Guillaume Pignol

Host institution: UGA

Laboratory: LPSC

Call for projects: Starting (PE2)

Project Name: NEDM – The Neutron Electric Dipole Moment: pushing precision to understand matter-antimatter asymmetry

Amount: €1.49m

Description :

The existence of a permanent electric dipole moment (EDM) of the neutron, or any subatomic particle, would have far-reaching implications from particle physics to cosmology.

Time inversion invariance and CP symmetry would be violated.

A new fundamental interaction generates the EDM, i.e. distorting the charge distribution inside the neutron, could also have generated the matter-antimatter asymmetry in the primordial Universe.

After 60 years of evolution, neutron EDM measurement techniques are now so advanced that experiments are sensitive to the microphysics associated with an energy scale beyond that accessible at the LHC.

This situation offers a high probability of discovery for the next generation of experiments.

At the same time, any improvement in accuracy is technically difficult.

Magnetic field control must surpass that of state-of-the-art atomic magnetometers.

The n2EDM project aims to improve accuracy by an order of magnitude or more.

Systematic effects must be controlled at an unprecedented level.

In particular, the use of a mercury comagnetometer based on the precession of 199Hg spins induces a set of false subtle effects due to the relativistic kinetic field.

I propose to initiate a comprehensive program to control these systematic effects beyond the current research program.

In particular, the proposed project includes an accurate determination of the 199Hg magnetic moment with an accuracy of 0.1 ppm.

For this, I will try a new approach: combine mercury and 4He magnetometry in the same cell.

As a by-product, this will also be suitable for a better determination of the magnetic moment of the neutron, a quantity of interest for metrology.

The recovery that I propose proves that all perturbations on neutron or mercury spins are controlled at the sub-ppm level, a decisive step in the quest for neutron EDM.