Hu Hongbo

Cosmic ray proton plus helium energy spectrum measured by the ARGO-YBJ experiment in the energy range 3-300 TeV

The ARGO-YBJ experiment is a full-coverage air shower detector located at the Yangbajing Cosmic Ray Observatory (Tibet, Peoples Republic of China, 4300 m a.s.l.). The high altitude, combined with the full-coverage technique, allows the detection of extensive air showers in a wide energy range and offer the possibility of measuring the cosmic ray proton plus helium spectrum down to the TeV region, where direct balloon/space-borne measurements are available. The detector has been in stable data taking in its full configuration from November 2007 to February 2013. In this paper the measurement of the cosmic ray proton plus helium energy spectrum is presented in the region 3-300 TeV by analyzing the full collected data sample. The resulting spectral index is

Performance of the muon detector A under TIBET III array

\gamma = -2.64 \pm 0.01

Updated study on multi-TeV cosmic-ray modulation with the Tibet III air shower array using the east-west method

. These results demonstrate the possibility of performing an accurate measurement of the spectrum of light elements with a ground based air shower detector.

Search for TeV GRBs using Tibet ASγ data

In order to observe gamma rays in the 100 TeV energy region, the 4500 m(2) underground muon detector array using water Cherenkov technique is constructed, forming the TIBET III+MD hybrid array. Because the showers induced by primary gamma rays contain much fewer muons than those induced by primary hadrons, significant improvement of the gamma ray sensitivity for TIBET III+MD array is expected. In this paper, the design and performance of the MD-A detector with large Tyvek bag is reported.

An updated search of steady TeV γ-ray point sources in northern hemisphere using the Tibet air shower array*

We study the sidereal and solar time modulation of multi-TeV cosmic rays using the east-west method with Tibet III air shower array data taken from November 1999 to December 2008. The statistics are twice the amount used in our previous paper. In this analysis, the amplitude of the observed sidereal time modulation is about 0.1%, and the modulation shows an excess from about 4 to 7 hours and a deficit around 12 hours in local sidereal time. The sidereal time modulation has a weak dependence on the primary energy of the cosmic rays. However, the solar time modulation shows a large energy dependence. We find that the solar time modulation is fairly consistent with the prediction of the Compton-Getting effect for high-energy samples (6.2 TeV and 12.0 TeV), but exceeds the prediction for the low-energy sample (4.0 TeV). Such a discrepancy may be due to the solar modulation or the characteristics of the experimental device in the near threshold energy.

ARGO-YBJ detector simulation using GEANT4

TeV energy emission from gamma ray bursts （GRB） is very important for studying the origin and the radiation mechanism of GRB. Searching for TeV GRBs is carried out by using the Tibet ASγ data. A GRB candidate is a shower cluster appearing in a given small sky window and a given time interval. An equi-zenith-angle method is used to estimate the background. In this analysis，two methods are applied in searching for possible GRBs signals，one considers the coincidence with satellite GRB data and the other doesnt. No significant TeV GRBs is detected in either case. The upper flux limit on top of the atmosphere at the 95% confidence level is estimated to be about 3.32×10 -9 —1.24×10 -7 cm -2 ·s -1 accordingly.

Observation of the thunderstorm-related ground cosmic ray flux variations by ARGO-YBJ

Using the data taken from Tibet II High Density (HD) Array (1997 February1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV γ−ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0 to 60.0 in declination (Dec) range, no new TeV γ−ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV γ−ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. Department of Physics, Hebei Normal University, Shijiazhuang 050016, China. Department of Mathematics and Physics, Tibet University, Lhasa 850000, China. Department of Physics, Shandong University, Jinan 250100, China. Institute of Modern Physics, Southwest Jiaotong University, Chengdu 610031, China. Department of Physics, Yunnan University, Kunming 650091, China. National Center for Space Weather, China Meteorological Administration, Beijing 100081, China. Physics Department and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China. Center of Space Science and Application Research, Chinese Academy of Sciences, Beijing 100080, China.Using the data taken from Tibet II High Density (HD) Array (1997 February–1999 September) and Tibet-III array (1999 November–2005 November), our previous northern sky survey for TeV γ-ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0° to 60.0° in declination (Dec) range, no new TeV γ-ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV γ-ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.