Future Plan ofFuture Plan ofthe Neutral Kaon Spectrometer the Neutral Kaon Spectrometer

22(NKS2) Experiment(NKS2) Experiment

Masashi KanetaDepartment of Physics

Tohoku University

Masashi Kaneta, Tohoku Univ. 22008/3/26 The Annual meeting of JPS.

Upgrade ProjectUpgrade Project

• Physics motivation– K+Y coincidence measurement

• Advantage– No Fermi motion correction– Reaction Plane will be defined

• Direct comparison with Model• Lambda polarization

• Detector upgrade– Replacing inner detector

• Replace straw drift chamber by a 3D tracker– increase the acceptance

• Two-side-read-out hodoscope– increase dE/dx and TOF resolution– better particle separation

Masashi Kaneta, Tohoku Univ. 32008/3/26 The Annual meeting of JPS.

NKS2 detectorsNKS2 detectors• Two Drift Chambers

– Cylindrical Drift Chamber (CDC) and Straw Drift Chamber (SDC)

• Two Hodoscope– Inner and Outer Hodoscope (IH and OH)

• Electron Veto630 m

m

400 mm

• New inner detectors should be fit in

630H x 110-400 tube

110 mm

EV CDCOH

SDC

IH

DesignDesign

Masashi Kaneta, Tohoku Univ. 52008/3/26 The Annual meeting of JPS.

Current/Future Inner Detectors Current/Future Inner Detectors PositionPosition

63

053

0

800

200

210

232

766

712

286

55

17.3º

1200

74

8

OH

78

IH

16

0

Liquid Deuterium target holder region

CDC

30

0

SDC

100

42.6º

38

0

VDC

65IH134

Masashi Kaneta, Tohoku Univ. 62008/3/26 The Annual meeting of JPS.

Vertex Drift Chamber DesignVertex Drift Chamber Design

•Requirements– As possible as small cell

• but limited by feedthrough (3mm)

– At least 6 layers with stereo wires

•Decision– Trapezoid (almost square)

cell shape– Half cell size: 4 mm– 8 layers– uu’ vv’ uu’ vv’

• increasing stereo angle with radius:6.0 - 11.1°

– Drift gas = Ar:Ethane(50:50)

55 mm

65 mm

137 mm

uu’uu’vv’

vv’

Masashi Kaneta, Tohoku Univ. 72008/3/26 The Annual meeting of JPS.

FrameFrame

• Concept– Less material– but to be strong

• ~216 kg total wire tension

• CFRP pillar– 20Lx40Wx0.5TH mm3 – 1.0TH = 0.004 X0

• target chamber: 0.009 X0IH: 0.012 X0

• End-cap 160 mm426 mm height of pillar

– 390 mm wire height

• This design has the most large safety factor in plans

Safety factor min: 6.2

Masashi Kaneta, Tohoku Univ. 82008/3/26 The Annual meeting of JPS.

43.7

ReadoutReadout

•FEE– ASD

• Sony ASD chip• GNA-220

– Align on VDC• like windmill

•TDC– VME multi-hit TDC

• Atlas muon TDC chip

• Amsk co.• same with CDC

bottomview

43.7

21.9

100

94.5

63.6

16.3

30°

side view

AcceptancAcceptancee

Masashi Kaneta, Tohoku Univ. 102008/3/26 The Annual meeting of JPS.

Acceptance for Acceptance for KK 00

SS or or

p - channel)K 0

S (+ - channel)

• The acceptance with new chamber– ~3 times for K0

S

– ~1.5 times for • Note: these values vary about 10%, depend on models

used for input

(1): all events(2): the two daughters pass

through VDC with two OH his(3): two daughters pass through OH Note: Decay volume cut is applied for (2) and

(3) and lost ~80% of events

Generated distribution: SLA model

Masashi Kaneta, Tohoku Univ. 112008/3/26 The Annual meeting of JPS.

Acceptance for Acceptance for KK 00

SS + + Events Events

• The acceptance will increase– ~8 times

(1): all events(2): the four daughters pass

through VDC with two OH Hits(3): four daughters pass through OH Note: No decay volume cut is applied

p - channel)K 0

S (+ - channel)

Masashi Kaneta, Tohoku Univ. 122008/3/26 The Annual meeting of JPS.

Polarization MeasurementPolarization Measurement

• Acceptance correction– May vary with

• Cos(Kcm), E

momentum• Polarization

– Test results• No Polarization dependences• P is smeared by resolution

– factor ~0.9

cosP 1A )(cos 0 N

d

dN

Acceptance decay parameter0.642 (PDG)

polarization

p

pt = p×p

t

CM

p

pp

Transverse polarizationmeasurement

pK

reaction planein CM

pN

Masashi Kaneta, Tohoku Univ. 132008/3/26 The Annual meeting of JPS.

Model Predictions: SelfModel Predictions: SelfPolarizationPolarization

of Kaon in CM [degree]

P

olar

izat

ion

SLA

(rK

K=

-2.0

87)

Kao

nMA

IDSA

1(P

. Byd

zolv

ski)

+p K ++ +n K 0+

ScheduleSchedule

Masashi Kaneta, Tohoku Univ. 152008/3/26 The Annual meeting of JPS.

ScheduleSchedule

March April May June July

VDC

IH

construction

check attest bench

Installationin NKS2

constructiondesign

• The test experiment of new detectors will be before summer shutdown

Test Exp.w/ Beam

Masashi Kaneta, Tohoku Univ. 162008/3/26 The Annual meeting of JPS.

SummarySummary

• The detector upgrade project is on going– Goal: K+Y coincidence measurement– Increasing acceptance of tracking– Increasing start time resolution of TOF

• better /K/p separation toward K++Y measurement

• New inner detectors– Expecting ~8 times K0

S+ events

• Schedule– Test experiment before summer– Beam time will be requested

Masashi Kaneta, Tohoku Univ. 402008/3/26 The Annual meeting of JPS.

MaterialsMaterials

• CFRP– C:H:O = 75:5:20– density = 1.55 g/cm3

– radiation length = 26.66 cm– 1 mm thickness = 0.0038 X0

• Scintillator– C:H = 8:8 atoms– density = 1.032 g/cm3

– radiation length = 42.43 cm– 5 mm thickness = 0.0118 X0

• Target cell– 0.009X0

Masashi Kaneta, Tohoku Univ. 412008/3/26 The Annual meeting of JPS.