Signatures of the tricritical point in QCD

Several approaches to QCD with two massless quarks at finite temperature T and baryon chemical potential mu suggest the existence of a tricritical point on the boundary of the phase with spontaneously broken chiral symmetry. In QCD with massive quarks there is then a critical point at the end of a first order transition lint; We discuss possible experimental signatures of this point, which provide information about its location and properties. We propose a combination of event-by-event observables, including suppressed fluctuations in T and mu and, simultaneously, enhanced fluctuations in the multiplicity of soft pions. [S0031-9007(98)07806-5].