Transcript Document
Next stage of a search for 2K(2
)-capture of
78
Kr
Valery V. Kuzminov Baksan Neutrino Observatory INR RAS
NON-ACCELERATOR NEW PHYSICS Dubna, Russia, June 20--25, 2005
1
Ju. Gavriljuk, V. Gavrin, A. Gangapshev, V. Kazalov, V. Kuzminov, N. Osetrova
Institute for Nuclear Research of the Russian Academy of Sciences, Moscow Russia
A. Shubin, G. Skorynin, I. Pul`nikov, A.Ryabukhin
FSUE PA “Electrochemical Plant”, Zeleznogorsk, Krasnoyarsk Region, Russia
S. Panasenko, S. Ratkevich
Karazin Kharkiv National University, Kharkiv, Ukraine
The work is performing in the frames of a Presidium RAS Fundamental Research Program “Neutrino Physics” and Supported by RFBR grant №04-02-16037 2
1.
78 Kr 36
Theory:
78 34 Se ** + 2 (2.88 MeV) T
ee
1 2
ee
T 1 2 22
y
21
y N 2
k
=
0.786
N ee M. Doi … 1992y
. 1994
y
, . 1996
y
Experiment:
T 2k 1 2 20
y
(90% C.L.) . 2000
y
3
2.
assumption
Se ** -----------------> Se * + Se *
K ab = 12.652 K
a
1 = 11.221
keV, keV 2K ab 1.00
=25.3 K
a
2 = 11.181 keV 0.52
K
b
1 = 12.491 keV 0.21
K
b
2 = 12.651
keV 0.01 keV
w
k =0.596
w
e =0.404
x-ray e-Auger
Se*
е а е а к к
Se*
е а к е а к
} 0.404
2 = 0.163
= 0.481
0 .
596 2 = 0.355
4
Schematic diagram of 2k-capture event
78 Se** 78 Se ** 78 Se 78 Se 5
Parameters of the counter
Cross-section of the counter + - anode 140 150
1.
Body’s material
2.
Total length, mm
3.
Fiducial length, mm
4.
Outer diameter, mm
5.
Inner diameter, mm
6.
Central anode material, mm
7.
Total volume, l
8.
Fid. Volume, l
9.
Pressure, at
10.
Capacity, pF
11.
Anode wire resistance , Ohm Cu 1160 595 150 140 g.p.tan., 0.010
11.0
9.16
4.51
31 613
6
Low background shield
1760 mm
Ca libra tion channel Signal Gas equipment
Kr Cu Pb
15 cm lead 8 cm borated polyethylene 18 cm copper 7
8
View of installation
9
78 Kr – sumple 1. Old 78 Kr – sumple, (48.64
l)
Isotopes Content (atomic percents) 78 94.070
80 5.910
82 < 0.005
83 < 0.005
84 < 0.005
86 < 0.005
85 Kr – activity 0.1
Bk
/
l Preliminary measurements
:
Bkg.
(20 100 keV) = 3700 h-1 (V=9.16
l, p=
4.55
at
) 2. New 78 Kr – sumple, (47.65
l)
Isotopes 78 80 82 83 84 86 Content (atomic percents) 99.810
0.170
< 0.005
< 0.005
< 0.005
< 0.005
85 Kr – activity 1.8
· 10 -3
Bk
/
l Preliminary measurements
:
Bkg.
(20 100 keV) = 67 h -1
Bkg. = Bkg.
|
own
?
+ Bkg.
K
r
-85 (V=9.16
l, p=
4.55
at
) 10
Electric scheme of the setup
PA1 & PA2
–
preamplifiers A1 & A2
–
amplifiers CS – coincidence scheme DO – digital oscilloscope
11
Real pulse sample
12
Spectrum of
109
Cd (88 keV)
R=6% Energy, keV R=6.5% R=15.9% Energy, keV 13
Background
(T=159 h) 1-point + 2-point + 3-point 10 5 0 0 2 1 0 0 40 20 0 0 40 20 0 0 20 20 20 40 60 1-point 80 100 120 40 60 2-point 80 40 60 3-point 80 100 120 100 120 120 100 80 60 40 20 0 0 20 40 60 Energy, keV 80 100 120
F
49
e
50 100
Time, h
150
t
42 200 14
Values of parameters for useful events with 3(
•
) ionizations
E, keV
1.6
2.9
11.2
E
1 a
E
2 a
E k
a 12.5
E k
b 25.3
E
S
N, chan.
26 46.5
181 202 409
R,%
44.7
35.1
16.9
16.0
11.3
2
, chan.
(95% C.L.) 10 13 26 27 41 N, chan.
16 36 23 60 155 207 175 229 368 450 15
Events in the region 25.3±2.5 keV (95% C.L.)
№, event E
S
E 1 , chan.
E 2 , chan.
E 3 , chan.
1 2 3 4 5 444 439 381 410 384 124 70 66 116 23 139 137 79 133 94 181 213 236 161 267
Effect =
0 Probability (p): 2.44 (90% С.L.)
E
1
a
;
E k
a
; E k
b
E
2
a
;
E k
a
; E k
b 0.773
0.985
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1.
2.
3.
Results:
Number of Kr-78 atoms - 1.08·10 24 Registration efficiency for 3(·)-events - 0.809
Probability for 3(·)-events - 0.355
T 1 2 24
N eff Limi t
:
N eff
134.
4
y
: T 1 2 2 К , 2
N eff
23 21
y
90% C.
L.
Se nsitivi ty
:
N eff
1.645
134.4=11.6: 22
y
90% C.L.
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