1. Breakup reactions of one-neutron halo nucleus 31Ne
Tokyo Institute of Technology
RIKEN Nishina Center
Takato TOMAI

2. Collaborators
Collaborators T. Tomai,A,C N. Kobayashi,B T. Nakamura,A Y. Togano,Q Y. Kondo,A S. Takeuchi,E A. T. Saito,A T. Ozaki,A A. Hirayama,A M. Yasuda,A H. Yamada,A T. Kobayashi,D S. Koyama,E S. J. Kim,F J. W. Hwang,F H. Otsu,C Y. Shimizu,C N. A. Orr,G J. D. Gibelin,G T. Aumann,H H. Sato,C P. C. Doornenbal,C H. Baba,C T. Isobe,C N. L. Achouri,G M. Marques,G F. L. Delaunay,G Q. Deshayes,G A. Revel,I O. Sorlin,I V. Panin,C I. Gašparić,J H. T. Törnqvist,H S. Y. Park,K I. K. Hahn,K Y. Kubota,C M. Sasano,C L. Stuhl,E D. H. Kim,K M. Matsumoto,A M. Parlog,G D. M. Rossi,H L. Atar,H S. Lindberg,L J. Kahlbow,H S. Paschalis,M S. Sakaguchi,N R. Reifarth,O L. Mullay,C F. Browne,P M. L. Cortes Sua,C S. D. Chen,C J. SteinhauserA
Institute TokyoTechA, Osaka U. RCNPB, RIKEN Nishina centerC, Tohoku U.D, U. Tokyo CNSE, Seoul N. U.F, LPC-ENSICAENG, GSIH, GANILI, IRBJ, Ewha W. U.K, Chalmers U. T.L, U. YorkM, Kyushu U.N, U. FrankfurtO, U. BrightonP, U. RikkyoQ

3. 31Ne? 31Ne Island of inversion What are revealed? Separation EnergyZ
31Ne
neutron
What are revealed? N
N=20+1 1n p-wave dominant halo (Jπ=3/2-)
Large interaction cross section
Low separation energy: Sn= MeV
Small spectroscopic factor: C2S(0+;2p3/2)=
7/2-
First, why we focused on Ne31?
核図表 ３１Neの場所 逆転の島 p wave halo 特徴
でもseparation energyとspectroscopic factorは間接的な見積もりだよ
Here, this is the nuclear chart, and island of inversion is shown here.
In the island of inversion, it is known that the nuclei have some features.
One is that the energy gap of N=20 become narrower, thus the configuration of neutron is changed into 2 particle 2 hole like this.
Ne31 is located at south shore of island of inversion. Ne31 has neutron number 20+1 and last 1 neutron is halo nuclei, with its spin and parity 3/2-, not f 7 half.
And there are 3 features, first, large interaction cross section, second, low separation energy Sn=0.15 MeV, and third, small spectroscopic factor C square S = 0.32.
However these values are indirect estimation, so we have to determine them precisely.
From:
Inclusive Coulomb breakup reaction cross section (Pb target)
Nuclear breakup reaction cross section (C target)
Interaction cross section (C target)
Separation Energy
Spectroscopic factor
→ Indirect estimation
[1] T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 103, (2009)
[2] M. Takechi et al. Phys. Lett. B 707 (2012) 357
[3] T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 112, (2014)

4. Previous work: Inclusive measurement 31Ne + Pb → 30Ne + X
Not
measured
C2S
High-Z C
Sn (MeV)
Estimated from “integrated” cross sections
Compared with some theoretical model (SM etc.)
タイトル 図の説明 比較です、 PbとCからこうなります、 微分断面積が必要だよね
So I introduce the previous work, which is inclusive measurement.
The reaction is shown as this picture. Incoming beam of Ne 31 reacts with lead target, and then breakup into Ne30 and neutron.
In inclusive measurement, we do not measure this emitted neutron. So we only obtain integrated cross sections. Comparing the integrated cross section with theoretical result such as shell model and equivalent photon method and so on, we can estimate the spectroscopic factor and separation energy like this. In this figure, the red line corresponds to Lead target and blue line corresponds to carbon target.
So this is the Estimated value so
Need “differential” cross sections
[1] T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 103, (2009)
[2] M. Takechi et al. Phys. Lett. B 707 (2012) 357
[3] T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 112, (2014)

