118682734
Detection of TeV gamma rays from Mrk 501 at high flaring state of activity in 1997 with the Tibet air shower array
The BL Lac object Mrk 501 came into a high flaring state in 1997, brightest in the sky at TeV energies. Using the air shower data obtained with a high density part of the Tibet II array, being operating at Yangbajing since 1996, we searched for γ-ray signals from this source during the period from February to August in 1997. The result shows a 3.7σ excess for showers with its mode energy 3 TeV for the whole period and 4.7σ excess for the period from April 7 to June 16. The estimated energy spectrum of γ rays is consistent with those obtained by imaging atmospheric Cherenkov detectors.
121713049
An approach to measure the spectra of primary protons, helium- and iron nuclei at the "knee" energies at a high altitude
We propose to build a simple detector array at a high altitude that records high energy electromagnetic components in air shower cores of the 'knee' energies. The Monte Carlo study shows that spectra of primary protons, helium- and iron nuclei at the 'knee' energy region can be obtained with a three years' exposure using this air shower core detector.
123166314
Search for gamma-ray bursts with the Tibet air shower array
We searched for multi-TeV counterparts to the gamma–ray bursts (GRBs) at keV energies detected by BATSE during the period from October 2, 1995 to March 18, 1999 using the data of the Tibet Air Shower Array. In the field of view of the array there were 70 GRBs detected by BATSE in this period. The search was done based on the sky survey within error circles of BATSE bursts and with time scales during 10 to several hundred seconds. No significant signals of counterparts were detected.
122896246
Performance of the Tibet II/HD air shower array
Tibet II Air Shower Array consisting of scintillation counters with lattice of 15 m spacing has been operated with very high trigger rate of about 200 Hz. The threshold enegy of this array is estimated to be about 8 TeV for proton induced showers. Tibet High Density (HD) Array with 7.5 m spacing has been operated with the trigger rate of 115 Hz. The Mode energy of this array is estimated to be about 3 TeV for proton showers. Angular resolution of the arrays are estimated to be 0.9 degree above 10 TeV for Tibet II array, and 0.85 degree above TeV for HD array, resepectively. The angular resolution of these arrays and other array performances are examined by observing the Moon shadow resulting from the cosmic ray deficit in the direction of the Moon. Using the deflection of the Moon shadow to the east-west direction, the error of the array can be estimated by observing the displacement of the shadow in the north-south direction, because it is free from the effect of geomagnetic field, especially at Yangbaji...
121168476
Primary proton spectrum around the knee deduced from the emulsion-chamber data obtained at Mts. Fuji and Kanbala
Abstract We have done extensive Monte Carlo simulations using the new simulation codes of CORSIKA and COSMOS to compare with the gamma-family data obtained at Mts. Fuji (3750 m above sea level) and Kanbala (5500 m above sea level). Then, we estimated the primary proton and helium spectra around the knee energy region using a multiple-layered feed-forward neural network as a classifier of primary particle kind. The selection efficiency of proton-induced family events is estimated to be 82%. The flux value of protons at 2×10 15 eV is (5.5±1.5)×10 −14 (m −2  s −1  sr −1  GeV −1 ). The result suggests heavy-enriched primary composition around the knee region.
122158750
An experiment to measure the spectra of primary proton, helium and iron nuclei at the 'knee' region at a high altitude
The possibility of measuring the energy spectra of some single elements (proton, helium and iron) in primary cosmic rays at the 'knee' energies, by setting up an air shower (AS) core detector in the ASγ array (4300 m a.s.l., Tibet, China) is investigated. Taking into account the sensitivity and the acceptance needed for this measurement, the feasibility of construction and operation of the apparatus at a high altitude, and the cost, it is shown that this aim can be achieved by a simple AS core detector that mainly measures the high-energy electromagnetic components in AS cores. In this paper, such a detector is described. With a three-year exposure, proton, helium and iron spectra at the 'knee' energy region can be obtained with three event samples selected by an artificial neural network (ANN).
115166512
Polynomial Representation of E6 and Its Combinatorial and PDE Implications
In this paper, we use partial differential equations to find the decomposition of the polynomial algebra over the basic irreducible module of E6 into a sum of irreducible submodules. It turns out that the cubic polynomial invariant corresponding to the Dicksons' invariant trilinear form is the unique fundamental invariant. Moreover, we obtain a combinatorial identity saying that the dimensions of certain irreducible modules of E6 are correlated by the binomial coefficients of twenty-six. Furthermore, we find all the polynomial solutions for the invariant differential operator corresponding to the Dickson trilinear form in terms of the irreducible submodules.