Study The Astrophysics Burst Phenomena With YBJ Data

The Argo - YBJ experiment ,located at the YangBaJing High Altitude Cosmic Ray Laboratory in Tibet (latitude 30.11°N, longitude 90.53°E), has been designed to decrease the energy threshold of traditional EAS array by exploiting the high altitude location(4300 m a. s. l.). The detector consists in a single layer of resistive plate chambers (RPC) and has a modular structure, the basic module being the cluster (5.7×7.6m~2) divided in 12 chambers. The whole carpet will be constituted of 154 clusters,130 of which have been installed so far, with an active detection area of about 5600m~2. In scaler mode, the single particle technique (SPT) has a low energy threshold of about 1GeV to photon. So, the SPT has a good advantage comparing to the old typical EAS array, the lower limit of the detector is 10GeV is reached.At these low energies, signals due to local (e.g. solar GLEs) and cosmological phenomena (GRBs) are expected as a significant enhancement of the counting rate over the background. In particular GRBs have been deeply studied in the KeV-MeV energy band, but only little information in the GeV range that have been provided in the past decade by EGRET measurements, that detected only 3 bursts at energy >1GeV, with one photon reaching 18GeV. At these energies the detection from space is hampered by the very low fluxes, requiring large collection areas; from ground the relevant energy range 1Gev-1TeV is partly covered by the Cerenkov telescopes though, due to their low duty cycle and small field of view, the observation of GRBs in coincidence with satellites is highly problematic. On the other side the the traditional EAS arrays have a typical threshold energy (50TeV) is too high. The large field of view and high duty cycle of the detector make the ARGO-YBJ for each cluster 4 low multiplicity channels are implemented for event multiplicities from 1 to 4. The search of high emission from GRBs started with the first GRB detection by the Swift satellite, since ARGO-YBJ experiment participates to the Swift Follow-Up program. The search is triggered by the detection with Swift, HETE, Integral satellite experiment. Up to May 31,2007 GRBs detected by these satellites were within the ARGO-YBJ field of view (θ<40°).The study of solar cosmic rays is also the duty of ARGO-YBJ, the thesis analyzed the GLE on January 20, 2005 using the neutron monitor and SPT data.