Interactions Of Cosmic Ray Nuclei Research Articles

Testing the superposition model in small CORSIKA shower simulations

The idea of superposition in the high-energy interactions of cosmic ray nuclei and the development of extensive air showers initiated by them has been known for more than half a century. It has been thoroughly and successfully tested in a number of simulations for primary energies around 1015 and above. In this work, we will investigate its applicability to lower energies. At the lowest energies, when the shower contains on average about one charged particle (or even less), deviations from the superposition model can be seen in the simulation results. Fluctuations of higher moments of the main shower parameters are systematically broader than expected. Further studies to confirm superposition in particular in the shower longitudinal profile are in progress. A correct description of the longitudinal development of the small shower, a precise description of its fluctuations on the observational level with a correct implementation of the superposition principle will enable to construct a simple and fast phenomenological algorithm generating small showers indispensable for the interpretation of measurements made using a small local shower array and determination of the flux of single, incoherent, secondary cosmic ray particles.

Improved photomeson model for interactions of cosmic ray nuclei

Photohadronic interactions are important for the sources and the transport of Ultra-High Energy Cosmic Rays (UHECRs). Current state-of-the-art cosmic ray transport simulations handle nuclear disintegration at energies of the Giant Dipole Resonance at a more sophisticated level, as well as the photohadronic interactions of nucleons in the high-energy regime above the pion production threshold. However, the interactions of nuclei above the pion production threshold are commonly modeled by treating the nucleus as a superposition of free nucleons—ignoring the effect of the nuclear medium. We construct an improved, inclusive model for the photomeson regime for nuclei with A ⩽ 56 by employing more accurate, data-driven parametrizations of the interaction cross section, the fragmentation of the primary nucleus and the inclusive pion production cross section that directly affects the production of astrophysical neutrinos. We apply our results to two multi-messenger scenarios (Tidal Disruption Events and Gamma-Ray Bursts) in which photonuclear interactions in the photomeson regime are the dominant cooling process for the highest energy cosmic rays. While we find moderate changes to the mass composition of UHECRs, the astrophysical neutrino fluxes exhibit a significant (factor of a few) reduction compared to the naive superposition of free nucleons for sources of UHECR nuclei with a populated cascade. The numerical code implementing the model has been made publicly available, which facilitates the integration of our results in similar frameworks.

Origin of cosmic ray electrons

Abstract Positrons (e + ) in cosmic radiation are believed to be produced by the interactions of cosmic ray nuclei with interstellar space. e + production spectrum had been calculated using a new set of invariant cross sections for the production of pions and kaons. In the case of e − , a primary component had been added to the secondary e − produced along with e + in the galaxy. The equilibrium spectra of both e + and e − were obtained and compared with the observations. An empirical relation is given for the energy loss rate due to inverse-Compton scattering, which connects smoothly the Thompson and Klein-Nishina regimes. It is found that a simple power law injection spectrum for e − can not explain the observed [e + / (e + + e − )] ratio, and one requires a spectral flattening below about 8 GeV. Flat e − spectrum similar to that in Crab supernova with a spectral break by one power around 5 GeV could explain both the observed spectrum and the [e + / (e + + e − )], suggesting that the sources of cosmic ray e − are supernovae energized by pulsars.

Can Galactic γ-Ray Background be due to Superposition of γ-Rays from Millisecond Pulsars?

The SAS 2 and COS B observations have established the existence of diffuse γ-rays in our Galaxy in various energy ranges. The diffuse radiation is attributed to the interaction of cosmic ray nuclei and electrons with the particles of interstellar atomic and molecular gas (via the decay of pions and bremsstrahlung, respectively). Inverse Compton scattering of interstellar photons by the high energy electrons of cosmic rays may also be contributing to this background. In addition some contribution may come from discrete sources of γ-rays.

High Energy Processes in Clusters of Galaxies and the Origin of Cosmic Rays.

We test the hypothesis of a universal cosmic ray intensity by calculating the secondary electron or positron production in the hadronic interactions of cosmic ray nuclei with intergalactic gas within clusters of galaxies. We find that the spectral characteristics of the radio synchrotron emission by these secondary electrons is not consistent with observations of the Coma cluster. Thus the hypothesis can be ruled out on cluster scales.

Ultra-High Energy γ-Ray Astronomy using an EAS Array: Search for Emission From 100 MeV Sources

Recently, a new branch of astronomy has emerged following the detection of ultra-high energy (UHE) γ-ray emission from Cygnus X-3 by Samorski and Stamm (1983). This discovery was made using the extensive air shower (EAS) array of the University of Kiel, Germany. Such arrays are designed to detect EAS, the cascades of secondary particles (mainly electrons and protons), which are generated in the atmosphere by the interaction of cosmic ray nuclei of energy greater than ˜ 1015 eV. These arrays are also sensitive to EAS initiated by primary γ-rays and, depending on their design, have angular resolutions as good as the SAS-II and COS-B γ-ray telescopes which operated at ˜ 100 MeV energies. At present, there is no effective way to veto proton or nucleus-initiated EAS and so one must look for a significant excess of EAS from within a cone of resolution centred on a suspected source direction.

