Steven Chester Strausz

Cosmic-ray proton and helium spectra: Results from the JACEE Experiment

Measurements of the cosmic-ray hydrogen and helium spectra at energies from 20 to 800 TeV are presented. The experiments were performed on a series of twelve balloon flights, including several long duration Australia to South America and Antarctic circumpolar flights. No clear evidence is seen for a spectral break. Both the hydrogen and the helium spectra are consistent with power laws over the entire energy range, with integral spectral indices 1.80 ± 0.04 and 1.68 -->+ 0.04−0.06 for the protons and helium, respectively. The results are fully consistent with expectations based on supernova shock acceleration coupled with a leaky box model of propagation through the Galaxy.

On intermittency in heavy-ion collisions and the importance of γ-conversion in a multi-dimensional intermittency analysis

Non-statistical fluctuations are used to probe the dynamical behaviour of multi-particle production in heavy-ion interactions at ultra-relativistic energies. In a one-dimensional analysis a 1〈ϱ〉-scaling is established and it is furthermore found that effects from higher-order particle correlations are small. In a two-dimensional analysis it is shown that a small background of particle pairs with a narrow opening angle can distort the observed signal. As an example we estimate the influence of γ-conversion and find that in our experiment γ-conversion alone gives results consistent with the experimental observations from a two-dimensional analysis. Whereas a two-dimensional analysis filters events where two particles are extremely close in phase space, the one-dimensional analysis picks out events with particles clustered in pseudorapidity, which are at the same time diluted in the azimuthal plane.

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.

Review of recent results on particle production from EMU01

Abstract The EMU01 Collaboration has employed emulsion chamber and pellicle detectors to accumulate a large database of heavy nucleus interactions. Samples include both minimum bias and central collisions, analyzed in a uniform manner to extract multiplicities and angular distributions of charged particles and nuclear fragments. We find that the main features of these distribution are well represented by geometrical superposition models. A unique feature of EMU01 is the use of emulsion chambers with thin foil targets to observe produced particle angular distributions with exceptionally high precision, permitting extension of fluctuations and correlations analyses beyond the resolution limits imposed by other experimental techniques. The data are generally well reproduced by interaction simulations such as FRITIOF (the Lund monte carlo for nuclear collisons) which include only conventional physics effects. However, the analysis of fluctuations and correlations via factorial moment and cumulant techniques yields some suggestive results which require further investigation, both by continued analysis of existing data and from Au and Pb beam exposures scheduled for the next few years.

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.

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.

Gamma rays at airplane altitudes

An examination of the gamma ray flux above 1 TeV in the atmosphere is needed to better understand the anomalous showers from point sources. Suggestions are made for future experiments on board airplanes.

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.