A. Obertelli, CEA Saclay

Nuclear Structure 2016

July 24th-29th, 2016, Knoxville, TN, USA

Recent results from

in-beam gamma spectroscopy at the RIBF

q  The SEASTAR setup at the RIBF

q  Structure of 78Ni Ø  78Ni (R. Taniuchi et al., unpublished)

q  Shape coexistence in neutron-rich nuclei at and beyond N=60 Ø  88,90,92,94Se (S. Chen et al., submitted, 2016)

Ø  98,100Kr (F. Flavigny et al., unpublished)

q  Structure and collectivity at N=70 in neutron-rich nuclei Ø  110Zr, 112Mo (N. Paul et al., unpublished)

q  Perspectives

Outline

2

Exploring nuclear structure far from stability

proton-neutron asymmetry

RIBF leading facility today In-beam gamma: One of the most powerful tools

Adapted from B. Bastin et al., PRL 99 (2007)

3

In-beam gamma spectroscopy at the RIBF

RIBF started operation in 2007 Worldwide  unique  intensi/es  Con$nuous  progression

year

Primary beam: 345 MeV/u RIB: around 200 MeV/u

DALI2 @ RIBF 186 detectors σE = 10% @ 1.3 MeV ε = 25% @ 1.3 MeV

S. Takeuchi et al., Nucl. Instr. Meth. A 763, 596 (2014)

Vertex tracker

MINOS at the RIBF

Project started in November 2010 In use at the RIBF since 2014

25/07/2016 A. Obertelli et al., Eur. Phys. Jour. A 50, 8 (2014)

proton

e-

60-200 mm liquid hydrogen target Vertex resolution : < 5 mm FWHM Detection efficiency > 90%

Target

Program based on (p,2p), (p,pn), (p,3p)

5

SEASTAR Shell Evolution and Search for 2+ Energies At the RIBF

http://www.nishina.riken.jp/collaboration/SUNFLOWER/experiment/seastar/index.html

Spokespersons: P. Doornenbal (RIKEN), AO (CEA)

6

79Cu

70,72Fe 66Cr 78Ni

Spokespersons: P. Doornenbal (RIKEN), AO (CEA)

80Zn

Primary beam 238U at 345 MeV/nucleon, mean intensity = 13 pnA Secondary beams at 250 MeV/nucleon, 100-mm target, Δβ/β = 20%

May 2014

SEASTAR Shell Evolution and Search for 2+ Energies At the RIBF

25/07/2016 7

DALI2

MINOS

DALI2-MINOS setup

Beam axis Z (mm) Beam axis Z (mm) Dop

pler

cor

r. en

ergy

(keV

) fixed β, fixed vertex β, vertex from MINOS

Cou

nts

(20

keV/

bin)

50

100

500 1000 15000

5

10

15

20 gate 683 keVCr66

Cou

nts

(20

keV/

bin)

50

100

500 1000 15000

5

10

15gate 866 keVFe70

Energy (keV)500 1000 1500

Cou

nts

(30

keV/

bin)

0

10

20

30

500 1000 1500

2

4

6 gate 520 keVFe72

Collectivity beyond N=40 in Cr, Fe isotopes C

ount

s (2

0 ke

V/bi

n)

50

100

500 1000 15000

5

10

15

20 gate 683 keVCr66

Cou

nts

(20

keV/

bin)

50

100

500 1000 15000

5

10

15gate 866 keVFe70

Energy (keV)500 1000 1500

Cou

nts

(30

keV/

bin)

0

10

20

30

500 1000 1500

2

4

6 gate 520 keVFe72

N36 38 40 42 44

Ener

gy (M

eV)

0.5

1

1.5

2

Cr isotopes LNPS-mLiteratureThis work

+2

+4

Neutron number36 38 40 42 44

)+)/E

(2+

= E

(44/

2R

2

2.2

2.4

2.6

2.8

3

3.2

Fe isotopes

Neutron number36 38 40 42 44 46

Second island of inversion

C. Santamaria et al., Phys. Rev. Lett. 115, 192501 (2015). See talk by A. Gillibert, wednesday

Similarity to the merging of the N=20 island of inversion and N=28 region of deformation P. Doornenbal et al., Phys. Rev. Lett. 111, 212502 (2013)

