Test of Isotopic Spin Conservation from an Experiment Limit onσ(d+d→He4+π0)

Abstract

The reaction $d+d\to {\mathrm{He}}^4+{\pi }^0$, which is forbidden by isotopic spin conservation, has been looked for at the 184-in. cyclotron. A beam of deuterons of 460 Mev kinetic energy was scattered from an extended target filled with deuterium gas at 25 atm pressure and at liquid-nitrogen temperature. The differential cross section in the center-of-mass system at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=90\mathrm{}$ deg was measured and a value of (18±2.3)×${10}^{-34\mathrm{}}$ ${\mathrm{cm}}^2$/sr was obtained. We consider this value to be an upper limit for the reaction; the data are consistent with no ${\pi }^0$ production. From a comparison of this upper limit with the theoretical prediction of the cross section for this reaction if isotopic spin need not be conserved, we conclude that isotopic spin is at least 93.5% conserved.