Speaker
Description
Neutron-neutron correlations, specifically in light exotic systems such as two-neutron halo nuclei, is a topic that has attracted a revived interest [1,2]. These correlations are known to play a key role in binding the Borromean system [3,4], thus shaping their properties and dynamics in nuclear collisions. The particular features of these nn correlations extend beyond the driplines and may give rise to two-neutron emitters, such as 26O [5], which exhibit an unbound ground-state resonance. Their main characteristic is being bound with respect to 1n emission but unbound with respect to 2n emission. Therefore, the decay is expected to proceed as a direct two-neutron emission, rather than the sequential decay that may be available for their excited states. The structure properties and decay dynamics of these systems can be studied within the three-body hyperspherical model [6,7], focusing on the relative-energy (or momentum) distributions, which can be then confronted to experimental data.
In Ref. [8] we proposed a method to characterize few-body resonances from the time evolution of the lowest eigenstates of a resonance operator in a discrete basis, with the aim of studying the population of these systems in knockout reactions. The relative-energy distributions in their decay can be computed by solving an inhomogeneus equation with a source term involving the resonance eigenstate [9,10]. In the computed distributions, the mixing of different hypermomenta is found to be crucial for their shape, reflecting different possible asymptotics. The method has been applied to ¹⁶Be [11] and ¹³Li [12], showing signatures of direct two-neutron decay, and in reasonable agreement with recent experimental observations. Calculations for ²¹B are ongoing.
[1] Kubota et al., Phys. Rev. Lett. 125, 252501 (2020).
[2] Corsi et al., Phys. Lett. B 840, 137875 (2023).
[3] Hagino K. and Sagawa H., Phys. Rev. C, 72 (2005) 044321.
[4] K. Hagino, H. Sagawa, J. Carbonell and P. Schuck, Phys. Rev. Lett. 99, 022506 (2007).
[5] Z. Kohley, et al., Phys. Rev. Lett. 110, 152501 (2013).
[6] M. V. Zhukov, et al., Phys. Rep. 231, 151 (1993).
[7] A. E. Lovell, F. M. Nunes and I. J. Thompson, Phys. Rev. C 95, 034605 (2017).
[8] J. Casal and J. Gómez-Camacho, Phys. Rev. C 99, 014604 (2019).
[9] L. V. Grigorenko et al., Phys. Rev. C 80, 034602 (2009).
[10] J. Casal and J. Gómez-Camacho, in preparation.
[11] Monteagudo et al., Phys. Rev. Lett. 132, 082501 (2024).
[12] P. André et al., Phys. Lett. B 857, 138977 (2024).
