Medium-mass nuclei with {Delta} excitations under compression

Journal Article · Wed Aug 01 04:00:00 EDT 2001 · Physical Review C

DOI:https://doi.org/10.1103/PhysRevC.64.024306· OSTI ID:40276980

Hasan, Mahmoud A; Vary, James P; Lee, T.-S. H.

The ground state properties of {sup 90}Zr, {sup 100}Sn, and {sup 132}Sn at equilibrium and at large amplitude compression are investigated. We use a realistic effective baryon-baryon Hamiltonian that includes N-N, N-{Delta}, and {Delta}-{Delta} interactions. We perform the calculations in no-core model spaces within the framework of the constrained spherical Hartree-Fock approximation. We specifically investigate the sensitivity to the sizes of the nucleon and {Delta} model spaces. At equilibrium, we find no case of mixing between nucleons and {Delta}'s in our largest model space of eight major nucleon shells plus 16 {Delta} orbitals. On the contrary, there is mixing in {sup 90}Zr, and {sup 132}Sn in the smaller model space of seven major nucleon shells plus eight {Delta} orbitals. Expanding the nucleon model space has a larger effect on reducing the static compression modulus and softening the nuclear equation of state than increasing the number of {Delta} states. Most of the excitation energy delivered to the system during compression is employed by two nuclei with a neutron excess (i.e., {sup 90}Zr, {sup 132}Sn) to create massive {Delta} resonances. On the other hand, in the {sup 100}Sn nucleus most of the excitation energy goes to a simple reduction in the binding, suggesting a suppressed role for the {Delta} states. Under extreme compression, at a density 2--3 times the normal nuclear density, the excitation of nucleons to {Delta}'s increases sharply up to 10% of the total number of constituents. At fixed excitation energy under compression, the number of {Delta} excitations is not dependent on the number of {Delta} states over the range studied. The {Delta}-excitation results are consistent with heavy-ion collision data, and suggest an important mean field mechanism for subthreshold pion production in particle-nucleus and nucleus-nucleus collisions.

• Research Organization: Iowa State University
• Sponsoring Organization: (US)
• DOE Contract Number: FG02-87ER40371; W-31109-ENG-38
• OSTI ID: 40276980
• Journal Information: Physical Review C, Journal Name: Physical Review C Journal Issue: 2 Vol. 64; ISSN 0556-2813
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
COMPRESSION
EXCITATION
GROUND STATES
HAMILTONIANS
NEUTRONS
NUCLEI
NUCLEONS
PIONS
PRODUCTION
SENSITIVITY