Abstract
The ARGO-YBJ air shower detector has been in stable data taking for five years at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300m a.s.l.) with a duty cycle > 86% and an energy threshold of a few hundreds of GeV. With the scaler mode technique, the minimum threshold of 1 GeV can be reached. In this paper recent results in γ -ray astronomy will be presented, including those from 4.5 years of observations of the blazar Mrk 421 in common with the Fermi satellite.
Highlights
The ARGO-YBJ air shower detector has been in stable data taking for five years at the YangBaJing Cosmic Ray Laboratory
The ARGO-YBJ experiment is located at Yangbajing
The detector carpet is connected to two different DAQ systems, which work independently: in shower mode, for each event the location and timing of each detected particle is recorded, allowing the reconstruction of the lateral distribution and of the arrival direction; in scaler mode, the counting rate of each cluster is measured every 0.5 s, with little information on the space distribution and arrival direction of the detected particles
Summary
The ARGO-YBJ experiment is located at Yangbajing (Tibet, P.R. China, 4300 m a.s.l.) and consists of a single layer of Resistive Plate Counters (RPCs) on a total area of about 110 × 100 m2. The detector carpet is connected to two different DAQ systems, which work independently: in shower mode, for each event the location and timing of each detected particle is recorded, allowing the reconstruction of the lateral distribution and of the arrival direction; in scaler mode, the counting rate of each cluster is measured every 0.5 s, with little information on the space distribution and arrival direction of the detected particles. The trigger of the shower mode was Npad ≥ 20 in a time window of 420 ns, with a rate of 3.5 kHz. In the scaler mode, for each cluster four scalers recorded the rate of counts ≥ 1, ≥ 2, ≥ 3 and ≥ 4 in a time window of 150 ns. The detector pointing accuracy, angular resolution and absolute energy calibration have been determined studying the deficit in the cosmic ray flux due to the Moon [3]
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