adam kozela 26/09/2014 1 study of the time-reversal violation with neutrons adam kozela institute of...

Adam Kozela 26/09/2014 1

Study of the Time-Reversal Violation

with neutrons

Adam Kozela

Institute of Nuclear Physics, PAN, Cracow, Poland

Angular correlations N and R nTRV@PSIElctric dipole moment of neutron nEDM@PSI


T- and CP-violation

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:

o (1998, CPLEAR, CERN),

o (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.

Observations Theories


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).


T p = - p

T J = - J

T= -

A- decay asymmetry (-0.1173)R, N – Correlation coefficients

e

pp

Pp

Jn

σT2

σT1

Angular correlation in neutron decay

n -> p e νe + 782 keV

(~885.7s)

-


e

pp

Pp

Jn

σT2

σT1

Korelacje kierunkowe w rozpadzie neutronu

mEp

EEpp

WEp

VEEp

pUj

J

EEp

pTEEpp

SEp

RmE

pEp

QE

Nj

J

EEpp

LEEpp

mEp

KEp

HEp

G

EEpp

DE

pC

Ep

BEp

Aj

J

Emb

EEpp

appEEJWp

p

1),,,,,,(

PDG:

= -0.1

03(4)

= 0

.980

7(30

)= -0

.237

7(25

)= -0

.000

4(6)

= -0

.118

8(7)


Contribution from complex phase δKM and θ-term negligible

(~10-12).

Standard ModelFinal state interaction

Correlation coefficients N, R and

exotic interactions

Allowing for nonzero exotic couplings in weak interaction

(Jackson, 57):

Beyond Standard Model:S, T – relative strength of scalar

and tensor couplings

NFSI~0.068 6∙10-4

RFSI~0.0006 6∙10-6

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).


Experimental setup (Mott Polarimeter),

top view

V-track

n


Correlation coefficients N and R our result

Former limmitations

NFSI~0.0686∙10-4

RFSI~0.00066∙10-6

V

SS

CCC

S'

A

TT

CCC

T'

NSM·100 RSM·100N ·100 R·100

68 0.662115 4125


Correlation coefficients N and R our result

Former limmitationsAnd our result

R = (4125)·10-3N = (62115)·10-3

NFSI~0.0686∙10-4

RFSI~0.00066∙10-6

V

SS

CCC

S'

A

TT

CCC

T'

[Phys. Rev. C 85, 045501]


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.

R = (4125)·10-3N = (62115)·10-3

V

SS

CCC

S'

A

TT

CCC

T'


+Q

-Q

Electric Dipole Moment

Simple case: Particle with spin:

+_ +_

+_

e

Electric dipole moment of particle with spinViolates both Parity and time Reversal Symmetry


nEDM – predictions

Current limit: 2.9·10–26 e·cm.

θ-term from QCD Lagrangian: even ~10-18

e·cm.

Contribution from complex phase δKM negligible

below ~10-32 e·cm.

nEDM@PSI final goal: 5·10-28 e·cm

nEDN[e·cm]

„Strong CP-problem”

~10-9


dn=(+0.2 ± 1.5 ± 0.7)·10-26 e·cm.

nEDM current precision

nd ≈ 2 µm


nEDM @ Paul Scherrer Institute

Ramsey resonance method of separate oscillating fields applied for Ultra Cold Neutrons. UCN; v<10m/s

[successor of RAL,Sussex,ILL]


Sample of polarized neutronsIn constant, uniform fields B (1 μT) and E (12 kV/cm).

RF „π/2” pulse (30 Hz).

Free precession of neutron spin T ~ 150200 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.

4.

3.

2.

1.

5.

Ramsey resonance method of

oscillating fields - principle

or

E


Ramsey resonance method of

oscillating fields - principle

x – working points

C1

C2

Statistical uncertainty:

NETd n

2

)(

21

21

CCCC

where:

visibility

E: electric field intensity,T: free precession timeN: number of neutrons counted after T.

Edn 4

)(


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…• …


Współczynniki korelacji N i R a amplitudy

wymiany leptokwarków

Wcześniejsze ograniczeniai nasz rezultat

R = 4125N = 62115

-1/3X

u

d

e

e

2/3X

u

d

e

e F f

H h

0 1

2/3

1/3Q

spin

LQ-wektorowe


Minimalny Supersymetryczny Model

Standardowy z łamaniem parzystości R

R = 4125

N = 62115

Le~

u d

e

e

Rd~

u

d

e

e

adam kozela 26/09/2014 1 study of the time-reversal violation with neutrons adam kozela institute of...

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