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Séminaires
Stéphanie Roccia (CSNSM, Paris Sud): Upper limit on the neutron EDM
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Europe/Paris
Amphi Georges Charpak (LPNHE)
Amphi Georges Charpak
LPNHE
Description
The quest for a non-zero electric dipole moment (EDM) in a non-degenerate system such as the electron, the neutron or the Hg atom is a powerful way to search for physics beyond the standard model in the CP violation framework, complementary to LHC experiments. A finite nEDM larger than the electro-weak Standard Model prediction (dn≤1E-31 ecm) might help to explain the baryon asymmetry of the Universe, and shed light onto the strong CP problem. So far, no evidence for such an intrinsic property was observed and the upper limit on the neutron EDM (nEDM), established in 2006 by the RAL/Sussex/ILL collaboration, is |dn|< 3 x 10-26 e.cm (90% C.L.) [C.Baker et al. PRL 97, 131801 (2006)].
At the Paul Scherrer Institute (PSI) in Switzerland the international nEDM-collaboration of 14 institutions (including the LPC-Caen, the LPSC-Grenoble and the CSNSM-Orsay) is performing an experiment using ultracold neutrons (UCN). It aims at lowering this limit at the 10-27 e.cm level within the next decade.
The experiment is currently taking blinded data with the best sensitivity ever. First data samples have been taken and used to analyze crucial systematic false nEDM effects, demonstrate the excellent control of the magnetic environment and to establish new analysis techniques, such as UCN spin-echo to determine the UCN energy spectra [S. Afach et al. PRL 115, 162502 (2015)]. A new understanding of the interplay between the gravity and the homogeneity of the magnetic field leads to a reevaluation of the limit on the neutron EDM.
