Program - Brookhaven National Laboratory

the trends in the experimental data, however no approach gives a satisfactory representation of all cross
sections data. The most crucial aspect is to describe the formation and emission of composite particles
in the pre-equilibrium state. We will discuss reaction mechanisms and we will propose a modified version
of the Kalbach systematics that improves TALYS results for proton- and neutron-induced reactions at
energies above 100 MeV [5].
[1] A. Koning, Subgroup 13, Intermediate energy data: final report and recommendations for follow-up,
Technical Report 187, Nuclear Energy Agency (1998) [2] S. Pomp et al., A Medley with over ten years
of (mostly) light-ion production measurements at The Svedberg Laboratory, Proceedings of the Scientific
Workshop on Measurements and Models of Nuclear Reactions, 15-27 May 2010, Paris, France, EPJ Web of
Conferences, 8, 07013 (2010) [3] R. Bevilacqua et al., Medley spectrometer for light ions in neutron-induced
reactions at 175 MeV, Nuclear Instruments and Methods in Physics Research A 646, 100-107 (2011) [4]
Y. Watanabe and D.N. Kadrev, Extension of quantum molecular dynamics for production of light complex
particles in nucleon-induced reactions, Proceedings of the International Conference on Nuclear Data and
Technology, April 22-27, 2007, Nice, France, EDP Sciences, 1121-1124 (2008) [5] R. Bevilacqua, Neutroninduced
light-ion production from iron and bismuth at 175 MeV, PhD Thesis, Uppsala University, May
2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149999
Session PC Nuclear Reaction Models
Thursday March 7, 2013
Room: Empire East at 3:30 PM
PC 1 3:30 PM
Numerical Simulations for Low Energy Nuclear Reactions to Validate Statistical Models
T. Kawano, P. Talou
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
The statistical theories - the Hauser-Feshbach model with the width fluctuation correction - play a central
role in studying nuclear reactions in the fast energy region, hence the statistical model codes are essential
for the nuclear data evaluations nowadays. In this paper, we revisit issues regarding the statistical model
calculations in the fast energy range, such as the inclusion of the direct channels, and the energy averaged
cross sections using different statistical assumptions. Although they have been discussed for a long time,
we need more precise quantitative investigations to understand uncertainties coming from the models
deficiencies in the fast energy range. For example, the partition of compound formation cross section into
the elastic and inelastic channels depends on the elastic enhancement factor calculated from the statistical
models. In addition, unitarity of S-matrix constrains this partition when the direct reactions are involved.
Practically some simple assumptions, which many nuclear reaction model codes adopt, may work reasonably
for the nuclear data evaluations. However, the uncertainties on the evaluated cross sections cannot go
lower than the model uncertainty itself. We perform numerical simulations by generating the resonances
using the R-matrix theory, and compare the energy (ensemble) averaged cross sections with the statistical
theories, such as the theories of Moldauer, HRTW (Hofmann, Richert, Tepel, and Weidenmueller), KKM
(Kawai-Kerman-McVoy), and GOE (Gaussian orthogonal ensemble). The scattering matrix elements for
the direct reactions are calculated with the CC (coupled-channels) model, and they are incorporated into
the simulations. These calculations are also compared with the statistical Hauser-Feshbach model with
the transmission coefficients calculated with the CC model, which is often employed in the nuclear data
evaluations for actinides.
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