An improved search of the nEDM

09.08.2011, Providence RI

Paul Scherrer InstitutPhilipp Schmidt-Wellenburg on behalf of the nEDM collaboration

An improved search of the nEDM

Philipp Schmidt-Wellenburg APS DPF Meeting, Brown University Providence RI, 9th August 2011 2/23

Baryon Asymmetry of the Universe

Sakharov criteria1. Baryon number

violation

2. C and CP violation

3. Thermal non-equilibrium

vs.

SM expectation:

1810~

n

nn BB

Observed*:

1010~

nBnnB

*WMAP


T

CP violation and EDM

→ CP violation so far only in weak decays

→ Might help explain BAU matter/anti-matter problem

→ Excellent probe for physics beyond the Standard Model (complementary to LHC)

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


Standard Model: CP violation

• QCD vacuum:

• Phase of CKM matrix:

aas GG

8

QCDeff LL

BE

ii

ii

ub

eccsscesccscss

ecssccessccccs

sscsc

VVV

VVV

VVV

323213232121

323213232121

31311

tbtstd

cbcscd

usud

Known from neutral K and B meson decays

dn≈ θ×10-15 e·cm → θ ≈ 10-10


nEDM from CKM Matrix

• No tree level contribution• No first loop contribution• No pure week interaction two

loop contribution• Only gluon two loop contribution

→ strongly suppressed

CP odd vertex

Standard Model nEDM:10-30 e·cm > dn >10-32 e·cm


+

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


The measurement technique

Measure the precession frequencies in a magnetic and electric field:

EdBμ nn 22

EdBμ nn 22



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

BBμEEdΔ nn 22

for dn<10-26 ω/ω < 2×10-9


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

2)(

n


Ultracold neutrons (UCN)

NT

dn

1

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


New UCN source @PSI

not yet at designed strength, ramping up


Apparatus


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

2

)(n

• changing polarity every ~ 1.5h • comparing frequency +/- polarity• aimed at sensitivity ω 60 nHz

1.5

mHz

Ramsey resonance curve



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

BBμEEdΔ nn 22

Active Stabilization and insitu field monitoring


Mercury co-magnetometer

¼ wave platelinear polarizer

Hg lamps

PM

polarization cell

HgO source

B0 ≈

1μ

T

• Average magnetic field (volume and cycle)

• σ(B) ~ 20 – 50 fT• Center of mass

different than UCN• Important Systematic effects

due to magnetic field gradients

τ = 140s


Corrected measurement

+ 12 Cesium magnetometers for field gradient measurements

50 p

T


Cesium magnetometers

Monitoring of vertical magnetic gradients

• Two cesium magnetometer arrays

• Stabilized laser• PID phase locked DAQ

1 2 3 4

5 … 11 12

±140kV


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 0.10ac fields 0.0 0.01 0.01Total -3.8 7.19 1.37


Uncompensated field drift

GhE

d nn

2

Magnetization through changing polarity



Ramping speed = 1 kV/sCharging current = 35 nA

+100

-100

E [kV]

time

100 s

400-500 s


No effect is observed at the level of 2.8 fT/cm

No effect is observed at the level of 2.8 fT/cm

Translates into


cm 101615 27false

n ed

Dedicated runs (daytime)

cm false

n e27109.0d


Conclusion • UCN source is ramping up

→ first data this year (50 nights)• Reduction of main systematic effects

• Further improvements on systematic effects winter shut-down 2011-2012

• 200 nights of data in 2012-2013

cm sysstat e2710)46?(nd

cm 10)2 2 ? ( 27

sysstat end


Paul Scherrer InstitutPhilipp Schmidt-Wellenburg on behalf of the nEDM collaborationalso at: 1Paul Scherrer Institut, 2PNPI Gatchina, 3Eidgenössische Technische Hochschule

The Neutron EDM Collaboration

M. Burghoff, S. Knappe-Grüneberg, A. Schnabel, L. Trahms, J. Vogt

G. Ban, Th. Lefort, Y. Lemiere, O. Naviliat-Cuncic, E. Pierre1, G. Quéméner

K. Bodek, St. Kistryn, G. Wyszynski, J. Zejma

A. Kozela

N. Khomutov

M. Kasprzak, P. Knowles, A. Weis, Z. Grujic

G. Pignol, D. Rebreyend S. Afach, G. Bison

N. Severijns, R. Chankova, S. Roccia

C. Plonka-Spehr, J. Zenner1

W. Heil, H.C. Koch, A. Kraft, T. Lauer , D. Neumann, Yu. Sobolev2

Z. Chowdhuri, M. Daum, M. Fertl3 , B. Franke3, M. Horras3, B. Lauss, J. Krempel, A. Mtchedlishvili, P. Schmidt-Wellenburg, G. Zsigmond

C. Grab, K. Kirch1, C. Kittel, A. Knecht, 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

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

Paul Scherrer Institut, Villigen

Eidgenössische Technische Hochschule, Zürich


Paul Scherrer InstitutPhilipp Schmidt-Wellenburg on behalf of the nEDM collaboration

Thank you

An improved search of the nEDM

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