Post on 11-Oct-2020
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Latest SEASTAR Results with MINOS+DALI2 in the 110Zr region
Nancy PaulCEA Saclay—Université Paris-Saclay
NUSTAR Annual Meeting, March 2017
Overview
2
Motivation and Setup
• E2+ as a probe of structure evolution
• The SEASTAR Campaign• MINOS+DALI2 @ RIKEN
Physics Cases—What happens beyond N=60?
• 88-94Se—shape coexistence?• 98-100Kr—quantum phase transition?• 110Zr—tetrahedral? harmonic oscillator?
Summary
• The emerging picture of 60<N<70 structure evolution
Motivation: Understanding Structure Evolution
3
126
82
8 2028
50
2
new magicnot magic
Evolution of nuclear structure with N/Z not fully understood• Disappearance of known magic numbers• Appearance of new magic numbers
stable nuclei
known nucleiunknown nuclei (prediction)
Probes of structure evolution• First 2+ excited states
(this work)• Masses, radii, transition
probabilities,…….
magic
not magic28
Clear signature for (non-)magic nuclei
Taken from B. Bastin et al, PRL 99 (2007)
Experiment: The SEASTAR Campaign
4
o Goal: First E2+, E4
+ measurements of selected most exotic nuclei through (p,2p) reaction
o Innovation: MINOS+DALI2 detectorso Spokespersons: P. Doornenbal and
A. Obertellio Multiyear campaign:
o 2014 ~78Nio 2015 ~110Zr and south o 2017 ~52Ar, 62Ti
2.6 2.7 2.8
Prot
on n
umbe
r Z
28
29
30
31
32
33b
79Cu
80Zn
2.6 2.7 2.8
28
29
30
31
32
Mass-to-charge ratio
1
10
102
103
104
c
78Ni
RRC
IRC
SRC
BigRIPS
RILAC2
fRC
ZeroDegree
Primary target
Secondary target (10 cmt LH2)MINOS (proton tracker)DALI2 (γ-ray detector)
0 50 m
a
Primary beam: 238UEnergy: 345 MeV/U, Intensity: 30 pnAβ @ MINOS: 0.6c
RIBF@ RIKEN
DALI2+MINOS detectors
5
DALI2o 182 NaI(Tl) scintillatorso 35% efficiency @ 500kevo 9% resolution (FWHM) @ 662 kevo ~15-160° angular coverage
Takeuchi et al, NIM A 763 (2014)
MINOSo LH2 target +TPCo Thick target → high luminosityo Reaction vertex → Doppler correctiono >95% 1p detection efficiency
Obertelli et al, EPJA 50 (2014)
à (p,2p) knockout reactions
MINOS
6
proton
proton
gamma
!"#$$%&')#''&)*&" =!,(1 − 01234,)
1 − 06�
Beam
!, = gamma energy in lab0=nucleus velocity at vertex
4,=photon emission angle relative to beam
Motivation: What Happens Beyond N=60?
7
N=60o Rapid onset of deformation @ N=60 in Zr chain—competing prolate
configuration, interacting p-n orbitals (Federman-Pittel mechanism, type II shell evolution
of Otsuka)o Same effect when removing protons?o Complicated shape coexistence—rich testing ground for structure modelso New effects at N=70?
Results: Se Isotopes And SCCM Calculations
8
o Measurement consistent with D1S+PCM calculations from Tomas Rodriguez
o Calculations show oblate-prolatetransition at N=56, then sharp prolate-oblate transition at N=58.
