Number 91 (Story #1), August 12, 1992 by Phillip F. Schewe and Ben Stein MEASUREMENTS OF MULTI-JET PRODUCTION RATES in deep inelastic muon-proton scattering support the theory of quantum chromodynamics (QCD). Stealing a march on HERA---the electron-proton collider in Hamburg, where proton-lepton (electrons instead of muons) scattering will be the exclusive concern---scientists at Fermilab (contact: Jorge Morfin, 708-840-4561) have studied what happens when a beam of 490-GeV muons is smashed into a stationary hydrogen target. Quite often the muon can be thought of as scattering not from the proton as a whole but from individual quarks within the proton. Some of these quark-muon interactions will be highly inelastic; that is, much of the collision energy will be converted into new particles, some of which emerge from the collision vertex in jets. QCD holds that in certain reactions, gluons (the carriers of the strong nuclear force between quarks) may also spawn jets through a sort of radiative process, much like photon bremsstrahlung. Fermilab has not only seen such multi-jet (in particular, 3-jet) events, but has for the first time measured their rate of production, a value which agrees with the QCD prediction. (M.R. Adams et al., 17 August issue of Physical Review Letters.)