Particle Physics Division

For more than 10 years now, Irfu physicists and engineers have been developing in Saclay the necessary equipment for the GBAR experiment, designed to test the behaviour of antimatter under terrestrial gravity. An important step has just been taken with the installation at the Cern of a new positron source using on an electron linac, and the transport to the Cern of the positron trapping system built at Saclay.

The new source produced its first positrons on November 17, 2017. The installation of the traps is in progress, to be operational when the antiprotons arrive, scheduled for spring 2018.

The D0 experiment at the Tevatron accelerator at Fermilab (Chicago), in which physicists from CEA/IRFU and CNRS/IN2P3 are involved, has measured a significant matter-antimatter _asymmetry_ in the behaviour of particles containing b quarks, known as B mesons (or beauty mesons) beyond the predictions of the standard model (the current theory of particle physics). This result has been submitted for publication in the Journal Physical Review D.

The BaBar experiment running on the PEP-II accelerator at SLAC (California) has been collecting data for ten years and has recorded sufficient events to probe the most subtle aspects of the Standard Model of particle physics and quantum field theory. By analysing the behaviour over time of the B-meson particle-antiparticle pairs produced in abundance, a team of researchers including participants from IRFU/SPP has been able to demonstrate that the Universe has no preferred direction, and therefore that Lorentz symmetry, touchstone of modern physics, still holds. This original work is similar in concept to the famous Michelson-Morley experiment that demonstrated the symmetry of the speed of light.