National Superconducting
Cyclotron Laboratory

Filomena Nunes
Filomena Nunes
FRIB Theory Alliance Managing Director
Theoretical Nuclear Physics
PhD, Theoretical physics, University of Surrey, England 1995
Joined NSCL in February 2003
Phone (517) 908-7471
Fax (517) 353-5967
Office 2107
nunes at nscl.msu.edu

Filomena Nunes

Professional homepage

I study direct nuclear reactions and structure models that are useful in the description of reactions. Unstable nuclei are mostly studied through reactions, because they decay back to stability, often lasting less than a few seconds. My group focuses on developing models for reactions with exotic unstable nuclei, and quantifying the uncertainties in those predictions. Reaction theory makes the critical connection between experiments such as the ones performed at  NSCL and the nuclear structure (or nuclear astrophysics) information we want to extract. Within the realm of direct reactions, we have studied inelastic excitation, breakup and transfer reactions.

The motivation to study these reactions are three-fold. Breakup and transfer reactions can be used as indirect methods to obtain capture rates of astrophysical relevance. These capture rates enter in the simulations of stars, and explosive sites such as novae, supernovae and  neutron star mergers. In addition, reliable models for some specific direct reactions are crucial for nuclear waste management and reactors. Finally, and most importantly, we also need reactions to unveil the hidden secrets of the effective nuclear force that binds some exotic systems and not others.

Nuclei are many body systems of large complexity. Describing a reaction while  retaining  all  the  complexity of the projectile and target nuclei would be a daunting task. Fortunately, to describe many direct reactions, only   a few structure degrees of freedom are necessary. Thus, we develop simplified few-body models that retain the important features.

Another important line of research in my group is the use of Bayesian statistical tools to quantify the uncertainty on our predictions and help in experimental design. The few-body methods we use rely on effective potentials between constituents that are not well known. The uncertainties coming from these effective potentials need to be quantified. An example of such studies is shown in the figures.

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We consider neutron elastic scattering on Ca48 at 12 MeV. The parameters in the effective n-Ca48 potential have been constrained recently with elastic scattering data (PRL 122, 232502). We compare the traditional Chi2 fiting procedure to the Bayesian approach, and show that the uncertainty bands for reactions observables obtained in the Bayesian approach as more realistic than the standard chi2 fitting. In Fig 1 we show the uncertainty bands obtained in the two approaches for the angular distribution and in Fig 2 we show the corresponding correlations between the potential parameters.

Selected Publications

Google Scholar

Direct comparison between Bayesian and frequentist uncertainty quantification for nuclear reactions, G.B. King, A. Lovell, L. Neufcourt, F.M. Nunes Phys. Rev. Letts. 122, 232502 (2019).

Constraining Transfer Cross Sections Using Bayes’ Theorem, A. E. Lovell, F. M. Nunes. Phys. Rev. C 97, 064612 (2018).

Optical potential from first principles, J. Rotureau, P. Danielewicz, G. Hagen, F.M. Nunes, and T. Papenbrock, Phys. Rev. C 95, 024315 (2017).

Establishing a theory for deuteron-induced surrogate reactions, G. Potel, F.M. Nunes, and I.J. Thompson, Phys. Rev. C 92, 034611 (2015)

Nuclear Theory and Science of the Facility for Rare Isotope Beams, A.B. Balantekin, J. Carlson, D.J. Dean, G.M. Fuller, R.J. Furnstahl, M. Hjorth- Jensen, R.V.F. Janssens, Bao-An Li, W. Nazarewicz,

F.M. Nunes, W.E. Ormand, S. Reddy, B.M. Sherrill, M. Phys. Lett. A 29, 1430010 (2014).