1. Study of the Time-Reversal Violation with neutrons
Angular correlations N and R
Elctric dipole moment of neutron
Adam Kozela
Institute of Nuclear Physics, PAN, Cracow, Poland

2. T- and CP-violation Observations Theories
II Low of Thermodynamics - „arrow of time”
Byron Asymmetry of the Universe.
Kaon decays: KL -> ππ (1964).
First observation of CP violation, (1988, NA31) difference in decay of KL, KS to π0 π0 i π+ π- .
Direct violation of T in kaon decays:
(1998, CPLEAR, CERN),
(2000, KTeV, Fermilab), KL-> π+ π- e+ e- .
Many observations of CP violation in the decays of B mesons (BaBar, SLAC), (Belle, KEK).
Recently: CP violation in the decay of D0 (LHCb).
Direct observation of T-violation in entangled BB meson system.
CP violation in CKM matrix, 3rd generation of quarks and imaginary phase δKM,
θ therm in effective Lagrangian of strong interaction allows for CP violation without flavour change.
Imaginary parts of coupling constants in weak interaction.
Final state interaction.

3. 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).

4. Angular correlation in neutron decayp p Pp Jn
(~885.7s)
σT1
n -> p e νe keV -
T p = - p
σT2
T s = - s
T J = - J
A- decay asymmetry ( )
R, N – Correlation coefficients

5. Korelacje kierunkowe w rozpadzie neutronuPp Jn
σT1
σT2
PDG:
= (7)
= (25)
= (30)
= (6)
= (4)

6. 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 new mechanism of T-(CP) violation, limit on Im(CS) i Im(CT).

7. Experimental setup (Mott Polarimeter), top view
V-track

8. Correlation coefficients N and R our result
NFSI~0.0686∙10-4
RFSI~0.00066∙10-6
Former limmitations
NSM·100
RSM·100
N ·100
R·100 68
0.6
62115
4125

9. 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, ]
N = (62115)·10-3
R = (4125)·10-3

10. 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.
N = (62115)·10-3
R = (4125)·10-3

11. Electric Dipole Moment
Simple case:
Particle with spin: +Q -Q e + _ + _ + _
Electric dipole moment of particle with spin
Violates both Parity and time Reversal
Symmetry

12. nEDM – predictions θ-term from QCD Lagrangian: even ~10-18 e·cm.
nEDN
[e·cm]
θ-term from QCD Lagrangian: even ~10-18 e·cm.
~10-9
„Strong CP-problem”
Current limit: 2.9·10–26 e·cm.
final goal: 5· e·cm
Contribution from complex phase δKM negligible
below ~10-32 e·cm.

13. nEDM current precision
dn=(+0.2 ± 1.5 ± 0.7)·10-26 e·cm. n
d ≈ 2 µm

14. 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

15. Ramsey resonance method of oscillating fields - principle
Sample of polarized neutrons
In constant, uniform fields B (1 μT) and E (12 kV/cm).
RF „π/2” pulse (30 Hz).
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
Second „π/2” pulse.
Analysis of neutron polarization. 1. 2. E 3. or 4. 5.

16. Ramsey resonance method of oscillating fields - principle
Statistical uncertainty: C2
where:
visibility
E: electric field intensity,
T: free precession time
N: number of neutrons counted
after T.
x – working points

17. nEDM @ PSI improvements
UCN source, 1000 UCN/cm3
Magnetometry and
magnetic field control
Solid D2,30l,~5K
New shielding
Surrounding Field Compensation
New co-magnetometers… …

19. Współczynniki korelacji N i R a amplitudy wymiany leptokwarków
spin 1
2/3 F f Q
1/3 H h
Wcześniejsze ograniczenia
i nasz rezultat
LQ-wektorowe
N = 62115
R = 4125

20. Minimalny Supersymetryczny Model Standardowy z łamaniem parzystości R