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Experimental investigation of spatial parity violation effectsin interaction of the polarized neutrons with light nucleiwith the purpose of determination of weak meson-nucleon
coupling constants
Low energy physics: neutron physics at En~10-3 eV
Search for the neutral currents in the weak NN-interaction.
Test of the validity of the meson exchange description of the weak NN-force.
Interpretation of the P-odd observables in complex nuclei and in the eN scattering experiments.
Electroweak interaction at low energy as the tools to study the strongly interacting limit of QCD.
[W. M. Snow. J. Res. NIST 110 (2005) 189]
P. V. Sedyshev.Frank Laboratory of Neutron Physics, JINR, Dubna, Russia
2
NN electroweak interactions at low energy
nC
sC
NL JJJJ sincos)(
1sin2)()( TJJ Css
Light quarks u, d, s.
C – Cabibbo angle, sinC 0.22
T – amount of isospin change
2,1,0)()( TJJ nn
2,0cos2)()( TJJ C
3
NN electroweak interactions at low energy
Description of the parity nonconservation NN interaction:Potential (meson-exchange) description: R. J. Blin-Stoil. Phys. Rev. 118 (1960)1605; G. Barton. Nuovo Cimento 19 (1961) 512; B. H. J. McKellar. Phys. Lett. B26 (1967) ; E. M. Heinly. Ann. Rev. Nucl. Part. Sci.19(1969) 367; E. Fischbach, D. Tadic. Phys. Rep. C6 (1973) 123; M. Gari. Phys. Rep. C6(1973) 318;B. Desplanques, J. Donoghue, B. Holstein. Ann. Phys. 124 (1980) 449; B. Desplanques. Phys. Rep. 297 (1998)
1.Amplitude description: G. S. Danilov. Phys. Lett. 18 (1971) 35, M. A.Box, B. H. J. McKellar, P. Pick, K. R.
Lassey J. Phys. G1 (1975) 493; B. Desplanques, J. Missener. Nucl. Phys. A300 (1978) 286.
Analysis using an EFT and chiral perturbation; calculation with use of lattice gauge theory: S.-L. Zhu, J. Puglia, B. R. Holstein, M. J. Ramsey-Musolf. Phys. Rev. D63 (2001) 033006.
4
One meson exchange model
R. J. Blin-Stoil. Phys. Rev. 118 (1960)1605; G. Barton. Nuovo Cimento 19 (1961) 512; B. H. J. McKellar. Phys.Lett. B26 (1967) ; E. M. Heinly. Ann. Rev. Nucl. Part. Sci. 19(1969) 367; E. Fischbach, D. Tadic. Phys. Rep. C6(1973) 123; M. Gari. Phys. Rep. C6 (1973) 318; B. Desplanques, J. Donoghue, B. Holstein. Ann. Phys. 124 (1980)449;B. Desplanques. Phys. Rep. 297 (1998) 1.
Strong NN interaction:Rrep 0.8 fm – repulsive core described byspin-spin interaction between quarks;RM 2 fm – one-meson exchange model;Intermediate distances – parameters arefitted
Weak NN interaction:RW,Z 10-3 fm – no direct exchange.Meson exchange.
N
N
N
N
MPV PC
N
N
N
N
MPC PC
5
One meson exchange model
N
N
N
N
, , PV PC
0, , ’ - exchange is forbidden, due to the CP-invariance; - exchange is strongly suppressed
± - T=1 - T=0, 1, 2 - T=0, 2
6
One meson exchange model PNC NN potential is characterized by weak meson exchange coupling constants [V. M.
Dubovik, et. al. PEPAN 18 (1987) 575; B. Desplanques. Phys. Rep.297 (1998) 1] :102101 ,,,,),( hhhhhfh
7
Weak meson-nucleon coupling constants
The MNN coupling constants are calculated from the flower-conserving part of the weak interaction [V. M. Dubovik, et. al. PEPAN 18 (1987) 575; B. Desplanques. Phys.Rep.297 (1998) 1]
Due to uncertainties in the effects of strong QCD, the range of predictions is broad.
