Pion Energy Spectra Research Articles

Isobaric Nucleon Model for Pion Production in Nucleon-Nucleon Collisions

A detailed quantitative model for pion production via excitation of one or both nucleons to an isobaric state with subsequent decay via pion emission is presented. The model is applied to the 0.8- to 3.0-Bev incident nucleon energy range and its predictions are compared to various experiments in this energy range performed at the Brookhaven Cosmotron. The isobaric state with isotopic spin and angular momentum=$\frac{3}{2}$ observed in the pion-nucleon scattering was assumed to be predominantly responsible for pion production in this energy range. The relative probability for isobar formation and subsequent decay with a variable total energy or mass in the isobar rest system were phenomenologically related to the ${\ensuremath{\pi}}^{+}\ensuremath{-}p$ interaction cross section. The energy or momentum spectra of pions, and nucleons, the variation of the ratio of double to single production, the angular correlation, and the $Q$ value distribution for pion-nucleon pairs have been calculated at various energies from 0.8- to 3.0-Bev and generally agree with the experimental results.

Pion Production in H and Be by 1.0- and 2.3-Bev Protons

The energy spectra of positive and negative pions produced in H and Be by 1.0- and 2.3-Bev protons have been observed at 32\ifmmode^\circ\else\textdegree\fi{} in the laboratory system. A fast scintillation counter telescope, including a magnet to select momenta, was used to analyze the direct 32\ifmmode^\circ\else\textdegree\fi{} beam of particles proceeding from a straight section of the Brookhaven Cosmotron. The pion spectra were transformed to the nucleon-nucleon center-of-mass system and were observed to be essentially similar in shape to the ${\ensuremath{\pi}}^{+}+p$ interaction cross section as a function of energy in the center-of-mass system. It was concluded that this interaction, which is believed to be due to the formation of a nucleon isobar with angular momentum and isotopic $\mathrm{spin}=\frac{3}{2}$, dominates the meson production process in the 1.0- to 2.3-Bev range. The assumption of a model, whereby meson production proceeds through excitation of one or both of the colliding nucleons to this isobar which subsequently decays by pion emission, resulted in a general qualitative explanation of the results, and also gave quantitative $\frac{{\ensuremath{\pi}}^{+}}{{\ensuremath{\pi}}^{\ensuremath{-}}}$ ratios in agreement with these experiments. The Fermi statistical theory was found, in general, to be contradicted by these results.

Production of Charged Pions from Hydrogen and Carbon

The cross sections and energy spectra of pions produced in the reactions $P+P\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+D$ and $P+P\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+N+P$ have been measured at three angles using 400-Mev protons. Both reactions contribute about equally to the total cross section. The total cross section is (4\ifmmode\pm\else\textpm\fi{}1) mb and the angular distribution is proportional to ($0.15\ifmmode\pm\else\textpm\fi{}0.06+{cos}^{2}\ensuremath{\theta}$).The energy spectra of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ produced in a carbon target at 90\ifmmode^\circ\else\textdegree\fi{} in the laboratory system has also been measured. We find $(\frac{d{{\ensuremath{\sigma}}_{\ensuremath{\pi}}}^{+}}{d\ensuremath{\Omega}})=(0.83\ifmmode\pm\else\textpm\fi{}0.11)$ mb ${\mathrm{sterad}}^{\ensuremath{-}1}$ per C nucleus and a $\frac{{\ensuremath{\pi}}^{+}}{{\ensuremath{\pi}}^{\ensuremath{-}}}$ ratio of 7.2\ifmmode\pm\else\textpm\fi{}1.5.

Energy Spectrum of Negative Pions Produced in Beryllium by 2.3-Bev Protons

Energy Spectrum of Negative Pions Produced in Beryllium by 2.3-Bev Protons