ucn magnetic storage and neutron lifetime
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UCN magnetic storage and neutron lifetime. V.F.Ezhov Petersburg Nuclear Physics Institute, Gatchina, Russia. ( ITEP - 2007 ). - PowerPoint PPT PresentationTRANSCRIPT
UCN magnetic storage and neutron lifetime
V.F.Ezhov
Petersburg Nuclear Physics Institute, Gatchina, Russia.
(ITEP - 2007)
After neutrino decoupling and electron-positron annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·109 K, at t ~ 98 s, the rate of two-body and three-body reactions become negligible compared to the one-body reaction. Only neutron decay then dominates.
CKM mixing matrix:
V F udG G V
A0 2
V
1G A 2
G 1 3
2
ud 2n
4908.7 1.9 sV
1 3
R R 2 2 2
ud F
kft 1 1
V G 1 3
Required experimental accuracy for n and A has to be about 10-3 and better.
Neutron decay and Standard Model
~1.5 % ~2.4 %
u
n d
d
u
d p
u
e-
eW-
GA
GV
u
n d
d
u
d p
u
e-
eW-
u
n d
d
u
d p
u
e-
eW-
GA
GV
GA
GV
W.MarcianoA.SirlinPRL 96, 032002 (2006)
ud us ub
cd cs cb
td ts tb
d V V V d
s V V V s
b V V V b
The best results for neutron lifetime
N beam:• 886.8±1.2±3.2 (NIST, 2003)• 889.2±4.8 (Sussex-ILL, 1995)
UCN storage in material trap:• 878.5±0.7± 0.3 (PNPI-ILL,2004)• 885.4±0.9±0.4 (KI-ILL, 1997) • 882.6±2.7 (KI-ILL, 1997) • 888.4±3.1±1.1 (PNPI, 1992) • 887.6±3.0 (ILL, 1989)
Particle data 2003 (without PNPI - ILL,2004):
n = (885.70.8) s
Neutron decay and Standard Model (status in 2003)
2 2 2nud us ubV V V
1 0.9924(28)
0.0076(28) 2.7
nud
00ud
us
ub
V 0.9717(13)
V 0.9738(5)
V 0.2196(23) PDG(2003)
V 0.0036(9) PDG(2003)
nA,
00ft
2us1 V
n 00ud udV V 0.0021(26)
0.8
n
A=-0.1189(8) PERKEO 2002
885.7 0.8 s PDG(2003)
Data analysis with the most precise measurements of neutron decay
2 2 2nud us ubV V V
1.0038 28 = 1.4 -
2 2 200ud us ubV V V
0.9992 15 = 0.5 +
n 00ud ud
3
However
V V
2.4 1.0 10
2.4Δ=2.4σ
ΔV
ud=
2.4σ
nVud
00Vud
n 878.5 0.8 s (A.Serebrov et al. 2005)
A=-0.1187(5) (PERKEO 2005)
=-1.2733(13)
nud
2ud us
us
00ud
ub
V 0.97614(95)
V 1 V 0.97420(47)
V 0.2257(21) PDG06
V 0.97377(27) PDG06
V 0.0043(3) PDG06
The improvement of the accuracy of A-measurements (factor of 3 or more) is extremely important.
Reflection of UCN by magnetic barrier W. Paul, in Proc. Int. Conf. on Nuclear Physics and Physics of Fundamental Particles, Chicago, 1951.
V.V. Vladimirskii, Sov.Phys. - JETP 12, 740, 1961 • Magnetic potential
• For magnetic moment of neutron • Nuclear potential of Be
• Magnetic field 1 T reflects neutrons up to 3.4 m/s, as Al.
•
• + for and
• – for
BU
17106.0 TeVU
eV7105.2
BBUF
)(
B
B
Probability of depolarization
• Precession of magnetic moment
• Adiabatic condition
• ( -- is the velocity of neutron)• For case of strong field • (B = 1T), B = 1T/mm and velocity v = 3.4 m/s one
can receive next relation for adiabatic condition:• 1.83108 >> 3.4103.
