Direction Sensitive Direct Dark Matter Search with
Super-High Resolution Nuclear Emulsions
KMI, Nagoya University
Tatsuhiro NAKA
on behalf of the NEWSdm collaboration

KMI2017, 5-7 Jan., 2017 (presentation : 6th, Jan.) @ ES hall, Nagoya University

1

Dark matter problem for various scale of universe
Global scale

Local scale
Gravitational lensing

DE

Dark Energy(68%)

Structure formation

Dark Matter(27%)
Ordinary matter
(5%)

DM

Planck 2013 results
BaryonPlanck 2013 results

High precision CMB measurement(WMAP, Planck) and relatedcosmology(1898-1974)
Fritz Zwicky(1928 - 2016 )Vera C. Rubin et al., Asro.phys.

Zwicky, F. (1933), Helvetica Physica Acta 6: J., 225:L107-111, 1978t110127, Bibcode:1933AcHPh...6..110Z

2

Dark matter property
 Thermal process☑ weak coupling and the massscale ⇒ WIMP dark mattere.g., SUSY, KK ・・☑ Difference of structure formation of galaxy
between observation and simulation⇒ warm dark matter (sterile neutrino ?), SIMP darkmatter Non-thermal process☑ Axion⇒ solution to “strong CP problem
Other discussion☑ self-interacting dark matter [ e.g., Abell3827, MNRAS 449 (2015) 3393 ]☑ AMS anomaly

2 x 10-26 cm3/s
ΩDM~<σ v>

Phys. Rev. D 86, 023506(2012)3

Approach of Dark Matter Search
Axion dark matter

warm dark matter

WIMP dark matter

 Strong CP problem for QCD
 Axion is derived by “PQ symmetry”
breaking

 Lighter mass particle with bit
larger velocity dispersion
e.g., sterile neutrino

Expected Mass ~ 100 µeV/c2

Anomaly of short base-line experiment isincompatible from dark matter becauseof too high mixing angle

 Weak scale from thermal relicabundance Massive particle as cold dark matter Encourage from some beyond SMtheory

Lattice QCD [Nature 593 (2016) 69-71]
Cosmology include topological defect[ Kawasaki + , PRD 91, 065014 (2015) ]aγγ
Primakoff processγ

μeV/c2

ν1
meV/c2W

W

ｌkeV/c2

Dark Matter mass

ν2

χ

Indirect detection

χ(LHC, Belle etc.)

Direct detection

GeV/c2SM(Fermi, AMS etc.)

Accelerator

SMTeV/c24

Dark Matter in the Milky Way galaxy

solar system

only visible

Astrophys. J. 295: 422-436, 1985

Local dark matter density : 0.3-0.5 GeV/cm3
 This value is independent on dark matter model Very much mount of DM is condensed in the halo because mean dark matter density in theuniverse is ~ 1.4 keV/cm3 (27 % of critical density ratio)

Dark matter flux on the earth ~ 100000 /cm2/sec @ 100 GeV/c2 dark matter
5

Dark matter wind
( from Cygnus ）Detection principle

Annual Modulation2 – 3 % variation

Diurnal Modulation
0.1 – 0.01 % variation

This is impossible for current technologies.
6Kinematics of direct DM detection
Dark Matter halo distribution

WIMP dark matter detection
Dark matter

Dark matter

Local dark matter density :0.3-0.5 GeV/cm3

Unknown parameter
And particle model dependenc

Target nuclei

keV scale energy
Nuclear recoil
Detection asIonization
PhononLight

Unknown parameter

Form factor effect to momentum transfer

Target and detector dependence Nuclear form factor
 Quenching factor⇒ it’s important for cross section andenergy reconstruction

7DAMA/NAI and DAMA/LIBRA

9 σ significance [1.17 ton・year]