DDH – B. Desplanques, J. F. Donoughu, B. R. Holstein [B. Desplanques, J. Donoghue, B.
Holstein. Ann. Phys. 124 (1980) 449] - used the quark model, SU(6) symmetry, the strong interaction effects are treated in RGT.DZ – V. M. Dubovik, S. V. Zenkin [V. M. Dubovik, S. V. Zenkin. Ann. Phys. 172 (1986) 100 ] – used the quark model, SU(6) symmetry, the strong interaction effects are treated in RGT.FCDH - G. B. Feldman, G. A. Crawford, J. Dubach, B. R. Holstein [G. B. Feldman et. al. Phys.
Rev. C43 (1991) 863] – included MN and M vertices. KM – N. Kaiser, U. G. Meissner [N. Kaiser, U. G. Meissner. Nucl. Phys. A 499 (1989) 699] – calculated within the framework of a nonlinear chiral effective Langragian.
)}
))(3
1
3
1
3
2(sin4(
2
1
)(sin)({cos2
5
552
552
552
ss
dduussdduussdduu
suusussuduududduG
H
W
CCpncS
8
Weak meson-nucleon coupling constants
Weak meson-nucleon coupling constants (in units of 10-7):
G. A. Lobov: f = 3.4∙10-7 [G. A. Lobov. Phys. At. Nucl. 65 (2001) 561.] is calculated by the method of QCD sum rules.
9
One meson exchange model
10210 FhEhDhChBhAfAPNC
Theories of PV phenomena in nuclei starts with solution of the strong, PV conserving,nuclear Hamiltonian and the admix P-odd components treating the weak meson-exchange potential as a perturbation:
E
V PNC
The PV observable is given by a linear combination of weak MNN constants:
Problems: Theoretical – for more than a few bodies the nuclear wave functions can not be exactlycalculated;Experimental – the small size of weak amplitudes relative to strong amplitudes ~10-7.
Task: using this theory to calculate electroweak effects in the NN interaction and todetermine the weak couplings from experiment.
10
Experiments
Observable Experiment, 10-7 f-0.12h1-0.18h1 h0+0.7h0 h1 h2 h0 h1
Azpp(13.6 MeV) -0.930.21 0.043 0.043 0.017 0.009 0.039
Azpp(45 MeV) -1.570.23 0.079 0.079 0.032 0.018 0.073
Azp(46 MeV) -3.34 0.93 -0.340 0.140 0.006 -0.039 -0.002
P(18F) 1200±3860 4385 34 -44
A(19F) -740±190 -94.2 34.1 -1.1 -4.5 -0.1
133Cs 800±140 60.7 -15.8 3.4 0.4 1.0 6.1
205Tl 370±390 -18.0 3.8 -1.8 -0.3 0.1 -2.0
PNC observables and theoretical coefficients, decomposed into the weak couplingcombinations.
E. G. Adelberger, W. C. Haxton. Ann. Rev. Nucl. Part. Sci. 35 (1985) 501; S. A. Page, et. al. Phys. Rev. C35(1987) 1119; J. Lang, et.al. Phys. Rev. C34 (1986) 1545; W. C. Haxton, et. al. Phys. Rev. Lett 86 (2001) 5247; W.M. Snow. J. Res. NIST 110 (2005) 189
11
The PNC constraints
best values
W. C. Haxton et. al. Phys. Rev. Let. 86 (2001) 5347
18F(1.081 MeV), P:
-1.0∙10-7 f 1.2∙10-7
10
210
065.0065.0
030.0074.0074.0
hh
hhhAz
11 5705944490 hhfP
In order to solve this problem, one needs more independent interpretable inexperiments.
