The role of tensor force in heavy-ion fusion dynamics

Lu Guo,Cédric Simenel,Long Shi,Chong Yu

doi:10.1016/j.physletb.2018.05.066

Lu Guo, Cédric Simenel + Show 2 more

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https://doi.org/10.1016/j.physletb.2018.05.066

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Abstract

The tensor force is implemented into the time-dependent Hartree–Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics is systematically investigated for Ca40+Ca40, Ca40+Ca48, Ca48+Ca48, Ca48+Ni56, and Ni56+Ni56 reactions which vary by the total number of spin-unsaturated magic numbers in target and projectile. A notable effect on fusion barriers and cross sections is observed by the inclusion of tensor force. The origin of this effect is analyzed. The influence of isoscalar and isovector tensor terms is investigated with the TIJ forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions. Our calculations of above-barrier fusion cross sections also show that tensor force does not significantly affect the dynamical dissipation at near-barrier energies.

Highlights

The tensor force is implemented into the time-dependent Hartree–Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically
The role of tensor force on fusion dynamics is systematically investigated for 40 Ca + 40 Ca, Ca + 48 Ca, 48 Ca + 48 Ca, 48 Ca + 56 Ni, and 56 Ni + 56 Ni reactions which vary by the total number of spinunsaturated magic numbers in target and projectile
The influence of isoscalar and isovector tensor terms is investigated with the TI J forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions

Summary

Nucleon transfer

The tensor force is implemented into the time-dependent Hartree–Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The introduction of tensor force improved the systematic agreement between model predictions and experimental data in the shell evolution of exotic nuclei [1], spin-orbit splitting [2], Gamow–Teller and charge exchange spin-dipole excitations [3] In spite of these indications in nuclear structure, most calculations for reaction dynamics ignored tensor force for decades both in macroscopic-microscopic approaches and self-consistent meanfield methods. Low-lying collective states and nucleon transfer, which have the strongest impact on near-barrier fusion, are very sensitive to the underlying shell structure, which is in turn affected by the tensor force. Another possible effect of tensor force is to modify dissipation in heavy-ion collisions.

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