Virtual State of theαParticle

The spectrum of neutrons produced in the forward direction from the breakup reaction $\mathrm{T}(d, pn)\mathrm{T}$ shows a pronounced peak at its high-energy end. Using standard techniques for calculating the energy dependence of cross sections for reactions leading to three-body final states, this peak is analyzed in terms of an $\alpha$-particle resonance slightly above threshold for the unbound T-$p$ system. Reasons are given for believing the virtual state to be $0^{+}$ with $T=0\mathrm{}$.