Custodial symmetry

In particle physics, the extra symmetry of the Higgs potential in the Standard Model In particle physics, the extra symmetry of the Higgs potential in the Standard Model responsible for keeping ρ {displaystyle ho } ≈ 1 and ensuring small corrections to ρ {displaystyle ho } is called a custodial symmetry.(Note ρ {displaystyle ho } is a ratio involving the masses of the weak bosons and the Weinberg angle). With one or more electroweak Higgs doublets in the Higgs sector, the effective action term | H † D μ H | 2 / Λ 2 {displaystyle left|H^{dagger }D_{mu }H ight|^{2}/Lambda ^{2}} which generically arises with physics beyond the Standard Model at the scale Λ contributes to the Peskin-Takeuchi T parameter. Current precision electroweak measurements restrict Λ to more than a few TeV. Attempts to solve the gauge hierarchy problem generically require the addition of new particles below that scale, however.