Hypernuclear large-scale analysis using

an emulsion overall scanning method

○Masahiro Yoshimoto, Kazuma Nakazawa (Gifu Univ.),

Junya Yoshida (ASRC JAEA) and a part of E07 collaborations

24 October 2018 1

新学術領域研究公募研究:少数多体ハイパー核大規模解析のためのエマルション全面探査法の高効率・高速化

J-PARC E07 experiment

24 October 2018 2

ｎｎ

ｐｐｎΞ-

X hypernucleus

ｎｎｐ

ｐΛΛ

LL hypernucleus

SSD

Emulsion Sheets

~1 mm

K+

X-

TargetK-

1.8 GeV/c

Ge detector

X-ray Ξ-Ag or Br

X-ray from X- atom

X13B,

X15C,

X17N

LL4H,

LL5He,

LL5H,

A=6~17

Experimental apparatus of E07J-PARC Hadron hall K1.8 beamline

KURAMA Magnet

TOF wall

Diamond target SSD

Emulsion module

3

Ge detector array

(Hyperball-X)

K-

Experimental apparatus of E07J-PARC Hadron hall K1.8 beamline

KURAMA Magnet

TOF wall

Diamond target SSD

Emulsion module

4

Ge detector array

(Hyperball-X)

K-

Thin ThinThick Thick

K-

1.8 GeV/c

K+

X-

Diamond

target (12C)

SSD

Emulsion

Hunting X- stop event

5

~360 predictions of X- tracks

in effective region

Beam direction

volume for readout

0.4mm Thin-type

1.0mm Thick-type

1.0mm Thick-type

~(+-200mm)2

~(+-10mm)2

Emulsion module

24 October 2018

s: 53mm s: 64mm

s: 26mrad s: 23mrad

Angular accuracy: reasonable

6

X

Y

Z

Scanning machine for the first plate

Tracks in X-Y space (1mm)2

upper layer

lower layer

track

Position accuracy: reasonable

with SSD->the first plate

24 October 2018

7

Emulsion layer

Emulsion sheet (thick-type)

track

Emulsion layer

40 μm plastic base

tracking

Objective lens

* Tracking with image processing

X- tracking in thick-type sheet

Optical microscope system

Stage

Image sensor

Objective lens(x50)

Tracking software

M.K.Soe et al., NIM-A 848 (2017) 66–72

24 October 2018

Nagara (長良) event

24 October 2018 8

ΛΛ6He

Λ5He

4He

𝑡

𝑝𝜋−

H. Takahashi et al., Phys. Rev. Lett. 87, 21 (2001).

J. K. Ahn et al., Phys. Rev. C 88, 1 (2013).

X-

μm

μm

@E373

Mino (美濃) event

24 October 2018 9

𝑝, 𝑑, 𝑡

4He

ΛΛ10Be 𝑜𝑟ΛΛ

11Be 𝑜𝑟ΛΛ12Be

𝜋−

𝑝

Λ5He

𝑝 4He

𝑡, 𝑑, 𝑝

Ekawa, H, et al. PTEP 2019, 2, 021D02 (2019)

@E07

μm

μm

Knowledge on double hypernuclei

The number of identified events is (only) two.

6ΛΛHe

Nagara event

11ΛΛBe

(most probable)

Mino event

24 October 2018 10

Λ-Λ interaction is

weak attractive,

so far…

Λ10Be

Λ

r r

ΛΛ

ΛΛ11Be

BΛBΛΛ

M(9Be) + MΛ - BΛ M(9Be) + 2MΛ - BΛΛ

DBΛΛ

BΛΛ [MeV] ΔBΛΛ [MeV]

6.79 ± 0.16 0.55 ± 0.17@E373

@E07

11

Possible interpretation BΞ- [MeV] uncertainty of BΞ- [MeV]

X- + 14N -> X15C -> L

10Be + L5He ~1.3 ± ~0.2

L5He -> 3-prong with p-

Condition:

(X-+12C,14N, or 16O) -> 2 single L hypernuclei (+ neutrons)

• Only “L10Be + L

5He” was accepted at the 1st vertex

• The decay of #1 and #2 are consistent with that of L10Be and L

5He

Measured BΞ- is significantly larger than that of atomic 3D state (0.174 MeV)

→ X hypernucleus!

IBUKI event @ E07

L10Be -> 4-prong

X-

X- + 14N → X15C X

15C → L10Be + L

5He

L10Be

ｎｎｐｐｎΞ

-L

5He decay

decay

20mm

Under preparation for publish

p-

24 October 2018

Nyaw’s Poster

Potentially detectable double hypernuclei in the

emulsion.

The visible (or detectable) events by the Hybrid method are

about 10% of all recorded events.

How can we detect the latent 1000 S=-2 system events in the emulsion?

Completely different approach from the conventional one, is necessary to search

for the entire event. No beam exposure.

= 公募研究のテーマ

24 October 2018 12

X- stop S=-2

system

Unique

identified

KEK-PS E373 ~650* 9 1

J-PARC E07hybrid method

2400 27 3

J-PARC E07

in total~105 ~1000 ??

*A.M.M.Theint, et al, . PTEP 2019, 021D01.

‘𝑛’ 𝐾−, 𝐾0 Ξ−

un triggered

triggered

‘𝑝’ 𝐾−, 𝐾+ Ξ−

un-detectableIn progress

Estimation

Double hypernuclei search by the Overall scanning

method.

