H. Nishimura

DM search with a TPC（ NEWAGE ）

Hironobu Nishimura

（ Kyoto University)K. Miuchi

T. Tanimori, H. Kubo,

S. Kabuki, K. Tsuchiya,

A. Takada, Y. Okada,

K. Hattori, K. Ueno, S. Kurosawa

A. Takeda (ICRR), H. Sekiya (ICRR)

Feb. 20, 2007 　 APPEAL07

(New generation WIMP search with an advanced gaseous tracker 　 experiment)

H. Nishimura

OUTLINE

Direction sensitive DM search

Micro-TPC

NEWAGE surface run

FUTURE PLANS & SUMMARY

Feb. 20, 2007 　 APPEAL07

H. Nishimura Jan 27, 2007 　 3rd MPGD workshop

１ . 　 Direction sensitive DM search　　　　“WIMP-wind” detection

The WIMP-wind

WIMPV0 =230 km/s

SOLAR SYSTEM220 km/s

PLB 578 (2004) 241

H. Nishimura Jan 27, 2007 　 3rd MPGD workshop

WHY “Direction-sensitive” ?Large mass for exclusion （ and indication ）

BUT Annual modulation is not enough…

Direction-sensitive for detection

WIMPWIMP WIND WIND γ γ

FF

Annualmodulation

direction

Asymmetry

H. Nishimura

Sensitivities Goal: Detect the WIMP-wind 　（ 2010~ ）

• underground ・ low pressure ( CF4 0.05 bar ) ・large volume （ 1m3 × N ）

CURRENT: • surface ・ CF4 0.2 bar ・ 30cm cube

Feb. 20, 2007 　 APPEAL07

sensitivity

H. Nishimura

2 micro-TPC (3D tracking device)

Feb. 20, 2007 　 APPEAL07Jan 27, 2007 　 3rd MPGD workshop

Position Encoder

PIC (×5000)

GEM(×10)

TPC

Particle tracks

e

Preprints: physics/0701085 K.Miuchi et.al

40cm

TPC

X readout （ 768ch ） Y

readout （ 768ch ）

FAGA position encoder（ 1536ch ）

23×28×31cm3

H. Nishimura

-PIC (gas gain 5000)• Pixel-type gas multiplier• 589824 pixels 400μm pitch• 768+768 readout

Feb. 20, 2007 　 APPEAL07

2D imaging device

28cm

23cm

30cm μPIC(Toshiba) Large area GEM

(scienergy)

Takada et. Al. PSD7

PIC

GEM

TPC 30cm

5mm

Particle tracks

e

GEM (gas gain 10)

140μm pitch

70μm diameter

400 μm

Anode

Cathode

140μmφ70μm

H. Nishimura

Readout electronics• 768 anode + 768 cathode• Digital (LVDS) signals at ASD• (X,Y,T) at the position encoder

　　　 for tracking

Feb. 20, 2007 　 APPEAL07

31cm

gas volume

Kubo et. al. IEEE/NSS 2005

TPC system

ENCODER

ASD

for energy

+ Summed analog signal

TPC 　 systemGas volume

• DRIFT length 31cm• CF4 0.2bar gas, sealed

100MHz, pipeline

H. Nishimura Jan 27, 2007 　 3rd MPGD workshop

TPC performance① 　 tracking400m digital “HIT” ( for tracking) + summed analog ( for energy)

F 500keV 5~6mm 　　 in 0.2atm CF4

F,C tracks

n

252Cf

YX-15cm15cm

15cm

-15cm

30cm

Z(drift)

0cm

X,Y image Z(time) projection

Fiducial 　 24×21.5×31cm3

(CF4 8.9g)FLAT response

trigger

Trigger ：z=0

cm 30

Preprints: physics/070118 K.Miuchi et.al

H. Nishimura

20062006 年年 1111 月月 1717 日日

TPC performance ②　 stability

Drift velocity: fast drop

⇒ slow decrease after 1 day

gain, energy resolution ：　 stable within 　 the systematic error

Jan 27, 2007 　 3rd MPGD workshopRecoil direction 　image

252Cf（ NE45°　 zenith35° ）

10

Cos

n

p

CF4+C4H10

252Cf run

Proton tracks

n252Cf

YX-15cm

15cm

15cm

-15cm

30cm

Z(drift)

0cm

CF4+C4H10 (9:1)

Protons have longer tracksn -> p forward scattering are seen (this is what we want to do with　　　　 WIMP -> F scatterings)

TPC performance ③ 　　　　　　　　　　　　　　　　　　　　　　 direction

Horizon

H. Nishimura

TPC performance④　 gamma-ray rejection

gamma-rays from 137Cs

• gamma efficiency 　＜　 2e-4 　（ statistics limited ）

137Cs　

neutron （ BG ）

With 137Cs

Without （ BG run ）

Spectrum

subtracted

H. Nishimura

Surface run①2006 Nov.1st ~ Nov.27th

exposure 0.15 kg days (=0.0089kg ×16.7days)

@Kyoto university (N35.03 　 E135.783 ）　Energy spectrum （ conventional method ）: consistent with neutron BG

Energy spectrum

3 Surface run

H. Nishimura

Surface run ②The sky map

flat neutron background is seen

North sky view seen by C and F nuclei(100-400keV)

DM direction

Horizon

Jan 27, 2007 　 3rd MPGD workshop

Surface run ③Cosθ distribution

consistent with a flat distribution

Cosθ 分布

(100-400keV)

DM limit

First result of

Direction Sensitive!!

