  We study the continuous absorbing-state phase transition in the
one-dimensional pair contact process with diffusion (PCPD). In previous studies
[Dickman and de Menezes, Phys. Rev. E, 66 045101(R) (2002)], the critical point
moment ratios of the order parameter showed anomalous behavior, growing with
system size rather than taking universal values, as expected. Using the
quasistationary simulation method we determine the moments of the order
parameter up to fourth order at the critical point, in systems of up to 40960
sites. Due to strong finite-size effects, the ratios converge only for large
system sizes. Moment ratios and associated order-parameter histograms are
compared with those of directed percolation. We also report an improved
estimate [p_c =0.077092(1)] for the nondiffusive pair contact process.

Statistical Mechanics