Performances of JEM–EUSO: energy and X max reconstruction

Abstract

by a large international collaboration, is designed to be launched within this 11 decade. In this article, we present the reconstruction of the energy of the 12 observed events and we also address the X max reconstruction. After discussing 13 the algorithms developed for the energy and X max reconstruction, we present such an energy range, and will unveil the sources of UHE cosmic rays and 10 the mechanisms of their production. JEM-EUSO is also being designed to 11 explore the neutrino and photon flux at UHE and, therefore, the discrimination 12 capability of the mission for these particles, with respect to charged UHECRs, of 3×3 mm size, covering a field of view on ground of roughly 500 × 500 m. 21The detector therefore consists of more than 3 · 10 5 pixels, which cover a field 22 of view of 500 km diameter. The structure of the focal surface can be seen in of the instrument, we refer the reader to [5], [6], [7]. For each observed event, 4 the arrival time, arrival direction, energy, and X max must be reconstructed to 5 recover the full observational information. 6In this paper, we present the algorithms developed to reconstruct the en-7 ergy and X max parameters for events observed by JEM-EUSO. These studies instrument and has been used in the present study. 222 Energy and X max reconstruction 23The PmtToShowerReco is the energy and X max reconstruction procedure de-24 veloped to reconstruct events observed by JEM-EUSO. The reconstruction is 25 structured in several subsequent steps, each of which performing a sub-task. 26The procedure is used for a first estimate of the shower parameters, like en-27 ergy and X max . The method, already described in [9], has been significantly 28 improved and, therefore, a detailed description of the algorithms has been 29 done. A schematic view of this algorithm is given in Fig. 2. 31The signal track selection 32The PmtToShowerReco receives the information in input on the timing and 33 position for all the counts detected on the focal surface. For the analysis we 34 only consider triggered events since this is the condition for data to be sent 35 to ground. More details on the trigger logic can be found in [10]. The PDMs 36 associated with a trigger (and neighboring PDMs) will therefore be sent to 37 ground. In Fig. 3, an example of simulated data received from the instrument 38 can be seen, including both signal and background. This is representing a 39shower event of 3·10 20 eV and 50 degrees zenith angle. At regular intervals, the 40shower spot crosses the PMTs gaps perpendicularly and, therefore, a decrease 41 in the detected intensity has to be expected. In Fig. 4, the counts detected The JEM-EUSO Collaboration we only see the counts that originated from the shower unlike in Fig. 3. The This particular shower is, therefore, clearly evolving to the right of the image 10 for a time duration of roughly 50 GTUs. 11The first task of the reconstruction must be the identification of the pixels 12and GTUs with signal. Several algorithms have been developed for this pur- is o...

The JEM-EUSO Program

“…The JEM-EUSO Program Andrea Santangelo in [3], [16], [17], [18]. The current baseline of the instrument is described in [19].…”

The JEM-EUSO observation in cloudy conditions

“…The observed temporal and topological profiles of the signals are used to retrieve the geometry and longitudinal development of the EAS (see Refs. [18][19][20] for details about technique and performances). In practice, the so-called shower-detector-plane (SDP), the plane containing the EAS track and the detector, is determined by orientation of the signals projected on the FS detector.…”

“…The apparent angular velocity of the light spot indicates the incident direction of the EAS within SDP, presuming that it moves with the EAS at the speed of light. Cherenkov footprint or other methods [3,19] can be used to determine the distance to the EAS. Knowing the EAS geometry and taking into account extinction loss, the arrival time distribution of photons, namely light curve, may be converted to the energy deposition profile along the EAS.…”

“…where A(E; H C , τ C ) and A 0 (E) are geometrical apertures as a function of energy for the case with the test cloud and for clear atmosphere condition, respectively. Table 1 summarizes the average ζ above 6.3×10 19 eV for different test clouds [11].…”

“…Detailed studies about the reconstruction in clear atmosphere condition are described in Refs. [18][19][20]. It should be emphasized that the information retrieved by the AM system may be of use to eliminate the low quality region in FOV based on local cloud properties [8,15].…”