First atoms of anti-hydrogen in the GBAR experiment

Patrice Perez (IRFU CEA Saclay, France)

The GBAR experiment at CERN aims to measure the acceleration of the Earth’s gravity on atoms of antimatter. Indirect measurements of the effect of gravity on antimatter indicate a standard effect. Until now, the experiments at CERN have focused on the precise measurement of the atomic spectra of antihydrogen atoms in order to test CPT invariance with antimatter. Today, three experiments are preparing a direct gravitational measurement, with the first result expected this year. Some theoretical models combining the quantum world and gravitation are predicting a violation of the equivalence principle. It will therefore be interesting to increase the precision of the measurements in order to test these limits. I will present the principle and progress of the experiment as well as the first result on the production of antihydrogen atoms via the charge exchange reaction between antiprotons and positronium ($\overline{p} + Ps \rightarrow \overline{H} + e^-$).