CoGeNT

Counts/30 days New search with different systematics
 Same detector with DAMA and search on southern hemisphere( SABRE, DM-ICE, PICOLON)
 More detail understand of detector and background in such very lowenergy response
DAMA : May 26th +- 7 days
Around 10 GeV mass region is very chaotic, and5.7 σ difference
other detectors are also just around energy
Muon by BOREXINO
threshold
Coherent scattering due to neutrino is July 7 +- 6 days
( June 29 +- 6 days)
final boundarXiv:1204.5180v38

Dark matter wind
( from Cygnus ）Direction sensitive search< 1 µm length insolid or liquid

Annual Modulation2 – 3 % variation

Diurnal Modulation
0.1 – 0.01 % variation

Directional detection(= detection as track)9Direction Sensitive detector

CYGNUS community

GaseousDetector
DRIFT
DMTPC

Solid detector
NEWSdmD3

Typically target mass scale ~ 10-100 g with lowpressure CF4 gas
MIMAC
NEWAGE+ Spin-dependent interaction searchHigh pressure Xe gas

Future project toward high scale + modelindependent directional search
ZnWO4Not demonstration yetfor low-velocity atom White paper : “ The Case For a Directional Dark Matter Detector And Status of Current
Experimental Efforts “, Int. Ann. Mod. Phys. A, Vol.25, No.1 (2010) 1-51
 Readout technology paper : “Readout technologies for directional WIMP Dark Matter detection“, Phys. Rep. Vol.662 (2016) 1-46

10

The NEWSdm Collaboration[Nuclear Emulsions for WIMPs Search with directional measurement]

Japan
Chiba
NagoyaRussiaLPI RAS Moscow
JINR Dubna
SINP MSU Moscow

Italy
Bari
LNGS
NaplesRomeTurkey
METU Ankara
arxiv.org/pdf/1604.04199v1.pdf

http://news-dm.lngs.infn.it

11Potential of Directional Sensitive SearchcygnusLikelihood ratio

SignalBackgroundNobs = 10101001000

WIMP mass [GeV/c2]

Direction information : Several 10 events
Gain of 100 times

Annual modulation : Several 1000 events

Likelihood ratio

Gaussian distribution Flat distribution

SignalBackgroundNobs = 100
12WIMP mass [GeV/c2]

Nuclear Emulsion [detection principle]
Charged particle
Ag coreSilver grain

electron-Developing
dissolved

Silver halide crystal (AgBr・I) in the polymer (gelatin)⇒Tracks are read out by microscope Spatial resolution ⇒ crystal size and the density
100 µm Sensitivity crystal ⇒ crystal size, deepness of electron traps, stability of latentimage specks
13Nuclear Emulsion [detection principle]
Charged particle
Ag coreSilver grain

electron-Developing
dissolved

Silver halide crystal (AgBr・I) in the polymer (gelatin)⇒Tracks are read out by microscope Spatial resolution ⇒ crystal size and the density
 Sensitivity crystal ⇒ crystal size, deepness of electron traps, stability of latentimage specks
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Nuclear emulsion [production]
That have been started since 2010 by support of KMI
 Self-production of device by scientists
 Now, this place is operated as the center for nuclear
emulsion users
This project is pioneer of that.

500nm

500nm

T. Naka et al., Nucl. Inst. Meth. A 718 (2013) 519-521

500nm

x1 scale machinex 3 scale machine

Install2010

2014

one batch scale~ 100 g device~ 300 g device

Cost per batch~ 10 K Yen~ 30 k Yen

Purpose

R&D, DM search

Mass production

Kobe Univ., Toho Univ., Univ. of Tokyo, Bern Univ. and others
for neutrino physics, cosmic-ray, muon tomography and other15motivationFine-grained Nuclear Emulsion[ Nano Imaging Tracker: NIT]NIT series
UNITNIT

NIT-60Device density : 3.3 +- 0.1 g/cm3
Elemental composition of NIT
Mass fraction

