If quarks are composite particles then excited states are expected. We have searched in pp¯ collisions for excited quarks (${\mathit{q}}^{\mathrm{*}}$) which decay to common quarks by emitting a W boson (${\mathit{q}}^{\mathrm{*}}$→qW) or a photon (${\mathit{q}}^{\mathrm{*}}$→qγ). The simplest model of excited quarks has been excluded for mass ${\mathit{M}}^{\mathrm{*}}$<540 GeV/${\mathit{c}}^2$ at 95% confidence level.

• Received 17 November 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.3004