blowout regime is demonstrated experimentally. The beam and plasma parameters are
chosen such that the matched beam channels through the plasma over more than 12 beam
beta functions without spreading or oscillating over a range of densities optimum for
observing both deceleration and acceleration. The wakefield decelerates the bulk of the
initially 28.5 GeV beam by up to 155 MeV; however, particles in the back of the same beam …