Shuhei Tsuji

Measurements of muons at sea level

We measure muon intensities at sea level by using the OKAYAMA cosmic-ray telescope in detail. Measured muons are also contained in the low-momentum region where they are strongly affected by geomagnetic field effects including the east-west effect. We report the zenith and azimuthal angular dependence of conventional muons in the momentum range 1.5-250 GeV/c in the zenith angular range .

Survival probability of charged particles dissipating their energies by radiation and ionization

The survival probabilities of charged particle traversing through matters are evaluated by solving the diffusion equation, taking account of radiation and ionization losses. The solutions corresponding to high and low incident energies are proposed respectively, and inaccuracies of the saddle point method appearing in case of large probabilities are removed by deriving the results via the complementary probabilities. The enough-accurate results will be valuable to improve the resolution of radiographic analyses with atmospheric muons, and others.

Update of the observation system for the primary energy spectrum with compact EAS arrays in LAAS experiment

The relation between the core distance and the time structure of extensive air shower (EAS) particles shown by Linsley provided to determine the primary energy by using compact EAS arrays. In an apparatus for restricting the zenith angle of EAS event, relocation and update of the apparatus was carried out. And the simulation for this upgrading was performed. We report the simulation results and comparisons of old and new apparatus.

The primary energy spectrum derived from Linsley method with simulations of heavy compositions in the LAAS mini array observation

The primary energy and its spectrum are obtained by using compact Extensive Air Shower (EAS) arrays, the apparatus for restricting the EAS zenith angle, and the Linsley method. In this work, we carried out the simulation and the data analysis by taking into account of proton and iron primaries. The primary spectral indices α(proton) and α(iron) are obtained as α(proton) = −2:47 ± 0:17 and α(iron) = −3:38 ± 0:25, respectively, in the single observation of a compact EAS array, in the primary energy region of 10 16 eV to 10 18:5 eV. Additionally, α(proton) = −3:12 ± 0:13 and α(iron) = −3:52 ± 0:17 are obtained with each composition in the synchronized observation between the compact EAS array and the apparatus for restricting the EAS zenith angle in the same primary energy region.