The STAR experiment
Data from the STAR experiment show angular correlations between pairs of high transverse-momentum charged particles, referenced to a "trigger" particle that is required to have pT greater than 4 GeV/c. The proton-proton and deuteron-gold collision data indicate back-to-back pairs of jets (a peak associated with the trigger particle at Δφ = 0 degrees and a somewhat broadened recoil peak at 180 degrees). The central gold-gold data indicate the characteristic jet peak around the trigger particle, at 0 degrees, but the recoil jet is absent.