A measurement is presented of the charged hadron multiplicity in hadronic
PbPb collisions, as a function of pseudorapidity and centrality, at a collision energy of
2.76TeV per nucleon pair. The data sample is collected using the CMS detector and
a minimum-bias trigger, with the CMS solenoid off. The number of charged hadrons is
measured both by counting the number of reconstructed particle hits and by forming hit
doublets of pairs of layers in the pixel detector. The two methods give consistent results.
The charged hadron multiplicity density, dN_(ch)/d_η|η=0, for head-on collisions is found to be
1612±55, where the uncertainty is dominated by systematic effects. Comparisons of these
results to previous measurements and to various models are also presented