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.↗
SEARCH · Search NASA
Results for “neutral pion”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
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.↗
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.↗
Production spectrum of gamma rays in interstellar space through neutral pion decay
A simple representation is obtained of the observed invariant cross section for the production of neutral pions in proton-proton collisions. Using this representation, the differential and integral production spectra of gamma rays in the galaxy are calculated 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 have only a limited effect on the gamma ray spectrum. Also determined is the gamma ray production spectrum through bremsstrahlung process for a typical interstellar electron spectrum derived from the radio spectrum in the galaxy.
Stephens, S. A.↗
Flare gamma ray continuum emission from neutral pion decay
We investigate, in detail, the production of solar flare gamma ray emission above 100 MeV via the interaction of high energy protons with the ambient solar atmosphere. We restrict our considerations to the broadband gamma ray spectrum resulting from the decay of neutral pions produced in p-H reactions. Thick-target calculations are performed to determine the photon fluences. However, proton transport is not considered. Inferences about the form of the proton spectrum at 10-100 MeV have already been drawn from de-excitation gamma ray lines. Our aim is to constrain the proton spectrum at higher energies. Thus, the injected proton spectrum is assumed to have the form of a Bessel Function, characteristics of stochastic energy at higher energies. The detailed shape of the gamma ray spectra around 100 MeV is found to have a strong dependence on the spectral index of the power law and on the turnover energy (from Bessel function to power law). As would be expected, the harder the photon spectrum the wider the 100 MeV feature. The photon spectra are to be compared with observations and used to place limits upon the number of particles accelerated and to constrain acceleration models.
Alexander, David↗
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.↗
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.↗
Inclusive production of high-energy neutral pions from pion-proton collisions at 14 GeV/c
Explore the source record for details and available documents.
Oneill, L. H.↗
Theoretical spectral distributions and total cross sections for neutral subthreshold pion production in carbon-carbon collisions
A coherent isobar formalism is employed to model subthreshold production of neutral pions in carbon-carbon collisions at energies below 100 MeV/nucleon. No arbitrary scale factors or adjustable free parameters are used in calculation of the Lorentz-invariant cross sections for pion production in the projectile, which produces an excited state that goes to M1 resonance in the target by conservation of spin and isospin. Pion production is also modeled for the projectile, which also reaches M1 resonance. The overall pion spectral distribution in the center of mass system is then integrated over the energy range 35-84 MeV/nucleon. The results expose an energy loss in the incident ions, as observed experimentally, and indicate that an isobar mechanism is responsible for higher energy pion production. Lower energy pions are a result of thermal processes.
Norbury, J. W.↗
Theoretical estimates of photoproduction cross sections for neutral subthreshold pions in carbon-carbon collisions
Using the Weizsacher-Williams method of virtual quanta, total cross section estimates for the photoproduction of neutral subthreshold pins in carbon-carbon collisions at incident energies below 300 MeV/nucleon are made. Comparisons with recent experimental data indicate that the photoproduction mechanism makes an insignificant contribution to these measured cross sections.
Norbury, J. W.↗
Secondary antiproton production in relativistic plasmas
The possibility is investigated that the reported excess low energy antiproton component of the cosmic radiation results from proton-proton (p-p) interactions in relativistic plasmas. Because of both target and projectile motion in such plasmas, the antiproton production threshold in the frame of the plasma is much lower than the threshold of antiproton production in cosmic ray interactions with ambient matter. The spectrum of the resultant antiprotons therefore extends to much lower energy than in the cosmic ray case. The antiproton spectrum is calculated for relativistic thermal plasmas and the spectrum is estimated for relativistic nonthermal plasmas. As possible production sites, matter accreting onto compact objects located in the galaxy is considered. Possible overproduction of gamma rays from associated neutral pion production can be avoided if the site is optically thick to the photons but not to the antiprotons. A possible scenario involves a sufficiently large photon density that the neutral pion gamma rays are absorbed by photon-photon pair production. Escape of the antiprotons to the interstellar medium can be mediated by antineutron production.