Heavy-Nucleus Interactions at 4-1000 GeV/Nucleon and a Collective Mechanism of Multiple Particle Production

Interaction of cosmic ray nuclei of different charge (z = 4-8; z = 10-14; z = 20-28) with the Ag, Br and C, N, O nuclei was analysed. The energy dependence was obtained for the following multihadron production characteristics; (a) half-angles θ1/2π of meson emission; (b) meson multiplicity per interacting nucleon; (c) shower particle quasi-rapidity distributions; (d) width of the quasi-rapidity distributions of mesons.The heavy-nucleus interactions were compared with nucleon-nucleon and nucleon-nucleus interactions, at intermediate and minimum impact parameters.A theoretical approach based on the assumption of a collective nuclear interaction mechanism and on the recently developed model of multihadron production in elementary interactions was used to interpret the experimental results.

Cosmic ray antiprotons and modified closed galaxy model

Observations suggest that a small flux of secondary antiprotons (p), created in the interaction of cosmic ray nuclei with interstellar gas, should also be present in the primary cosmic radiation. Calculations based on accelerator data for the production of p and existing models for the propagation of cosmic rays, predict too small a flux of p compared with the finite flux observed recently1. Although the observed excess could be attributed to the existence of primary cosmic ray antimatter, the experimental upper limits2,3 of the ratio of antinuclei to nuclei of charge |Z| ≥ 2 seem to contradict this. Here we use a ‘modified closed galaxy’ model to attribute this excess to secondary antiprotons. In this model, ∼50% of the observed cosmic ray nucleons are of recent origin and they propagate according to the ‘nested leaky box’ model, while the rest propagate according to ‘closed galaxy’ model. This model explains the observations on p and e+, and predicts more D and 3He than do the existing models.

Production spectrum of gamma rays in interstellar space through neutral pion decay

We have obtained a simple representation to the observed invariant cross-section for the production of neutral pions in proton-proton collisions. Making use of this representation, we have calculated the differential and integral production spectra of gamma rays in the Galaxy from interactions of cosmic ray nuclei with interstellar gas. It is shown that the uncertainties in deducing interstellar proton spectrum by demodulating the observed spectrum do not affect very much the gamma ray spectrum. We have also determined the gamma ray production spectrum through bremsstrahlung process for a typical interstellar electron spectrum derived from the radio spectrum in the Galaxy. From these, the total gamma ray production spectrum resulting from the interaction of cosmic rays with interstellar matter is compared with the observed gamma ray spectrum in the Galaxy and some inferences have been obtained. We also point out the possible uncertainty in the present calculation and suggest the improvements needed.

Spectral shape of cosmic rays over the Galaxy

In a previous paper (see ibid., vol.10, p.843 (1977)) the authors pointed out that there is fairly strong evidence for the intensity of cosmic ray positrons being lower than that expected from interactions of cosmic ray nuclei with interstellar matter using the simple 'leaky box' model. More general models of propagation of Galactic cosmic ray nuclei and positrons are examined and the discrepancy is present for other models too; only if the shape of the cosmic ray spectrum varies from place to place in the Galaxy does it appear possible to reconcile the positron data.

The energy spectrum of cosmic ray positrons

A calculation has been made of all the predicted energy spectrum of positrons generated by the positive pions and kaons produced in turn in the interactions of cosmic ray nuclei with the interstellar medium (ISM). A critical appraisal of the results and a comparison with the predictions of other workers are given. Experimental data on the measured energy spectrum have been considered and corrections have been made for the effect of solar modulation to enable derivation of the true interstellar spectrum of energetic positrons. Comparison with prediction gives evidence for the main component of cosmic rays responsible for the positrons-protons-having passed through rather less matter in the ISM than is the case of heavier cosmic ray nuclei. Possible explanations are put forward.

Cosmic ray electrons of E > 1 Gev-Some new measurements and interpretations

In the summer of 1971 we conducted new measurements of the primary electron spectrum from 1 to 20 Gev with our electron spectrometer telescope at Fort Churchill. This telescope has been calibrated by using electrons and pions of 0.5–15 Gev at Slac (Stanford Linear Accelerator) in early 1971 and again in 1972. The differential primary electron spectrum over the energy range 3–20 Gev is given by dj/dE = 100/E3±0.2 el/m² ster sec Gev, the integral spectrum by J(E) = 50/E2±0.2. These intensities are considerably lower than many earlier measurements above ∼5 Gev. It is observed that many showers have anomalous lateral distributions as determined in our telescope and must be rejected. This directly leads to the lower intensities. Our calibration results suggest that these events are due to interactions of high-energy protons. Our measured primary electron spectrum is uncomfortably close to that calculated for secondary electrons produced by the interaction of cosmic ray nuclei with interstellar hydrogen in the galaxy, and therefore the question of the origin of the high-energy electrons is reopened. The problem of the age of cosmic ray electrons must also be reexamined if our measured spectrum is found to extend to still higher energies.