Studying the Migdal effect in elements relevant to dark matter searches

Prof. Pawel Majewski (RAL/PPD) + Prof. Henrique Araujo (Imperial College London)

In 1939 Russian physicist Arkady Migdal predicted a new effect resulting from the quantum mechanics of atomic systems: if a projectile particle jolts the nucleus of an atom, there is a small probability that the atom will emit one of its electrons as it recoils - even at very low recoil energies. The MIGDAL collaboration  aims to detect and study this rare atomic process unambiguously.

Many of the most sensitive dark matter experiments find it easier to detect electrons than recoiling nuclei, the latter being predicted by the interaction of dark matter particles in many models. The Migdal effect helps in the search for dark matter: the nuclear recoil may be missed, but the Migdal electron can nonetheless be detected. This extends the reach of those experiments to lower dark matter masses.

The MIGDAL experiment aims to observe and then characterise the Migdal effect using an Optical Time Projection Chamber operating with low-pressure CF4 gas mixed with noble gases and other elements relevant to dark matter searches.

The experiment is now operating with a high-yield D-D neutron generator, and the first Migdal search is ongoing in pure CF4. The aim is to "photograph" the tell-take Migdal signature consisting of two tracks - a nuclear recoil and an electron - originating in a common vertex.

The successful PhD student will participate in the experiment hosted at the ISIS Neutron & Muon Source at the STFC Rutherford Appleton Laboratory. This rare event search requires sophisticated analysis techniques, including machine-learning tools, to observe and study the rare Migdal effect in new elements relevant to dark matter searches. Combined with the hands-on development and operation of the experiment, this will provide a well-rounded PhD experience!

For more details, contact Pawel Majewski ( ) or Henrique Araujo (