5. Exclusive measurement: Coulomb breakup reaction 31Ne + Pb → 30Ne + n
p30Ne
E30Ne
Invariant mass
Erel , Ex pn En
E1 strength
Halo: Soft E1
GDR
Equivalent photon method
~1 MeV
Exclusive measurement
同様にPb標的で反応させます 今度は中性子も測ります
そうすると運動量とエネルギーから不変質量が求まり、微分断面積が出せます
ここでEq photon meth.を使います
Photon numberかける E1 strengthで求まります
さらにE1 strengthはspectroscopic factorとinitial stateで書けます
図の説明 ハローではSoft E1が見られます
Virtual photonをかけるとソフトE1がenhanceされます
ハロー構造がdiff. cross sectionからわかります
Photon number × E1 strength
Photon num. (log)
dσ/dEx
Enhance Soft E1
[4] C. A. Bertulani, G. Baur, Phys. Rep. 163, 299(1988).
Ex (MeV)

6. Coulomb breakup reaction as a probe of halo structure
Example: Coulomb breakup of 19C
E1 strength
Different shape by
Separation energy
neutron orbital
spectroscopic factor
Virtual photon num.
19Cの例を示します
左の図の説明(軸、線の説明)
Snと軌道とC2Sによって違うよね
決定できるね！
Spectroscopic factor
Equivalent photon method:
Sn, l
[5] T. Nakamura et al. Phys. Rev. Lett. 83, 1112 (1999)

7. Experimental setup: BigRIPS @ RIBF
Superconducting
Ring
Cyclotron
Plastic 0.5mm×2
Primary beam
48Ca 345 MeV/u
Plastic 3mm
Ionization
Chamber F5
Primary target
Be 15mm ΔE
実験はRIBFでやりました
Ca48
Be標的
31Neカクテルビームを生成
BigRIPSで分離識別(Separated and identified)
SAMURAIに送られる
プラスチックとionization chamberからBrho, TOF, Delta Eを測り、粒子識別する
This experiment carried out using RIBF, RIKEN.
The experimental setup of BigRIPS is shown here.
Ca48 accelerated by SRC, reacts at the Be primary target. Then it produce cocktail beam including Ne31.
Plastic scintillators are located at F3, F5, F7 and F13. From F5 position, the magnetic rigidity is observed. And from F7 and F13 time, Time of flight is calculated.
And also an ionization chamber is located at F13. This determines the energy loss.
Then the secondary beam is transported to SAMURAI area.
Using these formula, particle identification has been done like this.
The horizontal axis is A/Z and vertical axis is Z. the Ne31 is here, and the intensity was around 50 counts/second. F3
Secondary beam
31Ne 240 MeV/u Bρ F7
F13
TOF
SAMURAI
Particle
Identification

8. Experimental setup: BigRIPS @ RIBF
33Na
Superconducting
Ring
Cyclotron
Superconducting
Ring
Cyclotron
31Ne
~50cps
Plastic 0.5mm×2
Primary beam
48Ca 345 MeV/u
Plastic 3mm
Plastic 3mm
Ionization
Chamber F5 F5
Primary target
Be 15mm
29F ΔE
粒子識別の結果
31Neはここ、10倍の強度を達成
他にも33Naや29Fが入っている F3 F3
Secondary beam
31Ne 240 MeV/u Bρ Bρ F7 F7
F13
TOF
SAMURAI
Intensity: 10 times higher than previous work

