  Event-by-event fluctuations of the mean transverse momentum of charged
particles produced in pp collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV, and
Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are studied as a function of the
charged-particle multiplicity using the ALICE detector at the LHC. Dynamical
fluctuations indicative of correlated particle emission are observed in all
systems. The results in pp collisions show little dependence on collision
energy. The Monte Carlo event generators PYTHIA and PHOJET are in qualitative
agreement with the data. Peripheral Pb-Pb data exhibit a similar multiplicity
dependence as that observed in pp. In central Pb-Pb, the results deviate from
this trend, featuring a significant reduction of the fluctuation strength. The
results in Pb--Pb are in qualitative agreement with previous measurements in
Au-Au at lower collision energies and with expectations from models that
incorporate collective phenomena.
