Development of an Aerogel Cherenkov Counter for the J-PARC E16 Upgrade F.Sakuma (RIKEN), M.Nakamura (TITECH), H.Kawai (Chiba-U), H.Ohnishi (RIKEN), M.Tabata (JAXA), M.Tokuda (TITECH) Motivation Aerogel Cherenkov Counter Present Status Summary 新学術領域「多彩なフレーバーで探る新しいハドロン存在形態の包括的研究」 領域研究会 @ 理研 2011/02/28-03/01 課題番号:22105516(平成22年度~23年度) 研究代表者:佐久間 史典(理化学研究所)
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Development of an Aerogel Cherenkov Counter for the J-PARC E16 Upgrade
Improvement of the acceptance overlap between e+e- and K+K-
index=1.034integration range :
300-800nm
index=1.034
use n=1.034, as same as KEK-PS E32560x60cm2 divided by 6 (or 10) sectors
10cm
60cm
readoutWLS + fiber + (FM)PMT
AC design
5
Goal : construct a prototype of ¼ size module
X 4 modules
Some Hints in detector development in Russia?
6
arXiv:hep-ex/0106016
endcapbarrel
Aerogel : t74mm, n=1.05WLS : BBQ
~8 p.e.
π momentum
candidate for PEP-N detector @ SLAC
Minimum Goal : KEK-PS E325 AC
7
AC
•n=1.034•12.5cm Aerogel•5 inch PMT (H6527)
1.1 p.e.
proton
pion8 p.e.
M.Ishino et al., NIM A457, 581
π Rejection: 1x10-2
@ 1.4GeV/c
0
1
2
3
4
5
6
0 2 4 6 8 10
mea
n #
of p
hoto
elec
tron
thickness of Aerogel [cm]
Panasonic
E325
Chiba-U
Aerogel
8
H6410 (2”)
Cosmic Ray
Aerogel
Mirror
We have checked 3-types of the aerogel (n~1.034):Panasonic-denkoKEK-PS E325Chiba-U
WLS
9
H6410(2”)
fiber x100
WLS
PMT
Cosmic Ray WLS (ELJEN EJ-299-27, t1mm)
Aerogel (t2cm)
clear fiber x100(φ1mm, single clad)
expected # of photon@ 1GeV/c π & n=1.034
transmission lengthn=1.034 (KEK)
xWLS(blue)
PMT
WLS (Cont’d)
10
fitting is failed…
w/ Aerogel
w/o Aerogelw/o Aerogel
w/ Aerogel
2cm2cm
1mm
1mm1mm
WLS (Cont’d)
11
--- What we have learned ---WLS (blue, t1mm) emits several photons with charged particlesWe cannot install a large amount of WLS in detector acceptance
present method of WLS+fiber readout cannot collect Cherenkov light from the Aerogel
--- What we have to do ---reconsider the configuration of the Aerogel and WLSincrease the fibers?usage of blue and green WLS?
Other Ways …
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R5543 x 52 @ RIKEN(from KEK-PS E325 GC)
BELLE ACNIM A453,321
development of a “normal type” Aerogel Cherenkov Counter with finemesh-PMTs such as BELLE AC.
development of a “reflection type” Aerogel Cherenkov Counter with optical mirrors such as E325 AC.
E325 ACNIM A457, 581
Summary
We have been developing an Aerogel Cherenkov Counter for the E16 upgrade in order to measure K+K- pair.
Development of WLS+fiber readout has been started, but we have to adjust the configuration of AC+WLS+fiber. Further study is required…
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14
Expected Photon Spectra
15
expected # of photon@ 1GeV/c π & n=1.034
transmission lengthn=1.034 (E325)
Aerogel
Detection
xπ 1GeV/c
Aerogel
Detection
l
π 1GeV/c
WLS (Cont’d)
16
WLS1mm
Aerogel6cm
H6410 (2”)
Aerogel6cm
WLS (Cont’d)
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PMT300~600nm
WLS300~400nm
Aerogel
Detection
l
π 1GeV/cWLS(blue)
PMT
WLS (Cont’d)
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H6410 (2”)
Aerogel9.4cm
trigger
trigger
Aerogel9.4cm
WLS1mm
trigger
trigger
Photon Fitting
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( ) ( ) ( )( )20 1
211
exp 1 exp! 22
n
n
x p npf x C
n nnλ λ
σπ σ
− +− = × −
∑
Poisson Gaussian
C : normalized factorλ : mean value of photoelectronp0 : pedestal peakp1 : distance of pedestal to single-photon σ1 : PMT resolution for single-photon
parameter parameter constant
constant
constant
SiAPD
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S8664-1010S8664-55
H4083
We purchased and tested SiAPDs.
But we CANNOT see the signal of a few photons on SiAPD, because of read-out electronics noise!
~7500 photons(gain : x50)
what we have learned is …“using low-gain devices for
Cherenkov detection is awful difficult!”
MPPC
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S10362-11-100C
S10362-33-100C
S10362-33-050CS10362
-33-025C
We purchased and tested MPPCs.
The dark count signals of ~Mcpswere confirmed as written in the product specification.
It seems that usage of the MPPCs for a single-photon detector
is too hard!Several tens of photons are required.
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Vector Meson, φJ.D.Jackson, Nuovo Cimento 34, 1644 (1964).
( ) ( )3* *0 0 0
*2 2
2 20 0
/
4
4
K
K
q q m m
q m m
q m m
Γ Γ =
= −
= −
mφが変化
( )3*0 0
2 * 20
2 20 0
/
4
4
K
K
q q
q m m
q m m
Γ Γ =
= −
= −
mKが変化
φ mass
K mass
Γ*/Γ
0Γ
*/Γ0
23
φ Puzzle
theoretical predictions− D.Lissauer and V.Shuryak, PLB253,15(1991).