(non) magic character of N=50 at (below) 78Ni

F. Nowacki, A. Poves, , ArXiv 1605.05103v1

Protons: full pf Neutrons: full sdg

Recent predictions for the spectroscopy of 78Ni

F. Nowacki and A. Poves, ArXiv 1605.05103v1

intruder prolate configuration

G. Hagen et al., ArXiv 1605.01477

Large Scale Shell model calculations by Tsunoda, Otsuka (University of Tokyo), private comm.: Ø  full pfg9d5 valence space Ø  2+

1 at 2.9 MeV Ø  intruder configuration at high excitation energy (0+

2: 4.1 MeV)

π-pf ν-gsd

10

First spectroscopy of 78Ni Analysis by R. Taniuchi (University of Tokyo)

2+1 predictions vary from one model/theory to another:

VMU (T. Tsunoda et al., PRC 89 (2014)): 2.3 MeV / 2.9 MeV with extended valence space pf-pfg9d5 (K. Sieja and F. Nowacki, PRC 85 (2012)): 4 MeV PFSDG-U (F. Nowacki, A. Poves et al., ArXiv): 2.9 MeV (intruder) / 3.1 MeV (gs configuration) QRPA (S. Péru et al., EPJA 50 (2014)): 2.7 MeV

0+1

(4+1)

2+1

(2+2)

2.7 MeV 3.3 MeV 3.8 MeV

Preliminary

Ongoing collaboration with Ogata, Otsuka, Tsunoda, Schwenck et al. for interpretation

SEASTAR second campaign

110Zr

Primary beam 238U at 345 MeV/nucleon, mean intensity = 30 pnA! Secondary beams at 250 MeV/nucleon, 100-mm target, Δβ/β = 30%

May 2015

88,90,92,94Se

82,84Zn 88Ge

98,100Kr

12

Shape transition and coexistence in Se isotopes

Analysis by S. Chen (RIKEN Nishina Center)

Energy (keV)500 1000 1500

Cou

nts

/ 10

keV

200

400

600

800

1000

500 1000

20

40Gate 959 keV

<5aM

500 1000

20

40Gate 547 keV

<5aMSe90Br(p, 2p)91(b)

Cou

nts

/ 20

keV

Energy (keV)500 1000 1500

Cou

nts

/ 10

keV

100

200

300

400

500

600

500 1000

10

20

30Gate 714 keV

<5aM

500 1000

10

20

30Gate 539 keV

<5aMSe92Br(p, 2pn)94(c)

Cou

nts

/ 20

keV

Energy (keV)500 1000 1500

Cou

nts

/ 20

keV

20406080

100120140160180200

500 1000

5

10Gate 642 keV

<4aMSe94Br(p, 2p)95(d)

Cou

nts

/ 25

keV

13

Shape transition and coexistence in Se isotopes

S. Chen et al., submitted (2016)

-  Gogny D1S interaction -  Full GCM for all quadrupole degrees of freedom -  Prediction for shape coexistence -  AND prolate to oblate shape transition at N=58-60 T. Rodriguez-Guzman, Madrid, Spain

-  Good agreement between expt and theory for 21+,22

+,41+

0

1

2

3

4

52 54 56 58 60

Ex (M

eV)

Neutron Number N

(a) Theo.

2+1

4+1

2+2

4+2

2+prol

4+prol

2+obl

4+obl

0+2 3+

1

52 54 56 58 60 0

1

2

3

Neutron Number N

(b) Exp.

2+1

4+1

2+2

4+2

2+1

4+1

2+2

4+2

14

88Se

90Se

92Se

94Se

Collectivity in heavy Kr isotopes

Analysis by F. Flavigny (IPN Orsay)

0

50

100

0

200

400

600

800

Counts

/ 1

0 k

eV

200 400 600 800

E(keV)

0

20

40

60

Counts

/ 2

0 k

eV

0 300 600 900-10

0

10

20

30C

ou

nts

/ 2

0 k

eV

(a) 99

Rb(p,2p)98

Kr gate 208 keV

gate 492 keV

(b) 101

Rb(p,2p)100

Kr 0

500

1000

1500

E(2

+)

(keV

)

(this work)

Kr (Z=36)

Sr (Z=38)

Zr (Z=40)

55 60 65Number of neutrons

0

3

61/E

(2+)

(MeV

-1)

(a)

(b)

(c)

100Kr

98Kr

100Kr

303

0

329

537

821

21

+

21

+

(02

+,2

2

+)

(41

+,2

2

+)

01

+

01

+

0

303

329

492

208

F. Flavigny et al., to be submitted (2016)

Spectroscopy of N=70 isotopes far from stability

17

Stabilizing shell effect at

N=70?