12
Experiments
dpn
Experiment in progress at LANSCE: M. T. Gerike, J. D. Bowman, R. D. Carlini, T. E. Chupp, K. P. Coulter, M. Dabaghyan, S. J. Freedman, T. R. Gentile, G. L. Green, F. W. Hersman, T. Ino, S. Ishimoto, G. L. Jones, B. Lauss, M. B. Leuschner, B. Losowski, R. Mahurin, Y. Masuda, G. S. Mitchel, S. Muto, H. Nann,S. A. Page, S. I. Penttila, W. D. Ramsay, S. Santra, P.-N. Seo, E. I. Sharapov, T. B. Smith, W. M. Snow, W. S. Wilburn, V. Yuan, H. Zhu. J. Res. NIST 110 (2005) 195; J. Res. NIST 110 (2005) 215
)02.002.0(045.0 11 hhfA
13
P-odd effects in extremely light nuclei
006.045.0 hft
Cluster and multiclaster schemes for 6,7Li: n + {d’} {n,d’} + .Calculation has been performed in the framework of the three body pick-up reaction mechanism.
7108.2 t
HnLi 36 ),( N. N. Nesterov, I. S. Okunev. JETPh Let. 48 (1988):
P-odd asymmetry in the 6Li(n,)3H reaction with cold polarized neutrons:
(with DDH best values), contribution from -exchange ~75%
n=760 b at Eth
14
P-odd effects in extremely light nuclei
Expected value = 1.110-7 (DDH), contribution from -exchange ~66%
n=3940 b at Eth
1010 014.0014.00094.0028.016.0 hhhhf
LiLinB 7*71
10 ),(
V. A. Vesna, Yu. M. Gledenov, P. V. Lebedev-Stepanov, I. S. Okunev,
A.V. Sinykov, Yu. M. Tchuvilsky, E. V. Shulgina.Phys. At. Nucl. 62
(1999) 522; S. Yu. Igashov, A. V. Sinykov, Yu. M. Tchuvilsky.
In: Proc. ISINN-11. Dubna 2003, 34
The modern formalism of RGM was used on the solution of Schroedinger equation.
P-odd asymmetry in the -emission by the de-excitation of the 1st excited state of 7Li for the reaction 10B(n,)7Li* with polarized neutrons.
15
Experimental investigations of the P-odd effects in light nuclei
V. A. Vesna1, Yu. M. Gledenov2, V. V. Nesvizhevsky3,A. K. Petukhov3,
P. V. Sedyshev2, T. Soldner3, E. V. Shulgina1,O. Zimmer4
1Petersburg Nuclear Physics Institute of RAS, Gatchina, Russia.2Frank Laboratory of Neutron Physics, JINR, Dubna, Russia.
3Institut Laue-Langevin, Grenoble, France.4Technische Universität, München, Germany
VVR-M reactor in PNPI, Gatchina, Russia; vertical channel.
PF1B instrument of the ILL reactor, Grenoble, France.
Averaged neutron wavelength: n = 4.7 Å,Integrated neutron flux: Fn~ (2 – 5)∙1010 s-1
Integral method of measurement; special experimental technique and data treatment
16
6Li(n,)3H experiment
1 exp. (2002): 18 days main run; polarizer: 10 5 cm
2 exp. (2005): 48 days main run; polarizer: 8 8 cm;
3 exp. (2006): 25 days, 0-exp.; polarizer: 8 8 cm
ILL, Grenoble, FrancePF1B instrument
[V. A. Vesna, et. al. JETP Lett 82 (2005) 519].
17
View of the PF1B experimental area
18
Experimental scheme
cos1~)( tW
pn n n
1 2 3 4 5
1 – polarizer; 2 – resonance spin-flipper; 3 – ionization chamber; 4 – guiding field; 5 – beam-stop. pn - neutron momentum; n - neutron spin.
pn
n
pt
Geometry of experiment: n || Pn || Pt.
The accuracy of the alignment: < 10-2.
Spin-flipper state was changed every 1 - 2 s.
NN
NN
P
1
19
Ionization chamber
The detector is an assembly of ionization chambers placed in a cylindrical duralumin vessel. The entrance and exit 70 150 mm windows are zirconium foils of thickness 0.5 mm.[Yu. M. Gledenov et. al. NIM A350 (1994) 517. ]
20
Ionization chamber
Detector includes 24 identical double ionization chambers.
