J-PARC における K 中間子原子核探索実験のための円筒形ドリフト・チェン

バーの開発 (J-PARC E15 実験 )

理研　佐久間　史典S.Ajimura1, G.Beer2, H.Bhang3, P.Buehler4, L.Busso5,6, M.Cargnelli4, J.Chiba7, S.Choi3, C.Curceanu5,8,

D.Faso5,6, H.Fujioka9, T.Fukuda10, Y.Fukuda11, C.Guaraldo5,8, T.Hanaki7, R.S.Hayano9, A.Hirtl4, M.Iio12, M.Iliescu5,8, T.Ishikawa9, S.Ishimoto13, T.Ishiwatari4, K.Itahashi12, M.Iwasaki12, P.Kienle4,14,

J.Marton4, Y.Matsuda12, Y.Mizoi10, O.Morra5,15, T.Nagae13, H.Ohnishi12, S.Okada12, H.Outa12, D.Pietreanu5,8, A.Sakaguchi1, F.Sakuma12, M.Sato11, M.Sekimoto13, D.Sirghi5,8, F.Sirghi5,8, S.Suzuki13,

T.Suzuki12, H.Tatsuno9, D.Tomono12, A.Toyoda13, E.Widmann4, T.Yamazaki9,12, H.Yim3, J.Zmeskal4

1Osaka University, Japan, 2University of Victoria, Canada, 3Seoul National University, South Korea, 4Stefan Meyer Institut fur subatomare Physik, Austria, 5INFN Sezione di Torino, Italy, 6Universita’

di Torino, Italy, 7Tokyo University of Science, Japan, 8Laboratori Nazionali di Frascati dell’INFN, Italy, 9University of Tokyo, Japan, 10Osaka Electro-Communication University, Japan, 11Tokyo

Institute of Technology, Japan, 12RIKEN, Japan, 13High Energy Accelerator Research Organization (KEK), Japan, 14Technische Universitat Munchen, Germany, 15INAF-IFSI, Sezione di Torino, Italy

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Physics MotivationJ-PARC E15 ExperimentCDCSummary

計 48 名、 6 ヶ国、 15 機関

Physics Motivation

2

K 中間子原子核は本当に

存在するのか ?

QGP neutronstar

SPS, RHIC, LHC

KEK-PS

W.Weise NPA553, 59 (1993).

E549@KEK-PS FINUDA@DANE

E548@KEK-PSOBELIX@CERN-LEAR

T.Yamazaki, A.Dote, Y.Akiaishi PLB587,167(2004).

さらなる実験的証拠が必要

3

J-PARC E15 Experiment3He(K-,n) 反応を用いて K-pp 束縛状態を見つ

けるK-

3He Reaction

全ての粒子を測定し、Missing mass spectroscopy

とInvariant mass reconstruction

により K-pp 束縛状態を見つける

Decay

K-ppcluster

neutron

p

p

-

Mode to decay charged particles

Missing

mass

Spectroscop

y

via neutron

Invariant

mass

reconstructio

n

4

E15 Setup

Q7

D4

Q8

FF

ES

J-PARCK1.8BR Beam Line

1GeV/cK- beam

p

p

nflight length = 12m

mass resolution for K-ppinvariant mass= 19MeV/c2 (CDC = 250m)missing mass= 12MeV/c2 (ToF = 150ps)

ToF Wall

CylindricalDetectorSystem

SweepingMagnet

5

Cylindrical Detector System (CDS)

~2m

counter Rad. Length

Target (L3He+cell) 1.55%

Vtx Chamber(GEM-chamber) 0.27%

CDC(He:C2H6=50:50) 0.48%

SolenoidMagnet

HodoscopeCounter

CylindricalDrift Chamber

TargetChamber

L3He Target

Kaon Decay Veto Counter

Z-VertexChamber

Charge Veto Counter

B

6

vtxK-pp vtx

p

p-

n~1300MeV/c

~400MeV/c~150MeV/c

~500MeV/c

Event-display for K-pp

p

p -

binding energy = 100MeV/c2

Geant4 を用いたシミュレーション前方 neutron を要求

Calculated using Geant4

7

材質 : アルミニウム、 CFRP重量 : 100kgワイヤー数 : 8136 ( 読み出し : 1816ch)総ワイヤー張力 : 600kg

aluminumend-plate

CFRP tube(t1mm)

aluminum block(x6)

