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

Proton rich nuclei Neutron rich nuclei Clustering phenomena

Outline

Studied through resonances

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

Introduction

Most desired energy range for the proton scattering experiments 5-10 MeV/u

Structure of 8B

2+ phase shift compared to ab initio calculations

2+ 0+ 3+

• P. Maris, P. Vary, and P. Navrátil,
• Phys. Rev. C 87, 014327 (2013)
• P. Navratil, et al.,

PRC82 034609 (2010)

• J. P. Mitchell, et al.

PRC 87, 054617 (2013)

elastic e.f. inelastic e.f.

7Be+p

Birmingham, December 2012

Examples

11N 14F 15F 19Na

GR, et al., PRL 92, 232502 (2004).

• 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). 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).
 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).

11Be ½+ g.s. 10Li (2-;1-) L=0 g.s. 9He ½+ g.s. ?

p + 8He -> 9Li(T=5/2) -> p + 8He

Decay of T=3/2 states back to elastic channel is suppressed due to the presence of the

• ther channels.

There are only two isospin allowed decay channels for T=5/2 states

9He through the T=5/2 IAR in 9Li

5 10 15 20 25 30 5 10 15 20 25 30

Differential Cross Section [mb/sr]

0.5 1 1.5 2 2.5 3

Center of Mass Energy [MeV]

5 10 15 20 25 30 (a) (b) (c)

158-175 Degrees 135-166 Degrees 124-160 Degrees

x5 x5 x5

Excitation function for 8He(p,p) elastic scattering

arXiv:1504.00879

• E. Uberseder, et al., submitted to PRL

T=5/2 states in 9Li populated in

8He+p resonance elastic

scattering

8He beam produced by ISAC

facility at TRIUMF No narrow states were observed There is clear evidence for a very broad 1/2+ state at ~2.5 MeV above the proton threshold, this corresponds to a ground state of

9He that is unbound by ~3 MeV Recent 8He(d,p) measurements indicate low lying 1/2+ and 1/2- states

T.Al. Kalanee, et al., PRC 88 (2013) 034301

PHYSICAL REVIEW C 74, 064314 (2006) A.S. Volya, V .G. Zelevinsky

22O+p ->23F(T>) ->22O+p 23O+p ->24F(T>) ->23O+p 24O+p ->25F(T>) ->24O+p

Chain of oxygen isotopes

Chain of Carbon isotopes

Consider 19C: 0.5

18C+n

1/2+ ?

18C+p 19N

T=7/2; 1/2+

T=7/2; ?

0.5

18N(T=3;0+)+n

5/2+ 1/2+

8Li(p,d)7Li 8Li(p,p)8Li 8Li(p,d)7Li*

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 18C+p example: structure of 19C (through IAS),

18C(g.s.), 17C(1h) and 16C(2h) can be studied in one run.

Clustering phenomena

• E. Epelbaum, et al., PRL 106, 192501 (2011)

Lattice EFT produces α-cluster like structures for the Hoyle and g.s. state of 12C A.M. Shirokov, et al., PRC 79, 014308 (2009)

Hoyle state 0+ Hoyle state is underbound in NCSM with JISP16 by 8 MeV!

12C(g.s.) 12C(Hoyle state)

Molecular structures in

10Be

π - bond

• J. Hiura and R. Tamagaki, Prog. Th.
• Phys. 52, 25 (1972), Suppl

σ - bond

4+ state

6+ state at 5.9 MeV?

6He+α excitation function

• D. Suzuki, et al.,
• Phys. Rev. C 87, 054301 (2013)

AT-TPC Data ANASEN ANASEN Data

Excitation functions for 14C+α

• M. Avila, GR, et al., PRC 90 (2014).

8 9 10 11 12 13 Eexc(MeV) 0.2 0.4 0.6 0.8 dσ/dΩ (mb/sr) Data Fit

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

18O

Texas Active Target (TexAT)

Vertex Error [cm] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 200 400 600 800 1000 1200 1400

Exploring clusters with active targets

α-transfer reactions (such as (6Li,d), (7Li,t) and (20Ne,16O) 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