The $t+n+n$ System and ${}^5\mathrm{H}$

The one-proton knockout channel from ${}^6\mathrm{H}\mathrm{e}$ ($240\mathrm{M}\mathrm{e}\mathrm{V}/u$) impinging on a carbon target has been investigated. The triton fragments originating from this channel were detected in coincidence with the two neutrons. A broad structure, peaked at 3 MeV above the $t+2n$ threshold, is observed in the $t+n+n$-relative energy spectrum. It is shown that this structure is mainly due to a $I^{\pi }=1/2^{+}$ resonance as expected for the ${}^5\mathrm{H}$ ground state, and from the observed angular and energy correlations, being used for the first time in ${}^5\mathrm{H}$ studies, that the neutrons to a large extent occupy the $p$ shell.

Figure 1

Relative energy spectrum of the $t+n+n$ system. The experimental data are shown with statistical uncertainties. The estimated cross section is $30(10)\mathrm{m}\mathrm{b}$. The solid line is the result of a three-body microscopic calculation assuming $I^{\pi }=1/2^{+}$ [2]. The dashed black line (iii) represents an excited ${}^6\mathrm{H}\mathrm{e}$ resonance and the gray dashed line (iv), a calculation using a realistic ${}^6\mathrm{H}\mathrm{e}$ wave function from Ref. 15, see text.

Figure 2

Projections of the probability distribution $\mathcal{W}(ϵ,\vartheta )$ in two different Jacobi coordinate systems. (i),(iii) are shown in Jacobi configuration $\mathbf{A}$ ($n-tn$), (ii),(iv) in configuration $\mathbf{B}$ ($t-nn$). The experimental data are shown with statistical uncertainties. The solid lines represent the fit to the distributions on the basis of HH expansion after convolution with the detector resolution.

Figure 3

Two dimensional plot of the probability distribution $\mathcal{W}\mathbf{(}ϵ,\cos (\vartheta )\mathbf{)}$, extracted using the series expansion of the final state wave function into the hyperspherical functions with amplitudes adjusted to fit the experimental data. The inset sketches the used coordinate system $\mathbf{B}$.