Interactions Of Cosmic Ray Protons Research Articles

Cross sections for the proton-induced production of krypton isotopes from Rb, Sr, Y, and Zr for energies up to 1600 MeV

The production by proton-induced reactions of stable and long-lived Kr-isotopes from Rb, Sr, Y, and Zr was investigated by using isotope dilution mass spectrometry of targets irradiated at PSI/CH, TSL/S and LNS/F. Cumulative cross sections were determined for energies between 81 and 1600 MeV, between 15.4 and 1600 MeV, and between 70 and 1600 MeV for the target element Rb, Sr, and Y, respectively. For Zr, three energies of 156, 569 and 1200 MeV were investigated. As a by-product, cross sections for the production of short-lived radionuclides from Rb are reported which were measured by γ-spectrometry prior to mass spectrometry. Flux determination and absolute calibration of cross sections was done by the reaction 27Al(p,3p3n) 22Na. The new experimental data are consistent with a large database established during recent years for describing the interactions of cosmic ray protons with matter. They provide a first complete basis for model calculations of cosmogenic krypton in stony meteoroids and planetary surfaces. For the target element Rb we report the first measurements at all. For Sr, only one earlier measurement existed. For Y, our data confirm earlier measurements up to 200 MeV and extend the data set up to 1600 MeV, while for Zr three new energy points complement and check the consistency of the new investigations with earlier work from Bordeaux. The new experimental data are compared with theoretical excitation functions calculated on an a priori basis using the hybrid model of preequilibrium reactions, an intranuclear cascade/evaporation model in form of the HET/KFA2 code and the semi-empirical systematics by Silberberg, Tsao and coworkers. The differences between theories and experiments demonstrate severe shortcomings of the predictive power of existing models and emphasize the importance of experimental determinations if high-quality data are required for applications.

The Galactic Diffuse Gamma‐Ray Spectrum from Cosmic‐Ray Proton Interactions

A new calculation of the Galactic diffuse gamma-ray spectrum from the decay of secondary particles produced by interactions of cosmic-ray protons with interstellar matter is presented. The calculation utilizes the modern Monte Carlo event generators, HADRIN, FRITIOF, and PYTHIA, which simulate high-energy proton-proton collisions and are widely used in studies of nuclear and particle physics, in addition to scaling calculation. This study is motivated by the result on the Galactic diffuse gamma-ray flux observed by the EGRET detector on the Compton Gamma-ray Observatory, which indicates an excess above about 1 GeV of the observed intensity compared with a model prediction. The prediction is based on cosmic-ray interactions with interstellar matter, in which secondary pion productions are treated by a simple model. With the improved interaction model used here, however, the diffuse gamma-ray flux agrees rather well with previous calculations within uncertainties, which mainly come from the unobservable demodulated cosmic-ray spectrum in interstellar space. As a possible solution to the excess flux, flatter spectra of cosmic-ray protons have been tested, and we found that the power-law spectrum with an index of about -(2.4 to 2.5) gives a better fit to the EGRET data, although the spectrum is not explained completely.

NEW MEASUREMENTS OF COSMIC RAY POSITRONS

Cosmic ray electrons consists of mostly negative electrons and a relatively smaller flux of positrons. A simple interpretation is that all the positrons, together with an approximately equal flux of negative electrons, are decay products of pions created in the interaction of cosmic ray protons with the interstellar medium, and the remaining negative electrons are produced in primary cosmic ray sources. However, the existing data on the positron fraction (e+/e++e−) does not support this simple picture. While the positron flux around a few GeV can be explained by the secondary production, there are apparently excesses of positrons both at lower and higher energies. This has stimulated many interpretation and conjectures of new astrophysical sources of positrons. Recently, there are new measurements from four different balloon experiments. They begin to show some discrepancy with the old data. A brief summary of the new results and their impact is given here.

Sources of high‐energy protons in Saturn's magnetosphere

The Pioneer 11 passage through the magnetosphere and trapped radiation of Saturn (closest approach September 1, 1979) revealed an especially intense region of high‐energy particle fluxes that places unique constraints on models for sources of high‐energy protons in the innermost radiation zones. Of special interest is the high‐intensity flux of protons with energies >35 MeV which was measured by the University of Chicago fission cell in the inner magnetosphere between the A‐Ring (2.3 Rs; Rs≡60,000 km) and the orbit of Mimas (∼3 Rs). The negative phase space density gradients derived from the proton and electron observations in this region [Simpson et al., 1980; McKibben and Simpson, this issue] imply that steady‐state inward diffusion from the outer magnetosphere will not be an adequate source for these high‐energy protons. We have examined the possibility that this component could result from direct injection in situ by the decay of secondary neutrons produced by high‐energy cosmic ray impacts on Saturn's atmosphere or rings (i.e., cosmic ray albedo neutron decay (Crand)). For the measured magnetic dipole moment of Saturn we determined from Störmer theory the cutoff magnetic rigidities and energies of galactic cosmic rays as a function of latitude, radial distance in the equatorial plane, and principal directions of incidence. The principal production of neutrons from Saturn's atmosphere occurs above ∼60° latitude. Using a radial diffusion coefficient inferred from 1‐MeV proton absorption measurements at the orbit of Mimas, we show that Crand is not adequate by a factor of 104 to maintain the observed fluxes of protons >35 MeV in the range 2.3 ≤L ≤3. We arrive at this result from two independent arguments based on injection strength and energy spectra, respectively. We also find that direct interactions of cosmic ray protons with matter in the A‐, B‐ and C‐rings fail by a factor >10² to produce a sufficient yield of neutrons. Finally, we investigated the neutron production by the high‐energy proton flux reported by Chenette et al. (1980) trapped on magnetic field lines passing through the rings. We proposed a relatively simple model which assumes that this trapped proton component originates in the secondary and tertiary production of protons by the incidence of cosmic ray protons so as to multiply the number of nuclear interactions from each primary. We found that although this assumption leads to a stronger source of neutron decay protons for the inner magnetosphere, the yield still fails by at least an order of magnitude to account for the observations. However, the Crand model may be viable if the actual diffusion coefficient for >35‐MeV protons is at least a factor ∼10 lower than that for 1‐MeV protons. The energy dependence of diffusion coefficients predicted by models of Jupiter's magnetospheric dynamics, possibly applicable to Saturn after rescaling of parameters, is discussed briefly. We discuss the problems associated with invoking neutron decay protons in the outer magnetosphere, as well as the injection of solar flare nucleons.

