  The ALICE collaboration measured charged particle production in
$\sqrt{s_{NN}}=2.76$ TeV Pb--Pb collisions at the LHC. We report on results on
charged particle multiplicity and transverse momentum spectra. All the results
are presented as a function of the centrality of the collision, estimated with
a Glauber Monte Carlo fit to multiplicity distributions reconstructed in
various detectors. The applicability of the Glauber model at LHC energies, the
precision of the centrality determination and the related systematic
uncertainties are discussed in detail.
  Particles are tracked in the pseudorapidity window $|\eta| \lesssim 0.9$\
with the silicon Inner Tracking System (ITS) and the Time Projection Chamber
(TPC), over the range $0.15 < \pt \lesssim 50$ GeV/$c$. The low-$p_t$ cut-off
is further reduced in the multiplicity measurement using "tracklets",
reconstructed in the 2 innermost layers of the ITS.
  The charged particle multiplicity is measured in $|\eta| < 0.5$ to be
$\mathrm{d}N_{ch}/\mathrm{d}\eta = 1601 \pm 60$ in 5% most central Pb--Pb
collisions, indicating an energy density a factor $\sim 3$ higher than at RHIC.
Its evolution with centrality shows a pattern strikingly similar to the one
measured at RHIC. Intermediate ($5 \lesssim \pt \lesssim 15$ GeV/$c$)
transverse momentum particles are found to be most strongly suppressed with
respect to pp collisions, consistent with a large energy loss of hard-scattered
partons in the hot and dense medium. The results are presented in terms of the
nuclear modification factor $R_{\mathrm{AA}}$ and compared to theoretical
expectations.
