JEM-EUSO Research Articles

Probing minimal supergravity via the Extreme Universe Space Observatory

An analysis is carried out within mSUGRA of the estimated number of events originating from upward moving ultra-high energy neutralinos that could be detected by the Extreme Universe Space Observatory (EUSO). The analysis exploits a recently proposed technique that differentiates ultra-high energy neutralinos from ultra-high energy neutrinos using their different absorption lengths in the Earth's crust. It is shown that for a significant part of the parameter space, where the neutralino is mostly a Bino and with squark mass $\sim 1$ TeV, EUSO could see ultra-high energy neutralino events with essentially no background. In the energy range 10^9 GeV < E < 10^11 GeV, the unprecedented aperture of EUSO makes the telescope sensitive to neutralino fluxes as low as 1.1 \times 10^{-6} (E/GeV)^{-1.3} GeV^{-1} cm^{-2} yr^{-1} sr^{-1}, at the 95% CL. Such a hard spectrum is characteristic of supermassive particles' $N$-body hadronic decay. The case in which the flux of ultra-high energy neutralinos is produced via decay of metastable heavy particles with uniform distribution throughout the universe is analyzed in detail. The normalization of the ratio of the relics' density to their lifetime has been fixed so that the baryon flux produced in the supermassive particle decays contributes to about 1/3 of the events reported by the AGASA Collaboration below 10^{11} GeV, and hence the associated GeV gamma-ray flux is in complete agreement with EGRET data. For this particular case, EUSO will collect between 4 and 5 neutralino events (with 0.3 of background) in ~ 3 yr of running. NASA's planned mission, the Orbiting Wide-angle Light-collectors (OWL), is also briefly discussed in this context.

Effects of atmospheric scattering and extinction on the retrieval of fluorescence and Cherenkov signals produced by extreme energy cosmic rays and neutrinos from space: role of lidar for their assessment and correction

The impact of extreme energy cosmic rays on the Earth's atmosphere is manifested by the generation of fluorescence and Cherenkov radiation: these effects constitute source fields that propagate and, once detected, provide an indirect way to deduce energy, trajectory, composition of the primary particle. Because of the relatively infrequent probability of detection of such effects at the ground, proposals have been advanced to observe them from space: one of the proposed experiments is EUSO (Extreme Universe Space Observatory). Both the generation and propagation of these fields are affected by the high variability of the atmospheric conditions: to limit the deriving uncertainties, the observations would greatly benefit by the support of adequate instrumentation to provide the status of the atmosphere at the time of detection. Thus the use of an optical radar––lidar––has been suggested to complement the EUSO capability. This paper discusses: (a) the distortion induced by different atmospheric conditions on the fluorescence and Cherenkov profiles acquired from space; (b) the lidar retrieval of the transmission and scattering characteristics of the atmosphere and the use of these data to correct the detected signals to reach a realistic assessment of the atmospheric sources and of the primary particle characteristics. The simulations are based on experimental results with regard to aerosol and cloud backscatter data, on a relatively simple transfer model and on realistic assumptions regarding the extinction to backscatter ratio.

Observation from space of ultra high energy cosmic rays with the EUSO experiment

The EUSO (Extreme Universe Space Observatory) experiment is currently under phase A study by the European Space Agency (ESA) for a possible installation as an external payload on the ESA Columbus module of the International Space Station. It is designed to study, by means of a space based UV digital camera, the Extensive Air Showers produced in the atmosphere by Ultra High Energy Cosmic Rays. The design of the EUSO Instrument is a challenging task, due to the many requirements and constraints. The basic facts of the current design of the EUSO Instrument will be described, with special emphasis on its photo-detector.

Present and future instrumentation for high-energy astrophysics in Italy

The high-energy astrophysics community in Italy is involved in several major international projects, which concern the study, design, development, and operation of telescopes in the field of high-energy astronomy and cosmic ray physics. A number of balloon- or space-borne missions, with important Italian participation, are presently either operative or recently ended (BeppoSAX, XMM-Newton, HETE-2), just launched (INTErnational Gamma-Ray Astrophysics Laboratory, in October 2002), under development (Claire, Swift, AGILE, Gamma-Ray Large Area Telescope), or under study (XEUS, Constellation-X, Lobster, Medium Energy Gamma-ray Astronomy, MAX, Gamma Air Watch, Extreme Universe Space Observatory, Interstellar/Intergalactic Medium and gamma ray Burst Observatory Spectroscopy Survey, Hard X-ray Modulation Telescope). The techniques, detection systems, and design concepts chosen for these telescopes are different and depend upon their operative energy range and scientific objectives. This work will focus on the current status of these instruments and on the possible future developments.

High-Energy Astronomy From The International Space Station

The European Space Agency, ESA, is currently studying 3 high-energy astronomy missions that use the International Space Station (ISS). These are Lobster-ISS, an all-sky imaging X-ray monitor, the Extreme Universe Space Observatory (EUSO) which will study the highest energy cosmic rays by using the Earth's atmosphere as a giant detector and XEUS — the X-ray Evolving Universe Spectroscopy Mission, a potential successor to ESA's XMM-Newton X-ray observatory. These first 2 missions will he attached to the external platforms on the Columbus module, while XEUS will visit the ISS to attach additional X-ray mirrors to enlarge the original 4.5 m diameter mirrors to the 10 m diameter required to observed redshifted iron lines from massive black holes in the early Universe.