Photino

A photino is a hypothetical subatomic particle predicted by supersymmetry (SUSY) theories in particle physics. It is the supersymmetric partner (superpartner) of the photon, the force carrier of electromagnetism. In SUSY theories, every Standard Model particle has a superpartner with a spin differing by 1/2. Therefore, since the photon is a boson with spin 1, the photino is a fermion with spin 1/2.

Like other neutralinos (superpartners of neutral gauge bosons and Higgs bosons), the photino is electrically neutral and interacts only weakly. In many SUSY models, the photino is predicted to be the lightest supersymmetric particle (LSP). If R-parity is conserved, a common assumption in SUSY models, the LSP is stable and could be a candidate for dark matter.

The photino's mass and interaction strength are determined by the specific details of the SUSY model. Experimental searches for photinos and other SUSY particles are ongoing at particle colliders such as the Large Hadron Collider (LHC). Direct detection experiments are also being conducted to search for dark matter particles, which could potentially include photinos.

The properties and even existence of the photino are currently unknown, and its detection would provide strong evidence for the validity of supersymmetry. If detected, it would have significant implications for our understanding of fundamental physics and the composition of the universe.

The photino primarily interacts with ordinary matter through the exchange of sfermions (superpartners of fermions). The strength of this interaction depends on the mass of the sfermion being exchanged, and in some models, the interaction may be very weak. This makes direct detection of photinos, especially those that constitute dark matter, challenging.