Atomic Fraction

Ag

0.44

0.10

Br

0.32

0.10

I

0.019

0.004

C

0.101

0.214

O

0.074

0.118

N

0.027

0.049

H

0.016

0.410

S< 0.001< 0.001

AgBr crystal size [nm]
 Elemental analyze
 SEM-EDX
 content for added chemical16

Electron microscope image

1 um

1.2

detected / exposed

Low-velocity ions trackingfor NIT device

Intrinsic potential for NIT device
Tracking efficiency

10.80.6
0.4

0.20Sensitization : Halogen-Accepter sensit.
Using Na2SO3Development : Low-temp standard MAA

Angular resolution of 1σ [rad]

020

0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
04060
Energy [keV]

80

100

Angular resolution
Scattering + crystal effect

Only scattering

0204060
80
Carbon Energy [keV]10017

New scanning system for nano-imaging tracking
PTS-2

alpha-ray track in the NITFirst system with epi-illuminateoptics High contrast image tosmall Ag grain New optical informationsuch as Plasmon resonance

Nagoya University
50 µm

Napoli University

Algorism was proposed by18
M. Kimura and T. Naka, NIMA 680 (2012)12

1st scanning High speed scanning Rough candidate events selection

2nd scanning Pinpoint scanning Rejection of accidental leakage
 Contaminated dust rejection using
image processing

3rd or more scanning High level analysis using cutting-edge
technologies
 Plasmon analysis

Minor [pix]Analysis Flowγ/β events are expected tobe distributed around
Ellipticity of one.

ex) Elli 1.25
Elli 1.0(events cannotexist in grayregion)

C 60 keV

Major [pix]Direction sensitive efficiency :~ 20-30 % @ 60 keVIntrinsic potential⇒ further tuning is needed because it has
dependence of chemical development and opticalcondition

Angular resolution :~ 0.5 rad. @ 60 keV⇒no so large dependence for energy

Accidental leakage event :~ 1 % spherical noise ⇒ to be rejected in 2nd scanning

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Roadmap of scanning system for nano-scale tracking
3[ PTS2 ] 40 g/y (current system)

Scanning speed [ kg/year]

Just started toconstruct
3[PTS3a] 120 g/y expected (x 3 higher than PTS2])⇒ Wider FOV due to higher vision camera
12.52[PTS3b] 500 g/y expected⇒ PTS3a + large DOF system
2020-

PTS4
2019 PTS3b’

0.5

1.51

2018PTS3b0.12

0.5

0.040-2016

1

2017-

[PTS3b’, PTS4] 1000 - 3000 g/y expected⇒ PTS3b + custom special lens, high framerate

2017PTS3a-2016
PTS2now

2018-2019 -202020

New Information for readout⇒ Localized surface plasmon resonance + + + +----

Light of microscope(electromagnetic wave)++++--- Nuclear recoil tracks havevery complicate structure
Dipole-moment of free electron in the nano metaric
with silver nano-particle
particle ( )   m ( ) This is very unique structurep  4 m a 3 1E0
 1 ( )  2 m ( )for that such as high dE/dx
particles 1 (l )  2 m (l )  0

300 nmInformation of nano-scale structure is extremely
important for discrimination from various backgrounds⇔ optical resolution : ~ 230 nm⇔ electron microscope : not realistic for actual
analysis by that strong limitation

 Resonance wavelength has visible region for several 10 nm silver⇒just good size for the tracks of NIT emulsion
45 nm depends on shape
60 nm
85andnm the size
 Dipole momentof nano-particle⇒ strong dependence on resonance peak and polarization21

New Information for readout⇒ Localized surface plasmon resonance Nuclear recoil tracks havevery complicate structurewith silver nano-particle
 This is very unique structure
for that such as high dE/dx
particles
300 nm++++--------++++

Dipole-moment of free electron in the nano metaric
particle3  1 ( )   m ( )p  4 m a

 1 ( )  2 m ( )E0

 1 (l )  2 m (l )  0

Information of nano-scale structure is extremely
important for discrimination from various backgrounds⇔ optical resolution : ~ 230 nm⇔ electron microscope : not realistic for actual
analysis by that strong limitation