95cm

106cm

sense wires: Au-plated W, 30mfield & guard wires: Au-plated Al, 100m

30cm

Cylindrical Drift Chamber (CDC)

A1 (3)

V1 (2)

U2 (2)

V2 (2)

A3 (2)

A2 (2)

U1 (2)

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六角形セル (drift length9mm)7 super layers (AUVAUVA)15 layers (r = 19.0548.45cm)wire length = 82cmsolid angle = 2.6

＋ : sense wire＊ : field wire○ : guard wire

Cell Configuration

9

Calculated using garfield-9

A1-1 (inner cell)

w/o magnetic field w/ magnetic field (0.5T)

100ns

200ns

100ns

200ns

磁場によって形はあまり変わらない

Isochrones of Drift Time

A1-1 (inner cell)

He:C2H6 = 50:50 He:C2H6 = 50:50

Gas Mixture

Ar:C2H6 = 50:50rad = 177.6mne = 50

He:C2H6 = 50:50rad =679.2mne = 27

velocity vs. E

BELLE CDC

Calculated using garfield-9xt relation

2x104 gain

He base : V1.9-2.2kVAr base : V2.2-2.5kV

Ar:C2H6 = 50:50 を使用He:C2H5 = 50:50 など He-base のガスの使用も考慮

10

11

Calculated using Geant4generated at the center of CDS0<p<1 GeV/c, flat distribution60<<120 degree, flat distributionaccepted = track with a CDH-hit

decay

proton>250MeV/c, kaon>150MeV/c, pion>50MeV/cenergy loss

magnetic field = 0.5T

Geometrical Acceptance

12

mass resolution K-pp

w/o chamber-smearing 5.8 MeV/c2 1.6MeV/c2

w/ chamber-smearing 18.7MeV/c2 2.5MeV/c2

expected mass resolution for K-pp and

momentum resolution for , K, p

p/p10% @p1GeV/c

Calculated using Geant4Spectrometer Performance

13

test module of HV-distributor

test chamber

Present Status of CDC

30cm~100cm

CDC の基本設計は済み、 2008 年初頭に完成予定試作機を作製し、 HV-distributor, preamp-board のテストを行っている今後、試作機を用いてガスのテストなどを行う予定

HV

preamp

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SummaryJ-PARC E15 実験は K 中間子原子核 (K-pp 束縛状態 ) の探索を行うE15 実験の主要な検出器である Cylindrical Drift Chamberは、 2008 年始めに完成予定であり、現在は HV, プリアンプ周りをテスト機を用いてテストしているE15 実験のスペクトロメーターは、 2009 年始めのビームタイムに向けて着々と準備が進められている

Solenoid Magnet Target System ToF Wall

backup

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16

layernumber

wiredirection

super-layer number ofcells

radius [cm] cell width[degree]

drift length[cm]

offset angle[degree]

tilt angle[degree]

1 X 19.05 0.83 02 X’ 20.4 0.89 03 X 21.75 0.95 04 U 24.85 0.87 3.725 U’ 26.2 0.91 3.926 V 29.3 0.92 3.957 V’ 30.65 0.96 4.128 X 33.75 0.88 09 X’ 35.1 0.92 0

10 U 38.2 0.80 3.4311 U’ 39.55 0.83 3.5512 V 42.65 0.84 3.5913 V’ 44 0.86 3.7114 X 47.1 0.82 015 X’ 48.45 0.85 0

A3 180 2 0

U2 150 2.4 7.2

V2 160 2.25 6.75

V1 100 3.6 10.8

A2 120 3 0

A1 72 5 0

U1 90 4 12

Detailed Cell Configuration

17

Vertex Resolution

x, ｙ

K-pp (~10mm) (~8mm)

z

K-pp, (~2mm)