Invariant-mass spectroscopy of extremely neutron-rich ... · Invariant-mass spectroscopy of...

Invariant-mass spectroscopy of extremely neutron-rich nuclei

with SAMURAI at RIBF

Yosuke Kondo

(Tokyo Institute of Technology)

ARIS2014, ITO International Research Center (University of Tokyo), June 1-6, 2014 1

Contents

1. Introduction of SAMURAI at RIBF

2. First experimental campaign using SAMURAI for physics programs (Day-One campaign)

Superconducting Analyzer for MUltiple-particles from RAdioIsotope Beam

RI beam from BigRIPS

target

superconducting

coil

pole(2m dia.)

rotate

vacuum chamber

Kinematically complete

measurements by detecting

multiple particles in coincidence

Superconducting Magnet

3T with 2m dia. pole (designed resolution 1/700)

80cm gap (vertical)

Heavy Ion Detectors

Proton Detectors

Neutron Detectors (NEBULA)

Large Vacuum Chamber

Rotational Stage Proton

Heavy Ion

Neutron

3 T. Kobayashi et al., NIMB317, 294, (2013)

• Kickoff all the detectors, DAQs for the xn+HI setup

• Beam transport to SAMURAI

• Heavy ion detectors optimization

• NEBULA calibration – Time-zero with high-energy gamma

– Efficiency measurement (inc. 2n cross talk) with 7Li(p,n) reaction

• Br scan for rigidity calibration

• Physics measurements – 17C 16C+n 17C 15B+n

– 15C 14C+n

– 14Be12Be+2n

Commissioning in March 2012

Everything worked perfectly !!

Primary Beam: 18O: 290 MeV/nucleon: 500 pnA

preliminary C

ounts

T. Sugimoto et al.,

Phys. Lett. B 654, 160 (2007).

E=68 MeV/nucleon 87(5) keV (1σ)

14Be (2+)

100 keV (1σ)

14Be (2+)

14Be+C

E=213 MeV/nucleon

Obtained only in 51min! 14Be: ~2x104 pps

Good Resolution as designed !

Erel (MeV)

Eth=6 MeVee

Co

un

ts

TOF(measured) - TOF(calculate) (ns)

σTOF=335(5) ps

7Li(p,n)7Be(g.s.+0.43MeV)

6Li(p,n)6Be

(4.4%)

Intrinsic Resolution: σTOF=263(6) ps

Unfolding the resolutions from other detectors

cf.) ~300 ps (designed value)

En:194MeV

Collaborators Tokyo Institute of Technology: Y.Kondo, T.Nakamura, N.Kobayashi, R.Tanaka, R.Minakata, S.Ogoshi, S.Nishi, D.Kanno, T.Nakashima LPC CAEN: N.A.Orr, J.Gibelin, F.Delaunay, F.M.Marques, N.L.Achouri, S.Leblond Tohoku University : T.Koabayshi, K.Takahashi, K.Muto RIKEN: K.Yoneda, T.Motobayashi ,H.Otsu, T.Isobe, H.Baba,H.Sato, Y.Shimizu, J.Lee, P.Doornenbal, S.Takeuchi, N.Inabe, N.Fukuda, D.Kameda, H.Suzuki, H.Takeda, T.Kubo Seoul National University: Y.Satou, S.Kim, J.W.Hwang Kyoto University : T.Murakami, N.Nakatsuka GSI : Y.Togano Univ. of York: A.G.Tuff GANIL: A.Navin Technische Universit¨at Darmstadt: T.Aumann Rikkyo Univeristy: D.Murai Universit´e Paris-Sud, IN2P3-CNRS: M.Vandebrouck

First experimental campaign using SAMURAI for physics programs

(Day-One campaign)

6

20Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg 40Mg

20Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na 37Na

17Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne 34Ne

17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O 25O 26O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 21C 22C

