QCD jets from coherent states

A recently proposed approach to the problem of infrared and mass singularities in QCD, based on the formalism of coherent states, is extended to discuss massless quark and gluon jets. Our results include all leading (In δ) terms as well as finite terms in the energy loss ϵ, in addition to the usual In ϵ associated with In δ. Our formulae agree with explicit perturbative calculations, whenever available. Explicit expressions for the total $K_T$ distributions are given which take into account transverse-momentum conservation. Predictions are also made for the $Q^2$ dependence of the mean $K_T^2$ for quark and gluon jets. Our jet $k_T$ distributions are extrapolated for low $K_T$ and shown to describe with good accuracy the data for eē → qq̄ → hadrons. Numerical predictions are also presented for the forthcoming PETRA, PEP and LEP machines.