  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 line. 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.
