Three Experiments Hint at Physics Beyond the Standard Model

The Standard Model of particle physics is a series of mathematical equations used to describe and predict the behaviour of all known particles and forces except gravity. These experiments call into question something known as lepton universality. A lepton is a type of fundamental, half-integer spin particle (spin being intrinsic angular momentum). Half-integer spin fermions are constrained by the Pauli exclusion principle while integer spin Bosons are not (fermions are subatomic particles with a half-integer spin while Bosons are force carrying particles with an integer spin). The Pauli exclusion principle says that two or more identical fermions cannot occupy the same quantum state within a quantum system. For example, if two electrons are on the same orbital with the same principal quantum number, angular momentum and magnetic quantum number values then they must have opposite half-integer spins of ½ and -½.

Lepton universality states that the interactions of these elementary particles are the same regardless of their different masses and lifetimes. The three experiments conducted were measuring the relative ratios of B meson decay. What they found was that the heavy tau lepton has a much higher decay rate when compared to the lighter electrons and muons than the standard model predicts. Together these experiments challenge lepton universality to a level of four standard deviations indicating a 99.95% certainty. However, to be sure that the standard model has to be revised a significance of at least five standard deviations is required.

Changing the Standard Model is no easy feat. Adaptations made to equations anywhere can easily have a knock on effect causing the maths elsewhere to stop making sense. However nothing is certain yet and these results may well be flawed.