21
Ionization chamber
Scheme of the double ionization chamber:H – high-voltage electrode;C – signal electrode;T – target electrode.Distances: TC=CH=10.5 mmThe working gas: Ar, p=2 at.UT=UH=-375 V, UC=0 V (trough the preamplifier)
Signal electrodes: fiberglass frame;gold-coated wires, 100 µm, step 4 mm.
High voltage electrodes: fiberglass frame;beryllium bronze wires, 100 µm, step 2 mm.
Target electrodes: aluminum frame, cassette.
22
Ionization chamber
23
Current method of the event detection
dE
tFtN npair
det
)cos1()(
4)(~)(
Fn(t) – neutron flux on the target;Number of charged particles in elementary solid angle: N(t)~ Fn(t) (/4)(1+cos);d/d=(/4)(1+cos) – differential cross section . Energy of emitted particle: E=E() – due to the finite thickness of target layer.Number of the electron-ion pairs, produced by a charged particle due to ionization:npair = E()/, - energy of pair creation;Number of the electron-ion pairs in sensitive volume of detector:
Current in the detector circuit:
dEew
tFweNtI npair
det
)cos1)((4
)(~)(
w – drift velocity.
[V. M. Lobashev. Phys. At. Nucl. 5 (1965) 957; V. M. Lobashev et. al Phys. Lett. (1967) 104; Yu. M. Gledenov et. al. NIM A350 (1994) 517. ]
24
Current method of the event detection
dE
dE
II
II
det
det
)(
cos)(
NN
NN
PII
II
P
11
cos
)(
cos)(
det
det
dE
dE
I+, I- - detector current at different directions of the neutron polarization
- mean cosine.
25
Targets
0 1 2 30
100
200
300
400
500
E, MeV
-component absorbtion
t
0 1 2 30
100
200
E, MeV
2.05 MeV
t , 2.73 MeVmax
max
The lithium targets are 450 g/cm2 layers of LiF (the enrichment with 6Li of 95 %) with size of 140х60 mm.
6Li(n,)3H, Q=4.78 MeV: Et=2.73 MeV, E=2.05 MeV.It~ (1+cos), I~ (1-cos) - in opposite phases.
Lithium fluoride is evaporated onto 14 m aluminum foil and covered with the foil of the same thickness. Targets absorbed 60% of beam intensity
cos = 0.75
26
Ionization chamber
Pn
n
Signal electrodes of all the “forward” sections as wellas the signal electrodes of the “backward” sections were joined in to two separate lines – “forward” and “backward”, respectively. The detector was designed as a two-channel system. The signs of investigated P-odd effect in the detector channels was opposite at synchronous measurements.
NN
NN
P
1
II
II
Pt
1
27
The electronics and data acquisition system
Control computer
ADC (ACL-8112pg)
Counter-Timer (ACL 7120) Flipper control
Interface controlling the integrator gates
Interator Integrator
D1
PA
PA
U Uconst U Uconst
D2
Guiding field control
28
Current signal preamplifier
Feedback capacitance and resistance
Input
Uconst
u
PA switch
Calibration signalinput
Uconst
Idet
u
+ - +
I U converter: Uout = IdetRfb
See: V. A. Knyaz'kov., et. al. Nucl.Phys. A417 (1984) 209; Yu. M. Gledenov et. al. NIM A350 (1994) 517
29
Integrator
K7
K6 K10
Input
Output to ADC
K6, K7 - switches are for the integration and reset of the integrator;K10 – switch connects the integrator and the ADC
- ++
+ + +
--
K10 – reading outT0 T1
Flipper state
“+” ON, “-” OFF
Deleting time
K7 – integrator reset
K6 – integration time
See: V. A. Knyaz'kov., et. al. Nucl.Phys. A417 (1984) 209; Yu. M. Gledenov et. al. NIM A350 (1994) 517
KuUI c /det
30
The electronics and data acquisition system
Control computer
ADC (ACL-8112pg)
Counter-Timer (ACL 7120) Flipper control
Interface controlling the integrator gates
Interator Integrator
D1
PA
PA
U Uconst U Uconst
D2
Guiding field control
All signals were measured with a programmable 12-bit ADC with 16 independent inputs in the structure of the multifunctional data acquisition card ACL-8112pg ADLink Technology Inc. The timing diagram was generated using the programmable counter-timer card ACL-7120ADLink Technology Inc. Accuracy of the integrator key control signals is 2∙10-5. Accuracy of the flipper state control signal is 2.5∙10-7.
