Search for the neutron electric dipole moment (nEDM) at PSI

In Memoriam: Mike Pendlebury 1936-2015 The nEDM collaboration has suffered a great loss with the passing of our friend and colleague Mike Pendlebury. The entire field benefited greatly from his many contributions throughout his long and distinguished career, during which he played a leading role in reducing the nEDM limit by a factor of 1000. A memorial service at the University of Sussex took place on Friday 29 April 2016. An obituary appeared in The Guardian on 23 September 2015.

Why does the Universe contain vast quantities of matter, but almost no antimatter?

In order to address this fundamental question, which has perplexed cosmologists for half a century, we need to look beyond our Standard Model (SM) of particle physics. Some of the most sensitive probes we have of such “new” physics arise from non-accelerator experiments. One such is the search for an electric dipole moment (EDM) of the neutron. EDMs violate both parity and time-reversal symmetries, and they therefore provide some of the tightest constraints upon models beyond the SM that attempt to reconcile the low level of CP violation observed in K and B systems with the large baryon asymmetry of the Universe. The current world limit of 2.9 x 10-26 e.cm, set in 2006 by the RAL-Sussex-ILL EDM collaboration, already requires considerable fine-tuning of MSSM parameters - the so-called "SUSY CP problem". The measurement is carried out by using NMR to determine the Larmor precession frequency, in parallel and antiparallel magnetic and electric fields, of ultracold neutrons trapped in a storage cell - a sort of atomic clock, but using neutrons instead of atoms. A change in frequency with applied electric field is the signature of an EDM. The level of precision is astonishing: the system can detect an energy-level splitting of 10-21 eV, and yet it is sensitive to aspects of physics at energy scales well beyond that achievable at the LHC.

What is the neutron electric dipole moment ?

The neutron electric dipole moment (nEDM) is a measure for the distribution of positive and negative charge inside the neutron. A finite electric dipole moment can only exist if the centers of the negative and positive charge distribution inside the particle do not coincide. So far, no neutron EDM has been found. Read more in the Wikipedia entry...

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Now running with the world's best-ever nEDM sensitivity!