of health conclusions emerges from the specific self-reported health measures. Boomers indicate they have relatively more difficulty with a range of everyday physical tasks, but they also report having more pain, more chronic conditions, more drinking and psychiatric problems, than their HRS earlier counterparts. This trend portends poorly for the future health of Boomers as they age and incur increasing costs associated with health care and medications. Using our health index, only those at the 75th percentile or higher are likely to be characterized as having good or better health.