Development of
Forward Aerogel Cherenkov Detector
for the H-dibaryon search experiment (E42) at J-PARC
Japan-Korea PHENIX Collaboration Meeting
Minho Kim
Korea Univ.
H-Dibaryon Search Experiment, E42
KUNPL
Drift chamber
Signal
: p(K-, K+)ΞBackground: p(K-, π+)ΣToF wall
“AC detector”
1.7 GeV/c
K- beam
“H-dibaryon”
Six quarks
Jπ = 0+
KURAMA
magnet
TPC
Helmholtz
magnet
2
Forward Aerogel Cherenkov Detector
Parabolic reflector
Aerogel
KUNPL
Will be installed at the
exit of Helmholtz magnet.
n=1.04,
110×110×20 mm3
π, K
Light box
Contents
Thin Al plate
1. Aerogel
Fine-mesh PMT
2. Fine-mesh PMT
Strong to B field
3. SPring-8 beam test
3
FAC Aerogel
KUNPL
Kaon emits
Cherenkov light.
pmin FAC can
reject is about
0.48 GeV/c.
Pion emits
Cherenkov light.
Refractive index should be
smaller than 1.04132.
4
FAC PMT, fine-mesh PMT
KUNPL
mean Npe = 1
Bad resolution for photon counting.
Mesh type dynode
 Not Gaussian shaped amplification.
Let’s assume one photoelectron
 mean ADC, +Q.
5
FAC Test Experiment at SPring-8
KUNPL
1. Parabola FAC
2. Teflon FAC
Installed at the
very end of LEPS
spectrometer.
3. Winston cone FAC
6
FAC Setup
6/9~7/4 run
Drawn by S.H. Kim
W.S. Jung
KUNPL
PMT16
PMT17
PMT2
PMT1
7/15~ 7/24 run
PMT2
Same |x|, |y| position.
Similar pion momentum
PMT1
range with similar statistics.
PMT17
PMT16
7
FAC Installation
KUNPL
1
480<x<700 mm
115<y<225 mm
1
Turned
off
2
2
480<x<700 mm
-225<y<-115 mm
8
Particles which passed through FAC
1.4
1.2
1
0.8
0.6
Below 3.0 GeV/c
for protons.
Mass*charge(GeV/c2)
0.5
-0.5
P
0.4
0.2
0
-0.2
-0.4
0
102
10
1
-1
π+
KUNPL
P
K+
K+
1.5
Counts
1
0
π-
0.5
2
π+
2.5
1
Above 0.5 GeV/c
for pions.
3
1.5
Mass*charnge (GeV/c2)
Momentum (GeV/c)
Particle identification with ± 2σ tolerance.
Kaon study  Pion study
Wide range of momenta pions.
9
Pion Efficiency
KUNPL
Parabola FAC
ADC threshold:
Proton misidentification
is less than 5 %.
Considered as
kaons.
Considered as
pions.
Pion efficiency
= (Events which pion leaves ADC bigger than threshold)
/ (All pion events in specific momentum range)
10
Pion Efficiency
1
0.98
0.7
0.7
1.1
1.1
1.2
1.2
1.3
1.3
1.5
1.5
1.6
1.6
Pion momentum (GeV/c)
Winston FAC
1.4
1.4
Parabola FAC
1
1
Teflon FAC
0.9
0.9
Pion efficiency
0.8
0.8
Pion efficiency
KUNPL
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
0.6
With nbar cut condition
1
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
0.8
0.6
Without nbar cut condition
Parabola
FAC
Pion momentum (GeV/c)
Parabola FAC shows better performance.
Maximum 0.980 efficiency on average with neutron bar cut
condition(>0.7 GeV/c).
11
Position Dependence of Efficiency
KUNPL
1
0.98
0.96
0.94
0.92
0.9
0.88
0.86
0.84
0.82
Maximum 0.992 on average.
0.8
0.6
Parabola FAC
0.7
0.8
0.9
1
1.1
1.2
Central
1.3
1.4
Inclusive
1.5
Boundary
1.6
Pion efficiency (GeV/c)
Exterior Cherenkov light goes towards
surrounding plane surface first.
Perfect fit (to aerogel area) light box is not
good.
12
Npe Study
24
180
25
KUNPL
0.8~0.9 GeV/c
22
160
Counts
Counts
120
100
80
60
0.7~0.8 GeV/c
20
Counts
Total (>0.7 GeV/c)
140
15
10
18
16
14
12
10
8
6
40
5
4
20
00
20
2
5
10
15
20
25
30
35
40
45
00
50
5
10
Npe
15
20
25
00
30
5
10
Npe
15
20
25
30
Npe
25
30
Counts
Counts
15
10
1.0~1.1 GeV/c
25
Counts
0.9~1.0 GeV/c
20
25
20
15
10
1.1~1.2 GeV/c
20
15
10
5
5
0
0
5
10
15
20
25
0
0
30
5
5
10
Npe
20
25
30
0
22
20
20
18
Counts
10
8
6
1.3~1.4 GeV/c
18
16
Counts
1.2~1.3 GeV/c
12
14
12
10
8
6
14
6
4
2
15
Npe
20
25
30
5
10
15
Npe
30
8
2
10
25
10
2
5
20
12
4
0
0
15
20
25
30
1.4~1.5 GeV/c
16
4
0
10
Npe
18
14
5
Npe
20
16
Counts
15
0
0
5
10
15
Npe
20
25
30
13
1.01
1.015
1.02
1.025
mean Npe
12
11.5
11
10.5
10
9.5
9
8.5
8
7.5
7
1.005
12
11.5
11
10.5
10
9.5
9
8.5
8
7.5
1.03
1.035
1/β2
sin2θ
KUNPL
7
0.05 0.0520.0540.0560.058 0.06 0.0620.0640.0660.068 0.07
mean Npe
Npe Study
Since Cherenkov angle is smaller
than 15 °, cosθ ≈ 1.
14
Summary & Plan
KUNPL
We tested three types of FAC and studied corresponding
pion efficiency.
We’re checking pion efficiency and Npe again.
From middle of November, we will start the test of full size
FAC mockup.
15