First Hints of Jet Quenching at RHIC

At this conference first data from RHIC has been presented. Spectra of charged hadrons and identified neutral pions obtained in central collisions exhibit a depletion at large transverse momenta compared to expectations deduced from $pp$ and $\bar{p}p$ data and lower energy heavy ion data. While spectra measured in peripheral collisions exhibit the expected power-law shape, spectra from central collisions are closer to exponential. In addition, a significant azimuthal anisotropy of high momentum charged particle production has been found. All observations are in qualitative agreement with theoretical predictions that quark matter formed in heavy ion collisions quenches jet production.