9. Experimental setup: SAMURAI @ RIBF
Plastic array
Neutron detectors
CsI(Na) array
γ-ray detector
CATANA
Plastic
0.5mm×2
NeuLAND
NEBULA
SAMURAI
Dipole Magnet
@ 2.9 T n
(TOF)
31Ne
~240 MeV/u
SAMURAIエリア
31Neは標的で反応して分解する
Charged
MWDCとHODF24で検出される
NeutronはNeuLANDとNEBULAで検出される
ガンマ線はCATANAで検出される
This is the experimental setup of SAMURAI area.
Incoming Ne31 reacts on carbon target or lead target. Emitted gamma-rays from excited energy are detected by gamma-ray detector CATANA.
Outgoing charged particles are changed the direction by SAMURAI dipole magnet at 2.9 tesla, and detected by 2 MWDCs and plastic array HODF24.
The magnetic rigidity is calculated from MWDCs, and TOF and Energy loss are calculated from HODF24.
Outgoing neutrons are detected by neutron detectors NeuLAND and NEBULA.
C target: 2.15 g/cm2
Pb target: 2.76 g/cm2
MWDC
(Bρ)
30Ne
Plastic array
HODF24
(TOF, ΔE)
Charged particle detectors

10. Result 1/4: Inclusive cross sections
Preliminary
PID of reacted particles (31Ne gated in upstream)
30Ne
C target (mb)
Pb target (mb)
31Ne→30Ne
89(3)
674(28)
Previous work
90(7)
720(61)
31Ne (beam)
図の説明
31Neビームにゲート、30Neはここ
Cross sectionはこの表のようになった、consistent
This is the result of particle identification at SAMURAI and inclusive cross sections.
Left figure shows the particle identification of this reaction, gated Ne31 incoming beam.
Here you can see the Ne30, reaction residual.
And right table shows the inclusive cross sections for each target.
This result is good agreement with previous work.
I will talk about Coulomb breakup reaction today.
Consistent with previous work
[3] T. Nakamura, N. Kobayashi et al.
Phys. Rev. Lett. 112, (2014)

11. Result 2/4: Exclusive diff. cross section of Coulomb breakup reaction
Preliminary
Pb(31Ne,30Ne+n) → Coulomb breakup spectrum
Nuclear breakup
component
[6]
Lead target
Carbon target ×Γ
Result 2
Pbスペクトルからcoulomb成分を導出
Pbにはnuclear成分が入っているのでCから見積もる
ΓはPbとCの核力成分の比で、3.86を使う
左の図: PbとCのスペクトル
右の図: Cを差し引いたもの
積分地は下のようになる
Integral 0–5 MeV: 479(18) mb
For Lead target
Integral 0–5 MeV: 392(18) mb
For Coulomb breakup
[6] K. Yoshida et al., Prog. Theo. Exp. Phys. 2014, 5, 053D03

12. Result 3/4: Excited state component of Coulomb breakup reaction
Preliminary
How is excited state component of 30Ne(2+) ?
31Ne + Pb → 30Ne + γ + n 2+ γ
Lead target
Exclusive (mb)
(require n)
Integral Erel=0-5MeV
31Ne→30Ne(total)
479(18)
31Ne→30Ne(2+)
136(24)
31Ne→30Ne(0+)
343(30)
Ratio( 0+ : 2+)
72(6)% : 28(5)%
31Ne
30Ne+n
励起状態の成分の見積もり、波動関数でいうとここに対応
Γ線を使って見積もる
クロスセクションは次のようになった
We assumed that there is only 1 components for Coulomb breakup reaction, however there is also excited state component in Coulomb breakup reaction in fact, so the wave function can be written like this.
Let’s focus on this component in this slide.
The left figure shows the gamma-ray spectrum of this reaction. You can see 1 peak corresponding to 1st excited state of Ne30.
The red curve is its response function.
From this fitting, we obtained the cross section of 2+ component for Lead target. This row is inclusive cross section and this row is integrated exclusive cross section.
30Ne(2+)
792 keV

13. Result 4/4: 1n separation Energy and spectroscopic factor
Preliminary
Fitted with 2 curves (30Ne(0+) 2p3/2 + 30Ne(2+) 2p3/2)
72%
28%
Sn (MeV)
C2S (30Ne(0+);3/2-)
C2S (30Ne(2+);3/2-)
This work
0.30(1)+sys.
0.32(1)+sys.
0.41(2)+sys.
Prev. work
---
SDPF-M
0.21
0.34
Total
30Ne(0+) 2p3/2
最後、分離エネルギーとC2Sを見積もる
スペクトルを0＋成分と２＋成分で、比を固定してフィッティング
０＋は赤いdashedで２＋は青いdashed
結果はこの表のようになった
これはdouble component haloであることを示している
We determined the 1 neutron separation energy and spectroscopic factor using this function, shown in previous slide.
This figure shows the coulomb breakup cross section, and the red curve corresponds to this formula.
From this fitting, we obtained Sn=0.3 MeV and Spectroscopic factor=0.39.
This result agrees with previous work.
30Ne(2+) 2p3/2
[3]T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 112, (2014)
Consistent with previous work
 double component halo 0+ 2+

