1Exploring multi-neutron decay nuclei

Yosuke Kondo(Tokyo Institute of Technology)

International Symposium on Clustering as a Window on the Hierarchical Structure of Quantum Systems (CLUSHIQ2022)
Oct.31 – Nov.3, 2022, Sendai, Japan

2What structure do many neutrons have?
• 2n system (di-neutron)

Y. L. Sun et al., Phys. Lett B814, 136072 (2021)
T. Nakamura et al., Phys.Rev.Lett.96, 252502(2006)
Y. Kubota et al., Phys.Rev.Lett.125, 252501(2020)
K. J. Cook et al., Phys.Rev.Lett.124, 212503(2020)– Unbound in free space– Di-neutron correlation appears in nuclei (6He, 11Li, 19B)

• 4n system (tetra-neutron)

K. Kisamori et al.,Phys.Rev.Lett.
116,052501(2016)– Resonance?
– 4n cluster or 2x2n clusters in n-rich nuclei?

• 6n system (hexa-neutron)
Expected to appear in very neutron-rich nuclei

M.Duer et al.,Nature 606,678-682(2022)

3Contents• Study of extremely neutron-rich nuclei 27,28O• Search for multi-neutron cluster in 10He

4Physics topics

Island of Inversion
20

N=2Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

129Z=231H2H3HN12B

10B

11Be96He 4He13C87O

11CLi10N1476CLiHeCB

Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

14N16F

18O

1715NF19O

1816N

Li98Li20O

1917N13C14C15C16C12B13B14B15B

Be 10Be 11Be 12Be8F1114F

21O

20

18N

17C

F

22O

2119

N

18C

17B

F

23O

22

20

N

19C

F

24O

23

21

N

20C

19B

F

25O

24

22N

26F

F

27F

29F

313437Na

NeFO

23N

22C

28O(4n emitter)

BeLi

He

N=8

N=16

N=20

• Neutron correlation• Island of inversion• Sudden change of neutron drip line (Oxygen anomaly)40

Mg

5Di-neutron correlation
Density of two
N=2neutrons

20Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
201713O

129Z=2qr 3 124
1HHe23HHN12B10B11Be96He13C87O11CLi10N1476CLiCBNa 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=815O

14N16F18O

1715NF

19O

1816N

Li

9LiF

20O

1917N13C14C15C16C12B13B14B

15B

Be 10Be 11Be 12Be8Island of Inversion

1114F21O2018N

17C

F

22O

21

19N

18C

17B

F

23O

2220

N

19C

F24O

2321

N20C

19B

F

25O

24

22N

26

F

27F

F

29F

31O

23N

22C26O(2n emitter)

Be

Li

8HeHe
Space
coordinate

N=8

N=16

N=20

• Neutron correlation– Di-neutron correlation is predicted in 26O• K. Hagino et al., PRC89, 014331 (2014)– What’s happen in 28O?

F

34

Ne37

Na

40Mg

6

Island of inversion
P. Doornenbal, Y.K et al.,
PRC95, 041301(R),N=2 (2017)20

Island of Inversion

Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

14ONa 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

16F

18F

19O

17F

20O

18F

21O

19F

22O

20F

23O

21F

24O

22F

25O

23O

24F

26F

2729F(5/2+)

29F(1/2+)

7.9%

1.0%

31H

Li28O(0+)

He 4He210.9%

H3H6LiHeN13LiNLi

814N15N16N17N18N19N20NLiHeN=8• Island of inversion

28F29F31Mg

NaNeFS. Bagchi et al.,PRL124, 222504, (2020)

ON 22N 23N
1p213/2
28922C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C1pC
C3/2
1f207/2
1f197/2
SDPF-M shell model
2081017B
B 11B 12B 13B 14B 15B
B
B
calculation predicts small
1d3/2
7910111214BeBeBeBeBe
Be
29282s1/20p0h prob. for F and O
1d5/2678911Z=212F34374028O
Doubly magic?
(Z=8, N=20)

81p1/2
1p3/2
1s1/2

2N=16

neutron– Where is the south boundary?
– Is 28O doubly magic?