Bdt
dn
1181083.1 Tsn
BBvBdtdBBn /
v
=25±2 sec
“UCN storage in the vessel with magnetic wall.” JETP Letters 23(3), 1976
Y.Y.Kosvintsev, Y.A.Kushnir, V.I.Morozov
Ю.Г.Абов, В.В.Васильев,В.В.Владимирский, И.Б.РожнинПисьма ЖЭТФ, т.44(8), 369, (1986).
Y.G.Abov, V.V.Vasil’ev, V.V.Vladirski, I.B.Rozhnin JETP Letters, 44(8), 369, (1986)
Main result:It was shown firstly that it’s possible to obtain τ > 700 sec in the magneto-gravitational trap.
Main problem of the current systems is too large electric power (about 100 kWt)
W. Paul, F. Anton, L. Paul, S. Paul, and W. Mampe, Z. f. Physik C 45, 25
(1989).
Sextupole torus. Rs orbit of circulating neutrons.
τ= 877 ± 10 s
The achieved usable field of 3.5 T permits the confinement of neutrons in the velocity range of 5 – 20 m/s corresponding to a kinetic energy up to 2 * 10-6 eV.
P.R. Huffman, C.R. Brome, J. S. Butterworth, K. J. Coakle,M. S. Dewey, S.N. Dzhosyuk, R. Golub, G. L. Greene, K. Habicht,S.K. Lamoreaux, C.E.H. Mattoni, D.N. McKinsey, F. E. Wietfeldt,
& J.M. Doyle Nature 403, 62, 2000
τ = 750+330−200 s.
The trapping region is filled with superfluid 4He, which is used to load neutronsinto the trap and as a scintillator to detect their decay. Neutrons have a lifetimein the trap of
The main problems: 1. Filling and empting. If
one use superconducting system, then he can’t switch on field too fast.
2. Huge setup and small storage volume
Magnetic wall
1 – permanent magnet2 – magnetic field
guide
2004
Detector of both polarization
• To control the depolarization of UCN we cover the inner trap walls with thin lay of fomblin that reflects depolarized UCN. In this case the depolarized UCN penetrate the magnetic barrier inside the solenoid and are measured by the UCN detector installed below the solenoid. Hence this detector may be used as monitor for depolarization losses during neutron storage.
• Monitor of trap filling• Preliminary neutron spectrum preparation• Absence of neutrons heating at the moment of magnetic
shutter switching on.• Possibility to divide fast and spin-flipped neutrons
Experimental advantages
0 20 40 60 80 100
-20
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
Lift is out of trap
Lift is opened & magnetic shutter is switched on
Lift is moved
Shutter is opened
Inte
nsi
ty (
n/s
)
Time (s)
Filling with magnetic shutter on(1) Filling without magnetic shutter(2) Stored UCN (3)
Problems
• Cleaning. Magnetic wall is an ideal mirror, as a result there are stationary trajectories.
• Efficiency of depolarized neutrons collection.
First stage: (2006)Neutron guide diameter 20 mmWithout forced spin-flip
Second stage: (2007)Neutron guide diameter 60 mmForced spin-flip is switched on
00
0 0
trap decay trap dep trap
leak dep trap
trap
leak
dN t N t N t dt
dN t N t dt
N N
N
0
0
( )
( ) 1
decay leak
decay leak
t
trap
tleakleak
decay leak
N t N e
NN t e
00
0
0
0
ln
ln
traptrap leak
decay
trap
trapleak
dep
trap
N TN N T N T
N
T N N T
N TN T
N
T N N T
1 10 0 1 1 1 1
0 0
0 1 0 1 1
ln lntrap traptrap leak trap leak
trap trap
N T N TN N T N T N N T N T
N N
T N N T T N N T
Lifetime no depended method of efficiency measuring
400 600
-0,4
0,0
0,4
Inte
nsi
ty n
/s
Time (s)
CDepolarization on and off
1020
0
20
Inte
nsi
ty n
/s
Time (s)
CDepolarization on and off
1000 301
1 2
3011100 301
2 1
1001
( ( ) ( ))
( ( ) ( ))
t
t
f t f t e dt
f t f t e dt
decay = 878.4 1.8 s.