14. Summary
We carried out the nuclear/Coulomb breakup reaction of 31Ne using SAMURAI at RIBF
Determined Coulomb breakup reaction differential cross section:
Preliminary result of 1n separation energy and spectroscopic factor
Future: Determine systematic errors
Sn (MeV)
C2S (30Ne(0+);3/2-)
C2S (30Ne(2+);3/2-)
This work
0.30(1)+sys.
0.32(1)+sys.
0.41(2)+sys.
Prev. work
---
さまりー

15. Purpose 1: Configuration of ground state using Coulomb breakup reaction 31Ne + Pb → 30Ne + n
Our experiments have 2 purposes.
First, observation of ground state using Coulomb breakup reaction.
This figure shows the schematic diagram.
A Ne31 is incoming with 240MeV/nucleon. When it passes near by Lead target, Ne 31 feels strong electric field. This can subscribe as absorption of virtual photon, and then breakup into Ne30 and neutron.
The differential cross section is shown in this formula. C square S is spectroscopic factor, N of Ex is virtual photon number and this part is E1 strength. Here (r) it includes the distance between Core and neutron, so this is sensitive to halo structure.
And also it is Depending on 1 neutron separation energy Sn and angular momentum l, so we can determine the halo structure.
Spectroscopic
Factor
Virtual Photon Num.
Distance (Core-n)
Depending on 1n separation energy Sn and angular momentum l
Determination of 31Ne halo structure

16. Purpose 2: Observation of deformation using nuclear breakup reaction 31Ne + C → 31Ne* → 30Ne + n
Excited energy can be calculated using this:
Second, purpose 2 is the observation of deformation using nuclear breakup reaction.
In this experiment, we used carbon target.
Incoming beam of Ne31 is excited by carbon target. The excited states are unbound because of low separation energy, so Ne31 breakup into Ne30 and neutron.
The excited energy can be calculated using this formula.
So we can determine the unbound excited state and compare with rotational band.
Observation of unbound excited state
Comparison with rotational band

18. Excited state component of Coulomb breakup reaction
Preliminary
How is excited state component of 30Ne(2+) ?
31Ne + Pb → 30Ne + γ + n
Lead target
Inclusive (mb)
(not require n)
Exclusive (mb)
(require n)
Integral Erel=0-5MeV
31Ne→30Ne(total)
674(28)
479(18)
31Ne→30Ne(2+)
234(30)
136(24)
31Ne→30Ne(0+)
440(41)
343(30)
Ratio(2+/0+)
53%
40%
We assumed that there is only 1 components for Coulomb breakup reaction, however there is also excited state component in Coulomb breakup reaction in fact, so the wave function can be written like this.
Let’s focus on this component in this slide.
The left figure shows the gamma-ray spectrum of this reaction. You can see 1 peak corresponding to 1st excited state of Ne30.
The red curve is its response function.
From this fitting, we obtained the cross section of 2+ component for Lead target. This row is inclusive cross section and this row is integrated exclusive cross section.
30Ne(2+)
792 keV

19. 1n separation Energy and spectroscopic factor (I)
Preliminary
Fitted with theoretical curve (assuming β=0):
Sn (MeV)
C2S (30Ne(0+);3/2-)
This work
0.306(26)
0.39(3)
Previous work
We determined the 1 neutron separation energy and spectroscopic factor using this function, shown in previous slide.
This figure shows the coulomb breakup cross section, and the red curve corresponds to this formula.
From this fitting, we obtained Sn=0.3 MeV and Spectroscopic factor=0.39.
This result agrees with previous work.
T. Nakamura, N. Kobayashi et al. Phys. Rev. Lett. 112, (2014)
Consistent with previous work
Fitting was NOT perfect