JEM-EUSO will pioneer Space observations of UHECR-induced Extensive Air Showers making measurements with unprecedented statistics at energies above 5×1019 eV. It will observe the primary energy and arrival direction of UHECRs, using a target volume far greater than it is possible from the ground. It will also be able to distinguish photon and neutrino induced showers from hadronic showers. Such data will shed light on the origin of the UHECRs, on the sources that are producing them, on the propagation environment from the source to the Earth and, possibly, on particle physics interactions at energies well beyond the ones achievable in man-made accelerators.
JEM-EUSO science also includes constraining the Galactic and extragalactic magnetic fields, the detection of extreme energy neutrinos and gamma rays, the verification of special relativity at extremely large Lorentz factors, the examination of possible quantum gravity effects at extreme energies, and the systematic surveillance of atmospheric phenomena.
Astrophysics and Cosmology
Main Science Objectives:
A new window on the unknown
Looking downward at the dark Earth atmosphere, JEM-EUSO will record such fluorescence light streaks as sketched in the Figure. EAS appear as a small disc-shaped luminous object which, when viewed continuously, moves on a straight path at the speed of light. The recorded amount of light is nearly proportional to the shower size at the various depths in the atmosphere. By imaging the motion of the fluorescence emission every few microseconds the arrival direction of the primary UHECR can be determined. The total amount of light recorded determines the energy of the primary UHECR. The cascade shape (especially the position of the shower maximum in the traversed slant depth) gives an indication of the nature of the primary.