 Resonance wavelength has visible region for several 10 nm silver
http://huransugo.cocolog⇒just good size forthe tracks of NIT emulsion
nifty.com/photos/uncategorized/2009/10/11/p1030930.jpg
45 nm
60 nmnmthe size
 Dipole moment depends on shapeof nano-particle85and⇒ strong dependence on resonance peak and polarization 22

Color information of signal in the NIT emulsion

Next new readout information to confirm
the signal
Color information of recorded events
 polarization dependence information
2μm

Polarization light dependence

Polarizer angle

 Particle ID (especially, electron and nuclear
recoil) contaminated noise identification
 super-high resolution⇒ improve the threshold (low-mass region search) Collaboration with computer scientist (Yandexin Russia)⇒ cutting-edge technologies for computer science
New system is under construction

23

Study for sensitivity with our detector
110 kg・y 90 % C.L. limit

0.90.8zero background caseNo directionality

Efficiency

0.7
0.6

Direction sensitivity
w/o threshold

0.5

Current crystal sensitivity w/oreadout loss

0.4
0.3
0.2

Not enoughcalibrated yet

0.10020406080
Recoiled energy of carbon [keV]100

 Sensitivity will be improved with direction information
 Readout loss will be improved by upgrade of optics
24

Intrinsic Backgrounds
1. Intrinsic radioactivity⇒ mostly understand using
mass-spectrometry and Ge
detector

2. Intrinsic Neutron emission⇒ Simulation using measured dataof radioactivity in the current device

U-238

Th-232

K-40

Ag-110m

C-14

1st prototype
device27669020(~400)

24000

Current device~27~635(~400)

24000

Ultra-low BG
device1-10~1< 35(~400)< 100

3. Dust contamination[ mBq/kg]
Process

SOURCE simulation [/kg/y](α, n) from 232Th chain

0.12 +- 0.04

(α, n) from 238U chain

0.27 +- 0.09

Spontaneous fission

0.8 +- 0.3

Expected nuclear recoil
tracks of > 100 nm +directionality

Total flux

1.2 +- 0.4

0.03- 0.05 /kg/y⇒ need to understand the source,
purification and discrimination by analysis
A. Alexandrov et al., Astropart. Phys. 80 (2016)16-2125

Pilot-run environment and shield
Gran Sasso underground laboratory, Italy

N2 gas
N2 gasPolyethren block
Refrigerant
Thermo-sensor

New site : Detector making
 Chemical treatment
 Clean roomNow on construction

Cooling system for NIT ~ 2 memulsion film installation

Pb block
Sheild design26

New potential of NIT detector toward large scale experiment[ cryogenic NIT emulsion device]
New phenomena in cryogeniccondition(around liquid N2 temperature)electron-Ionization

Ag corehole+
AgBr crystal

40 nm
Usual detection mechanism is ionization
LN2
Luminescence
due to radiation

Light

stal

PhotoluminescenceTime resolution and position self-trigger
Poster presentation at KMI2017 (no. 28) by Hiromasa Ichiki +Phonon

KrC

electron rejection power :better than 10-9 for cryogenic
90% C.L. device
27 2016
M. Kimura et al., Nucl. Inst. Meth. A (VCI2016)

Summary and schedule

Main study We need new method, technologies and information to break through current dark mattersearch situation.
 Directional dark matter search is one of the promising method for that
 NEWSdm collaboration propose the experiment using super-high resolution nuclear
emulsion (Nano Imaging Tracker: NIT) , and study toward large scale directional search.
 First demonstration about the capability of detecting the nuclear recoil as track by solid
detector
 Now, we are studying to understand the background and that rejection
2016-2017
Understanding of
background and the rejection2017- 2018
Detector upgrade2018 Scale-up of experiment

Preparation and Low-background run
Upgrade for BG discrimination
Proposalfor1kg
Readout system demonstrationtest run for 1-10 gscale experiment
scale
Physics run for SI cross section

New system for high-precision
analysis

New readout systemdemonstration

with direction sensitivity
28