<unoise>/Uc < 10-4
31
Reactor power fluctuations
f, Hz
Power of the reactor neutron flux fluctuation as a function of frequency
23 1010 n
F
Fn
E. A. Garusov, et. al. Kernenergie 2 (1983) 68
Compensation of the reactor power fluctuations [V. M. Lobashov, et. al. Nucl. Phys. A197 (1972) 241;
V. A. Knyaz'kov., et. al. Nucl.Phys. A417 (1984) 209; Yu. M. Gledenov et. al. NIM A350 (1994) 517.]
32
Data acquisition procedure
654321 ,,,,, uuuuuu
41 uuu 32 uuu
uuu
- Values are measuring synchronously for each detector channel.
4 sequence values are jointed with a + - - + pattern:
- A single measurement
The N sequence single measurements are joined into a series: N = 128.
Uc+, Uc
- - are recorded one time per series.
)/()/(
)/()/(
KuUKuU
KuUKuU
cc
cct
KuUc /
ccc UUU UKui
i 2
II
II
Pt
1
33
Compensation of the reactor power fluctuations
Synchronous values
Fif
i vu
Fibi vu
N
i
N
i
b
i
f
i LN 1 1
1
2
1)1(1
)(
N
iiNN
D
0dL
dD
22 1
1
i
b
ii
b
i
i i i
b
i
f
i
b
i
f
i
N
NL
bi
fii L L – compensation coefficient
Compensation coefficient is determined over a series meeting the requirement of minimal subtraction dispersion
Compensation: (f,b/) 80.
34
Suppression of the apparatus asymmetries
Pn n
B+
B-
- different neutron polarization: uf(b) = (u+ - u- ) ;
- compensation: u = (uf - Lub) ;
- different guiding field directions: = (B+) - (B-)
Test of the system: = (1.7 2.4)∙10-10
Main sources of apparatus asymmetry: signal of the flipper control;signals in the ground circuits;scattering electromagnetic fieldsof the working facilities
35
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
А. 1 канал, поле "+"
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
B. 2 канал, поле "+"
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
C = A - B
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
D. 1 канал, поле "-"
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
E. 2 канал, поле "-"
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4
F = D - E
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4 G = A - D
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4 H = B - E
0 100 200 300 400
-4,0x10-4
-2,0x10-4
0,0
2,0x10-4
4,0x10-4 I = C - F
Suppression of the apparatus asymmetries
36
N Run
N Series
5"" 10 5"" 10 )( """" A , 510A
1 )1( 76 29.016.7 30.021.7 21.022.0
)2( 76 31.079.9 33.054.9 22.073.0
)2()1( L 76 19.045.1 19.026.1 13.009.0
2 )1( 85 52.096.3 51.081.4 36.051.0
)2( 85 56.002.6 56.091.6 39.044.0
)2()1( L 85 34.005.1 34.000.1 24.002.0
3 )1( 79 38.041.16 38.017.16 27.012.0
)2( 79 42.090.15 42.040.16 30.005.0
)2()1( L 79 25.023.0 25.010.0 18.016.0
4 )1( 79 46.059.4 44.087.4 32.035.0
)2( 79 49.012.6 48.047.6 34.030.0
)2()1( L 79 30.093.0 29.089.0 20.001.0
5 )1( 20 04.159.9 13.158.10 76.034.0
)2( 20 14.146.12 20.139.10 83.062.1
)2()1( L 20 68.049.1 73.039.0 50.062.0
L = 0.8, noise = -(2.0 8.0)∙10 -7
Contribution to the main measurements (normalized value):
noise = -(0.4 1.5)∙10 -9
37
The left-right asymmetry: 6Li(n,)3H : lr = (1.06 0.04)∙10-4
p nnp p
1)90sin(~ o
, o0 ,
)sin()90cos(~),(~ onLR
npp
np
np pp
,
pnnpp
)sin(~
, o0 , o0 ,
)sin()90cos(~),(~ onLR
n
pp
np
np pp
,
pnn pp
)90sin(~ o
, o0 ,
1)cos()90sin(~),(~ onLR
n
np
pp
np pp
,
pnnLR ppW,1~)( : pn pp
, , ),(~
nLR
) , ( 1~)( pn pW : ),(~ pn p
38
The left-right asymmetry
Pn
n
Pn n
lr = (4.9 1.9)∙10-7
39
Test of LR-asymmetry
Pn
n
Pn
tLR ~ [pnpt]
40
Constant components and LR-asymmetry vs. angle between neutron and proton momenta.
