arXiv subjects

Live-Palm Kubushishi

Publications and source records attributed to Live-Palm Kubushishi.

6 recordsLinked to original sources

arXiv2026

Are breakup reactions sensitive to spectroscopic factors? (Spoiler alert: they ain't)

Halo nuclei are mostly studied through reactions. In breakup reactions, the projectile is sent upon a target, which induces the dissociation of the loosely-bound halo from the core of the nucleus. In most cases, a spectroscopic factor for the core-halo structure is inferred from experimental data. In this contribution, we present a new analysis of the Coulomb breakup of 11Be on 208Pb at 69A MeV measured at RIKEN. We use an effective multi-channel particle-rotor model of the projectile, which accounts for the excitation of the 10Be core. The calculations are in excellent agreement with the data, independently of the value of the spectroscopic factor. This confirms that breakup cross sections are insensitive to this value and that spectroscopic factors cannot be inferred from such measurements. In the near future, we plan to extend this idea to other reactions.

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arXiv2026

Halo-EFT: an effective and efficient tool to study reactions with halo nuclei

Halo nuclei are exotic nuclei, which exhibit a much larger matter radius than their isobars. This unusual size is now understood as a threshold effect, in which one or two valence nucleons are loosely bound to the core of the nucleus. Thanks to this loose binding, halo nuclei exhibit a strongly clusterised structure with a diffuse neutron halo surrounding a compact core. Being short lived, halo nuclei are mostly studied through reactions, such as breakup. In this talk we show that including Halo Effective Field Theory within existing reaction codes is both effective and efficient to analyse experimental data. We first apply this idea to study the Coulomb breakup of 19C within a Bayesian approach. Second, we extend Halo-EFT to include the core's excitation to test the sensitivity of the Coulomb breakup of 11Be on spectroscopic factors.

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arXiv2026

Insensitivity of the Coulomb breakup of halo nuclei to spectroscopic factors

Exotic nuclear structures such as halos are mostly studied using reactions. In Coulomb breakup, the radioactive projectile dissociates through its interaction with a heavy target. Often, a spectroscopic factor for the core-halo structure is inferred from experimental data. In this work, we present a new calculation of the Coulomb breakup of the one-neutron halo nucleus $^{11}$Be performed with a coupled-channel effective particle-rotor model of that nucleus, which accounts for the excitation of the $^{10}$Be core. Changes in the spectroscopic factor have no effect on the cross sections when the asymptotic normalisation coefficient is fixed, hence confirming the insensitivity of Coulomb-breakup cross sections to spectroscopic factors.

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arXiv2026

A short-range effective theory for single-neutron halo nuclei with a deformed core

We establish a short-range effective theory for deformed s-wave halos. The theory applies to a system in which neutrons are weakly bound to a core nucleus, and that core nucleus also exhibits a low-lying rotational band with a $0^+$ ground state and a first $2_1^+$ excited state. The effective theory then must have both halo degrees of freedom and degrees of freedom associated with rotation of the core. This leads to the particle plus rotor model of Bohr and Mottelson at leading order. We identify the relevant leading-order operators in the Hamiltonian that respect the symmetries of the system and the small parameters which define the effective theory's power counting. We carry out calculations for the $^{11}$Be and $^{17}$C systems in which we compute the low-lying positive-parity states of the core $+$ neutron systems up to the core$(2_1^+)$-neutron threshold. We do this for several different regulator parameters and establish that these energies can be renormalized using the leading-order set of operators. The spectrum is accurately described at leading order in both cases. Decay widths to d-wave core-neutron states have sizable cutoff dependence, but the Asymptotic Normalization Coefficients (ANCs) in $s$-wave channels exhibit regulator dependence of a size consistent with next-to-leading-order effects. We also compute Coulomb breakup observables and compare with experimental data, finding leading-order results in reasonable agreement with data for both ${}^{11}$Be and ${}^{17}$C. The addition of one next-to-leading-order operator renders the ANCs of all s-wave states stable with respect to the regulator. It consequently also removes most of the 30\% variation of the leading-order Coulomb dissociation cross section with the regulator.

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arXiv2025

Exploring core excitation in halo nuclei using halo effective field theory: an application to the bound states of $^{11}$Be

Halo effective field theory (Halo-EFT) has proved to be very efficient for describing halo nuclei within models of nuclear reactions. Its order-by-order expansion scheme enables us to single out the structure observables that are probed in reactions, and therefore improve the accuracy of their values inferred from experiment. This formalism is however limited by its breakdown scale. Structure effects beyond that scale cannot be considered explicitly in reaction models. To extend the usual Halo-EFT, we include core excitation considering a particle-rotor model. We apply it to the case of $^{11}$Be, the archetypical one-neutron halo nucleus. The corresponding set of coupled equations is solved using the R-matrix method on a Lagrange mesh. As a first application, we analyze in detail the structure of both bound states of $^{11}$Be and the $^{10}$Be-n phaseshifts at low energy in the corresponding partial wave as a function of the core deformation. We also compute the electric dipole transition between these bound states. The comparison of our results with existing \textit{ab initio} calculations, show that including core excitation within Halo-EFT can significantly improve the description of the $\frac{1}{2}^+$ ground state of $^{11}$Be over single-particle models. On the contrary, core excitation has a negative effect on the description of the $\frac{1}{2}^-$ bound excited state. This is probably related to the presence of Pauli-forbidden states in our two-body model of $^{11}$Be.

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arXiv2023

Effective field theory analysis of the Coulomb breakup of the one-neutron halo nucleus 19C

We analyse the Coulomb breakup of 19C measured at 67A MeV at RIKEN. We use the Coulomb-Corrected Eikonal (CCE) approximation to model the reaction and describe the one-neutron halo nucleus 19C within Halo Effective Field Theory (EFT). At leading order we obtain a fair reproduction of the measured cross section as a function of energy and angle. The description is insensitive to the choice of optical potential, as long as it accurately represents the size of 18C. It is also insensitive to the interior of the 19C wave function. Comparison between theory and experiment thus enables us to infer asymptotic properties of the ground state of 19C: these data put constraints on the one-neutron separation energy of this nucleus and, for a given binding energy, can be used to extract an asymptotic normalisation coefficient (ANC). These results are confirmed by CCE calculations employing next-to-leading order Halo EFT descriptions of 19C: at this order the results for the Coulomb breakup cross section are completely insensitive to the choice of the regulator. Accordingly, this reaction can be used to constrain the one-neutron separation energy and ANC of 19C.

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