First step to theNEWAGE

WE ARE 　 HERE

101 102 103

H. Nishimura Jan 27, 2007 　 3rd MPGD workshop

Go 　 undergroundJUST 　 started

KAMIOKA LAB-B2006/12/12

KAMIOKA LAB-B2007/1/19

SPring-8

KyotoKamioka

4 Next step…

H. Nishimura Jan 27, 2007 　 3rd MPGD workshop

SUMMARYμTPC ： 30cm cube in operation

• Gas: CF4: 0.2 bar • direction sensitive WIMP-wind detector

direction-sensitive method works!• On surface • Obtain First upper limit !!

NEWAGE ： underground run just started

H. Nishimura Feb. 20, 2007 　 APPEAL07

Gas gains • operation gain for MIPs ~50,000

Gain curves

Gain map

Gain uniformity • Maximum / minimum = 2.2

TPC 　 performance (with Ar+C2H6 gas)

Jan 27, 2007 　 3rd MPGD workshop

SpectraSpectra• Energy spectra from the whole volume

　　 (with energy corrections)

109Cd

linearity

Energy resolution

133Ba

241Am

Ag-KCu-K

Cs-KCu-K

Cu-K

59.5keV

60%@59.5keV

22.2+24.9keV

31keV

8keV

Jan 27, 2007 　 3rd MPGD workshop

Particle TrackingParticle Tracking muons

Electrons (~100keV)

Protons (~2MeV)

30cm

Neutrons（ 252Cf ）

511keV 　 ‘ s（ 22Na ）

Cosmic ray muons

Jan 27, 2007 　 3rd MPGD workshop

3D Spatial resolution3D Spatial resolution• Fit muon tracks with straight lines• plot the residuals

Residual muon tracks

dataFitted line

data

residual

Residual (short drift)

Residual (long drift)

)2

exp(2

22

2 rr

22222 )( lDdetectordiffusiondetector

Drif

t le

ngth

-PIC

mm1

mm2

mm51.0detector

cmmm/37.0D

)2

exp(2

22

2 rr

dependence on drift length

r [cm]　

r [cm]　

ｌ [cm] 　

検出器の方向依存感度マップ

検出器応答検出器応答の方向依存性（相対的）

• 線源を (50cm ,0 ,0) (0,50cm,0) (0,0,50cm) の 3 箇所（それぞれ 10k 事象）スキャンして測定：ほぼ等方な反跳を GENERATE

Track　length　threshold　:　　　3　mmdE/dx　threshold　　　　　　　　　　　:　　10　keV/cm　　　with　electron/nuclear　recoil　discrimination　ability　　　　　　　　　　　　　recoil　direction　sensitivity　(Bragg　curves)

gas Pressure[Torr]

Density[g/m3]

Xe 5 38

CF4 20 90

Need　to　study　low-pressure　μTPC

Sensitivity　to　WIMPs　

Properties　of　μTPC

Drift planeμ-TPCμ-TPC

N

N

N WIMPWIND

WIMP WIND

γ γ

FF

cos

CF4(Eth=40keV), MWIMP=50GeV

Very large asymmetry

Spin-dependent SI 3 detection sensitivities

Sensitivity　to　WIMPs　

SD　　with　CF4　20　torr

M WIMP [GeV]

W

IMP

-p [

pb]

SI　　　with　Xe　5　torr

M WIMP [GeV]

W

IMP

-n [

pb]

“Detection”　by　Forward/Backward　3σasymmetryAt Kamioka Observatory (1000 m.w.e)

0.3　m3year　exposure　　reach　the　best　sensitivity.300　m3year　exposure　will　test　the　MSSM　prediction.

エネルギー校正• ガラスに蒸着した 10B ( 厚さ 0.6μm )• ドリフトケージ内部にセット、外から 252Cf の中性子を減速して照射• 10B(n,a)7Li 反応 (Q=2.70MeV 1.8MeV for )• 原子核による校正、低エネルギーへの線形性は別途確認示す必要あり• 現状では、校正には 6 時間程度、見せれる絵には 12 時間程度かかって

いる

XY イメージ

keV

スペクトル

エネルギー vs 飛跡長

keV

Li

2000

スペクトル(GEANT4 ）

検出器応答

エネルギー分解能• 高エネルギー（ 5-8MeV ）では Rn のピークを使ってモ

ニタ• 40 ％ FWHM• これは検出器固有の数字（ゲインのばらつきが効いてい

る）

60%@59.5keV

検出器応答