Transition effect of air shower particles in plastic scintillators

The transition effect of air shower particles in the plastic scintillators near the core was measured by scintillators of various thickness. The air showers selected for the measurement were of 10,000. Results obtained are as follows: (1) the multiplication of shower particles in the scintillators is less than 20% for that of 50 mm thickness; (2) dependence of the transition effect on age parameter is not recognized within the experimental errors

Character of energy flow in air shower core

Energy per charged particle near the core of air showers was measured by 9 energy flow detectors, which were the combination of Cerenkov counters and scintillators. Energy per particle of each detector was normalized to energy at 2m from the core. The following results were obtained as to the energy flow: (1) integral frequency distribution of mean energy per particle (averaged over 9 detectors) is composed of two groups separated distinctly; and (2) showers contained in one group show an anisotropy of arrival direction

Lateral distribution of electrons of air showers

The lateral distribution of electrons (LDE) of the air showers of size 10 to the 5th power to 10 to the 6th power was studied within one MU. It was found that the LDE of the air showers observed is well represented by NKG function except for vicinity of the core. It was also found that LDE measured by thin scintillators does not differ from that measured by thick ones of 50mm thickness

A Re-evaluation of Evidence for Light Neutral Bosons in Nuclear Emulsions

Electron-positron pair-production data obtained by bombardment of emulsion detectors with either cosmic rays or projectiles with mass between one and 207 and kinetic energies between 18 GeV and 32 TeV have been re-analysed using a consistent and conservative model of the background from electromagnetic pair conversion. The combined data yield a spectrum of putative neutral bosons decaying to e+e- pairs, with masses between 3 and 20 MeV/c^2 and femtosecond lifetimes. The statistical significance against background for these "X-bosons" varies between 2 and 8 sigma. The cross-section for direct production of X-bosons increases slowly with projectile energy, remaining over 1,000 times smaller the the pion production cross-section.Comment: major revision with improved figures; accepted by Int J Mod Phys

Depth of maximum of extensive air showers and cosmic ray composition above 10**17 eV in the geometrical multichain model of nuclei interactions

The depth of maximum for extensive air showers measured by Fly's Eye and Yakutsk experiments is analysed. The analysis depends on the hadronic interaction model that determine cascade development. The novel feature found in the cascading process for nucleus-nucleus collisions at high energies leads to a fast increase of the inelasticity in heavy nuclei interactions without changing the hadron-hadron interaction properties. This effects the development of the extensive air showers initiated by heavy primaries. The detailed calculations were performed using the recently developed geometrical multichain model and the CORSIKA simulation code. The agreement with data on average depth of shower maxima, the falling slope of the maxima distribution, and these distribution widths are found for the very heavy cosmic ray mass spectrum (slightly heavier than expected in the diffusion model at about 3*10**17 eV and similar to the Fly's Eye composition at this energy).Comment: 11pp (9 eps figures

Influence of hadronic interaction models and the cosmic ray spectrum on the high energy atmospheric muon and neutrino flux

The recent observations of muon charge ratio up to about 10 TeV and of atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed interest into the high-energy interaction models and cosmic ray primary composition. A reviewed calculation of lepton spectra produced in cosmic-ray induced extensive air showers is carried out with a primary cosmic-ray spectrum that fits the latest direct measurements below the knee. In order to achieve this, we used a full Monte Carlo method to derive the inclusive differential spectra (yields) of muons, muon neutrinos and electron neutrinos at the surface for energies between 80 GeV and hundreds of PeV. The air shower simulator {\sc corsika} 6.990 was used for showering and propagation of the secondary particles through the atmosphere, employing the established high-energy hadronic interaction models {\sc sibyll} 2.1, {\sc qgsjet-01} and {\sc qgsjet-ii 03}. We show that the performance of the interaction models allows makes it possible to predict the spectra within experimental uncertainties, while {\sc sibyll} generally yields a higher flux at the surface than the qgsjet models. The calculation of the flavor and charge ratios has lead to inconsistent results, mainly influenced by the different representations of the K/$\pi$ ratio within the models. Furthermore, we could quantify systematic uncertainties of atmospheric muon- and neutrino fluxes, associated to the models of the primary cosmic-ray spectrum and the interaction models. For most recent parametrizations of the cosmic-ray primary spectrum, atmospheric muons can be determined with an uncertainty smaller than $^{+15}_{-13}$% of the average flux. Uncertainties of the muon- and electron neutrino fluxes can be calculated within an average error of $^{+32}_{-22}$% and $^{+25}_{-19}$%, respectively.Comment: 16 pages, 10 figures, version 2 includes analytic approximatio

Cosmic ray spectral hardening due to dispersion in the source injection spectra

Recent cosmic ray (CR) experiments discovered that the CR spectra experience a remarkable hardening for rigidity above several hundred GV. We propose that this is caused by the superposition of the CR energy spectra of many sources that have a dispersion in the injection spectral indices. Adopting similar parameters as those of supernova remnants derived from the Fermi $\gamma$-ray observations, we can reproduce the observational CR spectra of different species well. This may be interpreted as evidence to support the supernova remnant origin of CRs below the knee. We further propose that the same mechanism may explain the "ankle" of the ultra high energy CR spectrum.Comment: 5 pages, 3 figures and 1 table. Updated with the diffusion propagation model, accepted by Phys. Rev.

Further search for a neutral boson with a mass around 9 MeV/c2

Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1 transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0 level at 18.15 MeV, a significant deviation from IPC was observed at large pair correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the 12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9 MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table

Semi-analytic approximations for production of atmospheric muons and neutrinos

Simple approximations for fluxes of atmospheric muons and muon neutrinos are developed which display explicitly how the fluxes depend on primary cosmic ray energy and on features of pion production. For energies of approximately 10 GeV and above the results are sufficiently accurate to calculate response functions and to use for estimates of systematic uncertainties.Comment: 15 pages with 8 figure