ε = 0.90±0.02
2005-2006Volume 15 lNeutron elevator Storage time 874.6 -1.6
+4 sec.
0 500 1000 1500 2000 2500
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75In
ten
sity
Time
2200 2300401 401
401 2201
(400) 1/ ( ) ( )t t
N f t e dt f t e dt
1800 1900401 401
401 1801
(400) 1/ ( ) ( )t t
N f t e dt f t e dt
500 600401 2201
401 501
(400) 1/ ( ) ( )t t
N f t e dt f t e dt
…………………………………………………….
860 865 870 875 880 885 890195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
UC
N
decay
(s)
1000 s 1300 s 1800 s 2200 s 400 s
Convolution of different storage function to 400 s depended on neutron lifetime
877.4±1.7 s.
300 600 900 1200 1500 1800 2100 2400
16
32
64
128U
CN
Time (s)
22012300
2200 2200
2201
( ) decay
t
N f t e dt
1801 18011900 2200
1800 1800
1801 1801
( ) 1/ ( )decay decay
t t
N f t e dt f t e dt
878.6±1.8 s.
The best results for neutron lifetime
N beam:• 886.8±1.2±3.2 (NIST, 2003)• 889.2±4.8 (Sussex-ILL, 1995)
UCN storage in material trap:• 878.5±0.7± 0.3 (PNPI-ILL,2004)• 885.4±0.9±0.4 (KI-ILL, 1997) • 882.6±2.7 (KI-ILL, 1997) • 888.4±3.1±1.1 (PNPI, 1992) • 887.6±3.0 (ILL, 1989)
Particle data 2003 (without PNPI - ILL,2004):
n = (885.70.8) sMagnetic trap (2007)
878.2 1.6 s.Preliminary
Our plans
1. 2008 – increasing the volume to one order and increasing of magnetic barrier to 2 times
2. 2009 – run with new trap
• V.F.Ezhov,1 B.A.Bazarov,1 P.Geltenbort,2 F.J.Hartman,3 N.A.Kovrizhnykh,4 A.Z.Andreev, 1 G.Ban5, A.G.Glushkov, 1 M.G.Groshev, 1 V.A.Knyazkov, 1 G.D.Krygin, 1 A.R.Muller, O.Naviliat-Cuncic5 S.Paul, 3 R.Picker, 3 V.L.Ryabov, 1 A.P.Serebrov, 1 O.Zimmer3,2
• 1 - Petersburg Nuclear Physics Institute, Gatchina, Russia.• 2 - Institut Laue-Langevin, Grenoble, France.• 3 - Technical University, Munich, Germany.• 4 - Reseach Institute of electrophysical apparatus,
S-Petersburg, Russia.• 5 - Caen University, France
4x10-4 8x10-4 1,2x10-3 1,6x10-3 2x10-3
22
24
26
28
30
32
34
36
B Linear Fit of Data1_B
Qu
an
tity
of n
eu
tro
ns
afte
r 2
20
0 s
of s
tora
ge
tim
e
Vacuum (torr)
Vacuum dependence
1
1
1
0ln
0ln
ppt
NtN
NtN
p
torrsp 1 04.015.0
1/s 0.001131/880 decay
torr10 6p
))exp((0)( tpNtN pdecay
877.4±1.7 s.
878.6±1.8 s.
decay = 878.4 1.8 s.
decay = 878.2 1.6 s. Preliminary
ε = 0.90±0.02 2006-2007 Small diameter of neutron guide
Increased diameter of neutron guide