Slide: N. Paul, CEA

Spectroscopy of N=70 isotopes far from stability

18

New shell gap at N=70?

o  Weakening of spin-orbit splitting possible far from stability

Dobaczewski et al, PRL 72 (1994); Lalazissis et al, PLB 418 (1998)

o  Tensor force contribution to N=82 shell

gap becomes stronger when going from Z=50 to Z=40

Otsuka et al, PRL 97 (2006) o  Conflicting predictions for 110Zr

o Spherical or tetrahedral minimum, large N=70 shell gap

Dudek et al, PRL 88 (2002); Dudek et al, PRC 69 (2004); Bender et al, PRC 80 (2009)

o  Deformed Delaroche et al, PRC 81 (2010); Geng et al, PTP 110 (2003); Kortelainen et al, PRC 82 (2010); Skalski et al, NPA 808 (2008); Xu et al, PRC 65 (2002); Petrovici et al, J. Phys. Conf. Ser., Sorgunlu and Van Isacker

70 82

40

Slide: N. Paul, CEA

Energy (keV)0 100 200 300 400 500 600 700 800

coun

ts /

5 ke

V

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Spectroscopy of 112Mo

18

������+ � ���

�+ ���(�)

+ �(��)

�+ ��(�)

���

���

���

Analysis by N. Paul (CEA)

Energy (keV)0 100 200 300 400 500 600 700 800

coun

ts /

5 ke

V

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Spectroscopy of 112Mo

18

Energy (keV)100 200 300 400 500 600 700 800

counts

/ 1

0 k

eV

0

20

40

60

80

100

120

Energy (keV)100 200 300 400 500 600 700 800

co

un

ts /

10

ke

V

30−

20−

10−

0

10

20

30

40

50

������+ � ���

�+ ���(�)

+ �(��)

�+ ��(�)

���

���

���

Gamma-gamma spectra

B

A

A

B

Analysis by N. Paul (CEA)

Spectroscopy of 110Zr

19

Energy (keV)0 100 200 300 400 500 600 700 800

co

un

ts /

10

ke

V

0

50

100

150

200

250

300

100 200 300 400 500 600 700

Co

un

ts /

20

ke

V

10−

5−

0

5

10

15

20

25

100 200 300 400 500 600

Counts

/ 1

0 k

eV

10−

0

10

20

30

40

Gamma-gamma spectra

������+ � ���

�+ ���(��)

+ ��(��)�+ ��(��)

���

���

���

B

A

A B

Analysis by N. Paul (CEA)

Results: Systematics And Comparison With Theory

20

o  Continuous decrease of E(2+1)

going to more extreme N/Z along N=70

o  Continuous increase of R42, ~3 for 110Zr

o  5DCH, Gogny D1S M. Girod et al., CEA

o  SCCM, Gogny D1S T. Rodriguez-Guzman, Madrid

o  trends more pronounced than theoretical predictions

A100 105 110 115 120 125 130

42R

2

3

100 105 110 115 120 125 130

(keV

)1+

Ener

gy 2

0

200

400

600

800

1000

1200 Data, literatureData, this workGogny D1S + 5DCHGogny D1S + SCCM

110 112 114150200250300350400 Zoom

Results: Systematics And Comparison With Theory

21

o  Large scale shell model agrees well with experimental 2+

1 Togashi et al., arXiv 1606.09056v1

o  Attributes strong deformation to proton excitations to g9/2 that modify the neutron shell structure

o  Local increase of spin-orbit strength in Gogny D1S also gives better agreement to 2+ energies

Prot

on o

ccup

anci

es

0

1

2

3

4

5

6f5/2p3/2p1/2g9/2d5/2s1/2d3/2g7/2

SM D1S D1S mod.

