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.
This obituary appeared in .
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.
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.
Now running with the world's best-ever sensitivity!
1PTB, Physikalisch Technische Bundesanstalt, Berlin, Germany
2US, University of Sussex, Brighton, United Kingdom
3LPC, Laboratoire de Physique Corpusculaire, Caen, France
4JUC, Jagellonian University, Cracow, Poland
5HNI, Henryk Niedwodniczanski Institute of Nuclear Physics PAN, Cracow, Poland
6FRAP, Université de Fribourg, Fribourg, Switzerland
7LPSC, Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France
8UKY, University of Kentucky, Lexington, USA
9KUL, Katholieke Universiteit, Leuven, Belgium
10GUM, Institut für Physik, Gutenberg Universität, Mainz, Germany
11IKC, Institut für Kernchemie, Gutenberg Universität, Mainz, Germany
12CSNSM, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Paris, France
13PSI, Paul-Scherrer-Institut, Villigen, Switzerland
14ETHZ, Eidgenössische Technische Hochschule Zürich, Switzerland
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Picture taken at our collaboration meeting at Université de Fribourg, 17. January 2015
Picture taken at our collaboration meeting at LPSC Grenoble, 5. April 2014
Picture taken at our collaboration meeting at JU Krakow, 2. July 2013
Picture taken at our collaboration meeting at KU Leuven, 6. January 2012
Picture taken at our collaboration meeting at LPC Caen, 23. April 2010
Picture taken at our collaboration meeting at PSI, 9. October 2009
Picture taken at our collaboration meeting at PSI, 8. October 2009
Picture taken at our collaboration meeting in Garching, 17. October 2008
Picture taken at our collaboration meeting in Mainz, 18. October 2007
Picture taken at our collaboration meeting in Cracovia, 22. June 2007
Picture taken at our collaboration meeting in Fribourg, 21. April 2007