Fundamental measures

Fundamental measures

This activity includes several activities: manipulation of cold molecules, study of antimatter with collaborations at CERN, and measurement of the electric dipole moment of the electron

alt text

The experiment deals with the cooling of the internal and external degrees of freedom of a BaF beam. The achievements and perspectives converge towards the objective of obtaining a cold sample of molecules. The aim is to optimize the number of molecules and to control their movement in order to carry out precision measurements (which could be facilitated by the installation of a frequency comb and the arrival of the reference signal REFIMEVE) on the P and CP violation effects for which the BaF molecule is known to have a good sensitivity (dipole of the electron or parity violation effects in the nucleus).

Following the installation of the electrostatic decelerator, the immediate next step in the experiment will be to study neutralization, i.e. electron capture by BaF+ ions. For this, a jet of of cesium atoms promoted to a Rydberg state (Cs* ) will provide a source of cold electrons. The study of BaF+ /Cs* interactions will be the focus of our work: the aim will be to understand the mechanism and efficiency of charge transfer, and identifying in which final states BaF neutralizes itself. Finally, we also intend to use a negative ionic intermediate BaF– , more precisely a dipolar anion, for which the formation and neutralization will require specific studies.

For this ongoing and future work, we will develop new analytical tools (in in particular velocity imaging -VMI and a pulsed laser with optimized spectral linewidth at the Fourier limit)

The activity in antimatter was carried out within AEgIS (Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy) collaboration at CERN and continues via several collaborations:

1 – With Antoine Camper and Norwegian colleagues around the cooling of Ps and antihydrogen with the construction of incoherent nanosecond or coherent picosecond lasers (wavelength 121 nm and 243 nm) (theoretical paper in progress)

2 – With Chloé Malbrunot’s group at CERN concerning the demonstration of laser-stimulated de-excitation of hydrogen and antihydrogen atoms from their Rydberg states, as well as on the improvement of trapping and cooling in particular with a pulsed injected laser fabricated at LAC

Towards an Electric Dipole Moment (EDM)

with atoms and molecules in Matrix (EDMMA)

The existence of a measurable permanent electric dipole moment of the electron would imply the existence of new physics beyond the standard model of particle physics. Searches for this property can be performed in tabletop sizedexperiments which opens up a fascinating way to learn more about the fundamental symmetries of physics. Our project is based on precise measurements of the valence electron of the cesium atom. In order to have large quantities of atoms at our disposal we have initiated the EDM in matrix (EDMMA) project which traps atoms in cryogenic rare gas matrices. We obtained an ANR funding with the consortium LAC/ISMO/LPL/CIMAP. The experiment started in August 2021 with the delivery of the cryostat made by http://www.mycryofirm.com/. The EDMMA project is divided into two phases:

1 – In the first 2 years we will optimize the systems to obtain a large number of particles, optically polarizable and with long coherence times (to optimize the measurement of the energy perturbation: -d .E). This will be done through back and forth interactions between experimentalists (Cs in parahydrogen at ISMO, Cs in Ar at LAC) and theory experts in simulations and trapping site dynamics (CIMAP). The coherence measurements will be performed and optimized thanks to the involvement of the LPL which will also bring its expertise in ultra-precise spectroscopic measurements and metrology in cryogenic environment. One of the important goals of this first step will be to understand the trapping sites of Cs atoms in Ar or parahydrogen matrices in order to estimate the effects of the crystal field on optical manipulations or on the production of possible systematic effects.

2 – Then, in the second step, in an improved facility (magnetically shielded in particular) at LAC, we will study the limits and performances of many possible diagnostics required for an EDM measurement using magnetometry and spectroscopy with a careful study of systematic effects. The ultimate goal is to set limits for the first attempts of an EDM measurement.