Subtle Difference between Matter and Antimatter Observed

A subtle difference between matter and antimatter has been observed for the first time by the Large Hadron Collider beauty (LHCb) experiment at the European Organisation for Nuclear Research (CERN).

The work forms part of studies to understand why the Universe only contains matter when it is believed that matter and antimatter were created in equal amounts at the time of the Big Bang.

LHCb was specifically designed to look for small differences between matter and antimatter – called CP violation – in particles produced by the Large Hadron Collider (LHC). The first observation of CP violation was made in 1964 leading to the 1980 Nobel prize; a later discovery confirmed the theoretical description of the phenomenon and led to the 2008 Nobel prize. LHCb has now observed CP violation in B_s mesons, combined states made from beauty and strange quarks, and antiquarks.

Members of the LHCb collaboration analysed 70 trillion proton-proton collisions that took place in the heart of the detector. They looked at two variants of a decay of the B_s meson and its ‘mirror image’ where all particles are replaced by their antiparticles. A small differences in the rates at which these two decay modes happen demonstrated a difference of behaviour between matter and antimatter.

Professor Chris Parkes, from the University of Manchester’s School of Physics and Astronomy and spokesperson for the UK university groups involved in the LHCb collaboration, said: “This is an excellent result, consistent with the Standard Model [of particle physics], so it isn’t unexpected – we thought we should be able to make this observation with LHCb based on previous results. We’ve been able to confirm the discovery so soon due to the sensitivity of our detectors, the quality and quantity of data, and the precision of our analysis.”