F. E. Roberts

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.

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.

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.

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.