o No indication of N=56 subshell closure (90Se)
PCM
86Se 88Se 90Se 92Se 94Se
Figures from S. Chen and T.R. Rodriguez
Figure from S. Chen
Results: 98,100Kr (courtesy of F. Flavigny)
9
0
50
100
0
200
400
600
800
Co
un
ts /
10
ke
V
200 400 600 800
E(keV)
0
20
40
60
Co
un
ts /
20
ke
V
0 300 600 900-10
0
10
20
30
Co
un
ts /
20
ke
V
(a) 99
Rb(p,2p)98
Kr 190-220 keV
470-500 keV
(b) 101
Rb(p,2p)100
Kr
Gate
Gate
56 60 64Number of neutrons
0
0.5
1
1.5
E(2
1
+)
(Me
V)
(this work)
Kr (Z=36)
Sr (Z=38)
Zr (Z=40)
98Kr
100Kr
309(10)
0
329(7)
545(17)
21
+21
+
(02
+,2
2
+)
(41
+)
01
+0
1
+0
309
329
498
216
638(25)
638
(a) (b)827(20)
E(21+) evolution:
o Overall progressive decrease for Kro Not as brutal as Zr and Sr, but presento Stabilization at N=64Intruder configuration:o First evidence in neutron rich Kr isotopes
Results: 98,100Kr (courtesy of F. Flavigny)
10
o Coexistence of prolate and oblate shapes
o Prolate intruder state competing at low energy
o Origin of drop at N=62? Unclear from theory
96Kr
98Kr
100Kr
Motivation: 110Zr (Z=40, N=70)
11
o Conflicting theoretical predictionsoWeakening of spin-orbit splitting,
shell gap at N=70?
oTetrahedral symmetry?o40,70, both tetrahedral magic
numberso Dudek et al, PRL 88 (2002); Dudek et al, PRC 69
(2004);
oDeformed, shape coexistent?o 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; Bender et al. PRC 2009.
o Important benchmark for theory
Plot from Lorusso et al, PRL 114 (2015)
Astrophysical interest:o Shell-stabilized 110Zr potential
explanation for r-process model discrepancies before A=130 peak?
No existing evidence of stabilized 110Zr (published spectroscopy of 108Zr, beta decay lifetime of 110-112Zr)
Still missing direct structure measurement!
Results: 112Mo and 110Zr
12
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(�+) ���(�)
(�+) ���(��)
(�+) ��(��)
���
���
���
!!"!"!+
("+) #$%(##)
(&+) %'%("#)("+) &$%(##)
!"#
$"%
!"#
Energy (keV)0 100 200 300 400 500 600 700
Cou
nts
/ 10
keV
50
100
150
200
250
300 Zr110
Cou
nts
/ 5 k
ev
200400600800
100012001400160018002000
Mo112
100 200 300 400 5000
20
40
60
80 Gate 150-210 keV
100 200 300 400 500
0
20
40
60
80 Gate 190-250 keV
Results: 110Zr Theory Comparison
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��+ ��+
��-��+
��+��-
13
Tetrahedral predictions Tagami et al, PRC 87 (2013)
o Best agreement with MCSM calculationsà prolate deformation in ground stateTogashi et al, PRL 117 (2016)
o Qualitative agreement with Gogny and Skyrme calculationso Exclude tetrahedral symmetry in ground state of 110Zro 110Zrà Well deformed, rotational nucleus
Figure from Togashi et al, 2016
Z30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64
42R
2
3
(keV
)1+
Ener
gy 2
200
400
600
800
1000
1200
Results: N=70 Theory Comparison
Z30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64
42R
2
3
(keV
)1+
Ener
gy 2
200
400
600
800
1000
1200
Z30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64
42R
2
3
(keV
)1+
Ener
gy 2
200
400
600
800
1000
1200
14
NNDC-evaluated dataThis work
D1S+5DCH Delaroche, Girod, Libert(CEA)
D1S+PCMRodriguez (Madrid)
SLyMR0+PCMBally (CEA), Bender (IPNL), Heenen(Bruxelles)
Z30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64
42R
2
3
(keV
)1+
Ener
gy 2
200
400
600
800
1000
1200 N=70
R42
=E(
4 1+ )