Fully readout of the entire volume

of thick-type emulsion sheets.

Detecting double hypernuclei by

image recognition technique.

24 October 2018 13

Very challenging.

• Big data size. The entire data size of

microscope-image is ~100PB.

• A huge amount of vertex-like shapes.

• Difficulty of reconstructing of the events

due to the complex.

Thin ThinThick Thick

K-

1.8 GeV/cX-

Diamond

target (12C)

Emulsion

SSD

Double hypernuclei search by the Overall scanning

method.

24 October 2018 14

Approach 1:

Reconstructing the all stopping point of any

particles including X- particles in the emulsion.

Merit:

A well-established method for thin-type sheet.

First attempt for thick-type sheet.

Issue:

A huge amount of proton-stop event

Approach 2:

Detecting a cascade decay topology.

Merit :

No need to connect tracks across next sheets.

The basic concept is already proofed.J. Yoshida, et al.NIM A 847 (2017) 86–92

Issue:

Topologies of double hypernuclei are complex

Thin ThinThick Thick

K-

1.8 GeV/cX-

Diamond

target (12C)

Expected single Λ hypernuclei

Single Lambda hypernuclei are produced at the K- beam-Nucleus interaction.

~106 single hypernuclei are expected to be found totally by an estimation by

preliminary analysis of E07 emulsion sheet.

~1000 events of light single Λ-hypernuclei: 3ΛH, 4ΛH,

4ΛHe, etc.

Many heavier single hypernuclei will also be available.

24 October 2018 15

K- interaction

Single hypernuclei

@ E07

Cascade decay topology search

Our system recognizes vertex-like shapes by the following algorithm.

24 October 2018 16

J. Yoshida, et al.NIM A 847 (2017) 86–92

24 October 2018 17

Vertex cand.

24 October 2018 18

Alpha-decay cand.

Vertex

cand.

Applying Deep learning

The speed of eye-check-work limits the throughput of the Overall scanning

method.

The key is the reduction of eye-check-work

Firstly, we applied machine learning techniques to alpha decay selection.

24 October 2018 19

i-th layer

i-1

i+1

Kiso event Nagara event

12micron

12micron

80micron

140pixels

80micron

140pixels

24 October 2018 20

Double hypernuclei events

a, Alpha decay

events

b, blur

s, object on surface

t, Two or more

penetrated tracks

v, vertex

w, 2-vertex

20k images

10k images

152k images

75%

for training

25%

for validation

323k images

24 October 2018 21

OS：Ubuntu 14.04 LTSGPU：GeForce GTX 970Tool : Caffe: Deep Learning Framework developed by the BVLC

Network：AlexNetLearning time: 7.5 hours

Training

Accuracy(validation) : 96.6%

Loss (train) : 0.03

Loss (validation) : 0.13

in 2015

Training progress

24 October 2018 22

Lo

ss (

Cro

ss E

ntr

op

y)

Acc

ura

cy (

%)

For practical use of machine learning

Current achievements:

• More than 96% accuracy for typical simple shapes like alpha decay

Issue:

• Recognition of decay events of single and double hypernuclei

Future tasks:

• Recognition of complex topology.

• Validation by simulated images of hypernuclear events.

• Optimization of optics condition and machine learning.

24 October 2018 23

Precise measurement of

X- stop point

Some X- stop points are ambiguous due to

the dizziness of the track.

The shown event is identified

X- + 14N -> 9ΛBe + 5ΛHe + n

by kinematic analysis

When releasing neutral particles, the stop

point cannot be estimated kinetically.

Therefore, the uncertainty of BX is quite large,

3.5 MeV, due to the ambiguity of the stop point.

Precise measurement is essential to measure BX-

24 October 2018 24Kasagi’s Poster

X-

X-

9ΛBe

5ΛHe

0.2 mm~40 mm

245 mm

245

mm

10 mm

10 m

m

t = 0.22 mm

x

y

x

z

x

y

swelling

stripping

slicing

t = 0.45 mm

x

z

t=

0.4

5 m

m

>

> <

<

E373-T3

Detection of X- capture point

24 October 2018 25

Beyond the optical resolution

• The resolution of hard X-ray microscope at Spring-8 is 70 nm, which is

4 times higher than the optical microscope.

• Nondestructive tomography imaging is possible because of the high

transmittance.

24 October 2018 26FY2013 M. Yoshimoto Master thesis

Optical microscope Hard X-ray microscope

Fully automated readout system Vertex Picker

24 October 2018 27

Achieve 10x readout speed and

readout the all E07 emulsion sheets within two years

Field of view 110 μm x 140 μm

Framerate 60 fps

300 μm x 300 μm x6

170 fps x3

Summary

• More single and double hypernuclei are necessary as much as possible to

understand baryon-baryon interaction and hadron cluster including hyperon.

• 103 double hypernuclear events from ~105 X- absorption at rest and

106 single events are potentially detectable in E07 emulsion sheets.

• In this program, we will detect a huge number of the latent events in

emulsion by overall scanning method.

• The key issue is the reduction of eye-check-work using machine learning.

• Development of faster scanning system, track reconstruction of all stopping

particle, and precise measurement of vertices at super-fine-resolution.

24 October 2018 28