In the Standard Model of particle physics, elementary particles adhere to key symmetries: translations, rotations, and parity (P symmetry). Among the four fundamental interactions, only the weak force violates P symmetry. Mirror particles—hypothetical counterparts to known particles—could restore this symmetry.
In 1956, physicists Tsung-Dao Lee and Chen-Ning Yang proposed that the weak interaction violates parity to resolve the τ–θ meson decay puzzle. They designed experiments that soon confirmed this violation in weak interactions.
From the 1960s to 1990s, theorists sought ways to naturally restore parity. One idea involved mirror particles mirroring ordinary ones. This concept was formally outlined in 1991.
In the Standard Model, W bosons mediating weak interactions are left-handed, coupling only to left-handed quarks. Mirror particles would feature right-handed chirality, with right-handed W bosons, neutrinos, gluons, and more—each matching the mass of its ordinary counterpart.
Apart from chirality, mirror particles interact among themselves just like ordinary particles. They cannot interact with ordinary particles due to incompatible bosons, except via gravity, which acts universally through spacetime geometry.
In 1985, University of Toronto physicist Robert Holdom proposed a feeble interaction between ordinary and mirror sectors via 'Holdom bosons.' A particle could convert to its mirror via such exchange, though charge conservation limits this—only neutral particles like photons qualify. Experiments on neutrino oscillations and ortho-positronium decay support this.
Same topic: Antimatter Universe Exists Beyond the Big Bang According to New Model
Mirror matter likely formed at the Planck era's end, when gravity decoupled from other forces. Unequal production could make it a dark matter candidate, explaining DAMA/NaI's positive signals alongside null results from other detectors.
Beyond parity restoration, mirror matter addresses the GZK cutoff on cosmic ray energies through mirror neutrino oscillations. It could form stars, planets, and galaxies, detectable via gravitational effects.