A model for clusters of discrete gamma-ray sources

view Abstract Citations (11) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A model for clusters of discrete gamma-ray sources. Abdulwahab, M. ; Morrison, P. Abstract A model is proposed for certain discrete sources of approximately 100-MeV gamma-rays. The gamma-rays originate, as for the usual diffuse source, from the interaction of cosmic-ray protons with the gas of the interstellar medium (mostly in neutral-ion decay). But the cosmic rays are enhanced, because they have not spread far from their localized origin in strong Type I supernova explosions, and the gas is locally dense within the volumes of small random interstellar clouds. Such sources have distinct properties: (1) they cluster in kinematically allowed regions within about 1 kpc from recent supernova remnants; (2) they are not point gamma-ray sources, but extended over some tens of parsecs; therefore they are time-independent and certainly not pulsing; and (3) they do not emit much in any other wave band, except that they are rather thick radiators in the 21-cm line of H I. The model is fitted quantitatively to three gamma-ray sources reported near the Crab Nebula which tentatively show those features; other candidates are suggested for closer examination. Publication: The Astrophysical Journal Pub Date: April 1978 DOI: 10.1086/182659 Bibcode: 1978ApJ...221L..33A Keywords: Astronomical Models; Cosmic Rays; Gamma Ray Astronomy; Crab Nebula; Interstellar Gas; Radioactive Decay; Supernova Remnants; Supernovae; Space Radiation; Gamma-Ray Sources:Clusters; Gamma-Ray Sources: Models full text sources ADS |

An assessment of models for the γ-ray flux from the Galactic plane

An assessment is made of five models for the production of Galactic gamma rays, all of which involve the interaction of cosmic ray protons with neutral hydrogen. Conflict with either the gamma ray or radio data is found in four cases. The remaining model, in which the intensity of cosmic rays of energy of a few GeV is correlated with the matter distribution in the Galaxy, gives rough agreement with the experimental data at present available but it does not conform with the idea that cosmic rays should originate in young Galactic objects. A completely satisfactory model has yet to be found.

Intranuclear cascading in photographic emulsion at accelerator and cosmic-ray energies

The data on the interactions of cosmic-ray protons in nuclear emulsion have been analyzed in light of the results of recent exposures of emulsion to accelerator protons. Plots of $〈{log}_{10}tan\ensuremath{\theta}〉$ as a function of the number of evaporation prongs, ${N}_{h}$, display an energy-independent behavior which is exploited to determine the energies of cosmic-ray events. It is found that the energies quoted in the literature are generally too high. The average charged multiplicity is linearly related to ${N}_{h}$ from 30 GeV to 5 TeV. While a model of nuclear cascading based on direct production is consistent with these data from 30 GeV to 500 GeV, a model proceeding through an intermediate state gives better agreement at cosmic-ray energies.

Quark-Fragmentation Models for Very-High-Energy Production Processes

The qualitative features of models for high-energy production processes based on the fragmentation of the dressed quarks assumed to make up hadrons are discussed. It appears that, if quarks are very massive (i.e., quark mass $\ensuremath{\approx}10 \frac{\mathrm{GeV}}{{c}^{2}}$), such models could explain in a simple way the experimental elusiveness of quarks, the limitations on transverse momenta observed in production reactions, the average inelasticity observed in cosmic-ray proton interactions, the abundance of pions produced in high-energy collisions, and the large transverse momenta observed in air showers for primary particle energies above ${10}^{6}$ GeV.

Galactic cosmic-ray electrons

The production and equilibrium spectra of secondary electrons (negatrons and positrons) resulting from cosmic-ray interactions in the galaxy are calculated. These electrons arise from the decay of secondary pions and neutrons produced by nuclear interactions of cosmic-ray protons and alpha particles with the interstellar gas. The equilibrium flux is determined by escape of electrons from the galaxy and by ionization, inverse Compton, and synchrotron energy losses. A comparison of the calculated secondary electron equilibrium spectrum with the measured electron intensity, positron-negatron ratio, and nonthermal radio emission from the galactic halo suggests that an additional primary electron source of roughly the same magnitude is required.

Neutron production by cosmic ray protons in lead

A study has been made of the production of evaporation neutrons in the interactions of cosmic ray protons with lead nuclei. For the thick target used the mean number of neutrons produced (the mean `multiplicity') increases from 10 to 100 over the range of energy 0.2 to 200 GeV. At low energies, not greater than about 0.5 GeV, there is good agreement with the mean multiplicities computed by Metropolis et al. in 1958, but, as the energy increases, the observed multiplicities fall increasingly below expectation. At the highest energies, not less than about 10 GeV, there is evidence for a flattening of the multiplicity variation and the results are not inconsistent with a variation of the form expected from the Heisenberg model of the nucleon-nucleon collision.