N=20
Halo structure of 29F
Importance of p3/2contributions→ Disappearance of N=28 shellclosure7

Oxygen anomaly

Island of Inversion
20212223242526272829303132333435363738Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg
N=2T. Otsuka
et al., PRL105, 032501 (2010)2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

12913N12B

10B

11Be987OCCF18Drip15 line
14161711C10NNa 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35NaCBO

14NO

15NF

19O

1816NF

20O

1917N

13C

14C15C

16C12B

13B

14B

15B

Be 10Be 11Be 12Be

14F

21O

2018N

17CF

22O

2119N18C

17B

F

23O

2220N19CF

24O

2321N20C19BF

25O2422N

26FF

27F29F31343740Mg

NaNeFO

2328O

N22C

Oxygen anomaly

Be611Z=2
Li 7Li 8Li 9Li
Li3 3NF
6 an important
8role inHe 4He plays
HeHebinding of oxygens
1N=8H 2H 3H

N=16

N=20

Hagen et al., PRL108, 242501 (2012)• G.J. Holt
Suddenet al., Eur.Phys.change
J.A49, 39 (2013) of neutron drip line (Oxygen anomaly)– What is the origin?

8Invariant mass spectroscopy of 27O, 28O
28O: One-proton removal reaction of 29F

pn1

knocked-outproton
p29Fn28On24On~230MeV/upnn

recoilproton

n24O

p24On

pn4
pn3
Invariant massnpproton
targetpn2→4 neutrons coincidence is needed

27O: Two-proton removal reaction of 29Ne

1p1n removal reaction from 29F

9Experiment @ RIKEN-RIBF
Primary beam
48Ca (345MeV/nucleon )9Be target
29Ne/29F beam

To SAMURAI

Selection/identification of secondary beam

1028O measurement @ RIBF-SAMURAI
MINOS

MWDC

2Plastics
2 MWDCs

Superconducting
Dipole Magnet(B=2.9T@center)

NeuLANDNEBULAnDALI2nNeuLANDMINOSnMWDC

29Fn(from BigRIPS)

Hodoscope

15cm thick LH224O

NeuLAND+NEBULA→ ~ 50% efficiency for 1n11SAMURAI21 collaboration
Y.Kondo, T.Nakamura, N.L.Achouri, H.Al Falou, L.Atar,
T.Aumann, H.Baba, K.Boretzky, C.Caesar, D.Calvet,
H.Chae, N.Chiga, A.Corsi, H.L.Crawford, F.Delaunay,
A.Delbart, Q.Deshayes, Zs.Dombrádi, C.Douma, Z.Elekes,P.Fallon, I.Gašparić, J.-M.Gheller, J.Gibelin, A.Gillibert,
M.N.Harakeh, A.Hirayama, C.R.Hoffman, M.Holl, A.Horvat,
Á.Horváth, J.W.Hwang, T.Isobe, J.Kahlbow, N.KalantarNayestanaki, S.Kawase, S.Kim, K.Kisamori, T.Kobayashi,
D.Körper, S.Koyama, I.Kuti, V.Lapoux, S.Lindberg,
F.M.Marqués, S.Masuoka, J.Mayer, K.Miki, T.Murakami,
M.A.Najafi, K.Nakano, N.Nakatsuka, T.Nilsson, A.Obertelli,F.de Oliveira Santos, N.A.Orr, H.Otsu, T.Ozaki, V.Panin,
S.Paschalis, A.Revel, D.Rossi, A.T.Saito, T.Saito,
M.Sasano, H.Sato, Y.Satou, H.Scheit, F.Schindler,P.Schrock, M.Shikata, Y.Shimizu, H.Simon, D.Sohler,O.Sorlin, L.Stuhl, S.Takeuchi, M.Tanaka, M.Thoennessen,H.Törnqvist, Y.Togano, T.Tomai, J.Tscheuschner,J.Tsubota, T.Uesaka, H.Wang, Z.Yang, M. Yasuda,K.Yoneda
Tokyo Tech, Argonne, ATOMKI, CEA Saclay, Chalmers,CNS, Cologne, Eotvos, GANIL, GSI, IBS, KVI-CART,
Kyoto Univ., Kyushu Univ., LBNL, Lebanese-French
University of Technology and Applied Science, LPC-CAEN,MSU, Osaka Univ., RIKEN, Ruđer Bošković Institute, SNU,Tohoku Univ., TU Darmstadt, Univ. of Tokyo

