j-parc でのハイパー核ガンマ線分光実験用 ...

J-PARC でのハイパー核ガンマ線分光実験用散乱粒子磁気スペクトロメータ検出器の準備

状況

東北大理 , 岐阜大教 A, KEKB

白鳥昂太郎 , 田村裕和 , 鵜養美冬 A, 石元茂 B, 大谷友和 ,小池武志 , 佐藤美沙子 , 千賀信幸 , 細見健二 , 馬越 ,三輪浩司 , 山本剛史 , 他 Hyperball-J collaboration

JPS Meeting 2008 Yamagata K. Shirotori

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Contents

Introduction SksMinus components

Veto counters for beam decay events 4He target Other detectors

Summary

Introduction

The E13 experiment SksMinus setup


4

Reaction analysis :K1.8 + SksMinus

-ray detection : Hyperball-J⇒Reaction- coincidence

J-PARC E13 experiment

Hypernuclear -ray spectroscopy experiments on several light nuclei(4

He, 7Li, 10

B, 11B, 19

F)

(K-, - ) reaction @ pK = 1.5 GeV/c


5

SksMinus setup

SksMinus elements Particle tracking : SDC1~4 Time-of-flight : STOF Reaction ID : BAC, SAC (n=1.03) Veto counters

SMF : - from K- → - + SP0 : - from K- → - + 0

Target : Li2O, Teflon ((CF2)n),

Boron(10,11B) (~10 cm, ~15 g/cm2)

Liquid 4He (25 cm, 3.13 g/cm2)

_

Requirements for - of ~1.4 GeV/c Acceptance >100 msr, ~20o scattering angles Momentum resolution < 3 MeV/c (FWHM)

1 m

SksMinus

Veto counters for beam decay events

SP0 : Pi zero veto


7

Beam decay events

K- → - (63.4%)

⇒Muon filter (SMF)K- → - 0 (21.1%)

⇒Pi zero veto (SP0)

_K-

BAC SACTarget

Reaction

K-

BAC SACTarget

Decay

Cannot be distinguished

_

Huge trigger rateMissing mass background

Simulation


8

Side view

Scintillator

Lead

Target region

K- -

SP0 (Pi zero veto) : specifications

84%

Layer multiplicity0)

K-→ - 0

→

Number of hit layers

rays detected by shower counter(Lead converter)

To distinguish between Beam decay : K-→- 0

decay : N+→N+N (NMWD)⇒Number of hit layers >=3

0.2%

Number of hit layers

Simulation Simulation

3 3

Layer multiplicity200 MeV/c Neutron)


9

SP0 (Pi zero veto) : test experimente+ beam test experiment at Tohoku-LNS @ 100-300 MeV⇒Response is consistent with Geant4 simulation.

⇒Neutron beam test experiment at Tohoku-CYRIC (planned)

e+

Layer multiplicitye+)Event display

Pb Plastic Scintillator

Sideview

e+

Finger Counter


10

SP0 (Pi zero veto) : designAluminum Spacer

Lead

Plastic scintillator

SP0 design based on the range counter (KEK E559)

Full assembly

1352 mm

1816 mm

400 mm

170 mm

14 mm


11

SP0 (Pi zero veto) : designAluminum Spacer

Lead

Plastic scintillator

SP0 design based on the range counter (KEK E559)

1352 mm

1816 mm

400 mm

170 mm

Hyperball-J

SDC1SKS magnetSDC2

SP0 K-

Around Pi zero veto

500 mm

Liquid 4He target

4He experiment

⇒Charge symmetry breaking

(4H ⇔4

He)


13

4He target (Designed by S. Ishimoto)

Beam size : x~26 mm, y~4 mm Target cell size

: 120 mm×250 mm (2.7L)(outer cell 210×330)

Size fit to the inner space of Hyperball-J

Cooling power: 1.5 W @ 4 K

Hyperball-J frame

K--

Refrigerator

Target cell

Target cell (SUS)

300 mm

Mylar Mylar

100 mm Radiative heat shield (Al)

He pipe (Cu) Outer cell (Al)


