M. Fuki

Energy spectra of cosmic rays above 1 TeV per nucleon

Direct measurements of cosmic-ray nuclei above 1 TeV/nucleon have been performed in a series of balloon-borne experiments with emulsion chambers. The observed all-particle spectrum above 20 TeV is consistent with the results of the Proton satellite and many air shower experiments. The proton spectrum is consistent with a power law having an index of 2.76 + or - 0.09 up to at least 100 TeV, but an overabundance of helium by a factor of 2 above 2 TeV per nucleon is found when compared with the extrapolation from the low energies. For heavy elements (C through Fe), the intensities around 1 TeV/nucleon are consistent, within the statistical errors, with the extrapolation from lower energy data using the Spacelab 2 spectral indices. An enhancement for the medium-heavy components (C through Ca) above 200 TeV is indicated. The mean mass above 50 TeV indicates slightly higher values than the results of the air shower experiments. 37 refs.

JACEE emulsion chambers for studying the energy spectra of high energy cosmic ray protons and helium

Abstract Emulsion chambers are being used in a series of stratospheric balloon flights to study nuclear interactions, charge composition, and energy spectra of cosmic ray nuclei over the energy range 10 12 –10 15 eV. Charge identification involves grain, gap, and/or delta-ray counting in emulsion plates having different sensitivities on two sides of an acrylic base. Electromagnetic cascade energies are measured with resolutions of about 25% by the three-dimensional track counting method. This report describes the apparatus, the measurement techniques, and the analysis methods used to determine the primary proton and helium spectra.

Direct measurement of the composition and spectra of cosmic rays above 1 TeV/amu from Jacee

Abstract Direct measurements on cosmic ray protons through iron above about 1 TeV/amu have been performed in a series of balloon-borne experiments with emulsion chambers. The measured energy spectra of protons and helium are power laws with exponents of 2.77 ± 0.09 and 2.72 ± 0.11 in the energy range 5 to 500 TeV and 2 to 50 TeV/amu, respectively. The proton spectrum shows no evidence of the steepening near 2 TeV which was reported by other experiments. Helium has a slightly higher intensity compared to extrapolations from lower energy measurements. The heavier elements, carbon to sulfur, show a small tendency for intensity enhancement in the relative abundance above 10 TeV/amu.

Cosmic ray results from the jacee experiments

Abstract Studies of high-energy nucleus-nucleus interactions with balloon-borne JACEE emulsion chambers are summarized. High energy, high multiplicity interactions are found with high-energy-density (⩾ 2 GeV/fm3), high observed values (500 – 2,000 MeV/c), and several interesting pseudorapidity and/or azimuthal structures. Very short-range correlations of charged particles, and several other inclusive characteristics are discussed.

Study of correlations of positive and negative charged particles

Abstract Particle correlations of the central collision events of 32 S + Pb at 200 GeV/AMU have been studied by utilizing a Magnetic-Interferometric-Emulsion-Chamber (MAGIC) detector. Particle angles, momentum, and charge-signs are measured for all produced charged tracks for each event. Two-particle correlation functions, C 2 = dN (¦ p 1 − p 2 ¦= q )/ dp 1 dp 2 , for (++), (−−) and (+-) particles are examined. A source radius around 4 – 6 fm is observed for overall identical particle correlations, while unexpected short-range correlations of unlike-sign pairs are observed in the high rapidity region. An analysis of unlike-sign pairs in terms of resonance decays indicated that a large amount (40% relative to pions) of η or ω mesons (decaying into 3 π), or of scalar iso-scalar σ mesons (decaying into 2π) would be required to explain some of the data. Multi-particle charge-sign clusters are recognized; however, their “run-test” and “conjugate-test” show small deviations from statistical fluctuations.

High energy cosmic ray events of ultra-relativistic nucleus-nucleus collisions☆

Abstract Cosmic ray ultra-relativistic nucleus-nucleus collision events in the TeV/A region are analyzed. The average transverse momentum of non-peripheral events is examined and the breakdown of the limiting behaviour of this quantity is observed in events with high energy density. Close pairing or clustering of tracks is observed in many events. Possible explanations of the phenomena are discussed.

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.

Transverse momentum distributions and particle correlations from EMU05

Abstract Transverse momentum distributions and multi-particle correlations of charged particles in 200 GeV/AMU heavy-ion collisions are studied with the Magnetic-Interferometricr-Emulsion-Chamber (MAGIC) for central collision events in 16 O + Pb and 32 S + Pb interactions. The P T distribution of negative-charged particles below 1 GeV/c fits a single exponential, while that of positive particles contains additional contributions of both highand low-P T particles. The like-sign, two particle correlations indicate HBT interferences, while that of the unlike-sign pairs possibly suggests other components. The apparent, multi-particle, charge-sign clustering is studied with the run-test and with Monte Carlo simulations. Some of the data are consistent with chance coincidence and the HBT interference.

JACEE long duration balloon flights

JACEE balloon‐borne emulsion chamber detectors are used to observe the spectra and interactions of cosmic ray protons and nuclei in the energy range 1–100A TeV. Experience with long duration mid‐latitude balloon flights and characteristics of the detector system that make it ideal for planned Antarctic balloon flights are discussed.

Multiple photon emission in heavy particle decays

Cosmic-ray interactions, at energies above 1 TeV/nucleon, in emulsion chambers flown on high altitude balloons have yielded two events showing apparent decays of a heavy particle into one charged particle and four photons. The photons converted into electron pairs very close to the decay vertex. Attempts to explain this decay topology with known particle decays are presented. Unless both events represent a b to u transition, which is statistically unlikely, then other known decay modes for charmed or bottom particles do not account satisfactorily for these observations. This could possibly indicate a new decay channel.