W=130 W=140 spin-orbit

Perspectives

62Ti

56Ca

52Ar

SEASTAR 3/3 Experimental campaign expected in 2017

Collaborators

Development and local teams

Physics collaborations

S. Anvar, L. Audirac, G. Authelet, H. Baba, B. Bruyneel, D. Calvet, F. Chateau, A. Corsi, A. Delbart, P. Doornenbal, A. Gillibert, J.-M. Gheller, A. Giganon, T. Isobe, Y. Kubota, C. Lahonde-Hamdoun, V. Lapoux, D. Leboeuf, D. Loiseau, M. Matsushita, A. Mohamed, J.-Ph. Mols, T. Motobayashi, M. Nishimura, S. Ota, H. Otsu, C. Péron, A. Peyaud, E.C. Pollacco, G. Prono, J.-Y. Rousse, H. Sakurai, C. Santamaria, M. Sasano, R. Taniuchi, S. Takeuchi, T. Uesaka, Y. Yanagisawa, K. Yoneda and the BigRIPS team

N. Alamanos, G. de Angelis, N. Aoi, H. Baba, C. Barbieri, C. Bertulani, A. Corsi, F. Delaunay, Z. Dombradi, P. Doornenbal, T. Duguet, S. Franchoo, J. Gibelin, A. Gillibert, S. Go, M. Gorska, A. Gottardo, S. Grévy, J.D. Holt, E. Ideguchi, T. Isobe, A. Jungclaus, N. Kobayashi, T. Kobayashi, Y. Kondo, W. Korten, Y. Kubota, I. Kuti, V. Lapoux, S. Leblond, J. Lee, S. Lenzi, H. Liu, G. Lorusso, C. Louchart, R. Lozeva, F.M. Marques, I. Matea, K. Matsui, Y. Matsuda, M. Matsushita, J. Menendez, D. Mengoni, S. Michimasa, T. Miyazaki, S. Momiyama, P. Morfouace, T. Motobayashi, T. Nakamura, D. Napoli, F. Naqvi, M. Niikura, A. Obertelli, N. Orr, S. Ota, H. Otsu, T. Otsuka, N. Pietralla, Z. Podolyak, E.C. Pollacco, G. Potel, G. Randisi, F. Recchia, E. Sahin, H. Sakurai, C. Santamaria, M. Sasano, A. Schwenk, Y. Shiga, Y. Shimuzu, S. Shimoura, J. Simonis, P.A. Soderstrom, S. Sohler, V. Soma, I. Stefan, D. Steppenbeck, T. Sumikama, H. Suzuki, M. Tanaka, R. Taniuchi, K.N. Tuan, T. Uesaka, J. Valiente Dobon, Zs. Vajta, D. Verney, H. Wang, V. Werner, K. Wimmer, Zh. Xu, R. Yokoyama, K. Yoneda

Theory J.-P. Delaroche, M. Girod, J. Libert, F. Nowacki, K. Ogata, T. Otsuka, A. Poves, T. Rodriguez-Gusman, A. Schwenck, Y. Tsunoda

Special thanks for their work and material to S. Chen, F. Flavigny, N. Paul, C. Santamaria, R. Taniuchi

Summary

Ø  A unique physics program based on (p,2p) and (p,pn) reactions at the RIBF with DALI2 and MINOS is ongoing •  Shell evolution and search for 2+ states in neutron rich nuclei (SEASTAR) Two campaigns performed in May 2014, May 2015 for first spectroscopy of: 66Cr, 70,72Fe, 78Ni,79Cu, 82,84Zn, 88Ge, 88,90,92,94Se, 98,100Kr, 100Sr, 110Zr, 112Mo

q  78Ni doubly-magic / nature of 2+1 under discussion

q  Smooth shape transition at N=58 in heavy Se isotopes q  110Zr deformed, no stabilizing shell effect at Z=40, N=70

•  Analysis / interpretation of cross sections under way – recent theory developments •  Systematics of about 40 (p,2p), (p,pn) and (p,3p) cross sections on the way •  Exciting perspectives expected in 2017: 52Ar, 56Ca, 62Ti

25/07/2016

69Co(p,2p)68Fe at 200 MeV/nucleon

DALI2 AGATA/GRETINA 30 detectors

Simulations

MINOS at the RIBF

25/07/2016

High granularity detector (TPC)

AGET chip from the GET project (CEA, IN2P3, NSCL collaboration)

Specific electronics and Software

TPC > 30 cm long / 15 cm diameter > 90% efficiency < 5 mm FWHM resolution

> 4000 pads, size ∼4 mm2

Features •  Ar(85%)CF4(12%)iso(3%) gas drift velocity: 4.5 cm/µs dispersion: 200 µm × √cm •  AGET: digital, 512 time bin, 100 MHz individual discriminator / channel typical dead time of 100 µs / event

150 µm Mylar cell 60 – 200 mm long

Liquid H2 target