14

Around the target

Tight space around the target

⇒Optimal detector arrangement

for the 4He experiment

BAC

K-

SAC

-

PWO

Refrigerator

Target

PMTMagnetic shield

PWO

Target

PWO

210 mm

100 mm

Other detectors and Summary


16

Other detectors Drift chamber

SDC2 : Test and repair in Tohoku Univ. SDC3&4 : Ready (SDC1 : J-PARC E05 experiment)

Aerogel Cherenkov counter SAC, BAC : Basic design finalized

TOF counter Existing SKS TOF counter + additional scintillation

counter Muon filter

Iron block + scintillation counter = Existing things


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Summary J-PARC E13 experiment via the (K-, -) reaction

with pK =1.5 GeV/c Magnetic spectrometer, SksMinus and Hyperball-J

Preparation of SksMinus detectors Veto counters for beam decay events

Pi zero veto and Muon filter 4He target

Under construction with S. Ishimoto Other detectors being prepared on schedule

The experiment is scheduled in 2009.


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Backup


20

Beam Momentum

n


21

Calculated cross section for 7Li


22

Motivation : Charge symmetry breaking

Mass difference : +0-.

Statistics of old -ray data is poor,

in particular 4He(1+→0+) data.

Old data suggest large charge symmetry breaking in N interaction.

4H ⇔ 4

He

(n ⇔ p)

PL83B(1979)252

Hyperfragment (Stop K- reaction) + NaI detector

→ In-flight (K-, -) reaction + Ge detector Doppler shift correction & Low background


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Cross section of 4He(1+)&(0+)


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The modification of SKS

Momentum resolution0.1%FWHM (0.72 MeV/c)

@ 720 MeV/c, 2.2TMaximum central momentum

1.0 GeV/c @ 2.7T

Acceptance 100 msr @ 0.72GeV/c

2.2T 2.7T

~20° ~20°

Scattered particles are not focused and present drift chambers (SDC3,4) are small for large reaction angle (half acceptance).

1.05 GeV/c (+, K+) reaction (K+ 0.72 GeV/c)

Present SKS


25

The modification of SKS Keeping large acceptance and wide angular coverage by large drift chambers (2m×1m) (from BNL and Freiburg)

Incident beam angle and position of drift chambers are optimized by keeping acceptance for the 1.5 GeV/c beam condition.

Setup can be used for 1.1~1.8 GeV/c beam hypernuclear gamma ray spectroscopy experiment without modification.

~20°


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Simulation results of acceptance and momentum resolution

Acceptance at 1.4 GeV/c, ~130 msr Enough angular acceptance, ~20 degree Momentum resolution at 1.4 GeV/c ~2.1 MeV/c (FWHM)

Simulation Simulation


27

Particle identification

(K-, - ) → - or K-

Beam K- can greatly be decreased by SAC (n=1.03)

Time resolution of STOF ~150 ps (rms)

Simulation


28

Assumed Gaussian distributionx ~26.0 mmy ~4.0 mm(dx/dz) ~20 mrad (1.1°)(dy/dz) ~2 mrad (0.1°)

x y

Beam profile


29

Muon filter : SMF

- (through)- (Absorbed in iron)

SMF

Stopping/absorption points

Simulation


30

Muon filter : SMF

- (through)- (Absorbed in iron)

SMF


Simulation


31

Muon filter : SMF

~88% - detected at the trigger level>99% - detected by tracking analysis(- miss-ID ~2%)


-

-

X

Z

Simulation


32

Energy deposit of Miss-ID -

- : 1.51 % - : 0.32 %

e-/e+ : 0.47 % : 1.29 %

p/n : 0.17 % others : 0.16 %

- miss-ID ~2%⇒Eth> 2 MeV

Simulation


33

SksMinus setup

SksMinus elements Particle tracking : SDC1~4 Time-of-flight : STOF Reaction ID : BAC, SAC (n=1.03) Veto counters

SMF : - from K- → - + SP0 : - from K- → - + 0

Target : Li2O, Teflon, Boron(10,11B)

(~10 cm, ~15 g/cm2)

Liquid 4He (25 cm, 3.13 g/cm2)

_

Requirements for - of ~1.4 GeV/c Acceptance >100 msr, ~20o scattering angles Momentum resolution < 3 MeV/c (FWHM)

SKS

K-

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