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arXiv · 1906.04699

Study of multi-neutron emission in the $\beta$-decay of $^{11}$Li

F. Delaunay·N. L. Achouri·A. Algora·M. Assié·J. Balibrea·K. Banerjee·C. Bhattacharya·M. J. G. Borge·D. Cano-Ott·B. Fernández-Domínguez·L. M. Fraile·J. Gibelin·M. V. Lund·M. Madurga·F. M. Marqués·I. Marroquin·T. Martínez·E. Mendoza·N. A. Orr·M. Pârlog·X. Pereira-López·V. Pestel·K. Riisager·C. Santos·M. Sénoville·O. Tengblad·V. Vedia
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Abstract

The kinematics of two-neutron emission following the $\beta$-decay of $^{11}$Li was investigated for the first time by detecting the two neutrons in coincidence and by measuring their angle and energy. An array of liquid-scintillator neutron detectors was used to reject cosmic-ray and $\gamma$-ray backgrounds by pulse-shape discrimination. Cross-talk events in which two detectors are fired by a single neutron were rejected using a filter tested on the $\beta$-1n emitter $^9$Li. A large cross-talk rejection rate is obtained ($> 95 \%$) over most of the energy range of interest. Application to $^{11}$Li data leads to a significant number of events interpreted as $\beta$-2n decay. A discrete neutron line at $\approx$ 2 MeV indicates sequential two-neutron emission, possibly from the unbound state at 10.6 MeV excitation energy in $^{11}$Be.

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F. Delaunay, N. L. Achouri, A. Algora, M. Assié, J. Balibrea, K. Banerjee, C. Bhattacharya, M. J. G. Borge, D. Cano-Ott, B. Fernández-Domínguez, L. M. Fraile, J. Gibelin, M. V. Lund, M. Madurga, F. M. Marqués, I. Marroquin, T. Martínez, E. Mendoza, N. A. Orr, M. Pârlog, X. Pereira-López, V. Pestel, K. Riisager, C. Santos, M. Sénoville, O. Tengblad, V. Vedia. 2019-06-11. Study of multi-neutron emission in the $\beta$-decay of $^{11}$Li. https://doi.org/10.1393/ncc%2Fi2019-19098-5

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