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

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