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Search for multi-neutron system in extremely neutron-rich nuclei
Tokyo Institute of Technology
第4回クラスター階層領域研究会プログラム, online, 2020.05.28
He Wang
Content
• Motivation
• Experiment details
• Status
• Summary
New insight for hierarchyGalaxy1021 m
Material10-1 m
Molecule10-9 m
Atom 10-10 m
Nucleus10-14 m
Hadron10-15 m
Electron <10-18 m
Quark<10-18 m
• Nucleus + neutron cluster
• Connection between different hierarchy
Possible multi-neutron systems
n n
S=0
2n Halo Nuclei?
9Li
11Li
n
n
S2n=0.37MeV2n weakly-unbound nuclei?
24On
n26O
S2n= -0.018(5) MeV
Y. Kondo et al., PRL116,102503(2016).T.Nakamura et al., PRL96, 252502 (2006).
Tetra-neutron
Di-neutron
K. Kisamori et al., PRL. 116, 052501
• T=3/2 3NF?• Too strong attraction of 3NF,
which makes 4H bound• More experimental evidence
E.Hiyamaet al., PRC 93(2016)044004
Search exotic neutron cluster• Nuclei beyond neutron drip-line, 10He (4He and 6 neutrons) • (p,2p) reaction to access • Intense neutron-rich 11Li beam and advanced RI facility (SAMURAI) at RIBF
Di-neutron as new building blocks for nuclear structure? Existence of Tetra-neutron, Hexa-neutron?
10He
10He N
Z
11Li(d,3He)Invariant massof 8He+2n
11Li(p,2p)Invariant massof 8He+2n
14Be(CH2,X)Invariant massof 8He+2n
11Li(p,2p)Missing massTagged with 8He
11Li(d,3He)Missing massTagged with 8He/6He
8He(t,p)Missing mass
Deviations in previous measurements of 10He
Threshold
• g.s. ~1.4 MeV• Excited states:
Controversial
Experimental method• (p,2p) for neutron-rich nuclei• Missing mass method
p
p
p detector
p detector
Multi neutrons
p
10He11Li
~200MeV/u
4He
• Momentum and energies of two recoiled protons• To reconstruct mass and excitation energies for 10He
SRC
IRC
fRC
RRC
RILACECR
CSMGARIS &GARIS2
AVFRILAC2
RIPS
BigRIPS
ZeroDegreeSAMURAI
SHARAQ
SCRIT
KISS
SLOWRI
Rare RI Ring
RI Beam Factory @RIKEN
11Li
11Li 200MeV/u
NEBULA
n
2.9 Tesla
SAMURAI MAGNET
n
PDC1/2HODP
FDC24He
6He, t 8He
To tag recoiled proton in (p,2p)Angle and energytracker and total E detector
Experimental setup
Approved Construction proposal @ RIBF NP1812:Large-acceptance missing mass setup, CATANA PLUS and STRASSE at SAMURAISpokespersons: Takashi Nakamura (TiTECH) and Alexandre Obertelli (TU Darmstadt)
1) Missing mass spectroscopy (p,2p) and (p, p𝛼𝛼) 2) Missing mass + High resolution 𝜸𝜸-ray spectroscopy
SRASSE and CATANA plus• STRASSE: Silicon tracker • CATANA plus: Total energy detector
1) Missing mass spectroscopy (p,2p) and (p, p𝛼𝛼)
SRASSE and PFAD• STRASSE: Silicon tracker • CATANA plus: Total energy detector
Thin CH2 target for high resolution
• PFAD: Prototype• 1/3 Si trackers
PFAD: Prototype For Advanced Detector
Hamamatsu SSSD from Dr. Sasano, RIKEN
1/3 Si Tracker
1st inner layer SSD
49.1
mm
49.1
mm
76.8 mm
76.8 mm
Daisy chain
Bound 2 strips into 12nd inner layer SSD
Total channel:405416 SSD and 32 STS-XYTER chips
30mm 33mm
53mm
50mm
0.1mm CH2 target
Effective area: 49.1 mm ✕ 76.8 mm Thickness: 50𝝁𝝁m inner layer
100 𝝁𝝁m outer layer)Pitch size: 100 𝝁𝝁m
T. Tomai (TiTech) and R. Gernhaueser (TUM)
PFAD: Supporting frame
Cesium iodide Array for γ-ray Transitions in Atomic Nuclei at high isospin Asymmetry Originally designed for γ-ray calorimeter: 200ch CsI(Na) Planned
CATANA plus
p
p
Plus
Current CATANA L4-L8
Current CATANA plus
Channels 100 140Layers L4-L8 L2-L8Angle coverage [deg]
40-71 14-71
2p efficiency [%] 18 51
p
p
CATANA plus95 mm
105mm
125mm
138mm 148
mm
60Co~8% (FWHM)
N. Ebina, Bachelor thesis
• Test on prototype CsI for L2 and L3• Ready by 2020.12
2p coincidence eff. ~7.% Resolution: 0.7 MeV (𝜎𝜎)
11Li(p,2p)10He @ 200 MeV/uSimulation results
PFAD and CATANA plus: Efficiency and Resolution
10He
H. Liu (TU Darmstadt) and T. Tomai (TiTech)
Physics program at SAMURAI using (p,2p) reactions:2) High resolution γ-ray spectroscopy
STRASSE+ CATANA + LH2 target+High resolution gamma ray tracking detectors
Perspective
Summary
• Search for multi-neutron state in 10He
• Approved experimental program at RIBF, RIKEN
• Development on new device for (p,2p) with missing massSTRASSE/PFAD and CATANA plus
• TU Darmstadt: A. Frotscher, H. N. Liu, A. Obertelli, Y. L. Sun • TiTech: N. Ebina, Y. Kondo, T. Nakamura, T. Tomai, H. Wang• TU München: R. Gernhaueser, B. Michael• RIKEN: H. Otsu, M. Sasano, T. Uesaka• Rikkyo U.: Y. Togano• GSI:J. Haueser, C. Schmidt• LPC: F. Flavigny
Collaborators
Thank you
20
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