The phenomenology of scalar octets

We discuss the phenomenology of colour scalar octets. Namely, we consider the discovery potential of scalar octets at LEP, FNAL and LHC. Scalar octets decay mainly into two gluons and new hadrons composed from scalar colour octets are rather long lived $(\Gamma \leq O(10)Kev)$. For the scalar octet masses $M \geq O(50)Gev$ scalar octets producing at FNAL or LHC decay into two gluons that leads to additional four-jet events. We propose to look for scalar octets by the measurement of the distributions of differential cross sections on the invariant di-jet masses. Scalar octets naturally arise in models with compactification of additional space dimensions. In such models the branching ratio for the scalar octet bound state into two photons is $O(10^{-2})$ that leads to the events with two photons and two jets. We also point out that the current experimental data don't contradict to the existence of light ($M \sim O(1)Gev$) scalar octets. Light scalar octets give additional contribution into QCD $\beta$-function and allow to improve the agreement between deep inelastic and LEP data.