A Simultaneous Measurement of the (γ,n) and (γ,p) Reactions in 4He
A significant charge asymmetry in the nuclear force has been attributed to differences in the 4He(γ,n)3He and 4He(γ,p)3H cross sections below Eγ ∼ 35 MeV. To investigate this claim, we have performed a simultaneous measurement of these cross sections by measuring the recoiling 3He and 3H nuclei in the same detector system consisting of windowless ΔE proportional counters backed by silicon E detectors. We find, within our errors, that for 25 < Eγ < 35 MeV the ratio of the cross sections σ(γ,p)/σ(γ,n) is consistent with charge symmetry and with the predictions of shell-model calculations.
KeywordsTotal Cross Section Nuclear Force Cross Section Ratio Absolute Cross Section Lead Glass
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