UBC Theses and Dissertations

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UBC Theses and Dissertations

Reaction He# (He3, 2p)He4 and the diproton state Blackmore, Ewart William


The processes by which the three particle final state is formed in the He³(He³,2p)He⁴ reaction were investigated by observing the angular distribution of coincidence events between the two protons as a function of the angle between the protons. The reaction mechanism was determined by comparing the experimental distribution with those predicted for the various possible processes obtained from kinematic and phase space arguments. The reaction was found to proceed predominantly by sequential decays through unbound intermediate states and to a lesser extent by a direct instantaneous three body breakup. The majority of the two stage decays passed through the ground state of Li⁵ , The mean lifetime of this state was measured and found to be (1.0 ± .3) x 10⁻²¹ sec There was also good evidence of a sequential decay through the diproton state. In order to fit the shape of the observed distribution it was necessary to assume that a diproton system exists which is unbound by 600 keV and has a mean lifetime of 1.5 x 10⁻²² sec However another possible interpretation is that a direct breakup occurs and the angular distribution of the protons is distorted by an attractive final state two proton interaction similar to the scattering interaction, although whether this interaction would be strong enough to produce the observed distribution is not known. A more quantitative three body decay theory is therefore necessary in order to draw any firm conclusions about the existence of the diproton state.

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