8B 10B 11B 12B 13B 14B 15B 17B 18B 19B

7Be 9Be 10Be 11Be 12Be 14Be

6Li 7Li 8Li 9Li 11Li

3He 4He 6He 8He

1H 2H 3H

SAMURAI Day-One experiment (May 2012)

N=16 N=20

Z=8

N=8

7

First experimental campaign with SAMURAI for physics programs

1. Study of unbound nuclei 25O and 26O (SAMURAI02, Y. Kondo)

2. Coulomb breakup of 22C and 19B (SAMURAI03, T. Nakamura)

3. Study of unbound states of 22C, 21C, 19B, 18B (SAMURAI04, N. A. Orr/J. Gibelin)




17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O 25O 26O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 22C

8B 10B 11B 12B 13B 14B 15B 17B 19B



3He 4He 6He 8He

1H 2H 3H

Study of unbound nuclei 25O and 26O

8

Study of oxygen isotopes beyond the drip line – Drip-line anomaly – Three nucleon force – South extreme of the Island of Inversion – 2n radioactivity of 26O?

N=20

Z=8

N=8

Island of Inversion

Neutron drip line anomaly




17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 22C

8B 10B 11B 12B 13B 14B 15B 17B 19B



3He 4He 6He 8He

1H 2H 3H


Anomalous behavior of the neutron drip line

N=16 N=20

Z=8

N=8

9

What is the origin of this phenomenon?




17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 22C

8B 10B 11B 12B 13B 14B 15B 17B 19B



3He 4He 6He 8He

1H 2H 3H


Anomalous behavior of the neutron drip line

N=16 N=20

Z=8

N=8

10

What is the origin of this phenomenon?

G. Hagen et al. PRL 108, 242501 (2012) CC method with int. from chiral EFT (includes continuum and 3NF effects)

T. Otsuka et al., PRL105, 032501 (2010)

Drip line Drip line

N=20

Z=8

N=8




17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O 25O 26O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 22C

8B 10B 11B 12B 13B 14B 15B 17B 19B



3He 4He 6He 8He

1H 2H 3H

Z=9 is low-Z boundary of Island of Inversion at N=19 What about the other isotones?

Where is south boundary of Island of Inversion?

11

G. Christian et al., PRC85, 034327, (2012)

28F Ground state @ 220(50)keV

28F

Island of Inversion

N=19 isotones

L.V. Grigorenko et al. PRC 84, 021303 (2011)

Usual 1n decay G~MeV or keV

2n radioactivity of 26O?

12

L.V. Grigorenko et al. PRC 84, 021303 (2011)

Usual 1n decay G~MeV or keV

E. Lunderberg et al.PRL108, 142503 (2012)

Er < 200keV

2n radioactivity of 26O?

13

T1/2=4.5+1.1-1.5ps

(3ps systematic error)

2n radioactivity?

Z. Kohley et al,PRL110,152501 (2013)

C. Caesar et al.PRC88, 034313 (2013)

Excite state at 4.2MeV?

Er < 120keV (95% CL) t < 5.7ns

Large uncertainty of experimental study • Only upper limit is given for the ground state energy • Large systematic error in the lifetime measurement

Invariant mass method

iiidecay MpEE22

Decay energy (Relative energy)

Invariant mass 24O+2n

Edecay

n-decay threshold

neutron decay

26O

0MeV

26O (unbound)

24O n

n 1np

n

24O cp

2np

n

C

27F

one proton removal reaction

~210MeV/u

14 Necessary to detect all the decay particles

Experimental setup

27F ~210MeV/u (from BigRIPS)

24O

n

n

NEBULA

DALI2

MWDC

Hodoscope

Superconducting Dipole Magnet (B=3.0T)

C target (1.8g/cm2)

MWDC

2 MWDCs

Ionization Chamber

2Plastics

15

Experimental Results

16

Decay energy spectrum (26F+C25O24O+n)

50 times higher statistics!

