Recent results from the ARGO-YBJ experiment

The ARGO-YBJ experiment at YangBaJing in Tibet (4300 m a.s.l.) has been taking data with its full layout since October 2007. Here we present the first significant results obtained in gamma-ray astronomy and cosmic-ray physics. Emphasis is placed on the analysis of gamma- ray emission from point-like sources (Crab Nebula, MRK 421), on the preliminary limit on the antiproton/proton flux ratio, on the large-scale cosmic-ray anisotropy and on the proton-air cross section. The performance of the detector is also discussed, and the perspectives of the experiment are outlined

Astroparticle Physics with ARGO-YBJ experiment

The ARGO-YBJ experiment, installed at the Yangbajing Cosmic Ray Laboratory (Tibet, China), at 4300 m a.s.l., is a detector 100x110m2 large, made by a layer of Resistive Plate Counters (RPCs) consisting of a central carpet with almost full coverage extending over an area of about 5.500 m2, surrounded by a guard ring with partial coverage. The high space-time granularity, the full-coverage technique and the high altitude location make this detector a unique device for a detailed study of the atmospheric shower characteristics with an energy threshold of a few hundred GeV. These properties in addition to the large field of view and the high duty cycle enable the ARGO-YBJ experiment to monitor the sky in a continuous way. Results have been reached in a wide variety of fields ranging from Gamma Astronomy, to Solar Physics, from Cosmic Rays composition to hadronic interactions and proton-antiproton ratio. A summary of all these results will be presented and reviewed

Gamma astronomy with the ARGO-YBJ experiment

Very High Energy (VHE) g -astronomy and cosmic ray physics are the main goals of the ARGOYBJ experiment. The detector is located in Tibet (People's Republic of China) and is a full coverage Extensive Air Shower array consisting of a carpet of Resistive Plate Chambers (RPCs). Altitude and full coverage ensure an energy threshold of few hundreds of GeV for primary photons detected in shower mode, while the RPC time resolution gives a good pointing accuracy, thus allowing a high sensitivity to g -ray sources. The large eld of view (FoV) and the high duty-cycle allow the continuous monitor of the Northern sky in the declination band (10, +70). The detector operates also in scaler mode in order to look for Gamma Ray Burst (GRB) signals in the range 1-100 GeV in coincidence with GRB detection by satellites. After some detail about the performances of the detector, the present results concerning g -astronomy will be presented

Medium scale anisotropy in the TeV cosmic ray flux observed by ARGO-YBJ

Measuring the anisotropy of the arrival direction distribution of cosmic rays provides important information on the propagation mechanisms and the identification of their sources. In fact, the flux of cosmic rays is thought to be dependent on the arrival direction only due to the presence of nearby cosmic ray sources or particular magnetic-field structures. Recently, the observation of unexpected excesses at TeV energy down to an angular scale as narrow as raised the possibility that the problem of the origin of Galactic cosmic rays may be addressed by studying the anisotropy. The ARGO-YBJ experiment is a full-coverage extensive air showers array, sensitive to cosmic rays with the energy threshold of a few hundred GeV. Searching for small-size deviations from the isotropy, the ARGO-YBJ Collaboration explored the declination region , making use of about events collected from November 2007 to May 2012. In this paper, the detection of different significant (up to 13 standard deviations) medium-scale anisotropy regions in the arrival directions of cosmic rays is reported. The observation was performed with unprecedented detail. The relative excess intensity with respect to the isotropic flux extends up to . The maximum excess occurs for proton energies of 10–20 TeV, suggesting the presence of unknown features of the magnetic fields the charged cosmic rays propagate through, or some contribution of nearby sources never considered so far. The observation of new weaker few-degree excesses throughout the sky region is reported for the first time