Beta decay for neutron capture

Transcription

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

2 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, (2014) ICNT r process 2016

3 Nuclear Physics Uncertainties: (n,γ) (n,γ) uncertainties Monte-Carlo variations of (n,γ) rates within a factor (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, (2001) ICNT r process 2016

4 Current (n,γ) measurements ICNT r process 2016

5 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 OMP 95 Sr(n,γ) 96 Sr TALYS ICNT r process 2016

6 Uncertain extrapolations: gamma-ray strengths and level densities γ-ray strength functions Unexpected structural features. Level densities What is N,Z dependence of a? A.C. Larsen et al., Phys. Rev. C, 82, (2010) Al-Quraishi et al., Phys. Rev. C 63, (2001) S.N. Liddick 6

7 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 ICNT r process 2016

8 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. S.N. Liddick 8

9 Total Absorption Spectroscopy Need to know initial excitation energy Can t use beta-decay electron (three body process). Measure total γ-ray energy. Require high detection efficiency (low resolution detector). Knowledge of multiplicities. S.N. Liddick 9

10 ! A. Tonchev, et al. Photoscattering exeriment HIγS Talk at Oslo workshop Ex (MeV) ρ(ex) (MeV-1) Ge, known levels Ge, β-oslo, NSCL Zn(7Li,p) Ge, Ohio Univ., preliminary 76 Ge, CT mod. (lower limit) 76 Ge, HFB+comb. (upper limit) 6 7 It Works A. Voinov, T. Renstrom, A.-C. Larsen, et al. Preliminary Analysis - 70 Zn(7 Li,p)76 Ge reaction Experiment at Ohio University S.N. Liddick 10

11 It Works S.N. Liddick 11

12 69 Ni (n,γ) 70 Ni 64 Ni 69 Ni (n,γ) 70 Ni (β) 70 Co S.N. Liddick, A. Spyrou et al., Phys. Rev. Lett. (in press) R. Surman et al., AIP Advances, 4, (2014) S.N. Liddick 12

13 70 Ni Level Density and Gamma Strength S.N. Liddick 13

14 69 Ni(n,γ) 70 Ni S.N. Liddick 14

15 69 Ni(n,γ) 70 Ni Impact S.N. Liddick 15

16 Uncertainties S.N. Liddick 16

17 Higher mass nuclei Z = 50, N = 82 Compare statistical and direct neutron capture predictions. For example: 130 Sn Next Region R. L. Kozub et al., Phys. Rev. Lett. 109, (2012). M. Mumpower et al., Prog. Part. Nucl. Phys., 86, 86 (2016). Y. Xu et al., Phys. Rev. C, 90, (2014). S.N. Liddick 17

18 Practical Aspects (n,γ) 10-2 Masses 10-4 Half-lives S.N. Liddick 18

19 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 (NSCL), (CAREER), (JINA- CEE), and (M.M. and R.S) and the U.S. Department of Energy under contract DE- SC (R.S.), DE-AC52-07NA27344 (LLNL), and the National Nuclear Security Administration under Award No. DE-NA Funding is also acknowledged from the European Research Council, ERC Starting Grant GA , the Research Council of Norway grant no and by the Spanish Ministry MINECO under contract FPA C2-1-P. S.N. Liddick 19