12Neutron crosstalk
Same Wall event• Crosstalk … multiple hits caused by 1n– should be eliminated– Same wall event → position & timing & pulse
height information

Wall-1Wall-2Different Wall eventb 01b12• 2 hits are regarded as 1n if positions & timing are close• lose efficiency for small Erel

– Different wall event → velocity & pulse heightinformation• event is regarded as crosstalk if b01 > b12– because crosstalk neutron must be slow

Wall-1Wall-2• can measure up to Erel~0hit detector
T. Nakmura et al., Nucl. Instrum. Methods B376,156 (2016)
Y. Kondo et al., Nucl. Instrum. Methods B463, 173 (2020)

13

Decay energy spectrum(24O+3n coincidence)
29F+1H→24O+3n+X

n127O events

E012

n2E02

E01 24n3E03

OE0123
E01<E02<E0314Correlation in 27O decay
1.0 MeV < E0123 < 1.2 MeVSequential through 26O
4-body phase space

Contribution of 28O

n126O(2+)
25O
24O

27O

-3n0.018MeV -2n 26O(0+)-1nE012n2E02

E01 24
E0123

n3E03

O
E01<E02<E0315

Decay energy spectrum(24O+3n coincidence)
29F+1H→24O+3n+X

n1E012

n2E02

E01 24Gated by E012<0.08MeV= decay of 26O(0+)

n3E03

O
27O events

27O events

Er=1.09(4)MeV
G<0.18MeVE0123
E01<E02<E03

26O(2+)
25O
24O

27O-1n0.018MeV -2n 26O(0+)
Systematic error of Er : 0.02MeV

16

Decay energy spectrum(24O+4n coincidence)
29F+1H→24O+4n28O ground state

Success of 4n coincidence detection!

17

Theoretical predictions towards 28O
K. Fossez et al., PRC 96, 024308 (2017)

SM USDB: B. A. Brown, Int. J.
Mod. Phys. E26, 1740003 (2017)
SM+3NF: T. Otsuka et al., PRL105,032501 (2010)
SM+3NF sdf7/2p3/2:
CSM: A. Volya et al., PRL94,052501 (2005), A. Volya et al.,
PRC74, 064314, (2006)
IMSRG: V. Lapux et al., PRL117,052501, (2016), H. Hergert,private communication

This work

18

Correlation in 28O decay
E01234 < 1.0 MeV

K. Hagino et al., PRC89, 014331 (2014)
Opening angle of momentum vectors
E012
E034
in 26O decay
E01234n2n3n1E02
E03 n4
E01 24OE

Sequential through 26O

04

5-body phase space

E01<E02<E03<E04

26O(2+)
25O
24O-4n0.018MeV -2n 26O(0+)

qnn

27O-2n28O

P
Dineutron correlation enhances
back-to-back 2n emission

Future perspectives
Study of opening angle→ di-neutron correlation in 26,28O?

19Contents• Study of extremely neutron-rich nuclei 27,28O• Search for multi-neutron cluster in 10He

20

Multi-neutron system and multi-neutron cluster structure• 2n system (di-neutron)

Y. L. Sun et al., Phys. Lett B814, 136072 (2021)
T. Nakamura et al., Phys.Rev.Lett.96, 252502(2006)
Y. Kubota et al., Phys.Rev.Lett.125, 252501(2020)
K. J. Cook et al., Phys.Rev.Lett.124, 212503(2020)– Unbound in free space– Di-neutron correlation appears in nuclei (6He, 11Li, 19B)

• 4n system (tetra-neutron)

