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Title: Experimental determination of the symmetry energy of a low density nuclear gas

Abstract

Experimental analyses of moderate-temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon {sup 64}Zn projectiles with {sup 92}Mo and {sup 197}Au target nuclei reveal a large degree of {alpha} particle clustering at low densities. For these gases, temperature- and density-dependent symmetry energy coefficients have been derived from isoscaling analyses of the yields of nuclei with A{<=}4. At densities of 0.01 to 0.05 times the ground-state density of symmetric nuclear matter, the temperature- and density-dependent symmetry energies range from 9.03 to 13.6 MeV. This is much larger than those obtained in mean-field calculations and reflects the clusterization of low-density nuclear matter. The results are in quite reasonable agreement with calculated values obtained with a recently proposed virial equation of state calculation.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1] more »;  [2];  [2];  [3];  [4];  [5] « less
  1. Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
  2. (Italy)
  3. (Belgium)
  4. (Poland)
  5. (Japan) (and others)
Publication Date:
OSTI Identifier:
20990957
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.75.014601; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALPHA PARTICLES; CLUSTER MODEL; DENSITY; ENERGY-LEVEL TRANSITIONS; GASES; GOLD 197; GROUND STATES; HEAVY ION REACTIONS; MASS NUMBER; MEAN-FIELD THEORY; MEV RANGE; MOLYBDENUM 92; NUCLEAR MATTER; NUCLEONS; SYMMETRY; VIRIAL EQUATION; ZINC 64

Citation Formats

Kowalski, S., Natowitz, J. B., Shlomo, S., Wada, R., Hagel, K., Wang, J., Materna, T., Chen, Z., Ma, Y. G., Qin, L., Botvina, A. S., Fabris, D., Lunardon, M., Moretto, S., Nebbia, G., Pesente, S., Rizzi, V., Viesti, G., Cinausero, M., Prete, G., INFN and Dipartimento di Fisica dell' Universita di Padova, I-35131 Padova, INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, FNRS and IPN, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve, Jagellonian University, M Smoluchowski Institute of Physics, PL-30059, Krakow, and Department of Physics, Tohoku University, Sendai. Experimental determination of the symmetry energy of a low density nuclear gas. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.014601.
Kowalski, S., Natowitz, J. B., Shlomo, S., Wada, R., Hagel, K., Wang, J., Materna, T., Chen, Z., Ma, Y. G., Qin, L., Botvina, A. S., Fabris, D., Lunardon, M., Moretto, S., Nebbia, G., Pesente, S., Rizzi, V., Viesti, G., Cinausero, M., Prete, G., INFN and Dipartimento di Fisica dell' Universita di Padova, I-35131 Padova, INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, FNRS and IPN, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve, Jagellonian University, M Smoluchowski Institute of Physics, PL-30059, Krakow, & Department of Physics, Tohoku University, Sendai. Experimental determination of the symmetry energy of a low density nuclear gas. United States. doi:10.1103/PHYSREVC.75.014601.
Kowalski, S., Natowitz, J. B., Shlomo, S., Wada, R., Hagel, K., Wang, J., Materna, T., Chen, Z., Ma, Y. G., Qin, L., Botvina, A. S., Fabris, D., Lunardon, M., Moretto, S., Nebbia, G., Pesente, S., Rizzi, V., Viesti, G., Cinausero, M., Prete, G., INFN and Dipartimento di Fisica dell' Universita di Padova, I-35131 Padova, INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, FNRS and IPN, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve, Jagellonian University, M Smoluchowski Institute of Physics, PL-30059, Krakow, and Department of Physics, Tohoku University, Sendai. Mon . "Experimental determination of the symmetry energy of a low density nuclear gas". United States. doi:10.1103/PHYSREVC.75.014601.
@article{osti_20990957,
title = {Experimental determination of the symmetry energy of a low density nuclear gas},
author = {Kowalski, S. and Natowitz, J. B. and Shlomo, S. and Wada, R. and Hagel, K. and Wang, J. and Materna, T. and Chen, Z. and Ma, Y. G. and Qin, L. and Botvina, A. S. and Fabris, D. and Lunardon, M. and Moretto, S. and Nebbia, G. and Pesente, S. and Rizzi, V. and Viesti, G. and Cinausero, M. and Prete, G. and INFN and Dipartimento di Fisica dell' Universita di Padova, I-35131 Padova and INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro and FNRS and IPN, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve and Jagellonian University, M Smoluchowski Institute of Physics, PL-30059, Krakow and Department of Physics, Tohoku University, Sendai},
abstractNote = {Experimental analyses of moderate-temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon {sup 64}Zn projectiles with {sup 92}Mo and {sup 197}Au target nuclei reveal a large degree of {alpha} particle clustering at low densities. For these gases, temperature- and density-dependent symmetry energy coefficients have been derived from isoscaling analyses of the yields of nuclei with A{<=}4. At densities of 0.01 to 0.05 times the ground-state density of symmetric nuclear matter, the temperature- and density-dependent symmetry energies range from 9.03 to 13.6 MeV. This is much larger than those obtained in mean-field calculations and reflects the clusterization of low-density nuclear matter. The results are in quite reasonable agreement with calculated values obtained with a recently proposed virial equation of state calculation.},
doi = {10.1103/PHYSREVC.75.014601},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • We have calculated the nuclear symmetry energy E{sub sym}({rho}) up to densities of 4-5{rho}{sub 0} with the effects from the Brown-Rho (BR) and Ericson scalings with the in-medium mesons included. Using the V{sub lowk} low-momentum interaction with and without such scalings, the equations of state (EOSs) of symmetric and asymmetric nuclear matter have been calculated using a ring-diagram formalism where the particle-particle-hole-hole ring diagrams are included to all orders. The EOSs for symmetric nuclear matter and neutron matter obtained with linear BR scaling are both overly stiff compared with the empirical constraints of Danielewicz et al. [Science 298, 1592 (2002)].more » In contrast, satisfactory results are obtained by either using the nonlinear Ericson scaling or by adding a Skyrme-type three-nucleon force (TNF) to the unscaled V{sub lowk} interaction. Our results for E{sub sym}({rho}) obtained with the nonlinear Ericson scaling are in good agreement with the empirical values of Tsang et al. [Phys. Rev. Lett. 102, 122701 (2009)] and Li et al. [Phys. Rev. C 72, 064611 (2005)], while those with the TNF are slightly below these values. For densities below the nuclear saturation density {rho}{sub 0}, the results of the above calculations are nearly equivalent to each other and all are in satisfactory agreement with the empirical values.« less
  • We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nucleimore » are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.« less