Dermer, C. D.↗
Neutron star cooling and pion condensation
The nonstandard cooling of a neutron star with the central pion core is explored. By adopting the latest results from the pion condensation theory, neutrino emissivity is calulated for both pure charged pions and a mixture of charged and neutral pions, and the equations of state are constructed for the pion condensate. The effect of superfluidity on cooling is investigated, adopting methods more realistic than in previous studies. Our theoretical models are compared with the currently updated observational data, and possible implications are explored.
Umeda, Hideyuki↗
Cosmic gamma-rays from pion decay
The production of gamma rays from the decay of neutral pions produced in interstellar cosmic ray interactions was studied, limited to the total gamma ray intensity. Using the upper-limit gamma ray production, an upper-limit is obtained consistent with that obtained by Kraushaar. It is shown that whatever the shape of the gamma ray spectrum, the normalization has to be consistent with data of the total cross sections.
Stecker, F. W.↗
Cross-Section Parameterizations for Pion and Nucleon Production From Negative Pion-Proton Collisions
Ranft has provided parameterizations of Lorentz invariant differential cross sections for pion and nucleon production in pion-proton collisions that are compared to some recent data. The Ranft parameterizations are then numerically integrated to form spectral and total cross sections. These numerical integrations are further parameterized to provide formula for spectral and total cross sections suitable for use in radiation transport codes. The reactions analyzed are for charged pions in the initial state and both charged and neutral pions in the final state.
Norbury, John W.↗
A study of the interaction of neutral and charged particles
Preliminary experimental data on the number of charged neutral nuclear-active particles were obtained at 200 BeV. The ratio of the number of charged particles to the number of neutral particles was 2.1 + or - 0.3. Nuclear cascade curves in iron and distributions over the portions of energy transferred to neutral pions in lead were obtained for avalanches generated by charged and neutral particles. The characteristics of interactions of the charged neutral particles at the existing experimental errors showed no difference.
Kim, V. M.↗
Diffuse fluxes of cosmic high-energy neutrinos
Production spectra of high-energy neutrinos from galactic cosmic-ray interactions with interstellar gas and extragalactic ultrahigh-energy cosmic-ray interactions with microwave blackbody photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic gamma rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made, and the reasons for significant differences with previous estimates are discussed. Small predicted event rates for a DUMAND (deep underwater muon and neutrino detector) type detection system, combined with a possible significant flux of prompt neutrinos from the atmosphere above 50 TeV, may make the study of diffuse extraterrestrial neutrinos more difficult than previously thought.
Stecker, F. W.↗
Diffuse fluxes of cosmic high energy neutrinos
Production spectra of high-energy neutrinos from galactic cosmic ray interactions with interstellar gas and extragalactic ultrahigh energy cosmic-ray interactions with microwave black-body photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic gamma-rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made and the reasons fro significant differences with previous estimates are discussed. Predicted event rates for a DUMAND type detection system are significantly lower than early estimates indicated.
Stecker, F. W.↗
High-energy processes in solar flares
A detailed study of high-energy processes in solar flares is reported, including the production of neutrons and pions, and incorporating isobaric and scaling models and a recent compilation of pion production data (Dermer, 1986). The broad-band gamma-ray spectrum resulting from the decay of neutral pions, the bremsstrahlung of positrons and electrons from the decay of charged pions, and the annihilation in flight of positrons is evaluated. Also evaluated is the 0.511 MeV gamma-ray line resulting from the annihilation of the positrons which survive annihilation in flight. Calculations were based on an isotropic, thick-target model using the best available nuclear data and models. Results are compared with extensive observation of the June 3, 1982 flare (10-120 MeV gamma rays), 0.511 and 2.2 MeV line emission, nuclear line emission, high-energy neutrons, and interplanetary charged particles.
Murphy, R. J.↗