The amplitude and phase of the cosmic-ray anisotropy are well established experimentally between 10 11 eV and 10 14 eV. The study of their evolution in the energy region 10 14-10 16 eV can provide a significant tool for the understanding of the steepening ("knee") of the primary spectrum. In this Letter, we extend the EAS-TOP measurement performed at E 0 ≈ 10 14 eV to higher energies by using the full data set (eight years of data taking). Results derived at about 10 14 and 4 × 10 14 eV are compared and discussed. Hints of increasing amplitude and change of phase above 10 14 eV are reported. The significance of the observation for the understanding of cosmic-ray propagation is discussed.
We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Obser-\ud
vatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a mis-\ud
sion to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth’s nighttime\ud
atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by\ud
ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based obser-\ud
vation and we compute the annual exposure in nadir observation. The results are based on studies of the\ud
expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of\ud
clouds and different types of background light. We show that the annual exposure is about one order of\ud
magnitude higher than those of the presently operating ground-based observatories
A. S. 1)6Au=uIN(**), V. G. RYASSNY(**), 0. G. RYAZHSKAYA(**), 0. SAAVEDRA(*), V. P. TALQCHEIN(**), G. TRINCHERO(*), S. VERNE~TO(*), G. T. ZATSEPIN(**) and V. F. YAKUSHEV(**) (*) Istituto di C o s m o g w f e del C.N.R.
We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured angular distribution of muon intensity has been converted to the 'depth -vertical intensity' relation in the depth range from 3 to 12 km w.e.. The analysis of this relation allowed to derive the power index, γ, of the primary all-nucleon spectrum: γ = 2.78 ± 0.05. The 'depth -vertical intensity' relation has been converted to standard rock and the comparison with the data of other experiments has been done. We present also the derived vertical muon spectrum at sea level.PACS numbers: 13.85.T, 96.40.T
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