J-PARC でのハイパー核ガンマ線分光実験用 ...
description
Transcript of 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
2
Contents
Introduction SksMinus components
Veto counters for beam decay events 4He target Other detectors
Summary
Introduction
The E13 experiment SksMinus setup
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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)
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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)
JPS Meeting 2008 Yamagata K. Shirotori
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)
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
17
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.
JPS Meeting 2008 Yamagata K. Shirotori
18
Backup
JPS Meeting 2008 Yamagata K. Shirotori
20
Beam Momentum
n
JPS Meeting 2008 Yamagata K. Shirotori
21
Calculated cross section for 7Li
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
23
Cross section of 4He(1+)&(0+)
JPS Meeting 2008 Yamagata K. Shirotori
24
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
JPS Meeting 2008 Yamagata K. Shirotori
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°
JPS Meeting 2008 Yamagata K. Shirotori
26
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
29
Muon filter : SMF
- (through)- (Absorbed in iron)
SMF
Stopping/absorption points
Simulation
JPS Meeting 2008 Yamagata K. Shirotori
30
Muon filter : SMF
- (through)- (Absorbed in iron)
SMF
Stopping/absorption points
Simulation
JPS Meeting 2008 Yamagata K. Shirotori
31
Muon filter : SMF
~88% - detected at the trigger level>99% - detected by tracking analysis(- miss-ID ~2%)
Stopping/absorption points
-
-
X
Z
Simulation
JPS Meeting 2008 Yamagata K. Shirotori
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
JPS Meeting 2008 Yamagata K. Shirotori
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-