Isopin invariance in the reaction np → π0d

Abstract

A measurement of the differential cross section for the reaction np ~ TrOd has been made at the Lawrence Radiation Laboratory 184-inch cyclotron. A neutron beam with kinetic energies up to 720 MeV was incident on a liquid hydrogen target. The angle and momentum of the deuterons were measured using an analyzing magnet and wire spark chambers with a magnetostrictive readout. Deuterons were separated from protons by time-of-flight. The photons from the decaying ~r ° were not detected. The neutron energy was calculated from the measured deuteron angle and momentum. Out of 5 × 10 s events recorded, 1.1 × 10 s events were the desired ~r°d reaction. The cross sections were compared to those for the reaction rr+d ~ pp as a test of isotopic spin invariance in strong interactions. The symmetry of the cross sections about 90 ° was also investigated, and an upper limit of about 1% was placed on the real part of the ratio of isospin-violating to isospin-conserving amplitudes.

The PSI np Data and their Effect on the Charged pNN Coupling Constant

“…For the deuteron total cross section on a nucleus with mass number A we use [27] σ dA = 0.97(σ nA + σ pA ) .…”

Energy dependence of nucleon-nucleon inelastic total cross-sections

“…5.1 THE NN + d7r REACTIONS. -Reactions of this type were studied in several papers [40][41][42][43]. The consequences of the isospin conservation can be summarized as follows.…”

Charge independence studied in reactions

“…Fig. 3 shows the center-of-mass differential cross sections from the data of Wilson et al for the reaction (1) [22] together with those for the reaction (2) from the GEM collaboration at COSY [23] (reflected about cos θ = 0).…”

“…[48,49,55,60] were taken into account. Those from [22] and [61] were excluded on similar grounds as in the case of the charged channel. Although the error bars are small (see also Table 1) there seem to be systematical uncertainties.…”