Improved search for the neutron electric dipole moment

P. Schmidt-Wellenburg Slide 1Time and Matter, Montenegro, 06. Oct. 2010

Improved search for the neutron electric dipole moment

Philipp Schmidt –Wellenburg on behalf of the nEDM collaboration

Improved search for the neutron electric dipole moment

Philipp Schmidt –Wellenburg on behalf of the nEDM collaboration


Baryon asymmetry

We live in a material world

There is no evidence of Antimatter;

Where has it gone?

Sakharov criteria1. Baryon number

violation

2. C and CP violation

3. Thermal non-equilibrium

vs.

SM expectation:1810~

n

nn BB

Observed:

1010~

nBnnB


P

Purcell and Ramsey, PR78(1950)807; Lee and Yang; Landau

T

Symmetries and EDM

HEdBHT

HEdBHP

EdBH

)(

)(


P

Purcell and Ramsey, PR78(1950)807; Lee and Yang; Landau

T

Symmetries and EDM

A nonzero particle EDM violates P, T and, assuming CPT conservation, also CP.


CP-odd sources

fundamental CP-odd phasesEnergy

de

TeV

QCD

nuclear

atomic

, dq’, d d qq’,w

gNN nEDM

qq/qe interaction

EDM of Tl(paramagnetic)

EDM of Hg(diamagnetic)

e-N interaction

Adapted from:A. Ritz, NIMA 611 (2009) 117


nEDM is a test of flavor diagonal CP (so far CP only appeared in of diagonal elements of the CKM Matrix)

― background free search for new physics

CP violation of the neutron contribute to:– explaining baryogenesis problem

(Sakharov criteria)– magical fine adjustment of QCD θ-term

(θ < 10-9)– confining SUSY (MSSM) parameter space

complementary to high energy physics (LHC)

The role of an neutron EDM

M.J. Ramsey-Musolf, NIMA 611 (2009) 111


+

< 1μm

A brief history of nEDM searches

1950 1960 1970 1980 1990 2000 2010 202010-32

10-31

10-28

10-27

10-26

10-25

10-24

10-23

10-22

10-21

10-20

10-19

Standardmodel calculations

ORNL, Harvard MIT, BNL LNPI Sussex, RAL, ILL

Ne

utr

on

ED

M U

pp

er

Lim

it [e

cm]

Year of Publication

Supersymmetry predictions

RAL-Sussex-ILLdn < 2.9 x 10–26 e cmC.A.Baker et al., PRL 97 (2006) 131801

Smith, Purcell, Ramseydn < 5 x 10–20 e cmPR 108 (1957) 120

First Last

~ 50 years

Aimed at sensitivities at PSI:Intermediate: dn < 5 x 10-27 e cm (95% C.L.) Final: dn < 5 x 10-28 e cm (95% C.L.)


The measurement principle

Measure the difference of precession frequencies for parallel/anti-parallel fields:

E

ΔEE

BBμΔd

42

2

nn

for dn<10-26 ω < 60 nHz


The Ramsey technique

Free precessionat ω L

Apply /2 spinflip pulse...

“Spin up” neutron...

Second /2 spinflip pulse.

The Ramsey technique of separated oscillating fields

B0↑

B0↑ + Brf

B0↑

B0↑ + Brf

tT

rfnBt

2

rfnBt

2

Ramsey resonance curve

Sensitivity:

Visibility of resonanceE Electric field strengthT Time of free precessionN Number of neutrons

NETd

)( n


Ultracold neutrons (UCN)

NT

dn1

storable neutrons

(UCN)

V

E. Fermi, 1946 , Ya. B. Zeldovich Sov. Phys. JETP 9, 1389 (1959)

storage properties arematerial dependent

neV 350 NbVF

350 neV ↔ 8 m/s ↔ 500 Å ↔ 3 mK

magnetic60 neV/T

magnetic60 neV/T

gravity102 neV/m

gravity102 neV/m

strongVF

strongVF


PSI UCN source

Protons

Spallation targetEn~MeV D2O moderator

Neutrons thermalized to 25 meV

1mNeutron shutter

UCN storage volume

Neutron guide to experimentsUCN density: 1000/cm3

UCN convertor (solid D2)


n

• Source commissioning started fall 2009• nEDM setting up since middle of 2009• Full proton beam

(590 MeV, 2.2 mA, 1% duty cycle e.g. 8s/800s)

nEDM

PSI UCN beamline


RAL – Sussex – ILL apparatus on loan

ILL(phase I)

PSI(phase II)


Apparatus

5T magnetto spin polarize UCNs

Switchto distribute the UCNs todifferent parts of the apparatus

Spin analyzer

Neutron detector

Precession chamberwhere neutrons precesses

Vacuum chamber

Magnetic field coilsB0-correction coils

Electrode (upper)