, rad t, 10-8
~ 0
-0.01
-0.015
-10.8 4.4
-9.9 4.1
-7.4 4.2
Averaged value -9.3 2.5
P-odd asymmetry coefficient vs. the angle between neutron and triton momenta
Additional test of the LR-asymmetry
tPNC ~ pt t
LR ~ [pnpt]
41
Some results
0 100 200 300 400 500 600 700
0,6
0,8
1,0
Номер серии
6Li(n,)3HК
оэф
.ком
п.
L
0 100 200 300 400 500 600 7002,5
3,0
3,5
Номер серии
Uc2
[В] Uconst2
0 100 200 300 400 500 600 7002,5
3,0
3,5
Номер серии
Uc1
[В]
Uconst1
42
Some results
0 200 400 600
-6,0x10 -3
-3,0x10-3
0,0
3,0x10 -3
6,0x10-3
Номер серии
0 200 400 600-2,0x10 -5
-1,0x10 -5
0,0
1,0x10-5
2,0x10 -5
Номер серии
6Li(n, )3H
PN
Unnormalized () and normalized (PN) effects in the HnLi 36 ),( reaction
43
0-experiment
1.Two-channel system.2. Linear drift compensation. 3. Compensation of the reactor power fluctuations. 4. Reversal guiding neutron spin magnetic field at the detector.
44
0-experiment
45
0-experiment
beff NN
210/ effb NN
eff
bbeff
beffbeff
beffbeff
N
N
NNNN
NNNN
)()(
)()(
46
0-experiment
1. 8Li, -, Emax = 16.0 MeV, T1/2 = 0.84 s, = -(0.08 0.01)
2. 20F, -, Emax = 7.0 MeV, T1/2 = 11.0 s, - ?
3. 35Cl(n,p)35S, Ep = 0.6 MeV, = -(1.5 0.34)·10-4
4. Al, Ar, N: , , , p - ?
All targets were covered with aluminum foils with the thickness of 20 m.
0 = -(0.0 0.5) 10-8.
47
Results
P<cos> PNC 0
PNPI 0.66 -(5.4 6.0)∙10-8 (2.0 1.7)·10-8
ILL, PF1B 0.66 -(8.1 3.9)∙10-8
ILL, PF1B 0.70 -(9.3 2.5)∙10-8
ILL, PF1B 0.70 (0.0 0.5)·10-8
-(8.6 2.0)∙10-8 (0.2 0.5)·10-8
70 104.11 h006.045.0 hft
710)4.04.0( f
48
10B(n,)7Li*7Li+ experiment
1-polarizer; 2-adiabatic spin-flipper; 3,6-magneted plates of guide field; 4-lead collimator; 5-concrete wall; 7-lead shield, 8-B4C-shield; 9-Helmgoltz coils; 10-
detectors; 11-sample; 12-Li beam stop.
Detectors: NaJ(Tl) 200 mm 100 mm.Sample: 50 g of 10B, 85%, size 1601805 mm, 14 m Al-foil. For the light detection the “Hamamatsu” photodiodes were used.
