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YBJ Observatory
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Title: ARGO-YBJ: Status and Highlights
Authors: G. Di Sciascio, for the ARGO-YBJ Collaboration

The ARGO-YBJ experiment is in stable data taking since November 2007 at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm²). ARGO-YBJ is facing open problems in Cosmic Ray (CR) physics in different ways. The search for CR sources is carried out by the observation of TeV gamma-ray sources both galactic and extra-galactic. The CR spectrum, composition and anisotropy are measured in a wide energy range (TeV - PeV) thus overlapping for the first time direct measurements. In this paper we summarize the current status of the experiment and describe some of the scientific highlights since 2007.

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Title: Observation of the Cosmic Ray Moon shadowing effect with the ARGO-YBJ experiment
Authors: G. Di Sciascio, R. Iuppa, for the ARGO-YBJ collaboration

Cosmic rays are hampered by the Moon and a deficit in its direction is expected (the so-called Moon shadow). The Moon shadow is an important tool to determine the performance of an air shower array. In fact, the displacement of the shadow center, due to the bending effect of the Geomagnetic field on the propagation of cosmic rays, allows to set the energy scale of the primary particles inducing the showers observed by the detector. The shape of the shadow permits to determine the detector point spread function. The position of the deficit at high energy allows evaluating its pointing accuracy. Here we present the observation of the cosmic ray Moon shadowing effect carried out by the ARGO-YBJ experiment (Yangbajing Cosmic Ray Laboratory, Tibet, P.R. China, 4300 m a.s.l., 606 g/cm²) in the multi-TeV energy region with high statistical significance (70 standard deviations). By means of an accurate Monte Carlo simulation of the cosmic rays propagation in the Earth-Moon system we have studied the role of the Geomagnetic field and of the detector point spread function on the observed shadow.

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Yangbajing Cosmic Ray Observatory
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China probes into origin of universe on "roof of the world"

At the foot of snow-capped Tanggula Mountain, 789 matrix detectors and 5,000 square meters of carpet detectors are probing into the depths of the universe by analysing cosmic rays streaming into the mountain's basin, positioned at an altitude of 4,300 meters above sea level.
The Yangbajing Cosmic Ray Observatory, located in the Yangbajing basin of the Qinghai-Tibetan Plateau, which is 90 kilometres from Lhasa, Tibet Autonomous Region's capital, is part of China's quest to explore the universe.

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Chinese and German scientists are establishing an astronomical observatory in a Tibetan county 4,300 meters above sea level.
Construction of the observatory began on Monday in Yangbajain Township, of Damxung County in the suburbs of Tibet's regional capital Lhasa, said project leader Wang Junjie Tuesday.
The observatory would be operational in early 2011, after a state-of-the-art telescope was moved to the Tibet plateau from its current site in the Swiss Alps, said Wang, a researcher with the National Astronomical Observatories of the Chinese Academy of Sciences (CAS), in Beijing.

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Title: Underground Water Cherenkov Muon Detector Array with the Tibet Air Shower Array for Gamma-Ray Astronomy in the 100 TeV Region
Authors: The Tibet AS Gamma Collaboration: M. Amenomori, et al

We propose to build a large water-Cherenkov-type muon-detector array (Tibet MD array) around the 37,000 m² Tibet air shower array (Tibet AS array) already constructed at 4,300 m above sea level in Tibet, China. Each muon detector is a waterproof concrete pool, 6 m wide x 6 m long x 1.5 m deep in size, equipped with a 20 inch-in-diameter PMT. The Tibet MD array consists of 240 muon detectors set up 2.5 m underground. Its total effective area will be 8,640 m² for muon detection. The Tibet MD array will significantly improve gamma-ray sensitivity of the Tibet AS array in the 100 TeV region (10-1000 TeV) by means of gamma/hadron separation based on counting the number of muons accompanying an air shower. The Tibet AS+MD array will have the sensitivity to gamma rays in the 100 TeV region by an order of magnitude better than any other previous existing detectors in the world.

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Tibet Air Shower Arrays
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A mysterious surplus of energetic particles called cosmic rays is striking the Earth from the direction of the constellation Cygnus, suggests a controversial new study. If confirmed, the detection of this excess may help scientists figure out what produces these enigmatic high-speed particles.
Cosmic rays are speeding charged particles that appear to hit Earth in roughly equal numbers from all directions. Lower energy cosmic rays are thought to come from the shock waves around supernovae, but the source of the higher energy ones is still a mystery.
When a cosmic ray hits Earth's atmosphere, it produces a burst of charged particles and light. Sensitive detectors on the ground measure either the secondary particles or the light to try to determine the direction from which each cosmic ray came.
However, no one has been able to unequivocally trace cosmic rays to a specific object like the expanding shell of a supernova.
Now, observations have revealed what appears to be a broad area of enhanced cosmic ray activity in the sky. The data comes from the Tibet Air Shower Arrays, which detects the secondary particles produced when cosmic rays or high-energy radiation slams into the atmosphere.

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YBJ Observatory
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YBJ Observatory was founded in 1990. It has hosted the Tibet ASγ Experiment (Sino-Japanese Cooperation) ever since. After 6 years’ preparation, the ARGO -YBJ Project (Sino-Italian Cooperation) started its detector installation in 2000. Both of them aim at the research of the origin of high energy cosmic rays, the GRB physics in high energy, the correlation between the movement of the Cosmic ray sun shadow and the solar/interplanetary magnetic field and solar activity, etc. through the observation of air showers (AS) by AS array - a semi-full sky and continuous observation technique. Taking advantage of the YBJ high altitude, by increasing the density of scintillation detector, the ASγ Array has successfully observed γ rays from Crab Nebula and Mrk 501 (during its flaring period in 1997); by developing the traditional sampling AS array as a "carpet", the ARGO-YBJ full coverage array is intended for exploring the approximately 100 GeV uncultivated land and measuring the antiproton/proton ratio by cosmic ray moon shadow.

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90.46962E_30.14639N
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Latitude: 30.13516° Longitude: 90.52452°

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