The neutron EDM: exp. vs theory Proposed limits on dn (10-28) e·cm Progress at order of magnitude per decade Standard Model out of reach strong contrains on e.g. Super Symmetry Proposed limits on dn (10-28) e·cm C.A.Baker et al., dn < 310-26 ecm (90% CL)
Schema des EDM- Nachweises B E - + Polarisator Analysator B0 E RF-Spule RF-Spule Ww.-Zone freie Präzession Ww.-Zone
Ramsey’s Technique
Ein in Richtung B ausgerichteter Kernspin „Spitze“ des Spin-Vektors Einstrahlen eines resonanten HF-Pulses: …Auslenkung aus der Magnetfeldachse ( z-Achse ) :
2. Kernspin bei „90° Puls“ Ein „90°-Puls“ senkrecht zur B0 startet die Präzession
Ramsey-Resonanzkurve am nEDM Experiment (ILL-Grenoble)
Apparatus HV E = 7 kV/cm Neutron storage chamber B-field coils 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 · Bo E UCN Hg T2 100 s n Hg Sensitivity per batch cycle: 200 fT Sensitivity of neutron EDM magnetometer: 800 fT K. Green et al., NIM A 404 (1998)381
statistically limited !!! Angenommen das Neutron hätte die Größe der Erde... Sensitivity figure dN < 310-26 e cm x 1m 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 ) : 1 year of data ( 250 days ) : statistically limited !!!
B E nEDM Experiment am PNPI Gatchina UCN ( I.S. Altarev et al., Phys. At. Nucl. 59 ( 1996 )1152 ) UCN B E
Isolatorringe aus Glaskeramik ( Sitall )
Prinzipskizze des 3He-Magnetometers B Vakuumkammer Cs-Magnetometer 3He magnetometer UCN Leiter Shutter UCN Doppelkammer Ventile Magn. Abschirmung Kompressor 3He Vorratszelle 3He opt. Pumpzelle 3He Reservoir
n2EDM PSI – Skizze des Gesamtaufbaus