E(2 1+ )
vibrator
rigid-rotor
The New Picture Beyond N=60
15
N54 56 58 60 62 64 66 68 70 72
(keV
)1+
Ener
gy 2
0
200
400
600
800
1000
1200
1400
1600
Zr (Z=40)Sr (Z=38)Kr (Z=36)Se (Z=34)
ü Smooth behavior in Se consistent with shape coexistenceü Evidence for shape coexistence and rise in deformation at @ N=62ü 110Zr—well deformed, no magicity nor tetrahedral symmetry, shape coexistence
16
Thank you!A. Corsi, A. Obertelli, G. Authelet, F. Chateau, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, V. Lapoux, J-Y. Roussé, C. Santamaria, J.-P. Delaroche, J. Libert, M. Girod, B. Bally
T. Ando, S. Momiyama, R. Taniuchi, M. Niikura, H. Sakurai, T. Saito, K. Wimmer, S. Nagamine, T. Otsuka
A. Jungclaus, V. Vaquero
L. Cortes, V. Werner
A. Blazhev, M. Dewald,K. Moschner,
T. Arici, M. Górska, C. Lizarazo
R. Caroll, Z. Patel, Z. Podolyak, M. Rudigier, C. Shand
F. Browne, A. Bruce, C. Nobs
P. Doornenbal, H. Baba, S. Chen, T. Motobayashi, D. Steppenbeck, T. Uesaka
F. Flavigny, L. Olivier, S. Franchoo, A. Gottardo
J. Liu, Z. Xu
N. Nakatsuka
L.X. Chung, B. Linh
R. Orlandi
M. BenderP.-H. Heenen
T.R. Rodriguez
17
Backup Slides
Energy (keV)0 100 200 300 400 500 600 700 800
Cou
nts
/ 5 k
ev
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Backup: 112Mo—high stats case
18
Energy (keV)0 100 200 300 400 500 600 700 800
Cou
nts
/ 5 k
ev
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Energy (keV)0 100 200 300 400 500 600 700 800
Cou
nts
/ 5 k
ev
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Energy (keV)0 100 200 300 400 500 600 700 800
Cou
nts
/ 5 k
ev
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Energy (keV)0 100 200 300 400 500 600 700 800
Cou
nts
/ 5 k
ev
0
200
400
600
800
1000
1200
1400
1600
1800
2000 112Mo Experimental spectrum
Normalized bremsstrahlung background
Subtracted spectrum+fit
0
100
200
300
225 230 235 240Energy (keV)
Life
time
(ps)
Hal
f-life
(ps)
Backup: Experimental setup @ RIKEN
192.6 2.7 2.8
Prot
on n
umbe
r Z
28
29
30
31
32
33b
79Cu
80Zn
2.6 2.7 2.8
28
29
30
31
32
Mass-to-charge ratio
1
10
102
103
104
c
78Ni
RRC
IRC
SRC
BigRIPS
RILAC2
fRC
ZeroDegree
Primary target
Secondary target (10 cmt LH2)MINOS (proton tracker)DALI2 (γ-ray detector)
0 50 m
a
A/q2.55 2.6 2.65 2.7 2.75 2.8
Z
38
39
40
41
42
43
44
45
1
10
210
110Zr
112Mo
A/q2.55 2.6 2.65 2.7 2.75
Z
39
40
41
42
43
44
45
1
10
210
111Nb
113Tc
BigRIPS—entering LH2 target ZeroDegree—reaction products
A/q
Primary beam: 238UEnergy: 345 MeV/U, Intensity: 30 pnAβ @ MINOS: 0.6c
Energy (keV)0 100 200 300 400 500 600 700 800
coun
ts
0
50
100
150
200
250
300 subtracted spectrumsimu+bkg170 kev, 200 ps355 kev, 100ps
Proof of principle: 108Zr—two peak fit
20
0
100
200
300
400
500
600
700
800
900
140 150 160 170 180Energy (kev)
Hal
f−lif
e (p
s)
0
100
200
300
400
500
600
700
800
900
140 150 160 170 180Energy (kev)
Hal
f−lif
e (p
s)
From Kameda et al 2012
21+→ 01
+
chi221
+→ 01+
probability
110Zr—Forward Angles
21
Energy (keV)0 200 400 600 800 1000
Cou
nts
/ 5 k
eV
0
10
20
30
40
50
60
h_SpectrumDALI_forward
Proof of principle: Background subtraction-86Ge
22
Lifetime effects
23
keV0 50 100 150 200 250 3000
1000
2000
3000
4000
5000
6000
7000 180 kev, 0ps180 kev, 100ps180 kev, 200ps180 kev, 350ps
Half-life (ps) Centroid (keV)
0 180
100 173
200 167
350 159