The search for Gamma Ray Burst ( GRB ) emission in the energy range 1-100 GeV in coincidence with the satellite detection has been carried out using the Astrophysical Radiation with Ground-based Observatory at YangBaJing ( ARGO-YBJ ) experiment .
The high altitude location ( 4300 m a.s.l .
) , the large active surface ( \sim 6700 m ^ { 2 } of Resistive Plate Chambers ) , the wide field of view ( \sim 2 ~ { } sr , limited only by the atmospheric absorption ) and the high duty cycle ( > 86 % ) make the ARGO-YBJ experiment particularly suitable to detect short and unexpected events like GRBs .
With the scaler mode technique , i.e. , counting all the particles hitting the detector with no measurement of the primary energy and arrival direction , the minimum threshold of \sim 1 GeV can be reached , overlapping the direct measurements carried out by satellites .
During the experiment lifetime , from December 17 , 2004 to February 7 , 2013 , a total of 206 GRBs occurring within the ARGO-YBJ field of view ( zenith angle \theta \leq 45 ^ { \circ } ) have been analyzed .
This is the largest sample of GRBs investigated with a ground-based detector .
Two lightcurve models have been assumed and since in both cases no significant excess has been found , the corresponding fluence upper limits in the 1-100 GeV energy region have been derived , with values as low as 10 ^ { -5 } ~ { } erg cm ^ { -2 } .
The analysis of a subset of 24 GRBs with known redshift has been used to constrain the fluence extrapolation to the GeV region together with possible cutoffs under different assumptions on the spectrum .