Structure of light exotic nuclei and clustering phenomena studied - PowerPoint PPT Presentation

Structure of light exotic nuclei and clustering phenomena studied through the unbound states with ReA G.V. Rogachev

Outline Proton rich nuclei Neutron rich nuclei Clustering phenomena Studied through resonances

Introduction Structure of light nuclei can now be studied ab initio No Core Shell Model Green’s Function Monte Carlo Coupled Clusters Effective Field Theory (EFT) Lattice EFT Various observables, such as excitation energies, ANCs, widths, scattering phase shifts can be calculated ab initio and verified experimentally by measuring proton scattering excitation functions Most desired energy range for the proton scattering experiments 5-10 MeV/u

Structure of 8 B 7 Be+p 3 + elastic e.f. inelastic e.f. 2 + 0 + P. Navratil, et al., PRC82 034609 (2010) 2 + phase shift compared to ab initio calculations P. Maris, P. Vary, and P. Navrátil, Phys. Rev. C 87, 014327 (2013) J. P. Mitchell, et al. PRC 87, 054617 (2013)

GR, et al., PRL 92, 232502 (2004). 19 Na P. Boutachkov, GR, et al., PRL 95, 132502 (2005). GR, et al., PRC 67, 041603(R) (2003). J.P. Mitchell, GR, et al., PRC 82, 011601(R) (2010). J.P. Mitchell, GR, et al., arXiv:1303.0331 (2013). 
 GR, et al., PRC 64, 061601(R) (2001). V.Z. Goldberg, GR, et al., JETP Lett. 67, 1013 (1998). 14 F 15 F GR, et al., PRC 75, 014603 (2007). 
 V.Z. Goldberg and GR, PRC 86, 044314 (2012). L. Axelsson, et al., PRC 54, R1511 (1996). 
 K. Markenroth, et al., PRC 62, 034308 (2000). 
 K. Perajarvi, et al., PRC 74, 024306 (2006). 
 B.B. Skorodumov, GR, et al., PRC 75, 024607 (2007). 
 B.B. Skorodumov, GR et al., PRC 78, 044603 (2008). 
 11 N V.Z. Goldberg, et al., PLB 692, 307 (2010). 
 V.Z. Goldberg, et al., PRC 69, 031302(R) (2004). 
 B.B. Skorodumov, GR, et al., Phys. At. Nucl. 69, 1979 (2006). Examples Birmingham, December 2012

9 He through the T=5/2 IAR in 9 Li p + 8 He -> 9 Li(T=5/2) -> p + 8 He Decay of T=3/2 states back to elastic channel is suppressed due to the presence of the other channels. There are only two isospin allowed decay channels for T=5/2 states 11 Be ½ + g.s. 10 Li (2 - ;1 - ) L=0 g.s. 9 He ½ + g.s. ?

Excitation function for 8 He(p,p) elastic scattering T=5/2 states in 9 Li populated in 8 He+p resonance elastic 30 158-175 Degrees scattering 25 8 He beam produced by ISAC 20 Differential Cross Section [mb/sr] facility at TRIUMF 15 No narrow states were observed There is clear evidence for a very 10 x5 broad 1/2 + state at ~2.5 MeV (a) 5 above the proton threshold, this 0 30 corresponds to a ground state of 25 135-166 Degrees 20 9 He that is unbound by ~3 MeV 15 10 x5 (b) 5 Recent 8 He(d,p) 30 0 measurements 25 indicate low lying 124-160 Degrees 20 1/2 + and 1/2 - states 15 10 (c) T.Al. Kalanee, et al., x5 5 PRC 88 (2013) 034301 0 0.5 1 1.5 2 2.5 3 Center of Mass Energy [MeV] E. Uberseder, et al., submitted to PRL arXiv:1504.00879

