#1

“New” ILL EDM Experiment Systematic

Comment on “An Improved Experimental Limit on the Electric-Dipole Moment of the Neutron,” C.A. Baker, et al. [1]

S.K. LamoreauxYale University

R. GolubNorth Carolina State University

#2

ILL Experiment

1 UCN/cc10 kV/cm120 sec store1.5 x 10-26 e cm

199Hg Co-magnetometer—Systematic control

A new systematic“geometric phase” effect was found in this work (controllable at the 10-28 e cm level for our experiment)

#3

Gradient interference with E x v field

/

/

0

2

0r

r

B

cEaRBB

arBr Radial gradient

v x E fieldChanges sign withdirection

c

EaR 22

#4

Monte Carlo calculation of shift

#5

• Change in apparent ratio of gyromagnetic ratios is used to determine the gradient

• The gradient thus determined is used to evaluate the geometric phase systematic effect

• A comparison between magnetic field “up” vs. field “down” allows extraction of the true EDM

• Any effect that causes a shift in the ratio of gyromagnetic ratios that depends on the magnetic field direction will cause a systematic effect

#6

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#9

#10

Result of line intersection in [1]

#11

Two Versions of Systematic Effects

c.f. 25.7 due to Earth rotation

original final

#12

The systematic error appears as underestimated