A. I. Iyono

Rapidity and transverse momentum distributions in 6.4 TeV S+Pb interactions from CERN EMU05 experiments

Abstract Mixed transverse(P T ) momentum and rapidity distributions of charged particles produced in 200 GeV/AMU heavy ion collisions are obtained with Magnetic-Interferometric-Emulsion-Chamber ( MAGIC ) by CERN-EMU05 experiments. The P T spectra at different rapidity regions showed no anomalous enhancement of low P T components over a conventional, single exponential function with slope values ranging from 160 to 200 MeV/c.

Network observation of air showers as cosmic ray interferometer

Abstract The Large Area Air Shower (LAAS) group has been performing a network observation of extensive air showers (EAS) since 1996. Ten compact EAS arrays (stations) are scattered over a large part of Japan and operated independently and simultaneously. Each station has 4–12 scintillation counters and a Global Positioning System (GPS), which provides time stamps of EAS arrivals with an accuracy of 1 μs. The primary purpose of the network observation is to study large-scale correlations in ultra-high-energy cosmic rays, which are attracting much interest of the astroparticle physicists community in recent years. The present state of the network and some results from computer simulations are reported here.

The LAAS network observation for studying time correlations in extensive air showers

The Large Area Air Shower (LAAS) group has been performing a network observation of extensive air showers (EAS) since 1996 in Japan. Ten compact EAS arrays are operating simultaneously at distant stations (up to ≈1000 km) and detecting EAS with mean energy of ≈1015 eV. Each station has 4--12 scintillation counters and a Global Positioning System (GPS), which provides time stamps of EAS triggers with an accuracy of 1μs. As a consequence of the comparable time stamps, uniformly-adjusted detectors and a standardized data format among all stations, we can treat the independent observations as a gigantic EAS detector system as a whole. The primary purpose of the network observation is to study large-scale correlations in ultra-high-energy cosmic rays. On the other hand, three nearby stations within 1~km distance at Okayama area have a possibility to detect extremely-high-energy EAS (≈1019 eV) as coincident triggers of the three stations. The present status of the network and some results from computer simulations are reported here.

Rapidity spacings and intermittency analyses by differenciating charge-sign in 200 GeV/amu S + Pb interaction from CERN EMU05 experiments

Fluctuations in rapidity are examined, by using CERN EMU05 experimental data differentiating charge-sign in S + Pb collision at 200 GeV/amu. Rapidity spacing analyses show limiting fluctuations at higher order spacings, while Poisson fluctuations are universally indicated in the lower spacings. The limiting behavior suggests that a long-range positive correlation, such as Wigner repulsion, is in order in the rapidity space. No clear evidence for the intermittent phenomena has been observed in the resultant normalized factorial moments in all charged, positively and negatively charged particles, respectively.

Observation of early photon conversions in high‐energy cosmic‐ray interactions

High energy cosmic ray interactions were studied by the JACEE Collaboration using balloon‐borne emulsion chambers at high altitude. In high energy, yet low multiplicity interactions many secondary vertices were observed, probably due to decays of short‐lived particles. Early conversions of photons were found in the vicinity of these vertices. Conversion distances and angular distributions of the photons were studied.

Observation of coincident air showers over a very large area

Abstract A network observation of air showers ( E 0 ≈ 10 15 eV) has been performed since 1996 in Japan. Ten compact air shower arrays, scattered over a large part of Japan, are operated independently by each institute. To explore large-scale correlations in primary cosmic rays, air shower data from five arrays of the network are analyzed in terms of arriving phases of coincident air showers, hypothetically induced by ultra-high-energy γ-rays from point sources or by secondary particles from interactions of extremely-high-energy cosmic rays with interstellar matter. Four coincident event candidates with extremely small time differences are found out. Two of these events are observed in the direction of the Crab Nebula, a well-known ultra-high-energy γ-ray source. However, significances of the events are not enough to invoke the claim for the detection of large-scale correlations.

Interpreting anomalous electron pairs as new particle decays

In heavy particle decays found in cosmic ray interactions recorded in the JACEE emulsion chambers, multiple electron pairs were previously reported. These pairs apparently originated from conversions of photons emitted in the decays. It is difficult to explain the overall properties of these decays in terms of known heavy particle decay modes. A recently published compilation of low-energy nuclear data suggests the presence of excess electron pairs with invariant mass of about 9 MeV/c2, which may be explained by postulating the existence of a new neutral boson decaying into the electron pair. The feasibility of explaining the JACEE electron pairs with this hypothesis is presented.

Cosmic ray H and He spectra from 2 to 800 TeV/nucleon from the JACEE experiments

Results for the cosmic ray hydrogen and helium spectra up to 800 TeV, near the “knee” region, are presented. There is no sign of a break in either the hydrogen or helium spectra. The differential power law slopes are 2.80±0.04 for hydrogen and 2.68±0.06 for helium. With these new H and He measurements, together with earlier reported results for the heavier elements, the sum of the spectra give an all-particle spectrum that is in good agreement with the all-particle spectrum measured using extensive air showers.