### Abstract

We propose a measurable parameter H quantifying the halo nature of one-neutron halo nuclei (a) and investigate the properties of H, assuming the core + neutron (c+n) model for a. The parameter H is defined by H=[σabs(a)-σabs(c)]/σabs(n) with directly measurable absorption cross sections σabs of a, c, and n scattering at the same incident energy per nucleon. It varies with the one-neutron separation energy Sn in a range of 0≤H≤1, and the halo structure is most developed when H=1. This situation is realized only for s-wave halo nuclei in the Sn=0 limit. We consider Be11 and C15,19 as s-wave halo nuclei, Ne31 and Mg37 as p-wave halo nuclei, and C17 as an example of d-wave nonhalo nuclei. For each of halo nuclei, the value of H is deduced at a measured Sn from measured total reaction cross sections for c, n, and a scattering at intermediate and high incident energies where projectile breakup effects are negligible. The location of the resulting (Sn,H) is plotted in the Sn-H plane. The empirical values of H at the measured Sn are extrapolated to small Sn with model calculations based on the eikonal + adiabatic approximation. In the Sn-H plane, the model lines are well separated into three groups of s-wave halo, p-wave halo, and d-wave nonhalo particularly in the vicinity of Sn=0, and the s-wave halo lines are always above the other lines, since only the s-wave halo lines can reach a point (Sn,H)=(0,1) independently of the concrete form of the interaction between c and n. The relation among the three kinds of lines may be universal for any halo nucleus with small Sn. The point (Sn,H)=(0,1) can be regarded as a scale-invariant point in the sense that the z-integrated neutron density characterizing halo structure is invariant under the scale transformation there.

Original language | English |
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Article number | 064609 |

Journal | Physical Review C |

Volume | 93 |

Issue number | 6 |

DOIs | |

Publication status | Published - Jun 20 2016 |

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### All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics

### Cite this

*Physical Review C*,

*93*(6), [064609]. https://doi.org/10.1103/PhysRevC.93.064609

**Proposal of a directly measurable parameter quantifying the halo nature of one-neutron nuclei.** / Yahiro, Masanobu; Watanabe, Shin; Toyokawa, Masakazu; Matsumoto, Takuma.

Research output: Contribution to journal › Article

*Physical Review C*, vol. 93, no. 6, 064609. https://doi.org/10.1103/PhysRevC.93.064609

}

TY - JOUR

T1 - Proposal of a directly measurable parameter quantifying the halo nature of one-neutron nuclei

AU - Yahiro, Masanobu

AU - Watanabe, Shin

AU - Toyokawa, Masakazu

AU - Matsumoto, Takuma

PY - 2016/6/20

Y1 - 2016/6/20

N2 - We propose a measurable parameter H quantifying the halo nature of one-neutron halo nuclei (a) and investigate the properties of H, assuming the core + neutron (c+n) model for a. The parameter H is defined by H=[σabs(a)-σabs(c)]/σabs(n) with directly measurable absorption cross sections σabs of a, c, and n scattering at the same incident energy per nucleon. It varies with the one-neutron separation energy Sn in a range of 0≤H≤1, and the halo structure is most developed when H=1. This situation is realized only for s-wave halo nuclei in the Sn=0 limit. We consider Be11 and C15,19 as s-wave halo nuclei, Ne31 and Mg37 as p-wave halo nuclei, and C17 as an example of d-wave nonhalo nuclei. For each of halo nuclei, the value of H is deduced at a measured Sn from measured total reaction cross sections for c, n, and a scattering at intermediate and high incident energies where projectile breakup effects are negligible. The location of the resulting (Sn,H) is plotted in the Sn-H plane. The empirical values of H at the measured Sn are extrapolated to small Sn with model calculations based on the eikonal + adiabatic approximation. In the Sn-H plane, the model lines are well separated into three groups of s-wave halo, p-wave halo, and d-wave nonhalo particularly in the vicinity of Sn=0, and the s-wave halo lines are always above the other lines, since only the s-wave halo lines can reach a point (Sn,H)=(0,1) independently of the concrete form of the interaction between c and n. The relation among the three kinds of lines may be universal for any halo nucleus with small Sn. The point (Sn,H)=(0,1) can be regarded as a scale-invariant point in the sense that the z-integrated neutron density characterizing halo structure is invariant under the scale transformation there.

AB - We propose a measurable parameter H quantifying the halo nature of one-neutron halo nuclei (a) and investigate the properties of H, assuming the core + neutron (c+n) model for a. The parameter H is defined by H=[σabs(a)-σabs(c)]/σabs(n) with directly measurable absorption cross sections σabs of a, c, and n scattering at the same incident energy per nucleon. It varies with the one-neutron separation energy Sn in a range of 0≤H≤1, and the halo structure is most developed when H=1. This situation is realized only for s-wave halo nuclei in the Sn=0 limit. We consider Be11 and C15,19 as s-wave halo nuclei, Ne31 and Mg37 as p-wave halo nuclei, and C17 as an example of d-wave nonhalo nuclei. For each of halo nuclei, the value of H is deduced at a measured Sn from measured total reaction cross sections for c, n, and a scattering at intermediate and high incident energies where projectile breakup effects are negligible. The location of the resulting (Sn,H) is plotted in the Sn-H plane. The empirical values of H at the measured Sn are extrapolated to small Sn with model calculations based on the eikonal + adiabatic approximation. In the Sn-H plane, the model lines are well separated into three groups of s-wave halo, p-wave halo, and d-wave nonhalo particularly in the vicinity of Sn=0, and the s-wave halo lines are always above the other lines, since only the s-wave halo lines can reach a point (Sn,H)=(0,1) independently of the concrete form of the interaction between c and n. The relation among the three kinds of lines may be universal for any halo nucleus with small Sn. The point (Sn,H)=(0,1) can be regarded as a scale-invariant point in the sense that the z-integrated neutron density characterizing halo structure is invariant under the scale transformation there.

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U2 - 10.1103/PhysRevC.93.064609

DO - 10.1103/PhysRevC.93.064609

M3 - Article

VL - 93

JO - Physical Review C

JF - Physical Review C

SN - 2469-9985

IS - 6

M1 - 064609

ER -