ISOSPIN MIXING IN THE ⁴He BOUND STATE AND THE NUCLEON STRANGE FORM FACTOR

The contribution of isospin admixtures in the ground state of the ⁴He nucleus is studied using wave functions derived from the most modern nuclear interactions, including isospin symmetry breaking terms. The present calculations show that this contribution is larger than previous estimates had indicated. Its effect on parity violating elastic scattering of polarized electrons from ⁴He is investigated. In particular, a simple analysis of the recently measured left-right asymmetry at low Q² shows that the contribution of these isospin admixtures is of comparable magnitude to that associated with strangeness components in the nucleon electric form factor.