MeV Negative Pions Research Articles

A measurement of the forward charge-exchange cross section of 170 MeV negative pions in hydrogen

The measurement of the forward charge-exchange cross section sigma /sub 0/(0/sup 0/, omega ) for the process pi /sup -/ + p yields pi /sup 0/ + n was carried out at a pi /sup -/ energy of 170 plus or minus 3 Mev. The final result is sigma /sub 0/(0/sup 0/ + 8/sup 0/) = 5.023 + 0.26 mb/sterad. The meson-nucleon coupling constant f/sup 2/ was determined using all available data on sigma /sub 0/(0/sup 0/, omega ) from 95 to 290 Mev and is presented as a X/ sup 2/ fi t. (H.D.R.)

Scattering of 6-24 MeV Negative Pions by Hydrogen

Scattering of 6-24 MeV Negative Pions by Hydrogen

The scattering of 87 MeV positive pions on carbon and oxygen

Elastic and inelastic scattering angular distributions of 87 MeV positive pions on carbon and oxygen were measured with a total absorption scintillation spectrometer of high energy resolution. The elastic angular distributions are identical within the experimental error with those, measured for 87.5 MeV negative pions by Edelstein. The data can be fitted with the Kisslinger theory. The inelastic angular distributions are strongly peaked in the backward direction. The inelastic differential cross section even appreciably surpasses the elastic cross section at angles above about 100°. At several angles a peak is seen in the energy spectra of pions scattered from carbon, which has to be explained as resulting from quasi-free pion nucleon scattering.

The Elastic Scattering of 98 MeV Negative Pions by Hydrogen

The elastic scattering by hydrogen of negative pions with mean energy 98 MeV has been measured at 13 angles between 30° and 150° (lab.). The pion beam was monitored with a calibrated ionization chamber and its muon and electron contamination determined by means of a Cerenkov counter. This counter was also used in the scattering telescope to separate out the electrons produced by charge exchange γ-radiation. The results were corrected for Coulomb effects and a 3-parameter curve fitted to the nuclear parts. The curve is dσ/dΩ = (1 ± 0.027) [0.385 ± 0.008 + (0.276 ± 0.015) cos θ + (0.282 ± 0.031) cos2 θ].

Inelastic scattering of 150 MeV negative pions by carbon and lead

Energy sensitive counters of the Cerenkov or scintillation type were used in conjunction with a pulse height analyzer to measure the energy spectrum of 150 MeV negative pions scattered from carbon or lead at various angles. Most of the pions scattered into the backward hemisphere had an energy less than 40 MeV. This is in contrast to the result of a Monte Carlo calculation based on a simple Fermi gas model, in which most of the pions scattered backwards have energies above 60 MeV. The measurements indicate that the absorption of pions by carbon is about that predicted by the Monte Carlo calculation, while the absorption by lead is about 1/4 that expected.

Scattering of 10-30 Mev Negative Pions by Hydrogen

Fifty-seven ${\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{-}p$ scattering events in the energy range 10-30 Mev have been observed in a hydrogen bubble chamber. The $S$-wave scattering length $\frac{1}{3}{\ensuremath{\eta}}^{\ensuremath{-}1}(2{\ensuremath{\alpha}}_{1}+{\ensuremath{\alpha}}_{3})=0.077\ifmmode\pm\else\textpm\fi{}0.011$ is found to give the best fit to the data assuming ${\ensuremath{\alpha}}_{13}={\ensuremath{\alpha}}_{31}={\ensuremath{\alpha}}_{11}=0$, ${\ensuremath{\alpha}}_{33}=0.235{\ensuremath{\eta}}^{3}$. This result is combined with the results of other low-energy scattering experiments to give estimates of ${\ensuremath{\alpha}}_{1}$ and ${\ensuremath{\alpha}}_{3}$.

Large Angle Scattering of Negative Pions in Aluminum, Copper, and Lead

The total cross sections for backscattering of 32\ifmmode\pm\else\textpm\fi{}10 Mev negative pions in Al, Cu, and Pb have been measured. A stripped emulsion was embedded in a semi-infinite absorber, and exposed to an incident beam of ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons. The positions and direction of mesons stopping in the emulsion were recorded. The cross sections are proportional to the ratio of the backward flux to incident flux, both of which are observed on the same strip of emulsion. The conclusions of this investigation are: (a) the scattering is consistent with energy independence in the region of 32\ifmmode\pm\else\textpm\fi{}10 Mev; (b) the angular distribution has a maximum at 180\ifmmode^\circ\else\textdegree\fi{}; (c) the cross section for backscattering is proportional to the mass number $A$. The total nuclear backscattering cross sections (elastic and inelastic) for negative pions in Al, Cu, and Pb are 59.6\ifmmode\pm\else\textpm\fi{}11 mb, 192\ifmmode\pm\else\textpm\fi{}27 mb, and 577\ifmmode\pm\else\textpm\fi{}80 mb, respectively.