Methods for the Study of Particle Production Fluctuations
  We discuss various measures of net charge (conserved quantities) fluctuations proposed for the identification of critical phenomena in heavy ion collisions. We show the dynamical component of fluctuations of the net charge can be expressed simply in terms of integrals of two- and single-particle densities. We discuss the dependence of the fluctuation observables on detector acceptance, detection efficiency and colliding system size and collision centrality. Finally, we present a toy model of particle production including charge conservation and resonance production to gauge the effects of such resonances and finite acceptance on the net charge fluctuations. 
C. Pruneau, S. Gavin, and S. Voloshin