An evaluation of electron-photon cascades developing in matter, photon and magnetic fields

Abstract. Electromagnetic cascades in matter, photon fields, and magnetic fields are solved by a standard numerical method, integrating the diffusion equations of respective cascade processes numerically. Our results and those of Aharonian and Plyasheshnikov agree very well for cascades in matter and magnetic fields, though they show some slight discrepancies for cascades in photon fields of high incident energies. Transport properties of electron and photon spectra are also investigated by solving differential-difference equations for cascades with simplified cross-sections, and the spectra under the electron cooldown process are well explained quantitatively

New calculations and measurements of the Coulomb cross-section for the production of direct electron pairs by high energy nuclei

Recently, new calculations were made of the direct Coulomb pair cross section that rely less in arbitrary parameters. More accurate calculations of the cross section down to low pair energies were made. New measurements of the total direct electron pair yield, and the energy and angular distribution of the electron pairs in emulsion were made for O-16 at 60 and 200 GeV/amu at S-32 at 200 GeV/amu which give satisfactory agreement with the new calculations. These calculations and measurements are presented along with previous accelerator measurements made of this effect during the last 40 years. The microscope scanning criteria used to identify the direct electron pairs is described. Prospects for application of the pair method to cosmic ray energy measurements in the region 10 (exp 13) to 10 (exp 15) eV/amu are discussed

超伝導JACEEによる超高エネルギー原子核衝突の共同研究

研究期間:平成9-10年度 ; 研究種目:国際学術研究 ; 課題番号: 09044089原著には既発表論文の別刷を含む

The search for cosmic strangelets with the supersonic concorde and with JACEE\u27s circumpolar balloon flight in Antarctica

The search for cosmic strangelet nuclei was carried out by two experiments with emulsion chambers. A balloon-borne JACEE emulsion chamber was flown at 3.5 g/cm2 for 200 h in Antarctica (JACEE-10 experiment) and the Concorde flights were made by ECHOS at an atmospheric depth of 110 g/cm2 between Paris and New York. No nuclei with Z ≥ 30 survived after traversing 60-120 g/cm2 of the detector materials in the JACEE instruments. No evidence for a long mean free path were found in the zenith angle distribution for Z/β ≥ 26 nuclei. The exposure factor used by the JACEE was 72 m2 h sr. The intensity upperbounds, I ≤ (2.2-9.7) × 10-2/m2 h sr, were obtained for strangelets having an atmospheric attenuation length of 220-50 g/cm2, which corresponds to the case for mass number A = 100-10000 and Z/β ≥ 13. Concorde experiments (ECHOS) used both a thin and a thick emulsion chamber. The total exposure was 209 m2 h sr and no candidates with charge Z ≥ 30 were found. The largest track had Z/β = 28.6 ± 1.29 with β ∼ 1. Nuclei observed with charge 13 ≤ Z ≤ 30 were consistent with the survival intensity of ordinary nuclei. The flux bounds from the ECHOS experiments were I ≤ (2.1-5.0) × 10-2/m2 h for strangelets with mass number 100≤A≤1000. © J.C. Baltzer AG, Science Publishers

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