Only subatomic particles with a left-handed spin decay as a result of one of the fundamental forces, confirming that the Universe has a left-hand bias.

A team working on the LHCb experiment looked at the decay of trillions of subatomic particles known as Λ_b⁰ baryons emerging from collisions at the Large Hadron Collider at CERN, Europe's particle-physics laboratory near Geneva, Switzerland. During this decay, a bottom quark from the baryon can turn into an up quark. The team confirmed that the weak nuclear force — one of the four fundamental forces in the Universe — causes only bottom quarks with left-handed spin to decay into up quarks, as predicted by the standard model of particle physics.

Previous measurements had suggested that right-handed quarks might also decay in this way, which, if true, would have called for new fundamental forces of nature.

Nature Phys. http://doi.org/6kg (2015)