K. Kisamori et al.,Phys.Rev.Lett.
116,052501(2016)– Resonance?
– 4n cluster or 2x2n clusters in n-rich nuclei?

• 6n system (hexa-neutron)

10He (4He+6n)

M.Duer et al.,Nature 606,678-682(2022)

21

Previous experiments for 10He

6n threshold4n thresholdNo conclusive data for excited states
Close to the 4He+6n threshold→ 6n cluster structure

A. Korsheninnikov et al, Phys. Lett. B 326, 31 (1994).
T. Kobayashi et al, Nucl. Phys. A 616, 223c (1997).
H.T. Johansson et al, Nucl. Phys. A 842 15 (2010).
H.T. Johansson et al, Nucl. Phys. A 847 66 (2010).
S.I. Shidochuk et al., Phys. Rev. Lett. 108 202502 (2012)
Z. Kohley et al, Phys. Rev. Lett. 109, 232501 (2012).
M.D. Jones et al., Phys. Rev. C 91, 044312 (2015).
A. Matta et al., Phys. Rev. C 92, 041302(R) (2015).

22

Missing mass method in 11Li(p,2p) reaction
P1

11Li

200MeV/uaPa

10He

protontarget

P26n

𝑴¹⁰𝑯𝒆

2 =𝑴𝟔𝒏 2 =𝑀¹¹Li

2+P¹¹Li

𝑀¹⁰He 2 + P¹⁰He

22+ 𝑀𝑝 −−𝑀𝑝2

𝑀α 2 + 𝑃α+ 𝑃1

22−𝑀𝑝

22− P¹⁰He − 𝑃α+ 𝑃2

222− P¹¹Li − 𝑃1 − 𝑃22

Experimental setup (RIBF, RIKEN)CATANA(𝑬𝒑 )CsI(Na)ProtontargetNEBULA(Neutron detector)

Superconducting
dipole magnetnPFAD(𝜽𝒑 )Si tracker¹¹Li beam
200MeV/un

PDC1/2CH2 target

DE(10He) = 0.9MeV (FWHM)

FDC24He

Each left/rigft: two layers (inner/outer)
Each inner/outer: 2x100um thickness (X&Y)
0.2mm strip (0.1mmx2)

HODP

8He
6He

Charged particle detectors
6

PFAD Test experiment@ HIMAC

東工大理𝐴 , 理研𝐵 , TU Darmstadt𝐶 , LPC Cean𝐷 , 立教大理𝐸 , 北京師範大理𝐹
松井智輝𝐴 , 近藤洋介 A , 中村隆司A, 佐藤義輝A , 堀川晃太A , 礒部駆A , H.LeeA ,栂野泰宏B, 笹野匡紀B, 大津秀暁B, 田中純貴B, 王赫B , P.DoornenbalB,V.AlicindorC , A. ObertelliC , M. EnciuC , A. MattaD , F. FlavignyD ,武重祥子E , H.N. LiuF

PFADp Beam
120MeV
230MeVTop view

CH₂PFAD

BeamTarget

11Analyzed by T. Matsui
Gated by fiber layer( -5.0mm < Z < -3.5mm)

Preliminary results of test exp.
CH21mmProton elastic scattering

Fibers (vertical)

CH2 Fibers (horizontal)
0.1mm

countsTop view

Y (mm)

Beam line

X (mm)
12C(p,2p)

Backside view
Fibers0.25mmdiameter

X (mm)

Opening angle (deg)11Li(p,2p)10He experiment in January

26

NEBULA → NEBULA Plus (upgrade)
2 Wall config.
120 neutron detectors→4 Wall config.
90 new detectors from LPC-CAEN
120+90 neutron detectors
Enables 4 neutron coincidence detection
Oct.04Aug.2990 new detectors

Setting up is still going on for coming experiment27Summary• Study of extremely neutron-rich oxygen isotopes– First observation of 27,28O– Sequential decay through 26O ground state• Search for 6 neutron cluster in 10He
– Test of PFAD (Si tracker) @ HIMAC• Vertex reconstruction works successfully– 11Li(p,2p)10He experiment : Beam time is scheduled in January