49
10B(n,)7Li*7Li+ experiment
50
10B(n,)7Li*7Li+ experiment
Result of 2 previous runs: = (5.1 3.8)10-8,
“0-experiment”: 0 = -(0.7 3.7)10-8.
1st Experiment (ILL, 2001):Main run: = + (8.84.6)10-8
“0”-test: 0= - (14.83.3)10-8
2nd Experiment (ILL, 2002):
Main run : = - (11.06.6)10-8
“0”-test: 0= - (0.73.7)10-8
Additional measurement: (C)= (1.71.9)10-6 normalized: sc= (2.42.7)10-11
51
Results
best values
52
Summary
1. We have received nonzero result of the P-odd asymmetry of the triton emission fromthe 6Li(n,)3H reaction with cold polarized neutrons.
2. An accuracy of our measurements is 2.110-8. Such precision have not yet beenachieved in neutron experiments.
3. The f coupling constant extracted from the experimental data favors small value,close to that have been obtained in the 18F measurements.
4. Low f value means that still there is no detection of the neutral currents in nucleon-
nucleon interactions at low energy.
5. The measurements of the P-odd asymmetry of - quanta from the 10B(n,)7Li*7Li+will be continued. Next run will be September-November this year.
6. The joint analysis of the 6Li and 10B results allows one to extract the h0 coupling
constant and to obtain more strong restrictions on the f costant.
53
Thank youfor your attention.
54
Experiments at PF1B: the working gas – Ar;pressure – p = 2.4 atm in 1st measurement
p = 1.9 atm in 2nd measurement
0 100 200 300 400 500 600 7000,0
1,0
2,0
3,0
4,0
5,0
working point 375 V
Uou
t, V
UHV
, V
"forward" sections "backward" sections
Ionization operating mode
55
Suppression of the apparatus asymmetries
uf(B+) = (uf++vfsf)-uf-= (uf+ - uf-)+vf
sf
ub(B+) = (ub++vbsf)-ub- = -(ub+ - ub-)+vb
sf
u(B+) = (uf+ - uf-) + L(ub+ - ub-) + (vfsf - Lvb
sf)
(B+) = PNC + (vfsf - Lvb
sf)/Uc
uf(B-) = (uf++ vfsf) - uf- = -(uf+ - uf-) + vf
sf
ub(B-) = (ub++ vbsf) - ub- = (ub+ - ub-) + vb
sf
u(B-) = -(uf++ uf-) ) - L(ub+ - ub-) + (vfsf - Lvb
sf)
(B-) = -PNC + (vfsf - Lvb
sf)/Uc
56
Test of the ionization chamber
Output signal vs. the lithium shutter position
Output signal vs. the reactor power
Uconst = IdetRfb
PNPI, VVR-M reactor, vertical channel: Fn≈ 2∙1010 s-1
A systematic investigation was carried out for the various gas pressure (0.15 – 4 atm) and various gas mixture (Ar, Ar + %CO2).
57
58
tDn
Hen4
-spin rotationHep4
-2 0 2 4 6 8 10 12 145
0
-5
-10
-15
-20
-25
-30
18F
PP
h0 h
0
f
10B
01101100112200 )()()()()(sincos)( ZZZZZZZZWWCCWW JJJJJJJJJJJJJ
Light quarks u, d, s. C=0, S=0,
C – Cabibbo angle, sinC 0.222,0)(cos 002 TJJ WWC
1)(sin 112 TJJ WWC
2,1,0)( TJJ ZZ
T – amount of isospin change at transition
59
NN electroweak interactions at low energy
Z
Z
ZW
W
WWS J
mqJ
ggJ
mqJ
gH 22
22
22
1
2
)(1
2
Weak current-current Hamiltonian:
g,g´ - elektroweak coupling constants; JW,Z – hadronic part of the charged and neutral currents; mW, mZ – intermediate vector boson masses; G – Fermi constant
2,
2ZWmq
288 2
22
2
2 G
m
gg
m
g
ZW
ZZWWWS JJJJ
GH
2
W±Z0
JW JW
JW JWJZ JZ
JZ JZ
g g g g
~G ~G
low level limit