Another decay channel (25O23O+2n) can be studied

C.R.Hoffman et al., PRL100, 152502 (2008)

Edecay=770keV

Decay energy (MeV)

Co

un

ts /

50

keV

26F+C25O24O+n (preliminary)

24O+n

Edecay

n-decay threshold

Edecay=770keV 25Ogs

17

Ground state 5 times higher statistics better determination of energy

Excited state at ~1.3MeV First observation Most probably 2+

No peak at ~4.2MeV 18

Decay energy (MeV)

Co

un

ts /

10

0ke

V

27F+C26O24O+2n (preliminary)

Excited state（new）

Decay energy spectrum (27F+C26O24O+2n)

Er<200keV

Er<120keV (95% CL)

E. Lunderberg et al.PRL108, 142503 (2012)

C. Caesar et al.PRC88, 034313 (2013)

Ground state

Comparison with USDB calculation

Ground state – USDB predicts S2n= - 0.35MeV for 26O ground state (Almost consistent with experiment)

2+ state – Calculation overestimates at low Z effect of pf-shell? or continuum effect?

– E.g. Continuum shell model predicts 1.8MeV

A. Volya, V. Zelevinsky, PRC74, 064314 (2006)

19

26O 28Ne

30Mg

32Si 34S

36Ar

N=18

USDB

EXP new

B.A. Brown, W.A. Richter PRC74, 034315 (2006)

Difference between ground state energies of EXP and USDB calculation

N=18

(assuming Edecay=0 for 26Ogs)

Preliminary




17F 18F 19F 20F 21F 22F 23F 24F 25F 26F 27F 29F 31F

13O 14O 15O 16O 17O 18O 19O 20O 21O 22O 23O 24O 25O 26O

12N 13N 14N 15N 16N 17N 18N 19N 20N 21N 22N 23N

9C 10C 11C 12C 13C 14C 15C 16C 17C 18C 19C 20C 21C 22C

8B 10B 11B 12B 13B 14B 15B 17B 18B 19B



3He 4He 6He 8He

1H 2H 3H

SAMURAI Day-One experiment

N=16 N=20

Z=8

N=8

20

First experimental campaign with SAMURAI (May 2012)

1. Study of unbound nuclei 25O and 26O (SAMURAI02, Y. Kondo)

2. Coulomb breakup of 22C and 19B (SAMURAI03, T. Nakamura)

3. Study of unbound states of 22C, 21C, 19B, 18B (SAMURAI04, N. A. Orr/J. Gibelin)

Coulomb breakup of 22C and 19B ~Probe of di-neutron correlation~

21

e.g. 11Li

Low energy E1 excitation of 2n-halo

dineutron-like correlation

r1

r2 n

9Li

rc-2n

n

)(24

3

)1()1(

21

2

2

2

1

2

rrrrA

Ze

dEdE

EdBEB x

x

.deg48)22(78.1

)3MeV(18.042.1)1(

14

1812

22

rel

22

fme

EfmeEB

T.Nakamura et al.

PRL96,252502(2006)

What about heavier Borromean nuclei 22C and 19B?

S.Leblond

/M.Marques

/R.Minakata

New!

Preliminary

22C21C20C+n

24O

N=16

23N

22C

25F 26F 27F 29F

22N 21N

23O 22O

20C 21C

25O 26O

31F

27O 28O

30F 28F 24F 23F

Erel(MeV)

22N21C20C+n

s?

Counts

/100keV

Erel(MeV)

s? d?

1d5/2

2S1/2

1d3/2 16

20

Study of the unbound nucleus 21C (Spokesperson: N.A. Orr/J. Gibelin)

22

Counts

/40keV

Preliminary

S.Leblond

• SAMURAI is now available – SAMURAI collaboration page

http://ribf.riken.jp/SAMURAI/Collaboration/

• SAMRUAI Day-One Experimental campaign on 2012 1. Study of unbound nuclei 25O and 26O

• Higher statistics for 26O(0+)

• New observation of 26O(2+)

2. Coulomb breakup of 22C and 19B

3. Study of unbound states of 22C, 21C, 19B, 18B • Preliminary decay energy spectra have been obtained

Summary

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