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q Structure of 78Ni Ø 78Ni (R. Taniuchi et al., unpublished)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Ø 98,100Kr (F. Flavigny et al., unpublished)
q Structure and collectivity at N=70 in neutron-rich nuclei Ø 110Zr, 112Mo (N. Paul et al., unpublished)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
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+ �(��)
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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
������+ � ���
�+ ���(�)
+ �(��)
�+ ��(�)
���
���
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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
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�+ ���(��)
+ ��(��)�+ ��(��)
���
���
���
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