Chain of oxygen isotopes 22 O+p -> 23 F(T>) -> 22 O+p 23 O+p -> 24 F(T>) -> 23 O+p 24 O+p -> 25 F(T>) -> 24 O+p PHYSICAL REVIEW C 74 , 064314 (2006) A.S. Volya, V .G. Zelevinsky

Chain of Carbon isotopes Consider 19 C: 19 N 5/2 + 1/2 + 0.5 0.5 ? T=7/2; ? 18 C+n 18 N(T=3;0 + )+n 1/2 + T=7/2; 1/2 + 18 C+p

Measuring (neutron rich isotope)+proton elastic scattering excitation function using active target approach provides access to other reactions “for free”. The (p,d) and (p,t) reactions can be measured simultaneously to probe the structure of the ground state of the incoming beam (N,Z) and populate 1h and 2h states in (N-1,Z) and (N-2,Z) isotopes. Using previous 18 C+p example: structure of 19 C (through IAS), 18 C(g.s.), 17 C(1h) and 16 C(2h) can be studied in one run. 8 Li(p,d) 7 Li* 8 Li(p,d) 7 Li 8 Li(p,p) 8 Li

Clustering phenomena 12 C(Hoyle state) 12 C(g.s.) Hoyle state 0 + A.M. Shirokov, et al., PRC 79, 014308 (2009) Lattice EFT produces α -cluster like Hoyle state is underbound in structures for the Hoyle and g.s. state of 12 C NCSM with JISP16 by 8 MeV! E. Epelbaum, et al., PRL 106, 192501 (2011)

10 Be Molecular structures in J. Hiura and R. Tamagaki, Prog. Th. Phys. 52 , 25 (1972), Suppl π - bond σ - bond

6 He+ α excitation function 4 + state D. Suzuki, et al., ANASEN Phys. Rev. C 87 , 054301 (2013) AT-TPC Data 6 + state at 5.9 MeV? ANASEN Data

Excitation functions for 14 C+ α 18 O 0.8 Data Fit 0.6 d σ /d Ω (mb/sr) 0.4 0.2 0 8 9 10 11 12 13 E exc (MeV) M. Avila, GR, et al., PRC 90 (2014). While measuring alpha elastic (and inelastic) excitation functions with rare isotope beams to study clustering was very productive, measuring neutron (and other) decay channels is important for future progress toward more exotic nuclei and more exotic cluster configuration Combining compact active targets with highly segmented (position sensitive) neutron detectors

Texas Active Target (TexAT) 1400 1200 1000 800 600 400 200 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Vertex Error [cm]

Exploring clusters with active targets α -transfer reactions (such as ( 6 Li,d), ( 7 Li,t) and ( 20 Ne, 16 O) with active targets) can be employed to study clustering Another interesting experimental approach is to use ( α , α ’) to populate the exotic cluster configurations and identify their decay modes. This can naturally be realized with active targets (combined with neutron detectors).

Summary Resonance scattering with rare isotope beams provides reliable information on the structure of exotic nuclei and allows detailed direct comparison with the predictions of ab initio theoretical approaches Proton rich nuclei can be studied directly and neutron rich nuclei through the isobaric analog states Clustering phenomena in exotic nuclei can also be explored in resonance scattering experiments New experimental tools such as compact active targets combined with neutron detectors are needed for further progress

Acknowledgement Texas A&M University: G. Chubarian , V.Z. Goldberg , J. Hooker, C. Hunt, E. Koshchiy, H. Jayatissa, D. Melconian, B. Roeder, E. Uberseder, R.E. Tribble, Florida State University: A. Kuchera*, M.L. Avila**, D. Santiago-Gonzales***, L. Baby, K. Kemper, I. Wiedenhoever Louisiana State University: J. Blackmon, C. Deibel, K. Macon, L. Lienhardt TRIUMF : M. Alcorta, B. Davids * Present affiliation NSCL, Michigan State University ** Present affiliation Argonne National Laboratory *** Present affiliation Louisiana State University