Study of the Time-Reversal Violation
with neutrons
Angular correlations N and R
Elctric dipole moment of neutron
nTRV@PSI
nEDM@PSI
Adam Kozela
Institute of Nuclear Physics, PAN, Cracow, Poland
Adam Kozela
26/09/2014
1
T- and CP-violation
Theories
Observations

II Low of Thermodynamics - „arrow of time”

Byron Asymmetry of the Universe.

Kaon decays: KL -> ππ (1964).

First observation of CP violation, (1988, NA31)

CP violation in CKM matrix, 3rd generation
of quarks and imaginary phase δKM,
difference in decay of KL, KS to π0 π0 i π+ π- .


Direct violation of T in kaon decays:
o
(1998, CPLEAR, CERN),
o
(2000, KTeV, Fermilab), KL-> π+ π- e+ e- .

interaction allows for CP violation without
Many observations of CP violation in the decays
flavour change.
of B mesons (BaBar, SLAC), (Belle, KEK).

Recently: CP violation in the decay of D0
(LHCb).

θ therm in effective Lagrangian of strong

Direct observation of T-violation in entangled
BB meson system.
Adam Kozela
Imaginary parts of coupling constants in
weak interaction.

26/09/2014
Final state interaction.
2
Why neutron?

It is neutral… (application of high electric fields possible).

Long lifetime (886 sec, good and bad…).

Decays by weak interaction (known from TRV).

No effects from nuclear or atomic structure (for free neutrons
exact value of MF, MGT).

Small decay asymmetry A and small charges involved in decay
=> (small and precisely known final state interaction
correction).

Made of u and d quark (very small effect from KM-matrix).
Adam Kozela
26/09/2014
3
Angular correlation in neutron decay
Pp
Jn
(~885.7s)
σT1
n
->
p eνe + 782 keV
se
p
σT2
p
Tp=-p
Ts=-s
TJ = - J
A- decay asymmetry (-0.1173)
R, N – Correlation coefficients
Adam Kozela
26/09/2014
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Korelacje kierunkowe w rozpadzie neutronu
Pp
Jn
σT1
se
σT2
p
p
PDG:
 
W ( , J , s , E , E  , p , p  ) 
1 a
p  p
E E
m
b

E

p
p  p
p  p
p
p
 
s G
 H
 K
 L

E
E
E  m E E
E E


p
 A p  B p  C p  D p  p
j  E
E
Ep
E E

J












p
p

s
p

s
s  p 
 p  p
N s Q
 R
 Ss
 T p

j 
E
E E  m
E
E E
E E 


J





s
 p
s
 p
p  p p  s

U p
V
W
j 
E E
E
E E E  m

J
Adam Kozela




26/09/2014
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Correlation coefficients N, R and
exotic interactions

Contribution from complex phase δKM and θ-term negligible (~10-12).

Allowing for nonzero exotic couplings in weak interaction
(Jackson, 57):
NFSI~0.068 6∙10-4
RFSI~0.0006 6∙10-6
Beyond Standard Model:
S, T – relative strength of scalar
and tensor couplings

Standard Model
Final state interaction
N measurement: detector test (Re(S), Re(T) known well from other
experiments).

If measured R≠0
Im(C
Adam
Kozela
S) i
Im(CT).
new mechanism of T-(CP) violation, limit on
26/09/2014
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Experimental setup (Mott Polarimeter), top view
n
V-track
Adam Kozela
26/09/2014
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Correlation coefficients N and R our result
NFSI~0.0686∙10-4
RFSI~0.00066∙10-6
Former limmitations
NSM·100
N ·100
RSM·100
R·100
T 
68
Adam Kozela
62115
26/09/2014
0.6
4125S

C T  C 'T
CA
C S  C 'S
CV
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Correlation coefficients N and R our result
NFSI~0.0686∙10-4
RFSI~0.00066∙10-6
Former limmitations
And our result
[Phys. Rev. C 85, 045501]
T 
S 
N = (62115)·10-3
Adam Kozela
C T  C 'T
CA
C S  C 'S
CV
R = (4125)·10-3
26/09/2014
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Correlation coefficients N and R, our result
First measurement of correlation coefficients R i N in neutron
decay is consistent with Standard Model expectations and with
Time Reversal Symmetry.
T 
S 
N = (62115)·10-3
Adam Kozela
C T  C 'T
CA
C S  C 'S
CV
R = (4125)·10-3
26/09/2014
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Electric Dipole Moment
 Simple case:

Particle with spin:
+
Q
e
-Q
+
_
_+
Adam Kozela
_
+
Electric dipole moment of particle with spin
Violates both Parity and time Reversal
Symmetry
26/09/2014
11
nEDM – predictions

θ-term from QCD Lagrangian: even
~10-18
e·cm.
nEDN
[e·cm]
~10-9
„Strong CP-problem”

Current limit: 2.9·10–26 e·cm.

nEDM@PSI final goal: 5·10-28 e·cm

Contribution from complex phase δKM negligible
below ~10-32 e·cm.
Adam Kozela
26/09/2014
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nEDM current precision
dn=(+0.2 ± 1.5 ± 0.7)·10-26 e·cm.
d ≈ 2 µm
Adam Kozela
26/09/2014
n
13
nEDM @ Paul Scherrer Institute
[successor of RAL,Sussex,ILL]
Ramsey resonance method of
separate oscillating fields applied
for Ultra Cold Neutrons.
UCN; v<10m/s
Adam Kozela
26/09/2014
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Ramsey resonance method of
oscillating fields - principle
Sample of polarized neutrons
In constant, uniform fields B (1 μT) and
E (12 kV/cm).
1.
RF „π/2” pulse (30 Hz).
2.
E
3.
or
Free precession of neutron spin
T ~ 150200 s.
E↑↑B:
ωL+ = 2/ћ(μnB + dnE)
E↑↓B:
ωL- = 2/ћ(μnB - dnE)
dn = ћ/4 ∙Δω/E
4.
Second „π/2” pulse.
5.
Analysis of neutron polarization.
Adam Kozela
26/09/2014
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Ramsey resonance method of
oscillating fields - principle
C1
dn 
 (     )
4E
Statistical uncertainty:
s (d n ) 
C2
Adam Kozela
26/09/2014
2 ET
N
where:
visibility
x – working points

 
C1  C 2
C1  C 2
E: electric field intensity,
T: free precession time
N: number of neutrons counted
after T.
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nEDM @ PSI improvements

UCN source, 1000 UCN/cm3
Magnetometry and
magnetic field control

Solid D2,30l,~5K
•
•
•
•
Adam Kozela
New shielding
Surrounding Field Compensation
New co-magnetometers…
…
26/09/2014
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Adam Kozela
26/09/2014
18
Współczynniki korelacji N i R a amplitudy
wymiany leptokwarków
d
X
-1/3
u

e

spin
0
1
2/3
F
f
1/3
H
h
d
X
e
u
2/3
e


Q
e
Wcześniejsze ograniczenia
i nasz rezultat
LQ-wektorowe
N = 62115
Adam Kozela
R = 4125
26/09/2014
19
Minimalny Supersymetryczny Model Standardowy z
łamaniem parzystości R
e

~
e
L

e
d
u
d
~
dR
u

e
R = 4125
e

N = 62115
Adam Kozela
26/09/2014
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