  The extent of a locally equilibrated parton plasma in d + Au collisions at
sqrt(s_NN) = 200 GeV is investigated as a function of collision centrality in a
nonequilibrium-statistical framework. Based on a three-sources model,
analytical solutions of a relativistic diffusion equation are in precise
agreement with recent data for charged-particle pseudorapidity distributions.
The moving midrapidity source indicates the size of the local thermal
equilibrium region after hadronization. In central d + Au collisions it
contains about 19% of the produced particles, and its relative importance rises
with decreasing centrality.
