Beta decay for neutron capture Sean Liddick ICNT, June 7th, 2016

r-process calculations neutron star merger hot wind cold wind Abundance pattern is different for the different astrophysical scenarios. Does one of them reproduce the observed abundances best? Why can’t we tell? M. Mumpower, J. Cass, G. Passucci, R. Surman, A. Aprahamian, AIP Adv. 4, 041009 (2014)

Nuclear Physics Uncertainties: (n,γ) (n,γ) uncertainties 1000 100 10 5 Monte-Carlo variations of (n,γ) rates within a factor 100 – 10 – 2 (light – darker – dark bands) S.N. Liddick, A. Spyrou, et al., Phys. Rev. Lett. (in press) R. Surman and J. Engel, Phys. Rev. C, 64, 035801 (2001)

Current (n,γ) measurements

Neutron Capture – Uncertainties Hauser – Feshbach Nuclear Level Density Constant T+Fermi gas, back-shifted Fermi gas, superfluid, microscopic γ-ray strength function Generalized Lorentzian, Brink-Axel, various tables Optical model potential Phenomenological, Semi-microscopic Level density γ-strength function ALL 95Sr(n,γ)96Sr OMP TALYS

Uncertain extrapolations: gamma-ray strengths and level densities g-ray strength functions Unexpected structural features. Level densities What is N,Z dependence of a? Level density parameter, a, depends only on mass. A.C. Larsen et al., Phys. Rev. C, 82, 014318 (2010) Al-Quraishi et al., Phys. Rev. C 63, 065803 (2001)

One indirect technique: Oslo method Reaction based Populate the compound nucleus of interest through a transfer or inelastic scattering. Extract level density and γ-ray strength function. Calculate (n,γ) cross section. Excellent agreement with measured (n,γ) reaction cross section. Applicable close to stability. T.G. Tornyi, M. Guttormsen,et al., Phys. Rev. C 2014

Beta decay and reactions Measure beta decay of nucleus. Extract level densities and gamma-ray strength function Need total excitation energy of the daughter isotope.

Total Absorption Spectroscopy Need to know initial excitation energy Can’t use beta-decay electron (three body process). Measure total g-ray energy. Require high detection efficiency (low resolution detector). Knowledge of multiplicities.

It Works A. Tonchev, et al. Photoscattering exeriment – HIγS Talk at Oslo workshop 2015 A. Voinov, T. Renstrom, A.-C. Larsen, et al. Preliminary Analysis - 70Zn(7Li,p)76Ge reaction Experiment at Ohio University

It Works

69Ni (n,g) 70Ni 64Ni 69Ni 70Ni (b) (n,g) 70Co Highlight 69ni S.N. Liddick, A. Spyrou et al., Phys. Rev. Lett. (in press) R. Surman et al., AIP Advances, 4, 041008 (2014)

70Ni – Level Density and Gamma Strength Note paucity of known excited states in 70Ni

69Ni(n,g)70Ni

69Ni(n,g)70Ni Impact

Uncertainties

Next Region Higher mass nuclei Z = 50, N = 82 Compare statistical and direct neutron capture predictions. For example: 130Sn R. L. Kozub et al., Phys. Rev. Lett. 109, 172501 (2012). M. Mumpower et al., Prog. Part. Nucl. Phys., 86, 86 (2016). Y. Xu et al., Phys. Rev. C, 90, 024604 (2014).

Practical Aspects 10+1 (n,g) 10-2 Masses 10-4 Half-lives

Thanks Michigan State University Artemis Spyrou S.N. Liddick B.P. Crider K. Cooper A.C. Dombos D.J. Morrissey R. Lewis F. Naqvi C.J. Prokop S.J. Quinn A. Rodriguez C.S. Sumithrarachchi R.G.T. Zegers University of Oslo A.C. Larsen M. Guttormsen L. Crespo Campo S. Siem T. Renstrøm Central Michigan University G. Perdikakis S. Nikas Notre Dame M. Mumpower A. Simon R. Surman LLNL D.L. Bluel LANL A. Couture S. Mosby Universidad de Valencia B. Rubio This research was supported by Michigan State University and the Facility for Rare Isotope Beams and was funded in part by the NSF under Contract Nos. PHY-1102511 (NSCL), 1350234 (CAREER), 1430152 (JINA-CEE), 0822648 and 1419765 (M.M. and R.S) and the U.S. Department of Energy under contract DE-SC0013039 (R.S.), DE-AC52-07NA27344 (LLNL), and the National Nuclear Security Administration under Award No. DE-NA0000979. Funding is also acknowledged from the European Research Council, ERC Starting Grant GA 637686, the Research Council of Norway grant no. 210007 and by the Spanish Ministry MINECO under contract FPA2014-52823-C2-1-P.