The neutral-pion decay and the gamma radiation from our Galaxy
Neutral pion decay and galactic gamma radiation from demodulated cosmic ray spectrum, discussing neutral pion meson production
Cavallo, G.↗
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The interaction lengths of energetic pions and protons in iron
The interaction lengths of pions and protons in iron have been measured using an ionization spectrometer composed of alternating layers of iron and plastic scintillator. These measurements cover an energy range from 9.3 to 18 GeV. The interaction lengths were determined by accurate statistical analyses of the experimental data using the maximum likelihood method. The dependence of the interaction length on the parameters used to define an interaction was studied, and the results reported employ parameters chosen to minimize the percentage uncertainty in the interaction length. The mean interaction length of pions was found to be approximately 20% greater than that of protons.
Crannell, H.↗
Neutral-pion-decay gamma rays from the galaxy and the interstellar gas content
Knowledge of the total gamma ray production rate per H atom from the decay of pion(0) produced in interstellar cosmic ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated using the latest accelerator data on pion(0) production in pp interactions up to approximately 300 GeV. A simple but accurate approximation resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 + or - 0.23) x 10 to the minus 25th power/sec. consistent with the observed upper limit of 1.6 x 10 to the minus 25th power/sec.
Stecker, F. W.↗
Stopping pions in high-energy nuclear cascades.
Results of Monte Carlo calculations for the number and energy spectra of charged pions from nuclear-electromagnetic cascades developing in rock are presented for primary hadron energies ranging from 3 to 3000 GeV. These spectra are given as functions of the longitudinal depth in the absorber and the lateral distance from the cascade axis. The number of charged pions which stop in the absorber increases with the primary energy of the hadron initiating the cascade.
Jones, W. V.↗
Neutral-pion-decay gamma rays from the Galaxy and the interstellar gas content
Knowledge of the total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated here using the latest accelerator data on neutral pion production in p-p interactions up to about 1500 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 plus or minus 0.23) times 10 to the -25th power/sec, consistent with the observed upper limit of 1.6 times 10 to the -25th power/sec.
Stecker, F. W.↗
Neutral-pion decay gamma rays from the galaxy and the interstellar gas content
The total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is recalculated here using the latest accelerator data on the production of neutral pions in pp interactions up to 300 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained for this rate by considering a maximum galactic cosmic-ray spectrum taking modulation into account.
Stecker, F. W.↗
Inelastic interaction mean free path of negative pions in tungsten
The inelastic interaction mean free paths lambda of 5, 10, and 15 GeV/c pions were measured by determining the distribution of first interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi2 distribution is used to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy was observed. In tungsten, lambda for pions is 206 plus or minus 6 g/sq cm.
Cheshire, D. L.↗
Inelastic-interaction mean free path of negative pions in tungsten
The inelastic-interaction mean free paths (lambda) of 5-, 10-, and 15-GeV/c pions have been measured by determining the distribution of first-interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi-squared distribution is employed to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy has been observed. In tungsten, lambda for pions is 206 (plus or minus 6) g/sq cm.
Cheshire, D. L.↗
Neutral pion production in solar flares
The Gamma-Ray Spectrometer (GRS) on SMM has detected more than 130 flares with emission approx 300 keV. More than 10 of these flares were detected at photon energies 10 MeV. Although the majority of the emission at 10 MeV must be from electron bremsstrahlung, at least two of the flares have spectral properties 40 MeV that require gamma rays from the decay of neutral pions. It is found that pion production can occur early in the impulsive phase as defined by hard X-rays near 100 keV. It is also found in one of these flares that a significant portion of this high-energy emission is produced well after the impulsive phase. This extended production phase, most clearly observed at high energies, may be a signature of the acceleration process which produces solar energetic particles (SEP's) in space.
Forrest, D. J.↗
A study of gamma-families generated in nucleon-nucleus (NA) and pion-nucleus (pi A) interactions
The separation of the gamma families generated in nucleon-nuclear and pion-nuclear (PI-A) interactions is realized from the analysis of simulated gamma families. Some characteristics of NA and PI families and the influence of the process of inelastic charge-exchange of charged pions neutral ones type of PI + or - A yields are studied.
Azimov, S. A.↗
On the origin of the pion-decay radiation in the 1982 June 3 solar flare
The June 3, 1982 flare produced a wealth of observed gamma-ray, energetic particle, and neutron emissions. It is shown that the predictions of an interaction model developed for the June 3 flare by Murphy, Dermer, and Ramaty (1987) compare favorably with new data on the time-dependent flux on pion-decay emission from this flare. It is concluded that the particles which produced the bulk of the pions could have the same origin as the particle observed in interplanetary space from the June 3 flare.