High voltage lead

E B

E~12 kV/cm

B=1 T


Measuring frequencies with UCN

Sensitivity:NET

d

)( n

• changing polarity every ~ 400 s• comparing frequency +/- polarity• aimed at sensitivity ω 60 nHz

50 p

T


Monitoring of B-field drifts

Mercury lamp(readout mercury)

Hg polarizing system

Photomultiplier tuberead mercury light (UV)

Precession chamberwhere mercury precesses

4-layer Mu-metal shieldshields experiment fromexternal magnetic fields

Magnetic field coilsB0-correction coils

Electrode (upper)

Cesium magnetometer

+ Active B-field compensation (surrounding field compensation SFC)


Corrected measurement

Corrected with Hg magentometer

50 p

T

A Cesium magnetometer areawill allow measure field gradients


Sensitivities and magnetic stability

Cesium (ILL)

Mercury (ILL)

Cesium (PSI) w SFC

Steps to increase magnetic stability

1. Stability of the magnetic shield• Degaussing• Thermal effects• Mechanical effects

2. Surrounding field compensation (SFC)

3. Replacement of metals• Non-metal electrodes • Plastic shutters (Hg and neutron)

Allan standard deviation of magnetic field


Known systematic effects

EffectShift (see Ref.)

[10-27 e cm]σ (see Ref.) [10-27 e cm]

σ (at PSI) [10-27 e cm]

Door cavity dipole -5.6 2.00 0.10

Other dipole fields 0.0 6.00 0.40

Quadrupole difference -1.3 2.00 0.60

vE translational 0.0 0.03 0.03

vE rotational 0.0 1.00 0.10

Second-order vE 0.0 0.02 0.02

Hg light shift (geo phase) 3.5 0.80 0.40

Hg light shift (direct) 0.0 0.20 0.20

Uncompensated B drift 0.0 2.40 0.90

Hg atom EDM -0.4 0.30 0.06

Electric forces 0.0 0.40 0.40

Leakage currents 0.0 0.10 0.10

ac fields 0.0 0.01 0.01

Total -3.8 7.19 1.37

PRL 97, 131801 (2006)

After 2 years, statistics & systematics

dn = 0: |dn| < 5 x 10-27 e cm (95% C.L.) or, e.g.,

dn = 1.3 x 10-26 e cm (5σ)


n2EDM shield – conceptual study

Phase III

dn < 5 x 10-28 e cm (95% C.L.)


Conclusion

• The apparatus was successfully moved from ILL to the Paul Scherrer Institut

• The stability of the magnetic situation is being improved to profit in full scale of the increased UCN density

• The study and control of systematic effects has improved compared to the original experiment

• First neutrons will be welcomed end of year, the spectrometer will be ready

Ready for neutrons


also at: 1Paul Scherrer Institut, 2PNPI Gatchina

The Neutron EDM CollaborationM. Burghoff, S. Knappe-Grüneberg, A. Schnabel, L. Trahms

G. Ban, Th. Lefort, Y. Lemiere, E. Pierre, G. Quéméner

K. Bodek, St. Kistryn, J. Zejma

A. Kozela

N. Khomutov

P. Knowles, A.S. Pazgalev, A. Weis

P. Fierlinger, B. Franke1, M. Horras1, F. Kuchler, G. Petzoldt

D. Rebreyend , G. Pignol

G. Bison

S. Roccia, N. Severijns, N.N.

G. Hampel, J.V. Kratz, T. Lauer, C. Plonka-Spehr, N. Wiehl, J. Zenner1

W. Heil, A. Kraft, Yu. Sobolev2

I. Altarev, E. Gutsmiedl, S. Paul, R. Stoepler

Z. Chowdhuri, M. Daum, M. Fertl, R. Henneck, B. Lauss, A. Mtchedlishvili, P. Schmidt-Wellenburg, G. Zsigmond

K. Kirch1, F. Piegsa

Physikalisch Technische Bundesanstalt, Berlin

Laboratoire de Physique Corpusculaire, Caen

Institute of Physics, Jagiellonian University, Cracow

Henryk Niedwodniczanski Inst. Of Nucl. Physics, Cracow

Joint Institute of Nuclear Reasearch, Dubna

Département de physique, Université de Fribourg, Fribourg

Excellence Cluster Universe, Garching

Laboratoire de Physique Subatomique et de Cosmologie, Grenoble

Biomagnetisches Zentrum, Jena Katholieke Universiteit, Leuven

Inst. für Kernchemie, Johannes-Gutenberg-Universität, Mainz

Inst. für Physik, Johannes-Gutenberg-Universität, Mainz

Technische Universität, München

Paul Scherrer Institut, Villigen

Eidgenössische Technische Hochschule, Zürich


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