d n < 3 10 -26 e cm (90% cl) [e cm] the neutron edm: progress at order of magnitude per decade...
TRANSCRIPT
dn < 310-26 ecm (90% CL)
[ecm]
The neutron EDM:
Progress at order of magnitudeper decadeStandard Model out of reachstrong contrains on e.g. Super Symmetry
exp. vs theory
Proposed limits on dn
(10-28) e·cm
C.A.Baker et al.,
Polarisator Analysator
B0 E
RF-Spule RF-Spule
Ww.-Zone Ww.-Zonefreie Präzession
B B BE E
-+
0ˆˆ
n eH B d E I I
Schema des EDM- Nachweises
Ramsey’s Technique
Ein in Richtung B ausgerichteter Kernspin
1 cos (2 )x resB B t
„Spitze“ des Spin-Vektors
Einstrahlen eines resonanten HF-Pulses:
…Auslenkung aus der Magnetfeldachse ( z-Achse ) : xB t
2. Kernspin bei „90° Puls“
• Ein „90°-Puls“ senkrecht zur B0 startet die Präzession
Ramsey-Resonanzkurve am nEDM Experiment (ILL-Grenoble)
Apparatus
Neutronstoragechamber
HV
B-fieldcoils
E = 7 kV/cm
B = 1 T
Hg co-magnetometer
Neutron EDM result
dn < 310-26 ecm
Role of magnetometry in neutron EDM experiments● sensitivity of magnetometer much higher than neutron EDM magnetometer → trace systematics● magnetometer should „see“ same magnetic field → quality of normalization● no induced false EDM signals
Reading light beam
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Bo
EUCNHg
Sensitivity per batch cycle: 200 fT
Sensitivity of neutron EDM magnetometer: 800 fT
K. Green et al., NIM A 404 (1998)381
T2 100 s
n Hg
Sensitivity figure
at present: visibility: 0.5 ( neutron polarisation ) electric field: E 7 kV/cm ( limited by Hg co–magnetometer ) storage time : T = 130 s ( limited by T2 of Hg co-magnetometer ) Nucn/batch : N 13000 ( ucn 1 cm-3 - UCN density !!! )
1 day of data ( 360 Ramsey-cycles ) : ecmEDMn25
, 104 1 year of data ( 250 days ) : ecmEDMn
26, 105.2
statistically limited !!!
2nd
E T N
x 1m
Angenommen das Neutronhätte die Größe der Erde...
dN < 310-26 e cm
nEDM Experiment am PNPI Gatchina
ecmd n25101.1 ( I.S. Altarev et al., Phys. At. Nucl. 59 ( 1996 )1152 )
UCN
BE
Isolatorringe aus Glaskeramik ( Sitall )
Prinzipskizze des 3He-Magnetometers
(1) Vakuumkammer(2) Cs-Magnetometer(3) 3He magnetometer(4) UCN Leiter(5) Shutter(6) UCN Doppelkammer(7) Ventile(8) Magn. Abschirmung(9) Kompressor(10) 3He Vorratszelle(11) 3He opt. Pumpzelle(12) 3He Reservoir
B
n2EDM PSI – Skizze des Gesamtaufbaus