Ramaty, R.↗
The calculation of the contributions to low energy e+H2 scattering from sigma u+ and Pion u symmetries using the Kohn variational method
Above incident energies of about 2 eV, the contribution to the total cross section in positron+H2 scattering from the sigma g+ symmetry is insufficient to account for the experimental value. Calculations carried out of the lowest partial waves of sigma u+ symmetry and Pion u symmetry using the Kohn variational method are described. The contributions to the total cross section from the two equivalent partial waves of Pion u symmetry significantly reduce the discrepancy with experiment up to incident energies of 4 to 5 eV. Comparisons are made with recent R-matrix calculations performed by Danby and Tennyson.
Armour, E. A. G.↗
High-energy gamma-ray emission from pion decay in a solar flare magnetic loop
The production of high-energy gamma rays resulting from pion decay in a solar flare magnetic loop is investigated. Magnetic mirroring, MHD pitch-angle scattering, and all of the relevant loss processes and photon production mechanisms are taken into account. The transport of both the primary ions and the secondary positrons resulting from the decay of the positive pions, as well as the transport of the produced gamma-ray emission are considered. The distributions of the gamma rays as a function of atmospheric depth, time, emission angle, and photon energy are calculated and the dependence of these distributions on the model parameters are studied. The obtained angular distributions are not sufficiently anisotropic to account for the observed limb brightening of the greater than 10 MeV flare emission, indicating that the bulk of this emission is bremsstrahlung from primary electrons.
Mandzhavidze, Natalie↗
Gamma rays from pion decay - Evidence for long-term trapping of particles in solar flares
The energy spectrum and time dependence of the 50 MeV to 2 GeV gamma rays observed from the 1991 June 11 solar flare are analyzed. It is shown that the emission detected at the late phase of this flare with EGRET on the Compton Gamma-Ray Observatory can be explained by a model in which the bulk of the particles were accelerated during the impulsive phase and subsequently trapped in coronal magnetic loops. The observed spectrum was fit with a combination of pion decay radiation and primary electron bremsstrahlung. The 1991 June 11 data are compared with data for the 1982 June 3 and 1991 June 15 flares from which pion decay emission was also observed. The fact that the fluxes from these three flares are ordered in time in accordance with the predicted time dependence of emission produced by trapped particles provides support for the model.
Mandzhavidze, Natalie↗
Parameterized Cross Sections for Pion Production in Proton-Proton Collisions
An accurate knowledge of cross sections for pion production in proton-proton collisions finds wide application in particle physics, astrophysics, cosmic ray physics, and space radiation problems, especially in situations where an incident proton is transported through some medium and knowledge of the output particle spectrum is required when given the input spectrum. In these cases, accurate parameterizations of the cross sections are desired. In this paper much of the experimental data are reviewed and compared with a wide variety of different cross section parameterizations. Therefore, parameterizations of neutral and charged pion cross sections are provided that give a very accurate description of the experimental data. Lorentz invariant differential cross sections, spectral distributions, and total cross section parameterizations are presented.
Blattnig, Steve R.↗
Exclusive Reactions Involving Pions and Nucleons
The HZETRN code requires inclusive cross sections as input. One of the methods used to calculate these cross sections requires knowledge of all exclusive processes contributing to the inclusive reaction. Conservation laws are used to determine all possible exclusive reactions involving strong interactions between pions and nucleons. Inclusive particle masses are subsequently determined and are needed in cross-section calculations for inclusive pion production.
Norbury, John W.↗
Production of Pions in pA-collisions
Accurate knowledge of pion production cross section in PA-collisions is of interest for astrophysics, CR physics, and space radiation studies. Meanwhile, pion production in pA-reactions is often accounted for by simple scaling of that for pp-collisions, which is not enough for many real applications. We evaluate the quality of existing parameterizations using the data and simulations with the Los Alamos version of the Quark-Gluon String Model code LAQGSM and the improved Cascade-Exciton Model code CEM2k. The LAQGSM and CEM2k models have been shown to reproduce well nuclear reactions and hadronic data in the range 0.01-800 GeV/nucleon.
Moskalenko, I. V.↗
Quantum mechanical signature in exclusive coherent pion production
We calculate the coherent production of pions from subthreshold to relativistic energies in heavy-ion collisions using a quantum, microscopic, many-body model. For the first time, in this approach, we use harmonic oscillator wave functions to describe shell-model information. The theoretical quantum mechanical results obtained for the pion spectra represent an important improvement over our previous microscopic, many-body calculations.
NASA Discipline Radiation Health↗